Showing papers on "Transport phenomena published in 1975"

Charge pulse studies of transport phenomena in bilayer membranes. I. Steady-state measurements of actin- and valinomycin-mediated transport in glycerol monooleate bilayers.

Abstract: A charge pulse technique has been applied to studies of transport phenomena in bilayer membranes. The membrane capacitance can be rapidly charged (in less than a microsecond). The charge then decays through the membrane's conductive mechanism-no current flows through the solution or external circuitry. The resulting voltage decay is thus a manifestation of membrane and boundary layer phenomena only. There are a number of advantages to this approach over conventional voltage or current-clamp techniques: the rise-time of the voltage perturbation is not limited by the time constant deriving from the membrane capacitance and solution resistance, thus permitting study of extremely rapid rate processes; the membrane is exposed to high voltage for relatively short times and thus can be subjected to higher voltages without breakdown; the steady-state current-voltage behavior of the membrane can be deduced from a single charge pulse experiment; the charge (and therefore the integral of the ion flux through the membrane) is monitored allowing detection of rate processes too rapid to follow directly. In this paper we present what is primarily a steady-state analysis of actin (non-, mon-, din-, trin-)-mediated transport of ammonium ion and valinomycin-mediated transport of cesium and potassium ions through glycerol monooleate bilayers. We introduce the concept of the "intercept discrepancy", a method for measuring charge lost through extremely rapid rate processes. Directly observable pre-steady-state phenomena are also discussed but will be the main subject of part II.

Natural convection heating of liquids, with reference to sterilization of canned food

Abstract: In a model system the physical transport phenomena that occur during the sterilization of a canned liquid food were investigated. Flow phenomena and heat transfer were studied experimentally as well as theoretically. Experiments on flow patterns and temperature profiles revealed a boundary layer flow at the vertical sidewall, a stratified core in the upper part of the container and a perfectly mixed, unstratified region in the lower part of the container. A dimensionless correlation for the overall heat transfer coefficient from steam to liquid was determined. From the observed flow patterns and temperature profiles a simplified mathematical model was developed, with which temperature stratification in the liquid during heating could be simulated. The applicability of the simplified model for lethality calculations was briefly examined. Some attention was also paid to the effect of solid particles on heating characteristics of the container contents. Literature on the research of convection heating of liquids in closed containers was reviewed, as well as literature about the influence of temperature stratification on natural convection boundary layer flow.

An introduction to fluid mechanics and heat transfer, with applications in chemical & mechanical process engineering.

Abstract: Preface List of symbols Dimensionless ratios 1. Introduction and definitions 2. Fluid flow 3. The energy and momentum equations 4. Applications of the continuity, energy and momentum equations 5. Dimensional analysis applied to fluid mechanics 6. Flow in pipes and channels 7. Pumps and compressors 8. Heat conduction and heat transfer 9. Heat exchangers 10. Dimensional analysis applied to heat transfer 11. Heat transfer and skin friction in turbulent flow 12. Equations of motion for a viscous fluid 13. Boundary layers 14. Turbulent flow 15. Potential flow 16. Diffusion and mass transfer 17. The energy equation and heat transfer 18. Forced convection 19. Compressible flow in pipes and nozzles 20. Open-channel flow 21. Solid particles in fluid flow 22. Flow through packed beds and fluidized solids 23. Condensation and evaporation Appendix 1. Engineer's guide to vector analysis Appendix 2. Equations of motion for an inviscid fluid Appendix 3. Vorticity and circulation Appendix 4. Stress components in a viscous fluid and the equations of motion Appendix 5. Laminar boundary-layer flow Appendix 6. Heat transfer with laminar flow in a pipe Appendix 7. Conversion factors Examples Outlines solutions Index.

Transport phenomena of viscoelastic fluid in cross flow around a circular cylinder

Abstract: The dynamic equation with the generalized Maxwell model is solved numerically in moderate Reynolds number range. The results of calculation reveal the effect of elasticity in cross flow around a circular cylinder. The electrochemical method is used for the measurement of Sherwood number in cross flow of dilute polymer solutions. Comparison of calculated values with the experimental results shows good agreement.

Sensitivity of Laser Absorption Wave Formation to Nonequilibrium and Transport Phenomena

Abstract: Experiments have shown that laser absorption waves (LAW's) may be ignited in air from aerosols or solid surfaces at laser intensities below the clean air breakdown threshold. We present detailed numerical calculations of the formation and structure of such LA W's made with a two-temperature, Laprangian hydrodynamic computer program containing a fully coupled nonequilibrium breakdown chemistry, electron diffusion, and radiation transport. The detailed LAW structure is then interpreted to delineate the roles of the nonequilibrium, radiative, and transport processes in various regimes.

Departures from Fourier's law

Abstract: The constitutive equations for three heat conductors which depart from Fourier's Law in non-classical ways are derived.

Transport phenomena in Zonal centrifuge rotors: X. optimal gradient solution for velocity sedimentation

Abstract: An analysis is made to determine an optimal profile of a density gradient solution for a velocity-sedimentation method. A density-gradient solution is characterized by density and viscosity profiles as functions of radial distance from the rotatio axis. It is found that the optimal density-gradient solution is one whose density increases as the two-thirds power and whose viscosity increases as the one and one-third power of the radial distance. An optimal centrifugation time for a velocity sedimentation method is also derived in terms of known quantities, i.e., the light-end gradient density and viscosity, the standard sedimentation coefficients and densities of the particles to be separated, etc.

On entropy-free thermodynamics in solid and fluid mixtures

Abstract: The entropy-free thermodynamics, developed and discussed byJ. Meixner for one component systems, is extended to fluid and solid mixtures. The constitutive equations are formulated and their consequences for heat conduction, sound propagation and diffusion are given.