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  • Chemical Engineering  (87)
  • Aerodynamics
  • FLUID MECHANICS AND HEAT TRANSFER
  • GENERAL
  • Inorganic Chemistry
  • 1995-1999  (129)
  • 1990-1994
  • 1955-1959
  • 1995  (129)
Collection
Publisher
Years
  • 1995-1999  (129)
  • 1990-1994
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1413-1425 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adsorption of ethane from helium was measured in beds packed with 2.5 μm zeolite crystals and containing either a single hollow fiber or multiple fibers. THe single-fiber experiments indicate that the mass-transfer rate in bends containing zeolite 13X is limited by diffusion across the fiber wall and through macropores. FOr adsorption in single-fiber beds packed with zeolite 4A, mass transfer is limited by micropore diffusion within the particles. Breakthrough curves from beds containign 13X are adequately described with the linear driving force model, while curves from beds containing 4A are consistent with the Rosen model.Breakthrough curves from beds packed with zeolite 13X and containing multiple fibers can be predicted from the experiments with single-fiber beds when the fibers are evenly spaced. When fibers are unevenly spaced, the breakthrough curves are more disperse. Unevenly spaced fibers are the normal case. Even when fibers are evenly spaced, the productivity of hollow-fiber beds is expected to be no greater than that in conventional beds.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An investigation into the effect of isothermal aging on the development of transverse cracks in cross-ply laminates of two high temperature composite systems was performed. The composite materials investigated were BASF X5260/640-800 and DuPont Avimid K/IM6. Changes in the glass transition temperature, composite weight loss, crack density, and mode I intralaminar fracture toughness were monitored during isothermal aging in air at 177°C for up to 2232 h. The two laminate configurations used in this study include two variations of the generic cross-ply configuration [02/90n]s, in which n equals 1 and 2. The results of this investigation show that a layer of degraded material forms at the surface of the X5260/640-800 bismaleimide laminates and that the thickness of the degraded layer increases with aging time. After 744 h of aging, transverse cracks form in the surface plies and an increasing crack density evolves as aging time is increased; however, transverse cracks do not form in the inner 90° ply groups with aging during the time period investigated. The Avimid K/IM6 thermoplastic polyimide laminates, which show evidence of cracking prior to aging, do not exhibit any significant change in crack density with aging. The results of the aging experiments also show that the bismaleimide system exhibits a weight loss of 1.5% and an increase in glass transition temperature from 250°C to 300°C after 2232 h of aging at 177°C, while the thermoplastic polyimide system shows a weight loss of only 0.05% and an increase in glass transition temperature from 280 to 285°C after 2232 h. Changes in the resistance to crack formation are also seen in these materials during aging. The mode I intralaminar fracture toughness, a measure of resistance to transverse crack formation, shows a 50% decrease after aging for 2232 h for the bismaleimide system, while the behavior exhibited by the thermoplastic polyimide shows little evidence of a reduction.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 649-657 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The residence time distribution of the liquid phase within a three-phase monlith reactor is determined using tracer studies. The actual liquid residence time in the monolith, relevant for reactor design purposes, is calculated from overall residence time measurements using deconvolution by Fourier transform. The liquid-phase residence time decreases as liquid or gas flow rates increase, but the reactor Peclet number remains approximately constant. The residence time distribution and calculated values of the Peclet number reveal that the liquid phase is substantially well-mixed. Comparison with results from experiments in a single glass capillary reveals that the monolith channels become predominantly liquid-filled, particularly as the liquid flow rate becomes a significant fraction of the total flow rate.
    Additional Material: 13 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 446-455 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Studies of heat and mass transfer in packed beds, which disagree substantially in their findings, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse irregular shapes and sizes. We, in 349 runs, measured mass-transfer rates from naphthalene particles buried in packed beds by passing through air at room temperature. An exact analogy between convection of heat and mass makes it possible to infer heat-transfer coefficients from measured mass-trans-fer coefficients and fluid properties. Some beds consisted of spheres, naphthalene and inert, of the same, contrasting or distributed sizes. In some runs, naphthalene spheres were buried in beds of crushed shale, some in narrow screen ranges and others with a wide size range. In others, naphthalene lozenges of different shapes were buried in beds of crushed shale in various bed axis orientations. This technique permits calculation of the mass-transfer coefficient for each active particle in the bed rather than, as in most past studies, for the bed as a whole.The data are analyzed by the traditional correlation of Colburn jD vs. Reynolds number and by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: local Reynolds number should be based on the active-particle size, not the average for the whole bed; differences between shallow and deep beds are not appreciable; mass transfer is 26% faster for spheres and lozenges buried in shale than in all-sphere beds; orientation of lozenges in shale beds has little or no effect on mass-transfer rate; and for mass or heat transfer in shale beds, log(j·∊) = - 0.0747 - 0.6344logNRe + 0.0592log2 NRe.
    Additional Material: 15 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 337-345 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The monolith froth reactor, involving two-phase flow and a monolith catalyst, is developed. The flow within monolith channels, consisting of trains of gas bubbles and liquid slugs, is produced by forming a two-phase froth in a chamber immediately below the bottom of the monolith. The froth then flows upward into the monolith channels through pressure forces, which differs from previous methods since it may be carried out for a commercial-scale reactor. Because the liquid film which develops between the gas phase and the surface of the catalyst is extremely thin, two-phase flow within a monolith can provide reaction rates which are near their intrinsic values. Catalytic oxidation of aqueous phenol over copper oxide supported on γ-Al2O3 is used as a model reaction for investigating reactor performance. Generation of a froth is confirmed by visual inspection; the average bubble size is approximately that predicted by a force balance. The effect of externally controllable process variables (liquid and gas flow rates, temperature, and pressure) on the rate of phenol oxidation was investigated. Reaction rate increases with temperature or pressure increase and decreases with gas flow rate increase, achieving a maximum with respect to liquid flow rate. The activation energy calculated from the apparent reaction rate measured in the monolith froth reactor is similar to that of intrinsic value, suggesting minimal mass-transfer limitations.
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 202-210 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The melt viscosity of thermoplastic starch has been investigated as a function of temperature, moisture content, and processing conditions. The effects of various low molecular weight additives have also been studied. Starch melts exhibit power law behavior over the range of shear rates studied. Melt viscosity decreased with increasing temperature and moisture content (MC). The power law index m increased with increasing temperature. The consistency K decreased with increasing temperature and increasing moisture content. Moisture content during the pelletizing step influenced melt viscosities measured after equilibration to different MCs. All additives studied except glycerol monostearate (GMS) significantly lowered the melt viscosity of starch, some more effectively than water relative to starch with 15% MC. Starch with GMS had viscosities essentially the same as, or slightly higher than, starch/water. This behavior may be due to the presence of unmelted helical inclusion complexes of starch and GMS. Starch formulations at 160°C exhibited melt visocosities similar to an LDPE of melt index 1.8.
    Additional Material: 16 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1117-1123 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Double yields, as well as other complex yielding behavior, that are observed during the tensile deformation of the polyethylenes have been studied in a systematic manner. The conditions under which such yielding is observed were established by studying a set of linear polyethylenes and well-characterized ethylene copolymers of narrow molecular weight and composition distributions. A wide range in crystallinity levels were developed and the rate of deformation and the deformation temperature were varied. These experimental results make clear why such complex yielding processes are not always observed. A qualitative explanation, based on the postulate of a partial melting-recrystallization process during deformation, is given that encompasses all of the experimental data.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: Perfluorovinyl amine ; X-ray crystal structure ; nucleophile ; electrophile ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktion von Perfluorvinyl-Morpholin und Perfluorvinyl-Pyrrolidin mit Nukleophilen und ElektrophilenEs wird die Umsetzung von monofunktionellen und bifunktionellen Nukleophilen sowie des Elektrophils FNO mit Perfluorvinylaminen mitgeteilt. Die Perfluorvinylamine CF=CF2 und CF=CF2 wurden mit Dimethylamin und Diethylamin in Gegenwart kleiner Mengen Wasser umgesetzt zu CHFC(O)N(CH3)2 (1), CHFC(O)N(CH3)2 (2), bzw. CHFC(O)N(C2H5)2 (3). Mit Perfluorvinylpyrrolidin und Perfluorvinylmorpholin ergibt Ethanolamin die cyclischen Produkte CHF (4) bzw. CHF (5). Die Reaktion der Vinylamine mit (CH3)3SiOCH2CF3 in Gegenwart katalytischer Mengen von CsF ergibt cis- (6) und trans- (7) CF=CF(OCH2CF3) sowie cis- (8) und trans-(9) CF=CF(OCH2=CF3). Das elektrophile FNO reagiert langsam mit Perfluorvinylpyrrolidin und Perfluorvinylmorpholin und schneller mit (CH3)3CCF=CF2 zu CF(NO)CF3 (10), CF(NO)CF3 (11) bzw. (CF3)CF(NO)CF3 (12). Die Einkristall-Röntgen-Analyse wird zur Klärung der Produkte der kontrollierten Hydrolyse der Sultone von Perfluorvinylpyrrolidin wie des Sulfonsäureanhydrids C(O)CF2OS(O)2OCF2C(O) (13) eingesetzt. Die Röntgenstruktur von Perfluorbernsteinsäure · Monohydrat (14), die durch Hydrolyse von Perfluorvinylpyrrolidin mit einem Überschuß an Wasser erhalten wurde, wird erstmals mitgeteilt.
    Notes: In this study, both monofunctional and bifunctional nucleophiles, as well as the electrophile FNO, are reacted with perfluorovinyl amines. The perfluorovinyl amines CF=CF2 and CF=CF2 have been reacted with dimethylamine and diethylamine in the presence of small amounts of water to give CHFC(O)N(CH3)2 (1), CHFC(O)N(CH3)2 (2), and CHFC(O)N(C2H5)2 (3). With perfluorovinyl pyrrolidine and perfluorovinyl morpholine, ethanolamine gives the cyclized products CHF (4) and CHF (5), respectively. Reaction of the vinyl amines with (CH3)3SiOCH2CF3 in the presence of catalytic amounts of CsF results in the formation of cis- (6) and trans- (7) CF=CF(OCH2CF3) and cis- (8) and trans- (9) CF=CF(OCH2CF3). The electrophile FNO reacts slowly with perfluorovinyl pyrrolidine and perfluorovinyl morpholine, and more rapidly with (CF3)3CCF=CF2 to give CF(NO)CF3 (10), CF(NO)CF3 (11) and (CF3)3CF(NO)CF3 (12), respectively. Single crystal X-ray analysis is used to confirm the identity of the product obtained from the controlled hydrolysis of the sultone of perfluorovinyl pyrrolidine as the sulfonic acid anhydride C(O)CF2OS(O)2OCF2C(O) (13). The X-ray crystal structure of perfluorosuccinic acid monohydrate (14), which is obtained when the perfluorovinyl pyrrolidine sultone is hydrolyzed in excess water, is also reported for the first time.
    Additional Material: 4 Ill.
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  • 9
    Publication Date: 2013-08-31
    Description: Get Away Special (GAS) payload G-093, also called VORTEX (VOrtex Ring Transit EXperiment), is an investigation of the propagation of a vortex ring through a liquid-gas interface in microgravity. This process results in the formation of one or more liquid droplets similar to earth based liquid atomization systems. In the absence of gravity, surface tension effects dominate the drop formation process. The Shuttle's microgravity environment allows the study of the same fluid atomization processes as using a larger drop size than is possible on Earth. This enables detailed experimental studies of the complex flow processes encountered in liquid atomization systems. With VORTEX, deformations in both the vortex ring and the fluid surface will be measured closely for the first time in a parameters range that accurately resembles liquid atomization. The experimental apparatus will record images of the interactions for analysis after the payload has been returned to earth. The current design of the VORTEX payload consists of a fluid test cell with a vortex ring generator, digital imaging system, laser illumination system, computer based controller, batteries for payload power, and an array of housekeeping and payload monitoring sensors. It is a self-contained experiment and will be flown on board the Space Shuttle in a 5 cubic feet GAS canister. The VORTEX Project is entirely run by students at the University of Michigan but is overseen by a faculty advisor acting as the payload customer and the contact person with NASA. This paper summarizes both the technical and programmatic aspects of the VORTEX Project.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Goddard Space Flight Center, The 1995 Shuttle Small Payloads Symposium; p 221-229
    Format: application/pdf
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  • 10
    Publication Date: 2019-06-28
    Description: In the interaction of an acoustic field with a moving airframe the authors encounter a canonical initial value problem for an acoustic field induced by an unsteady source distribution, q(t,x) with q equivalent to 0 for t less than or equal to 0, in a medium moving with a uniform unsteady velocity U(t)i in the coordinate system x fixed on the airframe. Signals issued from a source point S in the domain of dependence D of an observation point P at time t will arrive at point P more than once corresponding to different retarded times, Tau in the interval (0, t). The number of arrivals is called the multiplicity of the point S. The multiplicity equals 1 if the velocity U remains subsonic and can be greater when U becomes supersonic. For an unsteady uniform flow U(t)i, rules are formulated for defining the smallest number of I subdomains V(sub i) of D with the union of V(sub i) equal to D. Each subdomain has multiplicity 1 and a formula for the corresponding retarded time. The number of subdomains V(sub i) with nonempty intersection is the multiplicity m of the intersection. The multiplicity is at most I. Examples demonstrating these rules are presented for media at accelerating and/or decelerating supersonic speed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-198162 , NAS 1.26:198162 , ICASE-95-39
    Format: application/pdf
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