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  • 1
    Digitale Medien
    Digitale Medien
    Solidification behavior of the theta system 2-propanol/poly(n-butyl methacrylate) (1995)
    Springer
    Rheologica acta 34 (1995), S. 172-181 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Thermoreversible gelation ; glass transition ; viscosity ; storage modulus ; loss modulus ; activation energies of flow ; entanglement molecular weights ; poly(n-butyl methacrylate) ; 2-propanol ; concentration and temperature influences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract Thermoreversible gelation of the system 2-propanol/poly (n-butyl methacrylate) — as detected by D'SC or dielectric experiments — does not manifest itself in a straightforward manner in the dynamic-mechanical properties. Its occurrence can, however, be seen in many ways: i) For constant composition of the system and a reference temperature lower than T gel, the storage modulus G′ is larger than the loss modulus G″ in the glass transition zone of the master curve and both vary in an almost parallel manner with the angular frequency ω over almost two decades (whereas this feature is normally found for other gelling systems within the rubber plateau or the flow region). ii) The entanglement molecular weight obtained from G″max is markedly less max than the entanglement molecular weight in the melt divided by ϕ2, the volume fraction of the polymer. iii) The temperature influences change from WLF like to Arrhenius-like behavior as T is lowered in the case of highly concentrated polymer solutions; analogous considerations hold true as ϕ2 is increased at constant T. iv) For sufficiently low temperatures, the activation energy of flow exhibits a maximum in the concentration range where the gelation is — according to DSC experiments — most pronounced. Like with ordinary non-gelling systems it is possible to construct master curves. On the basis of Graessley's theory identical dependencies are obtained for the variation of the entanglement parts of the stationary viscosity with shear rate and for the dependence of the entanglement part of the complex viscosity on the frequency ω of oscillation. Zero shear viscosity and limiting value of the complex viscosity for vanishing ω as a function of ϕ2 match smoothly and exhibit two points of inflection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00398437
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  • 2
    Digitale Medien
    Digitale Medien
    The relaxation of concentrated polymer solutions (1996)
    Springer
    Rheologica acta 35 (1996), S. 168-185 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Polymer solution ; relaxation ; viscosity ; scaling ; polystyrene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The focus of this paper is on the viscoelastic properties of concentrated polymer solutions and polymer melts. Dynamic mechanical measurements were performed on various polystyrene/ethylbenzene solutions with polymer concentrations ranging from 40% up to 100% and temperatures from Tg+30°C up to 70°C (230°C for polymer melts). The basis polymers are two commerical grade polystyrenes (BASF) with M W = 247 kg/mol and 374 kg/mol, respectively. To avoid solvent loss due to evaporating during the measurements, a special sealing technique was used. A phenomenological model which describes quantitatively the relaxation spectrum of concentrated polymer solutions from the flow regime up to the glass transition regime is developed. The relaxation data of the respective polymer melt and the glass transition temperature of the solution are the only input parameters needed. The temperature dependence is described by a universal, concentration invariant WLF-equation. The relaxation spectra are divided into two parts accounting for the entanglement and the segmental relaxation modes, respectively. The relaxation strength related to the flow and entanglement regime scale with c 2.3, whereas the segmental relaxation strength does not alter with concentration. All relaxation times change with concentration proportional to c 3.5. Flow curves can be calculated from these relaxation spectra and thus, our results are useful for engineering applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00396044
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  • 3
    Digitale Medien
    Digitale Medien
    Theoretical Demonstration of a Newly Designed Micro-Rotator Driven by Optical Pressure on a Light Incident Surface (1997)
    Springer
    Optical review 4 (1997), S. 447-449 
    Details
    ISSN: 1349-9432
    Schlagwort(e): optical micro-rotator ; cylindrical rotator ; optical torque ; optical tweezers ; ray-tracing ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A newly designed cylindrical optical micro-rotator which has slopes for trapping and rotation on its upper surface is proposed. The cylindrical shape is effective in decreasing viscous drag force (damping factor) in the medium. A ray-tracing method considering the beam waist is employed to analyze the radiation pressure exerted on the upper surface of the rotator. We have demonstrated optical trapping and high speed rotation for various optical beam parameters such as the lens numerical aperture and the Gaussian mode profile as well as rotator shape parameters including oblique angle, height and diameter.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10043-997-0447-9
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  • 4
    Digitale Medien
    Digitale Medien
    Fluorescence Study of the Relaxation Process in Excited Hetarylthiazole Cations (2000)
    Springer
    Journal of fluorescence 10 (2000), S. 161-161 
    Details
    ISSN: 1573-4994
    Schlagwort(e): Excited state ; quinolyl ; structural relaxation ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The absorption and fluorescence spectra of five cations protonated at the quinolyl nitrogen atom (IH+−VH+) and one ethylated (IEt+) cation were investigated. For these compounds (except VH+) both an anomalously large fluorescence Stokes shift (up to 238 nm) and a large short-wavelength fluorescence shift (up to 145 nm) at decreasing temperatures (down to 77 K) were observed. This is not the case for unprotonated molecules. The ground-state conjugation between quinolyl and another molecular fragment was found for II, IH+, IIH+, and IEt+. The relaxation process of excited cations is medium viscosity and temperature dependent. The experimental results are explained in terms of excited-state structural relaxation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009447226786
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  • 5
    Digitale Medien
    Digitale Medien
    Energy Deactivation of Electronic Excitation of 2-N-Piperidine-5-(2",2"-Dicyanvinyl)Thiophene Depending on the Solvent Viscosity (2000)
    Springer
    Journal of applied spectroscopy 67 (2000), S. 935-938 
    Details
    ISSN: 1573-8647
    Schlagwort(e): fluorescence ; viscosity ; picosecond spectroscopy ; conformer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Using the methods of picosecond laser spectroscopy and steady-state luminescence, we investigated the energy, spectral, and kinetic characteristics of 2-N-piperidine-5-(2",2"-dicyanvinyl)thiophene (PDCVTh) in solutions at room temperature. The mechanism of radiationless energy deactivation of electronic excitation in PDCVTh is interpreted in terms of the notions of conformational changes, controlled by medium viscosity, in a molecule after absorption by it of excitation energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004144623480
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  • 6
    Digitale Medien
    Digitale Medien
    On-line measurement of elasticity and viscosity in flowing polymeric liquids (1996)
    Springer
    Rheologica acta 35 (1996), S. 110-116 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Slit die ; on-line rheometry ; first normal stress difference ; hole pressure ; Stressmeter ; viscosity ; molten polymers ; multigrade oil elasticity ; high shear rates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract A new slit-die rheometer (the “Stressmeter”) for on-line and sample measurement of the viscosity, η, and the first normal stress difference, N 1, in steady shear flow for molten polymers and other high-viscosity liquids is described. Two liquid-filled transverse slots, located in one die wall near the center station, give pressures P 2 and P 3 from whose difference the wall shear stress σ is calculated. In the other die wall at a location opposite the center of the P 2 slot is a flush-mounted transducer, giving a pressure P 1. N 1 is calculated from the hole pressure P * = P 1−P 2. A metering pump, used to measure the flow rate Q, is supplied with melt either from an extruder (online mode) or from a pressurized sample cylinder (sample mode). The wall shear rate γ is calculated from Q and σ; the Weissenberg-Rabinowitsch correction and a new small-viscous-heating-correction algorithm (affecting σ) are used. Viscous heating corrections are small; entrance and exit errors are negligible. The instrument is tested by comparing its results with those obtained from cone-plate and capillary rheometers. Measurement ranges extend to σ = 200 kPa, γ = 3000 s−1, and temperature = 250°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00396037
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  • 7
    Digitale Medien
    Digitale Medien
    Curing effects on viscosity of reactive epoxy resin adhesives (1996)
    Springer
    Rheologica acta 35 (1996), S. 321-328 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Epoxy resin ; adhesive ; viscosity ; curing ; chemorheology ; reaction kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The influence of temperature and the extent of curing on the viscosity of a ,reactive epoxy resin adhesive is described and a mathematical model for the behavior is introduced. The temperature dependence of viscosity can be described by the WLF equation. The parameters required for the WLF equation are obtained from experiments in the temperature range where the crosslinking reaction has not yet been initiated. The viscosity and glass transition temperature increase with increasing curing. The glass transition temperature can also be described with an equation of the WLF type. Kinetic experiments on the epoxy resin adhesive enable a time and temperature dependent description of the extent of curing with a series reaction of the type A→B→C, where each partial reaction is of order n. The viscosity model and reaction kinetics enable calculation of the viscosity as a function of time and temperature, which agrees well with the experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00403532
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  • 8
    Digitale Medien
    Digitale Medien
    Translational diffusion of rubrene and tetracene in polyisobutylene (1997)
    Springer
    Rheologica acta 36 (1997), S. 209-216 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Translational diffusion ; probes ; rotation ; viscosity ; local segmental dynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The translational diffusion coefficients of rubrene and tetracene in amorphous polyisobutylene (PIB) were measured using the holographic fluorescence recovery after photobleaching technique. Over the temperature range from 400 to 235 K (T g =205 K), tracer diffusion coefficients from 10−7 to 10−14 cm2/s were observed. These diffusion coefficients have essentially the same temperature dependence as the rotational correlation times for these two probes in PIB. Both of these observables have a slightly stronger temperature dependence than does the viscosity. These results contrast strongly with the results of similar experiments on polystyrene and polysulfone. These results are consistent with the hypothesis that local segmental dynamics are more spatially homogeneous in PIB than in polystyrene and polysulfone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00366661
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  • 9
    Digitale Medien
    Digitale Medien
    Translational diffusion of rubrene and tetracene in polyisobutylene (1997)
    Springer
    Rheologica acta 36 (1997), S. 209-216 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Key words Translational diffusion ; probes ; rotation ; viscosity ; local segmental dynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The translational diffusion coefficients of rubrene and tetracene in amorphous polyisobutylene (PIB) were measured using the holographic fluorescence recovery after photobleaching technique. Over the temperature range from 400 to 235K (T g =205K), tracer diffusion coefficients from 10–7 to 10–14cm2/s were observed. These diffusion coefficients have essentially the same temperature dependence as the rotational correlation times for these two probes in PIB. Both of these observables have a slightly stronger temperature dependence than does the viscosity. These results contrast strongly with the results of similar experiments on polystyrene and polysulfone. These results are consistent with the hypothesis that local segmental dynamics are more spatially homogeneous in PIB than in polystyrene and polysulfone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00366661
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  • 10
    Digitale Medien
    Digitale Medien
    Polymer contribution to the thermal conductivity and viscosity in a dilute solution (Fraenkel Dumbbell model) (1997)
    Springer
    Rheologica acta 36 (1997), S. 269-276 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Key words Transport phenomena ; thermal conduction ; bead-spring models ; polymer solutions ; viscosity ; normal stresses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The phase-space kinetic theory for polymeric liquid mixtures is used to obtain an expression for the polymer contribution to the thermal conductivity of a nonflowing, dilute solution of polymers, where the polymer molecules are modeled as Fraenkel dumbbells. This theory takes into account three mechanisms for the energy transport: diffusion of kinetic energy (including the Öttinger-Petrillo term), diffusion of intramolecular energy, and the work done against the intramolecular forces. This paper is an extension of previous developments for the Hookean dumbbell model and the finitely-extensible dumbbell model. A comparison among the dumbbell results suggests that the thermal conductivity increases with chain stiffness. In addition, the zero-shear-rate viscosity and first normal-stress coefficient are also given for the Fraenkel dumbbell model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00366668
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  • 11
    Digitale Medien
    Digitale Medien
    Effective viscosity of porous particle suspensions (1997)
    Springer
    Rheologica acta 36 (1997), S. 483-484 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Suspension ; viscosity ; apparent viscosity coefficient ; coal ; oil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The attempt of quantitative description of suspension viscosity with regard to concentration of dispersed phase particles as well as particle (porous) — liquid phase interaction has been presented. Calculated apparent viscosity coefficients have been compared with measured viscosities of oil-coal suspension.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00396333
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  • 12
    Digitale Medien
    Digitale Medien
    Effective viscosity of porous particle suspensions (1997)
    Springer
    Rheologica acta 36 (1997), S. 483-484 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Key words Suspension ; viscosity ; apparent viscosity coefficient ; coal ; oil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The attempt of quantitative description of suspension viscosity with regard to concentration of dispersed phase particles as well as particle (porous) – liquid phase interaction has been presented. Calculated apparent viscosity coefficients have been compared with measured viscosities of oil-coal suspension.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00396333
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  • 13
    Digitale Medien
    Digitale Medien
    Steady shear viscosity of short fibre suspensions in thermoplastics (1998)
    Springer
    Rheologica acta 37 (1998), S. 289-298 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Key words Reinforced ; thermoplastics ; viscosity ; convergent channel ; shear-thinning ; fibre suspension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The rheological behaviour of a polyethylene, two polyamides and a silicone oil filled with different fibre contents are studied in capillary rheometry. The viscosity increase induced by the fibres is important for the silicone oil, and negligible for the polyethylene. The polyamide is intermediate. The same classification stands for the pressure loss in the convergent channel upstream from the capillary. A constitutive equation based on a cell model which takes into account the shear-thinning behaviour of the matrix is built. The predictions of the model are in correct agreement with the measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003970050116
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  • 14
    Digitale Medien
    Digitale Medien
    Ultrasonic devulcanization of waste rubbers: Experimentation and modeling (1996)
    Springer
    Rheologica acta 35 (1996), S. 616-630 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Rubber ; devulcanization ; revulcanization ; ultrasound ; cavitation ; viscosity ; model ; experiment ; mechanical properties ; gel fraction ; crosslink density ; pressure drop ; converging flow
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract Continuous ultrasonic devulcanization of ground tire rubber (GRT) and styrene-butadiene rubber (SBR) is considered. Experiments are performed under various processing conditions. Two recipes of SBR with different amounts of polysulfidic linkages are utilized. Gel fraction and crosslink density of devulcanized rubbers are measured and a unique relationship between them is established. Die characteristics with and without imposition of ultrasonic waves are determined. Devulcanized samples are revulcanized and mechanical properties are measured. In some cases, properties of revulcanized SBR samples exceeded those of virgin vulcanizates. This is explained based on the presence of a double network in the revulcanized rubber. A modification of acoustic cavitation and flow modeling of ultrasonic devulcanization of SBR and GRT is proposed using a concept of effective viscosity characterizing the flow of vulcanized particles before devulcanization combined with a shear rate, temperature and gel fraction-dependent viscosity of devulcanized rubber. Velocity, shear rate, pressure, and temperature field along with gel fraction, crosslink density and number of bonds broken are simulated. Predicted data on gel fraction, crosslink density, and pressure using the present modification of the model are found to be closer to experimental data then previously reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00396511
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  • 15
    Digitale Medien
    Digitale Medien
    Rheology and processing of salad dressing emulsions (1995)
    Springer
    Rheologica acta 34 (1995), S. 513-524 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Droplet size ; emulsion ; linear viscoelasticity ; mayonnaise ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract In order to study the influence that the processing parameters exert on the rheology and stability of salad dressing emulsions, both steady-state shear and oscillatory measurements, as well as droplet size distribution tests were performed. Emulsions containing a mixture of egg yolk and sucrose stearate as emulsifier were prepared using two different emulsification machines, a rotor-stator turbine and a colloidal mill. An increase both in energy input and in the temperature of processing yields higher values of the steady-state viscosity, an increase in emulsion stability and, generally, lower droplet size and lower polydispersity. Furthermore, a plateau region in the loss modulus versus frequency plots appears as the energy input and processing temperature increase. This effect has been analyzed by calculating the relaxation spectra of these emulsions. The results have been discussed taking into account the relationship between several structural parameters, such as interparticle interactions and droplet size distribution, and the rheological response of these emulsions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00712312
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  • 16
    Digitale Medien
    Digitale Medien
    Polymer contribution to the thermal conductivity and viscosity in a dilute solution (Fraenkel Dumbbell model) (1997)
    Springer
    Rheologica acta 36 (1997), S. 269-276 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Transport phenomena ; thermal conduction ; bead-spring models ; polymer solutions ; viscosity ; normal stresses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The phase-space kinetic theory for polymeric liquid mixtures is used to obtain an expression for the polymer contribution to the thermal conductivity of a nonflowing, dilute solution of polymers, where the polymer molecules are modeled as Fraenkel dumbbells. This theory takes into account three mechanisms for the energy transport: diffusion of kinetic energy (including the Öttinger-Petrillo term), diffusion of intramolecular energy, and the work done against the intramolecular forces. This paper is an extension of previous developments for the Hookean dumbbell model and the finitely-extensible dumbbell model. A comparison among the dumbbell results suggests that the thermal conductivity increases with chain stiffness. In addition, the zero-shear-rate viscosity and first normal-stress coefficient are also given for the Fraenkel dumbbell model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00366668
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  • 17
    Digitale Medien
    Digitale Medien
    Status of the round robin on the transport properties of R134a (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 63-78 
    Details
    ISSN: 1572-9567
    Schlagwort(e): R134a ; dilute gas ; refrigerant ; saturation properties ; 1,1,1,2-tetrafluoroethane ; thermal conductivity ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The paper contains a status report on an international project coordinated by the Subcommittee on Transport Properties of Commission 1.2 of the International Union of Pure and Applied Chemistry. The project has been conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of R134a. The project has involved the remeasurement of the transport properties of a single sample of R134a in nine laboratories throughout the world in order to test the hypothesis that at least part of the discrepancy could be attributed to the purity of the sample. This paper provides an intercomparison of the new experimental results obtained to data in this project for the viscosity and the thermal conductivity in both gaseous and liquid phases. The agreement between the viscosity data from the laboratories contributing to the project was improved with several techniques, now producing consistent results. This suggests that the purity of the samples of R134a used in previous work was at least partly reponsible for the discrepancies observed. For the thermal conductivity in the liquid phase the results of the measurements are also more consistent than before, although not for all experimental techniques. Not all of the previous measurements suffered from significant sample impurities, so the present measurements on a consistent high-purity sample can he used to detect data sets which are outhers, possibly because of impurities. Identification of laboratories and techniques with systematic differences may require the examination of data for several fluids. The implications for future measurements of the transport properties of other refrigerants are significant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01438958
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  • 18
    Digitale Medien
    Digitale Medien
    Measurements of the viscosity of new refrigerants in the temperature range 270–340 K at pressures up to 20 MPa (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 133-143 
    Details
    ISSN: 1572-9567
    Schlagwort(e): high pressure ; refrigerants ; vibrating wire ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A recently modified vibrating-wire instrument was employed to measure the liquid viscosity of a wide selection of new refrigerants under pressure. Calibration of the viscometer with water over the range of measurements confirmed that the estimated uncertainty of the measurements is 0.5%, while the precision is 0.3%. With this instrument, the viscosity of chlorofuorocarbons (CFC's) and alternative refrigerants. R11. R12. R22, R32. R124, R125. 11134a. R 141 b, and R152a, was measured over the temperature range from 270 to 340 K, from just above the saturation pressure up to 211 M Pa. The experimental data, represented by polynomial functions of temperature and pressure, are used in a comparative examination of other recently reported experimental measurements of the viscosity of all these refrigerants. to investigate the uncertainty with which the viscosity is known.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01438964
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  • 19
    Digitale Medien
    Digitale Medien
    Critical dynamics of a sheared micellar solution (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 355-361 
    Details
    ISSN: 1572-9567
    Schlagwort(e): critical dynamics ; micellar solution ; shear effects ; spinodal decomposition ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have investigated the dynamic behavior of a nonionic micellar solution of tetra-ethylene glycoln-decylether (C10 E4) in water near its critical point in the presence of shear. The non-Newtonian behavior of the viscosityν can be represented byν ν* = [ 1 +a(Sτ4)=]ω2, whereν* is the viscosity in the absence of shear,S is the shear rate. τ4 is the lifetime of the critical Iluctuations,a is a system-dependent constant, and ω = 0.02 In addition, we have found that, before attaining a steady state, the sheared mixture undergoing phase separation shows significant shear-dependent rheological effects due to the presence of concentration domains.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01441901
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  • 20
    Digitale Medien
    Digitale Medien
    The Viscosity of Toluene in the Temperature Range from 210 to 370 K at Pressures up to 30 MPa (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1367-1377 
    Details
    ISSN: 1572-9567
    Schlagwort(e): toluene ; vibrating-wire technique ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The paper presents new measurements of the viscosity of toluene over a temperature range from 210 to 370 K, from the saturation line up to pressures of 30 MPa. The measurements were performed with a vibrating-wire viscometer. The uncertainty of the measurements, confirmed above room temperature with the measurement of the viscosity of water, is estimated to be ±0.5%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021428819290
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  • 21
    Digitale Medien
    Digitale Medien
    Validation of an accurate vibrating-wire densimeter: Density and viscosity of liquids over wide ranges of temperature and pressure (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 781-802 
    Details
    ISSN: 1572-9567
    Schlagwort(e): cyclohexane ; density ; liquid ; pVT ; 1,1,1,2-tetrafluoroethanc (R134a) ; 2.2.4-trimelthylpentane ; vibrating-wire densimeter ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new vibrating-wire instrument for the meaasurement of the density of fluids at high pressures was described in a previous paper. The technique makes use of the buoyancy force on a solid sinker and detect, this force with a vibrating wire placed inside the measuring cell. Owing to the simple geometry of the oscillating element there exists a complete theoretical description of its resonance characteristics. enabling the calculation of the density of the fluid from their measurement. In the present paper a new method for the determination of the cell constants is outlined which permits the operation of the densimeter essentially as an absolute instrument. Furthermore. it is shown that the viscosity ol the fluid can be measured Simultaneously with the density. New results for three fluids are presented: for cyclohexane at temperatures from 298 to 348 K and pressures up to 40 MPa. for 2,2,4-trimethylpentane between 197 and 348 K at 0.1 MPa, and for 1,1,1,2-tetrafluoroethane from 197 to 298 K close to saturation. The sets of measurements where chosen with the intention of testing the performance of the apparatus. complementing previous work at higher pressures. The densities and viscosities measured exhibit the same accuracy for all of the three fluids over the entire temperature and pressure ranges and were obtained using the same set of cell parameters The precision of the densities is ±0.03% and their estimated accuracy is ±0.05%. File viscosities have a precision of ±0.6%, and an estimated accuracy of ±2%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01439190
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  • 22
    Digitale Medien
    Digitale Medien
    Revised Viscosities of Saturated Liquid Halocarbon Refrigerants from 273 to 353 K (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 909-912 
    Details
    ISSN: 1572-9567
    Schlagwort(e): halocarbons ; refrigerants ; saturated liquid ; vapor buoyancy effect ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper presents revised saturated liquid viscosities for 15 halocarbon refrigerants, that is, R11, R12, R22, R13B1, R152a, R113, R123, R123a, R143a, R114, R134a, R141b, R142b, R225ca, and R225cb, reported in our previous papers [1, 2], in which the vapor buoyancy correction for the sealed capillary viscometer was not applied. The maximum corrections amount to from 1.2% for R225cb to 17.4% for R143a. The erroneous data in our previous papers should be considered obsolete except for the low-vapor density refrigerants R11, R123, R123a, R113, R141b, R225ca, and R225cb, for which the maximum correction is 2.4%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006666308831
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  • 23
    Digitale Medien
    Digitale Medien
    Prediction of Fluid Mixture Transport Properties by Molecular Dynamics (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 437-448 
    Details
    ISSN: 1572-9567
    Schlagwort(e): alkanes ; carbon dioxide ; diffusion ; mixtures ; molecular dynamics ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Equilibrium molecular dynamics simulations of mixtures of n-decane with methane, ethane, and carbon dioxide and of the mixture carbon dioxide–ethane were performed using the anisotropic united atoms model for n-decane and one-and two-center Lennard–Jones models for the light components. The Green–Kubo relations were used to calculate the viscosity, thermal conductivity, and inter- and intradiffusion. Viscosities are predicted with a maximum deviation of 30% at low gas concentrations and less than 10% deviation at high gas concentrations. The viscosity and thermal conductivity are less sensitive to the cross interactions than the diffusion coefficients, which exhibit deviations between models and with experiments of up to 60%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022513411043
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  • 24
    Digitale Medien
    Digitale Medien
    Nonequilibrium Molecular Dynamics Simulation of the Rheology of Linear and Branched Alkanes (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 449-459 
    Details
    ISSN: 1572-9567
    Schlagwort(e): alkanes ; nonequilibrium molecular dynamics ; order tensor ; rheology ; shear thinning ; viscosity ; viscosity index
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Liquid alkanes in the molecular weight range of C20–C40 are the main constituents of lubricant basestocks, and their rheological properties are therefore of great concern in industrial lubricant applications. Using massively parallel supercomputers and an efficient parallel algorithm, we have carried out systematic studies of the rheological properties of a variety of model liquid alkanes ranging from linear to singly branched and multiply branched alkanes. We aim to elucidate the relationship between the molecular architecture and the viscous behavior. Nonequilibrium molecular dynamics simulations have been carried out for n-decane (C10H22), n-hexadecane (C16H34), n-tetracosane (C24H50), 10-n-hexylnonadecane (C25H52), and squalane (2, 6, 10, 15, 19, 23-hexamethyltetracosane, C30H62). At a high strain rate, the viscosity shows a power-law shear thinning behavior over several orders of magnitude in strain rate, with exponents ranging from −0.33 to −0.59. This power-law shear thinning is shown to be closely related to the ordering of the molecules. The molecular architecture is shown to have a significant influence on the power-law exponent. At a low strain rate, the viscosity behavior changes to a Newtonian plateau, whose accurate determination has been elusive in previous studies. The molecular order in this regime is essentially that of the equilibrium system, a signature of the linear response. The Newtonian plateau is verified by independent equilibrium molecular dynamics simulations using the Green–Kubo method. The reliable determination of the Newtonian viscosity from non-equilibrium molecular simulation permits us to calculate the viscosity index for squalane. The viscosity index is a widely used property to characterize the lubricant's temperature performance, and our studies represent the first approach towards its determination by molecular simulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022565427881
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  • 25
    Digitale Medien
    Digitale Medien
    Thermophysical Properties of Aqueous Solutions Near the Equilibrium Freezing Temperature (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 749-759 
    Details
    ISSN: 1572-9567
    Schlagwort(e): aqueous solutions ; capillary-rise method ; surface tension ; thermal conductivity ; transient hot-wire method ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Measurements of the surface tension, viscosity, and thermal conductivity of LiBr and LiSCN aqueous binary solutions have been performed to determine the thermophysical properties near the equilibrium freezing temperature. A differential capillary-rise method for surface tension and the transient hot-wire method for thermal conductivity were employed. Furthermore, a rotational viscometer was utilized for the measurement of viscosity. Correlation equations for the data of the aqueous binary test solutions as a function of temperature and concentration are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022626503214
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  • 26
    Digitale Medien
    Digitale Medien
    The Effect of Model Internal Flexibility Upon NEMD Simulations of Viscosity (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 45-55 
    Details
    ISSN: 1572-9567
    Schlagwort(e): viscosity ; NEMD simulation ; flexible models ; rigid bond lengths
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The influence of model flexibility upon simulated viscosity was investigated. Nonequilibrium molecular dynamics (NEMD) simulations of viscosity were performed on seven pure fluids using three models for each: one with rigid bonds and angles, one with flexible angles and rigid bonds, and one with flexible bonds and angles. Three nonpolar fluids (propane, n-butane, and isobutane), two moderately polar fluids (propyl chloride and acetone), and two strongly polar fluids (methanol and water) were studied. Internal flexibility had little effect upon the simulated viscosity of nonpolar fluids. While model flexibility did affect the simulated viscosity of the polar fluids, it did so principally by allowing a density-dependent change in the dipole moment of the fluid. By using a rigid model with the same geometry and dipole moment as the average flexible molecule at the same density, it was shown that the direct effect of flexibility is small even in polar fluids. It was concluded that internal model flexibility does not enhance the accuracy of viscosities obtained from NEMD simulations as long as the appropriate model geometry is used in the rigid model for the desired simulation density.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006600719847
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  • 27
    Digitale Medien
    Digitale Medien
    Densities, Viscosities, Sound Speeds, and Excess Properties of Binary Mixtures of Methyl Methacrylate with Alkoxyethanols and 1-Alcohols at 298.15 and 308.15 K (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1153-1174 
    Details
    ISSN: 1572-9567
    Schlagwort(e): density ; methyl methacrylate +alcohol binary liquid mixtures ; molecular interactions ; relative association ; solvation number ; sound speed ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The densities, viscosities, and sound speeds were measured for six binary mixtures of methyl methacrylate (MMA)+2-methoxyethanol (ME), +2-ethoxyethanol (EE), +2-butoxyethanol (BE), +1-butanol (1-BuOH), +1-pentanol (1-PeOH), and +1-heptanol (1-HtOH) at 298.15 and 308.15 K. The mixture viscosities were correlated by Grunberg–Nissan, McAllister, and Auslander equations. The sound speeds were predicted by using free length and collision factor theoretical formulations, and Junjie and Nomoto equations. The excess viscosities and excess isentropic compressibilities were also calculated. A qualitative analysis of both of these functions revealed that structure disruptions are more predominant in MMA+1-alcohol than in MMA+alkoxyethanols mixtures. The estimated relative associations are found to become less in MMA+alcohol mixtures than in pure alcohols. The solvation numbers derived from the isentropic compressibility of the mixtures, considering MMA as a solvent, showed that structure making interactions are also present in MMA + alkoxyethanols in addition to the structure disruptions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026402222130
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  • 28
    Digitale Medien
    Digitale Medien
    Thermophysical properties of natural gases for on-line metering (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 195-204 
    Details
    ISSN: 1572-9567
    Schlagwort(e): ethane ; gas metering ; methane ; natural gas ; prediction ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The evaluation of the background transport properties of natural gas multicomponent mixtures over a moderate temperature and pressure range around ambient is considered in the context of the development of certifiable sensors for the measurement of mass and energy fluxes. The best available, theoretically based procedures to predict the properties are compared with experimental information to test the internal consistency, accuracy, and range of validity of the prediction. This is of primary concern to the demonstration of the viability of such sensors. It is shown that for low to moderate pressures, it is possible to achieve an internal consistency of the order of a few parts in a thousand and an accuracy of better than ± I %. At very high pressures the predictive scheme is also satisfactory, with errors of the order of a few percent. However, the procedure employed here systematically underestimates the thermal conductivity of the gas mixtures studied for intermediate pressures owing to the neglect of the critical enhancement even for temperatures quite far removed from the critical. The range of conditions for which the critical enhancement of the thermal conductivity is significant in mixtures is explored with data for binary mixtures of methane and ethane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01438970
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  • 29
    Digitale Medien
    Digitale Medien
    A new apparatus for measuring high viscosity of solids (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 577-584 
    Details
    ISSN: 1572-9567
    Schlagwort(e): anelasticity ; laser interferometry ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new apparatus which is capable of measuring Newtonian viscosity as high as 108-1014 Pa · s has been developed. The upper and the lower faces of a cubic specimen 1 x 1 x I cm3 in size are respectively bonded to movable and fixed plates, and a constant shear stress is applied to the specimen. The displacement of the upper plate is measured and recorded as a function of time utilizing the HP-5528A optical laser measuring system. The sensitivity of the displacement measurement is 10 nm. Measurements at temperatures up to 200°C can be made by using a small furnace installed around the specimen. A variety of adhesive materials, polymers and ceramics, have been tested for the specimen-plate bonding. Aqueous Sauereisen cement showed a stable and rigid bonding in the experimental temperature range. Experiments for rubber (soft) and silicon crystal (hard) specimens have been performed to ascertain the reliability of the present method. The apparatus is also able to measure the anelasticity (mechanical relaxation) of solids, but is not adaptable to the measurement of the shear modulus of specimens; because the instantaneous displacement of the movable plate at the moment of the loading is mostly due to the rotational and inhomogeneous elastic deformations of the specimen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01441923
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  • 30
    Digitale Medien
    Digitale Medien
    Correlation and prediction of dense fluid transport coefficients. VII. Refrigerants (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 761-772 
    Details
    ISSN: 1572-9567
    Schlagwort(e): density ; high pressure ; refrigerants ; Tail equation ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous correlation of the coefficients of viscosity and thermal conductivity for the refrigerants R11, R12, R22, R32. R124, R125, R134a, R141b, and R152a in excellent agreement with experiment, over extended temperature and pressure ranges. Values for the roughness factors and correlations for the characteristic volume are presented. The overall average absolute deviations of the experimental viscosity and thermal conductivity measurements from those calculated by the correlation are 2.1 and 2.3%, respectively, over a temperature range from 200 to about 10 K below the critical temperature and a pressure range from saturation to about 40 MPa. Since the proposed scheme is based on recent and accurate density values, a Tail-type equation was also employed to correlate successfully the density of the refrigerants. The overall average absolute deviation of the experimental density measurements from those calculated by the correlation is ±0.08%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01438861
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  • 31
    Digitale Medien
    Digitale Medien
    Correlation and extrapolation scheme for the composition and temperature dependence of viscosity of binary gaseous mixtures: Carbon dioxide + ethane (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1245-1255 
    Details
    ISSN: 1572-9567
    Schlagwort(e): binary gaseous mixture ; carbon dioxide ; ethane ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Experimental viscosity data of ethane, carbon dioxide, and three mole fractions of the binary system carbon dioxide + ethane in the temperature range 293.15〈T⩽633.15 K and in the density range 0.01⩽ρ⩽0.05 mol·L−1 reported earlier were evaluated simultaneously to find out a useful correlation and extrapolation scheme for the viscosity of binary systems in the range of moderate densities. A procedure based on the ideas of the modified Enskog theory has been found to give the best results. Dependent on temperature, the collision diameters related to the equilibrium radial distribution function at contact are fitted to viscosity values of the pure substances and of at least one mixture. The results are compared with experimental data from the literature. A recommendation is given concerning the density range in which the first density contribution to the viscosity coefficient of the system carbon dioxide + ethane is sufficient to be included.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02081292
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  • 32
    Digitale Medien
    Digitale Medien
    Determination of the viscosity of various hydrocarbons and mixtures of hydrocarbons versus temperature and pressure (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1309-1334 
    Details
    ISSN: 1572-9567
    Schlagwort(e): density ; high pressure ; hydrocarbons ; mixtures ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamic viscosityη and densityρ of 10 pure substances and three binary systems were measured as a function of temperatureT (298.15, 313.15, 333.15, 353.15, and 363.15 K.) and pressureP (⩽100 MPa). The pure substances were toluene,p-xylene,m-xylene,o-xylene, methylcyclohexane, methylnaphthalene, decahydronaphthalene, phenyldodecane, heptamethylnonane, and tetramethylpentadecane (pristane). The three binaries were toluene + tetramethylpentadecane, toluene + methylnaphthalene, and toluene + heptamethylnonane, for molar fractionsx of toluene ranging between 0 and 1. The three binaries are highly “contrasted” systems, i.e., systems in which the viscosities of the pure components are very different for eachP, T pair. In all, 547 experimental determinations were carried out (279 experimental data for viscosity of the pure substances and 268 data concerning the mixtures: x⊋0 and 1).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02083543
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  • 33
    Digitale Medien
    Digitale Medien
    The viscosity of gaseous propane and its initial density dependence (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1335-1351 
    Details
    ISSN: 1572-9567
    Schlagwort(e): n-alkanes ; propane ; second viscosity virial coefficient ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Results of five series of high-precision viscosity measurements on gaseous propane, each differing in density, are reported. The measurements were performed in a quartz oscillating-disk viscometer with small gaps from room temperature up to about 625 K and for densities between 0.01 and 0.05 mol · L−1. The experimental data were evaluated with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficients deduced from the zero-density and initial-density viscosity coefficients for propane and for furthern-alkanes are in close agreement with the theoretical representation of the Rainwater-Friend theory for the potential parameter ratios by Bich and Vogel. A new representation of the viscosity of propane in the limit of zero density is provided using the new experimental data and some data sets from literature. The universal correlation based on the extended principle of corresponding states extends over the temperature range 293 to 625 K with an uncertainty of ±0.5 % and deviates from earlier representations by about 1 % at the upper temperature limit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02083544
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  • 34
    Digitale Medien
    Digitale Medien
    Viscosities of HFC-32 and HFC-32/lubricant mixtures (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 75-83 
    Details
    ISSN: 1572-9567
    Schlagwort(e): capillary viscometer ; free-volume model ; lubricant oil ; mixture ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A modified capillary tube method has been used to measure viscosities for HFC32 over a temperature range from -20 to 90°C and a pressure range from 0.1 to 5.3 M Pa, and for the liquid mixtures of HFC-32 with a synthetic polyolester oil at temperatures from 20 to 75°C and oil mass fractions from 0.44 to 1. Estimated uncertainties in the measured viscosities do not exceed ± 1.2 and ± 1.8°% for the pure fluocarbon and the mixtures, respectively. It is found that viscosity isotherms for HFC-32 at subcritical temperatures exhibit a minimum with increasing pressure, with the viscosity decreasing as much as 10% relative to its value at one atmosphere. Correlations are presented for dilute gas viscosities, excess viscosities, and saturated liquid and vapor viscosities. These correlations are shown to lit our data within experimental uncertainties. For HFC-32/lubricant mixtures, a free-volume viscosity model has been applied to correlate the experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01448211
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  • 35
    Digitale Medien
    Digitale Medien
    The thermal conductivity and viscosity of acetic acid-water mixtures (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 111-125 
    Details
    ISSN: 1572-9567
    Schlagwort(e): acetic arid ; aqueous mixtures ; thermal conductivity transient hot-wire technique ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity and thermal conductivity of acetic acid water mixtures were measured over the entire composition range and at temperatures ranging from 293 to 453 K. Viscosity measurements were performed with a high-pressure viscometer and thermal conductivity was measured using a modified transient hot-wire technique. A mercury filled. glass capillary was used as the insulated hot wire in the measurements. The l iscosity data showed unusual trends with respect to composition. At it given temperature. the viscosity was seen to increase with increasing acid concentration, attain a maximum. and then decrease. The thermal conductivity, on the other hand, decreased monotonically with acid concentration. A generalized corresponding-states principle using water and acetic acid as the reference fluids was used to predict both viscosity and thermal conductivity with considerable sucres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01448214
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  • 36
    Digitale Medien
    Digitale Medien
    Thermal conductivity and viscosity of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 293-328 
    Details
    ISSN: 1572-9567
    Schlagwort(e): 2,2-dichloro-1,1,1-trifluoroethane ; HCFC-123 ; R123 ; thermal conductivity ; thermal diffusivity ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The thermal conductivity and the viscosity data of CFC alternative refrigerant HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane: CHCI2-CF3) were critically evaluated and correlated on the basis of a comprehensive literature survey. Using the residual transport-property concept, we have developed the three-dimensional surfaces of the thermal conductivity-temperature-density and the viscosity-temperature-density. A dilute-gas function and an excess function of simple form were established for each property. The critical enhancement contribution was taken no account because reliable crossover equations of state and the thermal conductivity data are still missing in the critical region. The correlation for the thermal conductivity is valid at temperatures from 253 to 373 K, pressures up to 30 MPa, and densities up to 1633 kg m−3. The correlation for the viscosity is valid at temperatures from 253 to 423 K, pressures up to 20 MPa. and densities up to 1608 kg·m−3. The uncertainties of the present correlations are estimated to be 50% for both properties, since the experimental data are still scarce and somewhat contradictory in the vapor phase at present.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01443394
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  • 37
    Digitale Medien
    Digitale Medien
    Saturated liquid viscosity correlations for alternative refrigerants (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 361-372 
    Details
    ISSN: 1572-9567
    Schlagwort(e): ozone friendly ; refrigerants ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This article presents dimensionless equations for the temperature dependence of the saturated liquid viscosity of R32, R123 R124, R125, R134a. R141b. and R152a valid over a temperature range of engineering interest. The correlation has the form Φ n D =A +BT, where ΦD is the dimensionless fluidity (l ηD) andT D is a dimensionless temperature.n. A. andB are evaluated for each of the above refrigerants based on a least-squares fit to experimental data. This equation is found to provide an improved fit over those existing in the literature up toT D=0.8.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01443397
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  • 38
    Digitale Medien
    Digitale Medien
    Excess volumes and excess viscosities of binary mixtures of 1-bromo-2-methylpropane + an isomer of butanol at 298.15 and 313.15 K (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 347-359 
    Details
    ISSN: 1572-9567
    Schlagwort(e): activation energy ; binare mixtures ; free energy ; I-bromo-methypropane ; butanols ; viscosity ; excess volume
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Excess volumesV E, excess viscositiesη E, and excess free energies of activation of flow G*E at 298.15 and 313.15 K are reported for binary mixtures of 1-bronw-2-methypropane and each of the alcoholic isomers of I-butanol. The results were obtained from density and viscosity measurements and show positive values forV 4 and negative for bothη E andG *E for all mixtures over the entire composition range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01443396
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  • 39
    Digitale Medien
    Digitale Medien
    Mutual Diffusion Coefficient and Dynamic Viscosity Near the Critical Consolute Point Probed by Dynamic Light Scattering (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 791-803 
    Details
    ISSN: 1572-9567
    Schlagwort(e): binary mixture ; critical consolute point ; dynamic light scattering ; mutual diffusion coefficient ; nitroethane–isooctane ; triethylamine–water ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The possibility of applying dynamic light scattering to simultaneous determination of the mutual diffusion coefficient and the viscosity of binary liquid systems was studied near the critical consolute point. When seed particles are added to the system, the particle diffusion coefficient is measured, and the viscosity is obtained using the Stokes–Einstein relation. Since the amplitude of light scattered from concentration fluctuations is low in a mixture with a small difference between the refractive indices of the pure components, this approach allowed the determination of the viscosity of a critical mixture of nitroethane and isooctane, without a signal component from mutual diffusivity superimposed. In contrast, particle aggregation prevented the determination of the viscosity of a critical mixture of triethylamine and water. Despite this difficulty, and an unidentified contribution in the signals obtained, the mutual diffusion coefficient and the critical exponent v could be determined in this system without a noticeable influence from the addition of seed particles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022670816359
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  • 40
    Digitale Medien
    Digitale Medien
    Tests of Predictive Viscosity Models for Pure Liquids (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 815-823 
    Details
    ISSN: 1572-9567
    Schlagwort(e): alkanes ; alkanols ; alkenes ; aromatics ; corresponding states ; cycloalkanes ; esters ; liquids ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is of considerable importance to be able to predict accurately the viscosity of liquids over a wide range of conditions. In the present work, the ability of the three-parameter generalized corresponding states principle (GCSP) for the prediction of the viscosity of pure liquids is demonstrated. The viscosity of six different classes of pure liquids, viz., alkanes (19 compounds; 207 data points), cycloalkanes (6 compounds; 74 data points), alkenes (9 compounds; 146 data points), aromatics (4 compounds; 123 data points), alkanols (8 compounds; 89 data points), and esters (4 compounds; 28 data points) have been predicted over a wide range of temperatures using the three-parameter (T c, P c, θ) GCSP. Five options for the third parameter (θ) were studied, viz., Pitzer's acentric factor ω, molar mass M, characteristic viscosity η*, critical compressibility factor Z c, and modified acentric factor Ω, in addition to groups ωZ c and ΩZ c being treated as composite third parameters. Pressure effects were neglected. Good agreement between experimental and predicted values of viscosity was obtained, especially with either ω or η* being used as the third parameter. Furthermore, the viscosities of alkanes predicted by the TRAPP method and an empirical, generalized one-parameter model for liquid hydrocarbons provide comparisons with the more accurate GCSP method. The GCSP provides a simple and yet a powerful technique for the correlation and prediction of viscosities of a variety of pure liquids over a wide range of temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022674917267
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  • 41
    Digitale Medien
    Digitale Medien
    Viscosity and Surface Tension Measurements in Microgravity (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1005-1015 
    Details
    ISSN: 1572-9567
    Schlagwort(e): Co–Pd alloy ; electromagnetic levitation ; liquid metals ; microgravity ; Pd–Cu–Si alloy ; surface tension ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity and surface tension of liquid metals can be measured by observing the oscillations of a levitated drop. The frequency is related to the surface tension, while the viscosity determines the damping of the oscillations. If no external forces are present, as in microgravity, these relations are particularly simple and precise. During the recent Spacelab mission MSL-1, such experiments have been performed on Co–Pd and Pd–Cu–Si using the electromagnetic levitation facility TEMPUS. It was possible to obtain data over a wide temperature range, including the undercooled regime. While the temperature dependence of the surface tension remains linear over the complete range, the temperature dependence of the viscosity is much more pronounced and is discussed in terms of different models.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022686316437
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  • 42
    Digitale Medien
    Digitale Medien
    High-Temperature Containerless Viscosity Measurement by Gas-Film Levitation (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1071-1083 
    Details
    ISSN: 1572-9567
    Schlagwort(e): gas-film levitation ; high temperature ; oxide melts ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The gas levitation process development program has, so far, been focused mainly on contact-free manipulation, on molding and shaping of liquids, on high-temperature contact-free treatment, and on shaping and solidification of interesting materials for scientific and technical purposes. Recently proposed by Parayre for viscosity measurements, this process eliminates the perturbing effects of the container, in particular, that of crystallization when studying supercooled liquids. The method consists of extracting viscosity values from the damped decay of perturbed liquid drops floating on a gas-film. An apparatus has been designed and developed for viscosity values higher than 1 Pa·s and at temperatures up to 2000°C. The method was applied to a silicate glass of industrial interest containing 70 wt% per cent of SiO2, with viscosities ranging from 102 to 106 Pa·s. Experimental results are compared with the Vogel–Fulcher–Tamann law for viscosity predictions. This paper demonstrates the industrial and scientific interest of this new method for viscosity determinations, which can be used for the working and softening points of any glass. These results may lead to a better understanding of network-forming or network-modifying behavior in oxide glasses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022698619162
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  • 43
    Digitale Medien
    Digitale Medien
    Viscosity of Binary Mixtures of Alkyl Acetates with Hexane, Tetrachloromethane, and Trichloromethane (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1449-1465 
    Details
    ISSN: 1572-9567
    Schlagwort(e): alkyl acetate ; chloromethane ; Gibbs energy of activation ; hexane ; liquid mixtures ; molecular interactions ; tetrachloromethane ; trichloromethane ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity η for binary mixtures of methyl acetate (MA), ethyl acetate (EA), n-amyl acetate (nAA), isoamyl acetate (iAA), decyl acetate (DeA), and dodecyl acetate (DoA) with hexane and of MA, EA, nAA, and iAA with tetrachloromethane and trichloromethane has been measured at 303.15 K over the entire range of composition. The viscosity data have been correlated with the equations of Grunberg and Nissan; Hind, McLaughlin, and Ubbelohde; Tamura and Kurata; Katti and Chaudhri; McAllister; Heric and Brewer; and Auslaender. The viscosity deviations Δη and excess Gibbs energy of activation ΔG*E of viscous flow based on Eyring's theory have been calculated. The results have been analyzed in terms of disruption of dipolar association of alkyl acetate and molecular interaction between alkyl acetate and chloromethane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021441122016
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  • 44
    Digitale Medien
    Digitale Medien
    Transport properties of 1,1-difluoroethane (R152a) (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 731-757 
    Details
    ISSN: 1572-9567
    Schlagwort(e): 1,1-difluoroethane ; correlation ; critical region ; HFC-152a ; R152a ; thermal conductivity ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Based on reliable. carefully selected data sets. equations for the thermal conductivity and the viscosity of the refrigerant R 112a are presented. They are valid at temperatures from 240 to 440 K, pressures up to 20 MPa. and densities up to 1050 kg · m−3. including the critical region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01439187
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  • 45
    Digitale Medien
    Digitale Medien
    Survey of Experimental Data of Thermophysical Properties for Difluoromethane (HFC-32) (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1653-1666 
    Details
    ISSN: 1572-9567
    Schlagwort(e): critical parameters ; dielectric constant ; difluoromethane ; dipole moment ; heat capacities ; HFC-32 ; pvT behavior ; refractive index ; saturation densities ; second virial coefficient ; speed of sound ; surface tension ; survey ; thermal conductivity ; vapor pressure ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A survey of experimental data for HFC-32 was prepared at the Institute of Thermomechanics in connection with planned experiments. In tabular form, surveys of thermodynamic, transport, and other property measurements, including pvT behavior, second virial coefficient, vapor pressure, saturation densities, critical parameters, heat capacities, speed of sound, thermal conductivity, viscosity, surface tension, refractive index, dielectric constant, and dipole moment, are presented. Tables include author)s) name(s), reference, year of publication, ranges of measurements, number of points, stated uncertainty, sample purity, and experimental method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022697610870
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  • 46
    Digitale Medien
    Digitale Medien
    Correlation for Viscosity and Thermal Conductivity of Liquid Halogenated Ethane Refrigerants1 (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 367-375 
    Details
    ISSN: 1572-9567
    Schlagwort(e): correlation ; hard spheres ; liquid ; refrigerants ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity and thermal conductivity of liquid halogenated ethane refrigerants from about 200 K to near the critical temperature, at saturation and also at pressures up to 50 MPa, are shown to be satisfactorily correlated on the basis of a scheme developed by Dymond and Assael from consideration of hard-sphere theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006627411689
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  • 47
    Digitale Medien
    Digitale Medien
    New Correlation Functions for Viscosity Calculation of Gases Over Wide Temperature and Pressure Ranges (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1011-1031 
    Details
    ISSN: 1572-9567
    Schlagwort(e): dense fluids ; Rainwater–Friend theory ; second viscosity virial coefficient ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity of 14 supercritical gases over a wide temperature–pressure range is calculated with a new correlation scheme. Highly accurate realistic interatomic potentials of the noble gases are used in the Chapman–Enskog calculation of the zero-density viscosity and in the Rainwater–Friend theory to determine the initial density dependence of the viscosity. At densities beyond the range of the theory, a variant of the residual viscosity is developed. It is shown that the temperature dependence of the residual viscosity function increases with the number of atoms in the molecule. By including this temperature dependence, the accuracy of the predicted results improves significantly. The accuracy of this method is within the experimental uncertainties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026437702566
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  • 48
    Digitale Medien
    Digitale Medien
    Saturated Liquid Viscosity and Surface Tension of Alternative Refrigerants (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1225-1253 
    Details
    ISSN: 1572-9567
    Schlagwort(e): dynamic light scattering ; R23 ; R32 ; R123 ; R125 ; R134a ; R143a ; R152a ; refrigerants ; surface light scattering ; surface tension ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Light scattering by thermally excited capillary waves on liquid surfaces or interfaces can be used for the investigation of viscoelastic properties of fluids. In this work, we carried out the simultaneous determination of the surface tension and the liquid kinematic viscosity of some alternative refrigerants by surface light scattering (SLS) on a gas–liquid interface. The experiments are based on a heterodyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). R23 (trifluoromethane), R32 (difluoromethane), R125 (pentafluoroethane), R143a (1,1,1-trifluoroethane), R134a (1,1,1,2-tetrafluoroethane), R152a (1,1-difluoroethane), and R123 (2,2-dichloro-1,1,1-trifluoroethane) were investigated under saturation conditions over a wide temperature range, from 233 K up to the critical point. It is estimated that the uncertainty of the present surface tension data for the whole temperature range is less than ±0.2 mN·m−1. For temperatures up to about 0.95T c, the kinematic viscosity of the liquid phase could be obtained with an absolute accuracy of better than 2%. For the highest temperatures studied in this work, measurements for the kinematic viscosity exhibit a maximum uncertainty of about ±4%. Viscosity and surface tension data are represented by a polynomial function of temperature and by a van der Waals-type surface tension equation, respectively. The results are discussed in detail with comparison to literature data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006689724974
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  • 49
    Digitale Medien
    Digitale Medien
    Liquid Viscosity of Binary Mixtures of Methanol with Ethanol and 1-Propanol from 273.15 to 333.15 K (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 3-13 
    Details
    ISSN: 1572-9567
    Schlagwort(e): ethanol ; methanol ; mixtures ; 1-propanol ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The liquid viscosities and densities of two binary mixtures of methanol with ethanol and 1-propanol were measured in the temperature range from 273.15 to 333.15 K with a capillary viscometer and a glass pycnometer, respectively. The uncertainties in the measured viscosities were estimated to be smaller than 1.3%. The experimental viscosity values could be fitted to the Mertsch and Wolf equation within 2%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021438800094
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  • 50
    Digitale Medien
    Digitale Medien
    Viscosity and Excess Volume at High Pressures in Associative Binaries (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 161-189 
    Details
    ISSN: 1572-9567
    Schlagwort(e): excess activation energy of flow ; excess volume ; high pressure ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamic viscosity η and the density ρ of three pure substances (water, 2-propanol, diacetone alcohol) and the three associated binaries were measured versus temperature T (303.15, 323.15, and 343.15 K) and pressure P. For the binary systems the mole fractions x of each component were, successively, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1. For viscosity the experimental results (P≤100 MPa) represent a total of 540 data points: 54 for the pure substances and 486 for the binary mixtures (x≠0 and x≠1). For density the experimental results (P≤70 MPa) represent 1260 values: 126 for the pure substances and 1134 for the binary mixtures (x≠0 and x≠1). The mixtures with water are highly associative and the curves for the variation of η with composition exhibit a maxima. The variations of the excess activation energy of viscous flow ΔG E are discussed. Moreover, the measurements of ρ are sufficiently accurate to determine the excess volumes V E versus pressure, temperature, and composition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021455203728
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  • 51
    Digitale Medien
    Digitale Medien
    A High-Temperature Viscometer for Molten Materials (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 427-435 
    Details
    ISSN: 1572-9567
    Schlagwort(e): high temperature ; molten salts ; oscillating-cup viscometer ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An oscillating-cup viscometer for the measurement of the viscosity of molten materials from room temperature to 1400 K was developed. The instrument is described in detail and the working equations are presented. The operational behavior was tested with water at room temperature. Preliminary measurements show that the new viscometer is capable of measuring the viscosity of water at room temperature to within 0.2%. As the primary objective of this work is the establishment of standard reference data for high-temperature viscosity measurements in molten salts, molten metals, and molten semiconductors, references of earlier viscosity measurements of molten KNO3 are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022561326972
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  • 52
    Digitale Medien
    Digitale Medien
    Viscosity of Gaseous HFC-134a (1,1,1,2-Tetrafluoroethane) Under High Pressures (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1285-1295 
    Details
    ISSN: 1572-9567
    Schlagwort(e): HFC-134a ; Lennard–Jones potential ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity of gaseous HFC-134a (1,1,1,2-tetrafluoroethane) was measured with an oscillating disk viscometer of the Maxwell type from 298.15 to 398.15 K at pressures up to 5.5 MPa. Intermolecular potential parameters for the Lennard–Jones 12-6 model were determined from the viscosity data at 0.1 MPa. The viscosity equation developed by Krauss et al. was applied to correlate the present viscosity data. In addition, the correlations proposed by Stiel and Thodos and by Lee and Thodos were tested for fitting the experimental viscosity data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021919215793
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  • 53
    Digitale Medien
    Digitale Medien
    Prediction of the Viscosity of Supercritical Fluid Mixtures (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1297-1313 
    Details
    ISSN: 1572-9567
    Schlagwort(e): high pressure mixture ; supercritical fluids ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A method for predicting the viscosity of supercritical, multicomponent fluid mixtures, at any density, from the zero-density viscosity of pure components is presented. The method is based upon the results for a rigid-sphere model, suitably interpreted to apply to real fluids, and on the finding that the excess viscosity of pure supercritical fluids can be adequately described by a density function independent of temperature. The density range of the method extends to twice the critical density of the pure component with the smallest critical density. The only exception is for the methane-rich mixtures where the mixture density should not exceed 12000 mol·m−3. The uncertainty ascribed to the predictions made by this method is of the order of ±5%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021971232631
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  • 54
    Digitale Medien
    Digitale Medien
    Viscosity of Aqueous Solutions of CO2 at High Pressures (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1315-1323 
    Details
    ISSN: 1572-9567
    Schlagwort(e): carbon dioxide ; Flory's theory ; viscosity ; water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Experimental viscosity measurements of aqueous solutions of CO2 along three isotherms at 273, 276, and 278 K for pressures up to 30 MPa are reported. The measurements have been carried out in a falling capillary viscometer and have an estimated uncertainty of ±1.5%. The experimental values were compared with the correlation proposed by Kanti et al. derived from Flory's theory. The equation is in poor agreement with the experimental values, but the equations of Kanti et al. and of Grunberg and Nissan with one adjustable parameter yield good agreement with the experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021923316701
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  • 55
    Digitale Medien
    Digitale Medien
    Viscosity and Density at High Pressures in an Associative Ternary (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1325-1341 
    Details
    ISSN: 1572-9567
    Schlagwort(e): density ; excess activation energy of viscous flow ; high pressure ; ternary mixture ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamic viscosity η and the density ρ of the associative ternary mixture water+diacetone alcohol+2-propanol have been measured as a function of temperature T (303.15, 323.15, and 343.15 K) and pressure P (≤100 MPa). The experimental results correspond to 698 values of η and ρ. With reference to the 54 values previously published on pure substances and 486 values for three corresponding binaries, the system is globally described by 1188 experimental values for various values of P, T and composition. The results for η are discussed in terms of excess activation energy of viscous flow.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021975300772
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  • 56
    Digitale Medien
    Digitale Medien
    Liquid Densities, Kinematic Viscosities, and Heat Capacities of Some Ethylene Glycol Dimethyl Ethers at Temperatures from 283.15 to 423.15 K (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1343-1358 
    Details
    ISSN: 1572-9567
    Schlagwort(e): corresponding states ; density ; ethylene glycol dimethyl ether ; group-contribution method ; heat capacity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Liquid densities and heat capacities at 1 MPa, and kinematic viscosities at atmospheric pressure of monoethylene glycol dimethyl ether (MEGDME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TrEGDME), tetrathylene glycol dimethyl ether (TEGDME), pentaethylene glycol dimethyl ether (PeEGDME), and polyethylene glycol 250 dimethyl ether (PEGDME 250) were measured in the temperature range from 283.15 to 423.15 K. For each substance, experimental data were correlated with temperature using empirical polynomial equations. The experimental data were also used to evaluate the predictive capability of some estimation methods of liquid densities and heat capacities for the studied ethylene glycol dimethyl ethers. The densities estimated by the Yen–Woods equation agree with our experimental values with a root-mean-square relative deviation (RMSD) of 3.21% for all ethylene glycol dimethyl ethers. The best estimated results of liquid heat capacities were obtained from the Rowlinson equation based on the corresponding-states principle, with a RMSD of 1.12%. The group-contribution methods give the worst results, especially at high temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021927417610
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  • 57
    Digitale Medien
    Digitale Medien
    Correlation and Prediction of the Transport Properties of Refrigerants Using Two Modified Rough Hard-Sphere Models (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 149-161 
    Details
    ISSN: 1572-9567
    Schlagwort(e): viscosity ; thermal conductivity ; rough-hard-sphere ; refrigerants ; refrigerant mixtures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Two methods are presented for the correlation and prediction of the viscosities and thermal conductivities of refrigerants R11, R12, R22, R32, R124, R125, R134a, R141b, and R152 and their mixtures. The first (termed RHS1) is a modified rough-hard-sphere method based on the smooth hard-sphere correlations of Assael et al. The method requires two or three parameters for characterizing each refrigerant but is able to correlate transport properties over wide ranges of pressure and temperature. The second method (RHS2) is also a modified rough-hard-sphere method, but based on an effective hard-sphere diameter for Lennard–Jones (LJ) fluids. The LJ parameters and the effective hard-sphere diameter required in this method are determined from a knowledge of the density–temperature behavior of the fluid at saturation. Comparisons with the rough-hard-sphere method of Assael and co-workers (RHS3) are shown. We also show that the RHS2 method can be used to correlate as well as predict the transport properties of refrigerants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021438516081
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  • 58
    Digitale Medien
    Digitale Medien
    Correlation of dense fluid self-diffusion, shear viscosity, and thermal conductivity coefficients (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 155-165 
    Details
    ISSN: 1572-9567
    Schlagwort(e): correlation methods ; dense liquids ; diffusion coefficient ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A general procedure has been developed for simultaneously fitting any two of the self-diffusion coefficient, the viscosity (as the fluidity), and the thermal conductivity (as its reciprocal) as Dymond reduced coefficients, (D*,η*,λ*), to a simple function of the volume and the temperature for dense fluids. For example,D*=ζ1+ζ2 V r/(1+ζ3,/V r), whereV r=V[1-ζ1(T−T r)-ζ2(T−T r)2].T r is any convenient temperature, here 273.15 K. AsV r is common to the two properties, only eight coefficients, ζj and ζk are required. Such reduced transport-coefficient curves are geometrically similar for members of groups of closely related compounds. The procedure has been extended to give “family” curves for such groups by fitting a pair of transport properties for three substances from the group in a single regression. Overall, fewer coefficients are required than for other schemes in the literature, and the fitting functions used are simpler. The curves so constructed can be used for the correlation of data obtained from different sources, as well as interpolation and, to a limited extent, extrapolation. A comparison is made for a number of compotmd groups between simultaneous fits of the pairs (D−η ), (D−λ), and (η−λ)
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01438966
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  • 59
    Digitale Medien
    Digitale Medien
    Viscosity and density of liquid mixtures ofn-alkanes with squalane (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 773-779 
    Details
    ISSN: 1572-9567
    Schlagwort(e): capillary viscometer ; density ; n-butane ; n-hexane ; squalane ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Viscosity and density measurements are reported for binary liquid mixtures ofn-butane andn-hexane with squalane in the temperature range from 273 to 333 K. The viscosity measurements have been carried out by using a capillary viscometer calibrated with standard liquids. that is. JS5, JSIO, JS20, and water. The uncertainty in the viscosity data was estimated to be ± 1.7%. The density needed for the calculation of the viscosity has been measured by using a glass pycnometer within an accuracy of ±0.04%. In the prediction of the viscosity, the scheme of Assael et al. fails for mixtures of this type differing greatly in size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01438862
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  • 60
    Digitale Medien
    Digitale Medien
    Measurement of density, sound velocity, surface tension, and viscosity of freely suspended supercooled liquids (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 545-555 
    Details
    ISSN: 1572-9567
    Schlagwort(e): density ; levitation technique ; supercooling ; surface tension ; sound velocity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Noncontact methods have been implemented in conjunction with levitation techniques to carry out the measurement of the macroscopic properties of liquids significantly cooled below their nominal melting point. Free suspension of the sample and remote methods allow the deep excursion into the metastable liquid state and the determination of its thermophysical properties. We used this approach to investigate common substances such as water,v-terphenyl. succinonitrile, as well as higher temperature melts such as molten indium, aluminum, and other metals. Although these techniques have thus far involved ultrasonic, eletromagnetic, and more recently electrostatic levitation, we restrict our attention to ultrasonic methods in this paper. The resulting magnitude of maximum thermal supercooling achieved has ranged between 10% and 15% of the absolute temperature of the melting point for the materials mentioned above. The methods for measuring the physical properties have been mostly novel approaches, and the typical accuracy achieved has not yet matched the standard equivalent techniques involving contained samples and invasive probing. They are currently being refined, however, as the levitation techniques become more widespread and as we gain a better understanding of the physics of levitated liquid samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01441920
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  • 61
    Digitale Medien
    Digitale Medien
    Viscosities of Multicomponent Silicate Melts at High Temperatures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 309-323 
    Details
    ISSN: 1572-9567
    Schlagwort(e): experiment ; model ; silicate melts ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In the present work; the viscosities in the quaternaries CaO–Fe n O–MgO–SiO2, Fe n O-MgO–MnO–SiO2, and CaO–MgO–MnO–SiO2 and the quinary CaO–Fe n O–MgO–MnO–SiO2 were studied. The experimental technique employed was the well-established rotating cylinder method, using a Brookfield digital viscometer mounted over a specially designed graphite furnace. Generally, iron crucibles were used along with iron spindles. Periodic calibrations of the experimental setup were made using the standard reference slag recommended by the European Union. The measurement's were carried out up to a maximum temperature of 1773 K in all cases. The reliability of the measurements were checked at different rotation speeds as well as during thermal cycling, and excellent reproducibility of the results was noted. The experimental viscosity values were incorporated into a viscosity model. Equations based on the model for calculating the viscosities of the quarternary systems CaO–Fe n O–MgO–SiO2, Fe n O–MgO–MnO–SiO2, and CaO–MgO–MnO–SiO2 and the quinary system CaO–Fe n O–MgO–MnO–SiO2 are provided.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021419406512
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  • 62
    Digitale Medien
    Digitale Medien
    Viscosity of R134a, R32, And R125 at Saturation (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 365-373 
    Details
    ISSN: 1572-9567
    Schlagwort(e): R134a ; R32 ; R125 ; refrigerants ; vibrating-wire viscometer ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper reports the results of the measurement of the viscosity of R134a close to the saturation line in the vapor phase. The new measurements were carried out in a vibrating-wire viscometer specially constructed for the purpose, and the results have an accuracy of ±2%. In addition, the opportunity is taken to present a reevaluation of earlier measurements along the saturation line of the viscosity of R32 and R125. Improved equations of state for these fluids are now available and can be employed to generate improved values for the viscosity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022640617694
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  • 63
    Digitale Medien
    Digitale Medien
    Viscosity Measurements of Ammonia, R32, and R134a. Vapor Buoyancy and Radial Acceleration in Capillary Viscometers (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 401-434 
    Details
    ISSN: 1572-9567
    Schlagwort(e): ammonia ; alternative refrigerants ; capillary viscometer ; R32 ; R134a ; saturated liquid ; radial acceleration correction ; vapor buoyancy ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The saturated liquid viscosity of ammonia (NH3) and of the hydrofluorocarbons, difluoromethane (CH2F2, R32) and 1,1,1,2-tetrafluoroethane (CF3–CH2F, R134a), was measured in a sealed gravitational viscometer with a straight vertical capillary. The combined temperature range was from 250 to 350 K. The estimated uncertainty of the ammonia measurements is ±3.3 and ±2 to 2.4% for the hydrofluorocarbons with a coverage factor of two. The results are compared with literature data which have been measured with capillary viscometers of different design. Agreement within the combined experimental uncertainty is achieved when some of the literature data sets are corrected for the vapor buoyancy effect and when a revised radial acceleration correction is applied to data which were obtained in viscometers with coiled capillaries. An improved correction for the radial acceleration is proposed. It is necessary to extend inter-national viscometry standards to sealed gravitational capillary instruments because the apparent inconsistencies between refrigerant viscosity data from different laboratories cannot be explained by contaminated samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022644718603
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  • 64
    Digitale Medien
    Digitale Medien
    Viscosity of Gaseous R404A, R407C, R410A, and R507 (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 777-790 
    Details
    ISSN: 1572-9567
    Schlagwort(e): gaseous ; R404A ; R407C ; R410A ; R507 ; refrigerants ; saturation ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper presents new measurements of the viscosity of gaseous R404A (52 wt% R143a, 44 wt% R125, 4 wt% R134a), R407C (23 wt% R32, 25 wt% R125, 52 wt% R143a), R410A (50 wt% R32, 50 wt% R125), and R507 (50 wt% R143a, 50 wt% R125). These mixtures are recommended as substitutes for the refrigerants R22, R502, and R13B1. Measurements were carried out in an oscillating-disk viscometer. The obtained values of the viscosity are relative to the viscosity of nitrogen. The experiments were performed at atmospheric pressure over the temperature range 297 to 403 K. and near the saturation line up to pressures of 0.6 P crit. The estimated uncertainty of the reported viscosities are ±0.5% for the viscosities at atmospheric pressure and ± 1% along the saturation line, being limited by the accuracy of the available vapor pressure and density data. The experimental viscosities at atmospheric pressure are employed to determine the intermolecular potential parameters, σ and ɛ, which provide the optimum representation of the data with the aid of the extended law of corresponding states developed by Kestin et al. A comparison of the experimental viscosity data with the values calculated by REFPROP, both at atmospheric pressure and along the saturation line, is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022618832289
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  • 65
    Digitale Medien
    Digitale Medien
    Viscosity Measurements of Industrial Alloys Using the Oscillating Cup Technique (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1791-1800 
    Details
    ISSN: 1572-9567
    Schlagwort(e): molten metals ; oscillating cup ; superalloy ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Molten metal processing can be effectively simulated using state-of-the-art computer algorithms, and manufacturers increasingly rely upon these tools to optimize the design of their operations. Reliable thermophysical properties of the solid, solid + liquid, and liquid phases are essential for effective computer simulation. Commercially available instruments can measure many of the required properties of molten metals (e.g., transformation temperatures, thermal conductivity, specific heat, latent heat, and density). However, there are no commercially available instruments to characterize several important thermophysical properties (e.g., emissivity, electrical resistivity, surface tension, and viscosity). Although the literature has numerous examples of measurements of surface tension using the sessile drop and the oscillating drop techniques, literature references are sparse with regard to measurements of emissivity, electrical resistivity, and viscosity. The present paper discusses the development of an oscillating cup viscometer and its application to characterizing the viscosity of fully molten industrial alloys. The theory behind the oscillating cup technique is reviewed, and the design details of the current instrument are discussed. In addition, experimental data of the viscosity of several nickel-based superalloys are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022670232252
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  • 66
    Digitale Medien
    Digitale Medien
    Prediction of the Thermal Conductivity and Viscosity of Binary and Ternary HFC Refrigerant Mixtures (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 23-34 
    Details
    ISSN: 1572-9567
    Schlagwort(e): HFC-32 ; HFC-125 ; HFC-134a ; hard-sphere theory ; mixture ; refrigerant ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous prediction of the thermal conductivity and the viscosity of binary and ternary HFC refrigerant mixtures, consisting of HFC-32, HFC-125, and HFC-134a. In this prediction scheme, the hypothetical molecular parameters of HFC refrigerant mixtures were assumed to be the molar average of the pure component values. The close agreement between the predicted values and the experimental results of thermal conductivity and viscosity demonstrate the predictive power of this scheme.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006696518938
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  • 67
    Digitale Medien
    Digitale Medien
    Thermophysical Properties of Gaseous Tungsten Hexafluoride from Speed-of-Sound Measurements (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 185-206 
    Details
    ISSN: 1572-9567
    Schlagwort(e): equation of state ; intermolecular potential ; speed-of-sound ; thermodynamic properties ; transport properties ; tungsten hexafluoride ; virial coefficients ; viscosity ; WF6
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The speed of sound was measured in gaseous WF6 using a highly precise acoustic resonance technique. The data span the temperature range from 290 to 420 K and the pressure range from 50 kPa to the lesser of 300 kPa or 80% of the sample's vapor pressure. At 360 K and higher temperatures, the data were corrected for a slow chemical reaction of the WF6 within the apparatus. The speed-of-sound data have a relative standard uncertainty of 0.005%. The data were analyzed to obtain the ideal-gas heat capacity as a function of the temperature with a relative standard uncertainty of 0.1%. These heat capacities are in reasonable agreement with those determined from spectroscopic data. The speed-of-sound data were fitted by virial equations of state to obtain the temperature dependent density virial coefficients. Two virial coefficient models were employed, one based on square-well intermolecular potentials and the second based on a hard-core Lennard–Jones intermolecular potential. The resulting virial equations reproduced the sound-speed data to within ±0.005% and may be used to calculate vapor densities with relative standard uncertainties of 0.1% or less. The hard-core Lennard–Jones potential was used to estimate the viscosity and the thermal conductivity of dilute WF6. The predicted viscosities agree with published data to within 5% and can be extrapolated reliably to higher temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006617223481
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  • 68
    Digitale Medien
    Digitale Medien
    The physical properties of alloys in the liquid and “mushy” states (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 1151-1161 
    Details
    ISSN: 1572-9567
    Schlagwort(e): alloys ; density ; electrical resistivity ; enthalpy ; heat capacity ; high temperatures ; surface tension ; thermal conductivity ; thermal diffusivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Data on the physical properties of alloys at high temperatures are urgently needed for the mathematical modeling of high-temperature processes such as casting, welding, secondary refining, dip melting, spray forming, and metal powder production. Data are required for those properties which are involved in heat and fluid flow in high-temperature processes. Levitated drop methods have been adopted to measure the surface tensions, densities, and enthalpies of commercial alloys, and rapid, transient methods have been developed to measure thermal conductivities to avoid the problem of convection. The results obtained for the properties of commercial alloys for the liquid and “mushy” states are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01442002
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  • 69
    Digitale Medien
    Digitale Medien
    Physical and Thermodynamic Properties of Aqueous 2-Amino-2-Methyl-1,3-Propanediol Solutions (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1175-1184 
    Details
    ISSN: 1572-9567
    Schlagwort(e): absorption ; AMPD ; carbon dioxide ; density ; solubility ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Densities and viscosities of mixtures of 2-amino-2-methyl-1,3-propanediol (AMPD)–water were measured at temperatures of 30, 40, 50, 60, and 70°C. The solubility of N2O in the aqueous AMPD solutions was measured at temperatures of 30, 40, and 50°C. The concentrations selected for study were 10, 20, and 30 mass% AMPD for all three temperatures. The experimental values for density and viscosity were correlated as functions of temperature. The maximum deviations were less than 0.005% for densities and 0.3% for viscosities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026454206200
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  • 70
    Digitale Medien
    Digitale Medien
    Thermophysical Properties of Tetramethylmethane and Tetramethylsilane Gas Calculated by Means of an Isotropic Temperature-Dependent Potential (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1439-1461 
    Details
    ISSN: 1572-9567
    Schlagwort(e): diffusion ; intermolecular potentials ; Raman and Rayleigh spectra ; second virial coefficients ; tetramethylmethane ; tetramethylsilane ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An isotropic temperature-dependent potential (ITDP) is calculated for the description of binary interactions in gaseous tetramethylmethane, C(CH3)4, and tetramethylsilane, Si(CH3)4. The potential parameters of C(CH3)4 and Si(CH3)4 are determined by solving an inverse problem of minimization of the sum of weighted squared relative deviations between experimental and calculated pure gas viscosity (η), second (pVT)-virial coefficient (B), and second acoustic virial coefficient (β) data. At T=0 K they are obtained for C(CH3)4 and Si(CH3)4, respectively, as repulsive parameter n=28.02(12) and 20.79(11), equilibrium distance r m=5.7790(30)×10−10 and 5.9051(36)×10−10 m, potential well depth ε/k B=586.32(42) and 674.75(91) K, and the first excited-level enlargement δ=0.0141(3)×10−10 and 0.0188(3)×10−10 m. The influence of the temperature on the potential parameters r m(T) and ε(T) is implied in the temperature dependence of the effective excited-state enlargement, calculated via the vibrational partition function. The calculated complete sets of normal vibrational frequencies for C(CH3)4 and Si(CH3)4 are consistent with the available experimental data. In addition, good agreement is observed between the calculations and new Raman spectroscopic measurements on C(CH3)4. Tables for recommended thermophysical properties (B, η, and self-diffusion ρD) and effective potential parameters (r m and ε) of the two globular gases are given for the temperature range between 250 and 800 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006706510540
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  • 71
    Digitale Medien
    Digitale Medien
    Viscosity of Alcohol–Ethene Mixtures at Pressures up to 195 MPa (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 43-69 
    Details
    ISSN: 1572-9567
    Schlagwort(e): alcohols ; density ; ethene ; high pressure ; hydrogen bond ; mixtures ; vinyl acetate ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Viscosities of several alcohol–ethene and vinyl acetate–ethene mixtures were measured with a rolling-ball viscometer. The viscosity measurements were performed at temperatures from 298 to 413 K and pressures up to 195 MPa with an estimated uncertainty of ±2%. The appearance of hydrogen bonds forming alcohol associates has a notable effect on the viscosity of alcohol–ethene mixtures above an alcohol mole fraction of about 0.2. This could be noticed from the deviation of the viscosity from the Arrhenius law, which occurs when alcohol associates are formed. An effect of pressure on the association of alcohol molecules through hydrogen bonding was not observable from the viscosity data. A new method for the description of the temperature- and pressure-dependent parameters in the McAllister and Dizechi models is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021494917841
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  • 72
    Digitale Medien
    Digitale Medien
    Direct Determination of the Interaction Potentials of He–N2, Ne–N2 and Ar–N2 from the Extended Principle of Corresponding States (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 227-237 
    Details
    ISSN: 1572-9567
    Schlagwort(e): collision integrals ; corresponding states ; molecular beam ; potential energy function ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The pair-potential energy functions for He–N2, Ne–N2, and Ar–N2 have been determined from a direct inversion of the experimentally reduced viscosity collision integrals obtained from the corresponding-states correlation. The resulting potentials are in excellent agreement with the potentials independently obtained from molecular beam scattering measurements. The potentials have been used to predict the diffusion and viscosity coefficients for each system, and they are found to be in reasonable agreement with experimental values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021411421475
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  • 73
    Digitale Medien
    Digitale Medien
    Viscosity of saturated R152a measured with a vibrating wire viscometer (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 867-876 
    Details
    ISSN: 1572-9567
    Schlagwort(e): 1,1-difluoroethane ; mechanical damping ; R152a ; refrigerants ; vibrating wire viscometer ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Earlier reported values of the viscosity coefficient of the refrigerant R152a (1,1-difluoroethane) have been recalculated with an improved value for the mechanical damping of the vibrating wire viscometer. The measurements were taken along the saturation line both in the saturated liquid and in the saturated vapor every 10 K from 243 up to 393 K by means of a vibrating wire viscometer The damping of the vibration of the wire is a measure for the viscosity provided that the mechanical damping is subtracted. The latter is usually measured in vacuum. It turns out that the damping value measured in this way depends on the vacuum pressure and on the way the wire has been handled before. It appeared that the damping applied previously, measured after 6 days of pumping, is too small, resulting in values of the viscosity coefficient which are too large. The effect on the data for the saturated-liquid viscosity is small, but the new saturated-vapor viscosity data agree much better with the unsaturated-vapor data reported by Takahashi et al.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02093469
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  • 74
    Digitale Medien
    Digitale Medien
    The viscosity of liquid toluene at elevated pressures (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 877-882 
    Details
    ISSN: 1572-9567
    Schlagwort(e): high pressure ; toluene ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper reports new measurements on the viscosity of toluene at pressures up to 500 MPa at 299 K and pressures up to 435 MPa at 323 K. The results are in close agreement with recent viscosity measurements from a vibrating-wire viscometer at pressures up to 250 MPa but confirm earlier measurements from a falling-body viscometer which show that the recently recommended polynomial expression for the representation of the pressure dependence of the viscosity of toluene up to 250 MPa underestimates the viscosity if applied at 500 MPa by about 30%. Modification of this polynomial expression by inclusion of one additional term is found to represent the data satisfactorily over the whole pressure range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02093470
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  • 75
    Digitale Medien
    Digitale Medien
    Dynamic viscosity measurements by photon correlation spectroscopy (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 433-443 
    Details
    ISSN: 1572-9567
    Schlagwort(e): particle diffusion ; photon correlation spectroscopy ; R123 ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is shown that absolute values for the dynamic viscosity of liquids can be obtained using photon correlation spectroscopy. The technique is based on the measurement of the particle diffusion coefficient of spheres dispersed in a liquid. In the experiments both PMMA and silica particles were used as a seed. This includes the first application of newly industrially produced silica samples for the goal of viscosity measurements. Experiment results are presented for various liquids at ambient conditions, including some alcohols, alkanes, and the refrigerant R123. Most of the data agree quite well with reference values. Requirements for suitable seed particles and possible reasons for deviations from reference data are discussed. Measurements in liquid mixtures indicate the general possibility for the simultaneous determination of dynamic viscosity and molecular diffusion coefficient in a single experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01441909
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  • 76
    Digitale Medien
    Digitale Medien
    Viscosity of Gaseous HFC-143a (1,1,1-trifluoroethane) Under High Pressures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 435-443 
    Details
    ISSN: 1572-9567
    Schlagwort(e): corresponding states ; HFC-143a ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity of gaseous HFC-143a(1,1,1-trifluoroethane) was measured with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressure at each temperature under subcritical conditions or up to 9 MPa under supercritical conditions. Intermolecular potential parameters of HFC-143a for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation as functions of temperature and density is proposed to interpolate the present experimental results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022696702673
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  • 77
    Digitale Medien
    Digitale Medien
    Viscosity of Gaseous HFC-125 (Pentafluoroethane) Under High Pressures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 445-453 
    Details
    ISSN: 1572-9567
    Schlagwort(e): corresponding states ; HFC-125 ; oscillating-disk viscometer ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper reports experimental results lor the viscosity of gaseous HFC-125 (pentafluoroethane) under high pressures. The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressures at each temperature at subcritical conditions or up to 9 MPa at supercritical temperatures. Intermolecular scaling parameters of HFC-125 for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation is proposed to interpolate the present experimental results as a function of temperature and density.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022648819511
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  • 78
    Digitale Medien
    Digitale Medien
    A New Apparatus for Combined Measurements of the Viscosity and Density of Fluids for Temperatures from 233 To 523 K at Pressures up to 30 Mpa (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 485-505 
    Details
    ISSN: 1572-9567
    Schlagwort(e): combined viscosity/density measurement ; density ; magnetic suspension balance ; magnetic suspension coupling ; single-sinker densimeter ; viscometer ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new apparatus for measuring the viscosity and density of fluids is presented. The main element of the instrument is an electronically controlled magnetic suspension coupling. For the density measurement (buoyancy principle according to the single-sinker method), this coupling is used for the contactless transfer of the forces acting on a sinker in the measuring cell to an analytical balance. The coupling also serves as a frictionless bearing for a slender rotating cylindrical body which is slowed down due to the viscous drag of the fluid surrounding the cylinder. The viscosity of the fluid can be directly determined from the decay rate of the rotational frequency. The new combined viscometer-densimeter covers a viscosity range of 5 to 150 μPa·s and a density range from 20 to 2000 kg·m−3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Test measurements on the viscosities and densities of nitrogen and carbon dioxide at 253, 293, and 523 K at pressures up to 30 MPa show an estimated total uncertainty of ±0.6 to ±1.0% in viscosity and of ±0.02 to ±0.05% in density.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022601003582
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  • 79
    Digitale Medien
    Digitale Medien
    The Viscosity Anomaly Near the Lower Critical Consolute Point (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 889-898 
    Details
    ISSN: 1572-9567
    Schlagwort(e): critical behavior ; lower critical solution point ; mixture ; viscosity ; water ; 3-methylpyridine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Shear viscosity measurements for a critical mixture of 3-methylpyridine + heavy water near a lower critical consolute point are reported. The background contribution was determined from viscosity measurements of mixture at a noncritical composition. In the entire investigated temperature range T c – T≤ 15.6 K, the viscosity of the critical mixture exceeds the background contribution, and the critical enhancement is important. The increase of the viscosity near critical is found in the temperature range T c–T≤ 1.82 K. The critical exponent y = 0.0415 ± 0.002 and the wave number Q = (0.40 ± 0.07) nm−1 are determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022639304064
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  • 80
    Digitale Medien
    Digitale Medien
    Prediction of the viscosity for molecular fluids from the dilute-gas properties via the inversion procedure for spherically symmetric pair potentials (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 683-693 
    Details
    ISSN: 1572-9567
    Schlagwort(e): dense fluid ; interaction potential ; inversion algorithm ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A prediction scheme is presented for the viscosity and translation part of the thermal conductivity (“frozen” thermal conductivity) of molecular fluids via the application of the original inversion algorithm for spherically symmetric pair potentials. The latter allows us to invert the centrally symmetrical effective interaction potential for two types of dilute-gas properties- - the pressure second virial coefficient and the low-density gas viscosity. Such a potential is then used for the computation of fluid transport properties, Several weakly anisotropic molecular systems were considered (N2OCOCO2CH4), Analysis of the results obtained reveals that the class of spherically symmetric potentials may still be used for the prediction of fluid transport coefficients from the dilute-gas equilibrium and kinetic characteristics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01441514
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  • 81
    Digitale Medien
    Digitale Medien
    Thermodynamic and Transport Properties of Binary Mixtures Containing 1,3-Dioxolane (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1435-1448 
    Details
    ISSN: 1572-9567
    Schlagwort(e): benzene ; cyclohexane ; cyclopentane ; density ; 1,3-dioxolane ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper reports density and viscosity measurements for the binary mixtures of cyclopentane or cyclohexane or benzene with 1,3-dioxolane at 283.15, 298.15, and 313.15 K. From the experimental data, excess volumes and excess viscosities were calculated and the results were fitted to a Redlich–Kister-type equation. The results are discussed in terms of molecular interactions. The Prigogine–Flory–Patterson and Blomfield–Dewan theories were used to analyze the results at 298.15 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021489005178
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  • 82
    Digitale Medien
    Digitale Medien
    Transport Property Measurements on the IUPAC Sample of 1,1,1,2-Tetrafluoroethane (R134a) (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1-22 
    Details
    ISSN: 1572-9567
    Schlagwort(e): R134a ; dilute gas ; refrigerant ; saturation properties ; 1,1,1,2-tetrafluoroethane ; thermal conductivity ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper reports the results of an international project coordinated by the Subcommittee on Transport Properties of Commission I.2 of the International Union of Pure and Applied Chemistry. The project has been conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of R134a and culminates the effort which was initially described in 1995. The project has involved the remeasurement of the transport properties of a single sample of R134a in nine laboratories throughout the world in order to test the hypothesis that at least part of the discrepancy could be attributed to the purity of the samples. This paper provides an intercomparison of the new experimental results obtained for the viscosity and thermal conductivity in the vapor, liquid, and supercritical gas phases. The viscosity measurements were made with a variety of techniques including the vibrating wire, oscillating disk, capillary flow, and falling body. Thermal conductivity was measured using transient bare and anodized hot wires, steady-state anodized hot wires, and light scattering. Agreement between a variety of experimental techniques using the standard round-robin sample is necessary to demonstrate that some of the discrepancies in earlier results were due to sample impurities. Identification of disagreement between data using one experimental technique relative to other techniques may suggest modifications that would lead to more accurate measurements on these highly polar refrigerant materials. It is anticipated that the new data which have been measured on this IUPAC round-robin sample will aid in the identification of the reliable data sets in the literature and ultimately allow the refinement of the IUPAC reference-data correlations for the transport properties of R134a.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006690702100
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  • 83
    Digitale Medien
    Digitale Medien
    The Viscosity of Toluene in the Temperature Range 210 to 370 K1 (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 291-299 
    Details
    ISSN: 1572-9567
    Schlagwort(e): measurements ; toluene ; vibrating-wire technique ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The paper reports new measurements of the viscosity of toluene along the saturation line over a temperature range of 210 to 370 K. The measurements were performed in a vibrating-wire viscometer, properly adjusted for these low-temperature measurements. The uncertainty of the measurements, confirmed above room temperature with the measurement of the viscosity of water, is estimated to be ±0.5%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006628008963
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  • 84
    Digitale Medien
    Digitale Medien
    Prediction of the Viscosity of Liquid Mixtures: An Improved Approach1 (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 357-365 
    Details
    ISSN: 1572-9567
    Schlagwort(e): liquid ; mixtures ; prediction ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A recently developed theoretically based scheme for the prediction of the viscosity of gas mixtures is modified by making use of the hard-sphere theory and applied to the prediction of the viscosity of liquid mixtures. Preliminary results are compared with viscosity measurements of mixtures of n-hexane with toluene and with cyclohexane, and demonstrate the predictive power of this scheme.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006675327619
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  • 85
    Digitale Medien
    Digitale Medien
    Viscosity Measurements on Gaseous Argon, Krypton, and Propane1 (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 301-318 
    Details
    ISSN: 1572-9567
    Schlagwort(e): argon ; gas ; krypton ; measurement ; propane ; vibrating-wire viscometer ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new vibrating-wire viscometer was designed to perform quasi-absolute measurements of very high precision on gases. It was applied to determine the viscosity of argon at temperatures of 298.15, 348.15, and 423.15 K and pressures up to 20 MPa, and the viscosity of krypton at 298.15 and 348.15 ,K and pressures up to 16 MPa. Furthermore, several isothermal series of viscosity measurements on gaseous propane were carried out. The subcritical isotherms at 298.15, 323.15, 348.15, and 366.15 K were restricted to 95% of the saturated vapor pressure, the supercritical isotherms at 373.15, 398.15, and 423.15 K to 20 MPa. In general, the measurements are characterized by a reproducibility of ±0.05% and an accuracy of ±0.2%. However, close to the critical point an accuracy of ±3% has to be accepted, mainly due to the uncertainty of the density. In this context the influence of the equation of state used for propane is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006667125801
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  • 86
    Digitale Medien
    Digitale Medien
    Viscosity of Toluene+Cyclopentane Mixtures: Measurements and Prediction (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 621-637 
    Details
    ISSN: 1572-9567
    Schlagwort(e): cyclopentane ; high pressures ; mixtures ; toluene ; vibrating wire ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract New measurements of the viscosity of binary mixtures of toluene+cyclopentane are presented. The measurements, performed in a vibrating-wire viscometer, cover the temperature range from 210 to 310 K at pressures up to 25 MPa. The concentrations studied are 60 and 30%, by weight, toluene. The uncertainty of the measurements, confirmed at room temperature and higher temperatures with the measurement of the viscosity of water, is estimated to be ±0.5%, increasing to ±1% at temperatures below 240 K. The present measurements are employed to examine the predictive power of two recent theoretically based schemes proposed for the calculation of the viscosity of mixtures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006633300959
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  • 87
    Digitale Medien
    Digitale Medien
    Viscosity of Gaseous HCFC-123 (2,2-Dichloro-1,1,1-Trifluoroethane) in the Temperature Range from 323.15 to 423.15 K and at Pressures up to 2 MPa (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 695-701 
    Details
    ISSN: 1572-9567
    Schlagwort(e): HCFC-123 ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The viscosity of gaseous HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane) was measured with an oscillating-disk viscometer of the Maxwell type at temperatures from 323.15 to 423.15 K and at pressures up to the saturated vapor pressure at each temperature in subcritical conditions or up to 2 MPa under supercritical conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006641502777
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  • 88
    Digitale Medien
    Digitale Medien
    Modeling Viscosity of Multicomponent Electrolyte Solutions (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 367-378 
    Details
    ISSN: 1572-9567
    Schlagwort(e): viscosity ; aqueous solutions ; electrolytes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A comprehensive model for calculating the viscosity of aqueous electrolyte solutions has been developed. The model includes a long-range electrostatic interaction term, contributions of individual ions, and a contribution of specific interactions between ions or neutral species. The long-range electrostatic term is obtained from the Onsager–Fuoss theory, whereas the individual ionic contributions are calculated using the Jones–Dole B coefficients. A technique for predicting the temperature dependence of the B coefficients has been developed on the basis of the concept of structure-breaking and structure-making ions. The contribution of specific interactions between species, which is dominant for concentrated solutions, has been found to be a function of the ionic strength. The model reproduces the viscosity of aqueous systems ranging from dilute to concentrated solutions (up to ca. 30m) at temperatures up to 573 K with an accuracy that is appropriate for modeling industrially important systems. In particular, the viscosity of multicomponent systems can be accurately predicted using parameters obtained from single-solute systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022501108317
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  • 89
    Digitale Medien
    Digitale Medien
    The Viscosity of Gaseous n-Butane and Its Initial Density Dependence (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1085-1097 
    Details
    ISSN: 1572-9567
    Schlagwort(e): n-alkanes ; n-butane ; second viscosity virial coefficient ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract New relative high-precision measurements of the viscosity η of gaseous n-butane were carried out in an oscillating-disk viscometer. Seven series of measurements were performed between 298 and 627 K. in the density range from 0.01 to 0.05 mol·L−1. Isotherms recalculated from the original experimental data were analyzed with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficient deduced from the zero-density and initial-density viscosity coefficients for n-butane are in good agreement with the representation of the Rainwater–Friend theory. The new experimental data and some data sets from the literature were used to develop a representation for the viscosity of n-butane in the limit of zero density on the basis of the extended principle of corresponding states. It has been shown that an individual correlation is needed to represent the experimental data between 293 and 627 K with an uncertainty of ±0.4%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022633508086
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  • 90
    Digitale Medien
    Digitale Medien
    Viscous Behavior and Shear-Induced Structural Changes in Perfectly Oriented Liquid Crystals (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1143-1153 
    Details
    ISSN: 1572-9567
    Schlagwort(e): nematic liquid crystals ; nonequilibrium molecular dynamics simulation ; phase transition ; rheology ; smectic liquid crystals ; structure of fluids ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The anisotropy of the viscosity and shear-induced structural changes are studied via nonequilibrium molecular dynamics (NEMD) simulations for two types of model liquid crystals which possess both isotropic and smectic phases. These models are (a) perfectly oriented Gay–Berne particles and (b) r −12-soft-spheres plus an r −6-interaction with a P 2-anisotropy. Results are presented for the Miesowicz viscosity coefficients in the nematic phase. Presmectic effects are observed. Structural changes are revealed by snapshots of configurations and by the static structure factor, presented in analogy to scattering experiments. The shear-induced transition from the smectic to the nematic phase is analyzed. Similarities between magnetorheological fluids and discotic systems which can form columnar phases are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022693726742
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  • 91
    Digitale Medien
    Digitale Medien
    DIPPR Project 882: Transport Properties and Related Thermodynamic Data for Binary Mixtures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 237-245 
    Details
    ISSN: 1572-9567
    Schlagwort(e): critical properties ; data bank ; density ; diffusion coefficients ; evaluated data ; organic mixtures ; solubility ; surface tension ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract DIPPR Project 882 was organized to develop a computerized databank of selected and evaluated physical, thermodynamic, and transport properties for mixtures of primarily organic compounds. The properties include: liquid viscosities, liquid thermal conductivities, mutual diffusion coefficients, excess volumes and densities, surface tensions, critical temperatures, critical pressures and densities, and solubilities of sparingly soluble organic compounds. The collection is not complete. It is estimated that the complete collection covers about 90% of the mixture classes, contains about 85% of the binary systems published, references about 80% of the data sources, and is a repository for about 85% of all the data published (these estimates exclude density and solubility where the coverage was not intended to be comprehensive). Exhaustive literature searches were made. The data from the original literature were assessed and differences from the pure component values derived from the DIPPR Project 801 and other reliable evaluated data sources for pure compounds were noted. In cases where the differences were excessive, the data sets were rejected. The total collection consists of about 2140 mixture/property pairs covering 361 mixture classes. The results of the project are distributed as five books in the series Transport Properties and Related Thermodynamic Data of Binary Mixtures published by the American Institute of Chemical Engineers and in electronic form as the DIPMIX Database on Transport Properties and Related Thermodynamic Data for Binary Mixtures distributed by the Thermodynamics Research Center.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021454919716
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  • 92
    Digitale Medien
    Digitale Medien
    The Viscosity of Gaseous Isobutane and Its Initial Density Dependence1 (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 329-341 
    Details
    ISSN: 1572-9567
    Schlagwort(e): isobutane ; second viscosity virial coefficient ; transport property ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Results of new relative high-precision measurements on gaseous isobutane are reported. Six series, each differing in density, were performed in a quartz oscillating-disk viscometer from 297 to 627 K and for densities between 0.010 to 0.048 mol·L−1. Isothermal values recalculated from the original experimental data were evaluated with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficient derived from the zero-density and initial-density viscosity coefficients agree with the representation of the Rainwater–Friend theory when using energy and length scaling factors specific for the interactions of the isobutane molecules. With the same scaling factors an individual correlation in the limit of zero density was developed including only a few values from the literature. The uncertainty of the zero-density viscosity correlation is estimated to be ±0.4%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006671226710
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