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  • 1
    Electronic Resource
    Electronic Resource
    Design and testing of a high-temperature emissometer for porous and particulate dielectrics (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 87-93 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new, high-temperature (500–1500 °C) emissometer has been designed, assembled, and tested. The apparatus is unique in that it may be used to measure the emittance of media that are semitransparent and show substantial surface roughness, internal voidage, and/or chemical inhomogeneities throughout the emitting volume. Data reduction procedures are developed and an analysis of systematic error sources and experimental uncertainty is presented. The emittance of a high-purity alumina was measured at several temperatures in the wavelength range from 2 to 14 μm. Results are compared to published values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139125
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  • 2
    Electronic Resource
    Electronic Resource
    Miniature fiber-optic refractometer for measurement of salinity in double-diffusive thermohaline systems (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 291-296 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Information on salinity and temperature distributions is important in the study of thermohaline systems. In order to overcome difficulties associated with existing measurement methods, a miniature fiber-optic probe has been developed. The probe, which is capable of local quasisteady and fluctuating salinity and temperature measurements, is easily constructed, calibrated, and utilized. Probe measurements compare favorably with results obtained using a slant-wire shadowgraph technique and clearly show local phenomena in double-diffusive thermohaline systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138346
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of salinity distributions in salt-stratified, double-diffusive systems by optical deflectometry (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2538-2542 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Reliable salinity measurements in double-diffusive thermohaline solutions are necessary to understand relevant system behavior. An optical technique, which has previously been used to investigate solute diffusion in isothermal systems, is employed to measure the salinity distribution in a double-diffusive thermohaline system. The technique is verified by comparison with independent salinity measurements, and its use in a double-diffusive system reveals detailed salinity distribution information. When used with the shadowgraph method of flow visualization, the salinity measurement technique permits a more quantitative interpretation of the shadowgraphic results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139107
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of the turbulent flow field in a free-surface jet of water (1995)
    Springer
    Experiments in fluids 18 (1995), S. 397-408 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Measurements of the mean velocity and turbulence intensity are presented for a rectangular jet of water ejecting into a gaseous ambient. Data are reported for streamwise locations up to 30 nozzle widths from the discharge and spanwise locations covering the inner 80% of the jet width. The flow conditions at the nozzle discharge were controlled by using different nozzle designs (parallel-plate and converging) and flow manipulators (wire grid and screens). The results track the mean velocity and turbulence intensity profiles with streamwise distance, highlighting changes in both the profile shapes and magnitudes for both measured quantities. Independent of nozzle configuration, the mean velocity profile was shown to be most nonuniform and the turbulence intensity most nonhomogeneous at the nozzle discharge. With increasing streamwise distance, the mean velocity profile underwent a gradual transition to a completely uniform condition, while the turbulence field decayed and became homogeneous. The rate of viscous dissipation was shown to depend strongly on the nozzle exit condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208462
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  • 5
    Electronic Resource
    Electronic Resource
    Heat transfer through granular beds at high temperature (1984)
    Springer
    Heat and mass transfer 18 (1984), S. 221-226 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wird eine Methode vorgestellt zur Bestimmung der Parameter, die benötigt werden um die Wärmeleitfähigkeiten des Granulates im Festbett ohne Einfluß des Fluids zu korrelieren. Ein Versuchsaufbau wurde entworfen und damit die Wärmeleitfähigkeiten für mehrere Festbett-Konfigurationen über einen großen Temperaturbereich gemessen. Die Messungen lieferten die von einem vorhandenen theoretischen Modell benötigten Parameter, außerdem wurden durch Modelrechnungen die Parameter bestimmt, die Einfluß auf die Wärmeleitfähigkeit haben. Es wurde festgestellt, daß die Wärmeleitfähigkeit mit wachsender Temperaturdifferenz über die Betthöhe ansteigt.
    Notes: Abstract A comprehensive approach has been followed to determine parameters needed to correlate thermal conductances of packed beds comprised of granular opaque particles in a non-participating fluid. An apparatus has been designed and used to measure thermal conductances for several packed beds over a wide temperature range. Parameters required by an existing theoretical model were inferred from the measurements, and model calculations were performed to determine those parameters which affect thermal conductance. The thermal conductance of packed beds has been found to increase with the temperature difference across the bed thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007133
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  • 6
    Electronic Resource
    Electronic Resource
    Numerical study of the effects of transport phenomena on macrosegregation during unidirectional solidification of a binary substance (1992)
    Springer
    Heat and mass transfer 27 (1992), S. 1-10 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Die in einer Richtung ablaufende Verfestigung einer binären Substanz ist mit Hilfe einer kontinuierlichen Formulierung modelliert worden um die durch eine instabile Dichteumkehrung induzierte Strömungsbewegung zu untersuchen. Die lokale und globale Rückverteilung der Teilchen ist in jeder der 3 Simulationen ermittelt worden, um die Einflüsse der Permeabilität der Zwei-Phasen-Region und der Abkühlrate zu erfassen. Die lokale Entmischung von fleckenartigen eutektischen Einschlüssen, die von starken Gradienten in der Zusammensetzung umgeben waren, ist mit, in der breiartigen Region vorhandenen, diskreten Kanälen in Verbindung gebracht worden, die vor einer vollständigen Verfestigung existierten. Diese Kanäle dienten, auf Grund ihres geringsten Widerstandes, dem Transport des zwischen den Dendriten vorhandenen Fluidums zur darüberliegenden Flüssigkeit. Der Großteil der fleckenartigen Einschlüsse befand sich in der am meisten durchlässigen Zwei-PhasenRegion, wohingegen die Bildung dieser Einschlüsse, während der durch Wärmeleitung domierenden Verfestigung, unterbunden wurde, welches im Fall der höchsten Abkühlrate für den längsten Zeitabschnitt auftrat. Die normale Entmischung, in Verbindung mit einer axialen Variation der mittleren Zusammensetzung des Festkörpers, die darauf zurückzuführen ist, daß die Kanäle den Transport des am Lösungsprodukt mangelnden Fluids in der Zwei-Phasen-Region unterbunden haben, wurde ebenfalls ermittelt.
    Notes: Abstract Unidirectional solidification of a binary substance has been modelled using a continuum formulation to investigate the macrosegregation resulting from fluid motion induced by an unstable density inversion. Localized and global species redistribution was predicted in each of 3 simulations, which examined the effects of mushy zone permeability and cooling rate. Localized segregation in the form of freckle segregates, which were composed of eutectic material surrounded by large compositional gradients, was linked to discrete channels that existed in the mushy zone prior to its complete solidification. The channels acted as paths of least resistance for the transport of interdendritic fluid into the overlying bulk liquid. Freckles were most pronounced for the more permeable mushy zone, while conduction dominated solidification, which occurred over the longest interval for the case involving the largest cooling rate, inhibited freckle formation. Due to the rejection of solute deficient (less dense) fluid from the mushy zone via the channels, normal segregation associated with axial variations in the average composition of the solid was also predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589972
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  • 7
    Electronic Resource
    Electronic Resource
    Secondary flow in horizontal channels heated from below (1987)
    Springer
    Experiments in fluids 5 (1987), S. 334-343 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Experiments have been performed to investigate onset and development of the buoyancy driven secondary flow in a horizontal parallel plate channel with uniform bottom heating. Flow visualization in water (Pr ≈ 7) was performed by injecting a continuous sheet of dye into the bottom boundary layer just up-stream of the heated surface, and operating conditions in the ranges 125 〈 Re 〈 1,000 and4.7 x 104 〈 Gr * 〈 8.0 x 106 were considered. Top, side, and end views revealed onset of the secondary flow as thermal plumes, which rise from the heated surface and form pairs of counter-rotating vortices. Subsequent development of the flow is characterized by a breakdown in the regular plume structure and transition to buoyancy driven turbulence. Onset of the secondary flow is advanced by increasing the heat flux and/or decreasing the flow rate, and results may be correlated in terms of a critical Grashof number and a dimensionless longitudinal distance. Liquid crystal sheets applied to the heated surface reveal significant spanwise temperature variations due to the secondary flow. The unsteadiness of the flow is discussed and comparisons are made to previous experimental and numerical work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277712
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  • 8
    Electronic Resource
    Electronic Resource
    Heat transfer, development length, and friction factor correlations for the asymptotic region of a laminar arc constrictor (1969)
    Springer
    Heat and mass transfer 2 (1969), S. 150-162 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Ein genaues Gleichgewichtsmodell für die laminare Strömung eines Plasmas durch den beheizten Bereich eines eingeschnürten Plasmagenerators wird formuliert. Die daraus resultierenden Gleichungen werden für ein Argongas unter Benutzung einer Differenzenmethode gelöst. Die Wandreibung und der Wärmeübergang werden mit Hilfe der Impuls- und Energiegleichungen für einen weiten Bereich von Strömungsmengen und Stromstärken ermittelt. Reibungswiderstandszahlen, berechnet mittels dieser Methode, stehen in Übereinstimmung mit empirischen Werten innerhalb von zehn Prozent. Wärmeübergangswerte stimmen größenordnungsmäßig mit Voraussagen überein, die an Hand eines vereinfachten Lichtbogenmodelles gemacht wurden. Eine dimensionslose Kenngröße, der sogenannte Ohmsche Heizungsparameter, der eigentümlich für den eingeschnürten Lichtbogen ist, wird benutzt für eine Korrelation mit der mittleren Nusselt-Zahl in dem asymptotischen Lichtbogenbereich. Wenn die Stoffwerte der Flüssigkeit auf die Durchschnittstemperatur bezogen werden, dann nimmt das Produkt aus der Reibungswiderstandszahl und der Reynolds-Zahl für Stromstärken unterhalb von 200 Amp einen konstanten Wert an und ändert sich mit dem Ohmschen Heizungsparameter für größere Stromstärken. Dimensionslose Beziehungen für die thermische Einlauflänge werden ebenfalls angegeben; ihre Übereinstimmung mit experimentellen Ergebnissen ist gut.
    Notes: Abstract A rigorous equilibrium model is formulated for the laminar flow of plasma through the heating region of a constricted arc plasma generator. The resulting equations are solved for an argon gas using an implicit finite-difference scheme, and the wall shear stress and heat transfer are computed from momentum and energy balances for a wide range of flow rates and arc currents. Friction factors based on this method are in agreement with empirical values to within approximately 10 per cent, and heat transfer calculations agree with the orders of magnitude predicted by a simplified arc model. A dimensionless number peculiar to the constricted arc, the so-called Ohmic heating parameter, is used to correlate the mean Nusselt numbers in the asymptotic arc regime. When the fluid properties are based on the mean temperature, the product of friction factor and Reynolds number is found to be a constant for currents below 200 Amp and to vary with the Ohmic heating parameter for larger currents. Correlations are also presented for the thermal development length, and the agreement with experiment is good.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751162
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  • 9
    Electronic Resource
    Electronic Resource
    Interaction of external and double-diffusive convection in linearly salt-stratified systems (1986)
    Springer
    Experiments in fluids 5 (1986), S. 49-58 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A series of experiments has been performed for a linearly salt-stratified system heated from below. The experiments were intended to investigate the relative influence of external and double-diffusive convection on (i) entrainment of salt-stratified fluid into adjacent layers of convecting fluid, and (ii) formation of multiple mixed layers within stable, salt-stratified fluid layers. External convection effects were altered by placing a horizontal grid in the convecting fluid layer. An assortment of flow visualization techniques revealed that external convection can strongly influence entrainment of salt-stratified fluid and multiple mixed layer formation. However, the techniques could not resolve the possible significance of the double-diffusive entrainment mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272425
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  • 10
    Electronic Resource
    Electronic Resource
    Solidification of a binary mixture in a square cavity with a free surface (1989)
    Springer
    Heat and mass transfer 24 (1989), S. 279-288 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Die Verfestigung einer NH4Cl-H2O Lösung in einem quadratischen Hohlraum mit freier Oberfläche wurde numerisch und experimentell untersucht. Die Verfestigung ist durch die Koexistenz dreier Phasen, einer festen, eines Zwei-Phasen-Gebietes (fest und flüssig), sowie einer flüssigen gekennzeichnet, wobei die Strömung innerhalb der flüssigen und der Zwei-Phasen-Region durch Oberflächenspannungsgradienten sowie durch einander entgegenwirkende thermische und konzentrationsabhängige Auftriebskräfte angetrieben wird. Theoretische und experimentelle Ergebnisse lassen darauf schließen, daß (i) Oberflächenspannungskräfte eine Zellularströmung im obersten Teil des Hohlraums aufbauen und deren Entwicklung mit fortschreitender Zeit verstärken, (ii) eine Anreicherung dieser oberen Zelle mit Wasser ein Wiedereinschmelzen angrenzender verfestigter Regionen induziert, sowie (iii) der letztlich erreichte statische Endzustand durch eine Liquidusfront, deren Dicke mit zunehmender Tiefe ebenfalls zunimmt, charakterisiert ist. Vorhergesagte und beobachtete Ergebnisse unterscheiden sich jedoch sowohl in bezug auf das chronologische Muster der Mehrzellenströmungsentwicklung als auch in der Zeit, die benötigt wird, um den statischen Endzustand zu erreichen. Die Unterschiede werden den gewählten Modellannahmen und Unsicherheiten, die die Struktur der Zwei-Phasen-Region betreffen, zugesprochen.
    Notes: Abstract Solidification of an NH4Cl-H2O solution in a square cavity with a free surface has been studied numerically and experimentally. Solidification is characterized by the coexistence of solid, mushy (solid plus liquid), and liquid regions, and flow within the liquid and mushy regions is driven by surface tension gradients, as well as by opposing thermal/solutal buoyancy forces. Theoretical and experimental results indicate that (i) surface tension forces spawn a cellular flow at the top of the cavity and enhance its development with increasing time, (ii) water enrichment of the top cell induces remelting of adjoining solid, and (iii) final steady-state conditions are characterized by a liquidus front whose thickness increases with increasing depth. However, predicted and observed results differ with respect to the chronological pattern of multicellular flow development and the time required to achieve steady-state conditions. Differences are attributed to selected model assumptions and to uncertainties concerning mushy region structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01597233
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