Showing papers on "Transport phenomena published in 1982"

Transport Phenomena with Single Aerosol Particles

Abstract: This is a review of theory and experiments related to single aerosol particle transport processes. The theories of mass, heat, momentum, and charge transfer are outlined, with emphasis on mass transport in the continuum and noncontinuum regimes. Included in the discussion of mass transfer are single and multicomponent droplet evaporation, a comparison of the results of solutions of the Boltzman equations for Knudsen aerosol evaporation and growth and experimental methods for the study of single droplet evaporation or growth. Of particular concern here are the experimental apparati and techniques developed for single particle measurements. These range from the Millikan oil drop experiment through the electrostatic balance (the Millikan condenser with automatic stabilization of the particle) to the electrodynamic balance. The principles and applications of these instruments are reviewed.

Transport equations for multicomponent anisotropic space plasmas - A review

Abstract: An attempt is made to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic field configurations, multicomponent plasma flows with large temperature differences between the interacting species, and plasma flows that contain anisotropic temperature distributions. In addition, if Maxwell's equations of electricity and magnetism are added to the system of transport equations, they can be used to model electrostatic shocks, double layers, and magnetic merging processes. These transport equations also contain terms which act to regulate both the heat flow and temperature anisotropy, processes which appear to be operating in the solar wind.

Transport properties in a spin polarized gas, II

Abstract: The general results obtained in a preceding article (with the same title) are appliede to the study of transport phenomena in a spin polarized gas at low temperature, with particular emphasis on particle indistinguishability effects in collisions. A simple theory of spin diffusion is pressented and the response of the gas to a spin orientation gradient is calculated, taking into account the "identical spin rotation effect". The hydrodynamic equations of evolution of the spin orientation give rise to oscillations (spin waves). .....

Advances in Transport Processes

Abstract: 1. Optical Techniques in Transport Phenomena (C.V. Herman, D. Mewes and F. Mayinger). 2. Heat and Fluid Flows in Manufacturing Processes (Wen-Jei Yang). 3. Impinging-Stream Contactors: Fundamentals and Applications (A. Tamir). 4. Indirect Liquefaction of Coal: Fischer-Tropsch Synthesis and Transport Processes in Slurry Bubble Column Reactors (S.C. Saxena). 5. Crystallization (A. Mersmann). 6. Discontinuities and Interfaces in Transport Phenomena Coupled with Kinetics and Relaxation (G. Astarita and R. Ocone). 7. Radiative Heat Transfer Enhancement to Layers of Semitransparent Fluids (M. Hasatani and Y. Itaya). 8. Czochralski Process (A. Hirata, Y. Okano, K. Yakushiji and B. Harrison). 9. Engineering Analyses of Foam Columns (D. Desai and R. Kumar). Index.

Dispersion resulting from flow through spatically periodic porous media II. Surface and intraparticle transport

Abstract: A rigorous theory of Brownian particle flow and dispersion phenomena in spatially periodic structures is presented within the context of generalized Taylor dispersion theory. The analysis expands upon a prior work, which was limited to transport within the continuous phase, to include convective and diffusive transport of the tracer particle within the interior of the discontinuous phase, as well as surface adsorption and transport along the phase boundary separating the discontinuous and continuous phases. Incorporated within the generalization are considerations of tracer particles of non-zero size, and situations wherein external forces act upon the tracer, the novel effect of each being to cause the tracer to move with a different velocity from that of the fluid in which it is suspended. Applications to various chromatographic separation phenomena are cited. Extensions of the analysis to heat-transfer problems and to situations involving homogeneous, first-order chemical reactions are also made. Both Eulerian and Lagrangian interpretations of the tracer transport phenomena are given.

Turbulent Heat Transfer

Abstract: Heat transfer problems in turbulent flows are mainly described by empirical relationships Nu = Nu(Re, Pr). The progress of modeling the turbulent heat transfer is quite poor. For the turbulent momentum transfer on the other hand we have a lot of semiempirical modeling assumptions which lead to good results for engineering purposes. After an introduction into the closure assumptions for the turbulent momentum transfer the turbulent heat transfer, in particular the turbulent Prandtl number are discussed. Finally a model to predict the turbulent Prandtl number is proposed. It can be used to calculate heat transfer correlations Nu(Re, Pr).

Sound and transport phenomena in spin-polarized3He-4He solutions

Abstract: Transport phenomena in partially spin-polarized3He-4He solutions are investigated. The polarization causes considerable changes in kinetic coefficients and also gives rise to new dissipative processes, such as spin thermodiffusion and second viscosity. The transport coefficients are calculated for degenerate and nondegenerate3He↑-4He solutions. The absorption of first- and second-sound waves is studied. Second-sound propagation is affected by weak dipole interactions and its velocity depends significantly on the frequency.

Behaviour of oxygen impurities in the Frascati Tokamak

Abstract: The transport of oxygen in a high-density, long-duration discharge of the Frascati Tokamak (FT) was studied both experimentally and numerically. Low ionization states peak quite internally where Te=150 eV and ne=0.8 1014 cm-3. A code (OSSFTC) was prepared including atomic processes and transport phenomena. Neoclassical collisional transport and charge exchange processes are inadequate to justify this phenomenon and there is evidence of strong anomalous diffusion. The values and the radial dependence of the diffusion coefficient are presented for different phases of the discharge.

Correlation and prediction of thermophoretic and inertial effects on particle deposition from non-isothermal turbulent boundary layers

Abstract: The problem of small particle deposition which can cause hot stage corrosion and/or fouling in combustion turbines operating on fuels containing ash or inorganic salts is investigated Two boundary layer transport phenomena are shown to assume importance in these cases: particle thermophoresis (migration down a temperature gradient) and particle inertia Thermophoretic and eddy transport across turbulent boundary layers without and with particle inertia effects are quantitatively analyzed The effects of streamwise blade curvature on particle transport across turbulent boundary layers are determined It is shown that these phenomena destroy the analogy between mass and heat transfer or mass and momentum transfer Also studied are the effects on particle deposition of distributed or localized wall blowing, surface roughness, and mainstream turbulence

Finite Element Techniques in Transport Phenomena

Abstract: A wide spectrum of processes involving transport of physical quantities of a variety of types can be successfully modeled by assuming that the transport takes place mainly through the basic processes of diffusion and convection.

Heat conduction in a nearly collisionless molecular gas

Abstract: Transport phenomena in molecular gases and the respective field effects have so far been analyzed in the hydrodynamic and Knudsen regimes. In between there is a rather large gap covered by the transition regime. For the case of heat conduction through a diatomic diamagnetic gas between parallel plates an attempt is made to partially bridge the gap by the beginning of a density expansion derived through iteration of an integral form of the Boltzmann equation. Second-order perturbation in non-sphericity of both intermolecular and gas-wall interactions is applied to determine the effect of a magnetic field. Explicit expressions are derived for a simple model.

Influence of a turbulent diffusion flame on transport phenomena to a reacting surface

Abstract: To study the influence of a turbulent diffusion flame on transport phenomena to a reacting surface we used a previously designed simulation apparatus Velocity, temperature and turbulence profiles were obtained by laser doppler velocimetry and compensated thermocouples measurements Stable species profiles were obtained by chromatographic analysis of samples withdrawn from the reactive zone We developed a q -e turbulence model and a probabilistic combustion model Agreement between theory and experiment is particularly good for mean temperature and velocity values, heat flux to the wall, mass burning rates and mass transfer numbers The velocity overshoot is also predicted satisfactorily and related to the increase of the pressure gradient For the turbulence intensity, agreement is good below the flame, above it the discrepancy is related to low-frequency flame oscillations due to the diffusion of transverse temperature perturbation Finally, this model can be used to study the influence of turbulence on the mass burning rate of solid materials

A scaling analysis of thermoacoustic convection in a zero-gravity environment

Abstract: This paper presents a scaling analysis of a one-dimensional thermoacoustic convection heat transfer process in a zero-gravity environment. The relative importance of the terms in the governing equations is discussed for different time scales without attempting to solve the equations. The scaling analysis suggests certain generalizations that can be made in this class of heat transfer problems.

Plasma transport drift equations

Abstract: The problem of describing a collision-dominated plasma in a strong magnetic field in terms of the transport equations is investigated It was pointed out earlier that the standard Braginskii-type equations are limited in scope, and various generalizations of these equations to make them applicable to a plasma in a magnetic field with straight force lines were proposed In contrast, the present authors derive transport equations for an arbitrary magnetic-field geometry, using as a basis a drift kinetic equation with a collision term The obtained system of transport equations reduces to equations for the density, longitudinal velocity, and temperature for each plasma component These equations contain the so-called drift fluxes and forces, constituting certain combinations of higher moments By way of example of the use of the drift transport equations, the problem of plasma rotation in a tokamak is considered The authors propose that the new transport equations will be found useful also for an analysis of the role of viscosity and thermal conductivity in the instabilities and transport phenomena in a plasma confined by a curvilinear magnetic field

Nonlinear Transport Phenomena in MX3

Abstract: It was confirmed from experiments of the Hall effect that the non-linear conductivity of NbSe3 results from depinning of CDW's. The non-linear conductivity was also observed in the monoclinic phase of TaS3. The field dependence of the conductivity was very similar to that observed in the CDW state of NbSe3.

The calculation of transport phenomena in electromagnetically levitated metal droplets

Abstract: A mathematical representation has been developed for the electromagnetic force field, fluid flow field, and solute concentration field of levitation-melted metal specimens. The governing equations consist of the conventional transport equations combined with the appropriate expressions for the electromagnetic force field. The predictions obtained by solving the governing equations numerically on a digital computer are in good agreement with lifting force and average temperature measurements reported in the literature.

Transport phenomena in dissociating gases

Abstract: On the basis of the Chapman—Enskog method, a mathematical formalism of kinetic theory is developed for investigating transport phenomena in rarefied gases with allowance for an equilibrium dissociation reaction. The contribution of the dissociation collision integrals to the transport coefficients is estimated. The results of the estimate show that the presence of dissociation collisions in the gas does not have an appreciable influence on the coefficients of shear viscosity, thermal conductivity, and diffusion. On the other hand, the influence of the equilibrium dissociation reaction on the coefficient of bulk viscosity must be appreciable.

Transport phenomena of hydrogen diluted in argon at high temperatures

Abstract: The present course of study presents the transport properties of the hydrogen/Argon mixtures at different percentages of hydrogen in argon at high temperatures. Hydrogen has been selected because it is an exceptionally clean fuel and is superior to natural gas and oil in many engine combustion applications at data of its transport properties are needed especially at high temperatures. The calculations of the transport properties of the mixtures are based on Chapman - Enskog expansion. The viscosity and the thermal conductivity and diffusion have been calculated and the results are plotted against temperatures.