D. R. Jeng

Momentum and heat transfer on a continuous moving surface in a power law fluid

This analysis examines the momentum and heat transfer occurring in the laminar boundary layer on a continuously moving and stretching two-dimensional surface in a non-Newtonian power law fluid. The Merk-Chao series expansion is used to generate ordinary differential equations from the partial differential momentum equation in order to obtain universal velocity functions. For the problem of combined momentum and heat transfer in the boundary layer of the moving sheet, a general power series is used to describe the fluids velocity and temperature. Examples for a non-linear surface velocity and a linearly stretching surface velocity are provided.

Momentum and Heat Transfer on a Continuous Moving Surface

Determination du transfert de chaleur et de quantite de mouvement dans la couche limite laminaire sur une surface mobile avec une vitesse de surface arbitraire et une temperature de surface non uniforme

Momentum and heat transfer in power-law fluid flow over two-dimensional or axisymmetrical bodies

Abstract Momentum and heat transfer in power-law fluid flow over arbitrarily shaped two-dimensional or axisymmetrical bodies are examined theoretically. The Merk type of series expansion technique is used for the momentum analysis. For convective heat transfer, a generalized coordinate transformation is employed to analyze the temperature field in a laminar boundary layer for the body with a step change in the surface temperature distribution. In both momentum and heat transfer, the solution to the governing equations are obtained as universal functions which are independent of the geometry of the problem. The numerical and closed-form solution to the universal functions are found and then applied to analyze wedge flow and flow over a circular cylinder.

Momentum and heat transfer in a power-law fluid with arbitrary injection/suction at a moving wall

Abstract The momentum and heat transfer in the laminar boundary layer of a non-Newtonian power-law fluid flowing over a flat plate, which is moving in the direction opposite to the uniform main stream, and with arbitrary fluid injection/suction along the plate surface, are analyzed. The partial differential equations are decomposed into a sequence of ordinary differential equations using the Merk–Chao series to obtain universal velocity and temperature functions that are independent of the fluid injection/suction distribution profile. Results are tabulated as a function of the problem parameters. Friction coefficients and Nusselt numbers are calculated for constant fluid injection/suction along the plate.

Mixed convection to power-law fluids from two-dimensional or axisymmetric bodies

Abstract Momentum and heat transfer in mixed-convective, power-law fluid flow over arbitrarily shaped two-dimensional or axisymmetric bodies are examined theoretically. The Merk-Chao series expansion technique, with three mixed convection parameters, is used for the analysis. Solutions to the governing equations are obtained as universal functions which are independent of the geometry of the problem. Using the wall derivatives of these universal functions, results are given for the flow over the flat plate, the horizontal circular cylinder and the sphere. The results are compared with the literature for the limiting cases of forced and natural convection.

Numerical simulation of rarefied gas flow through a slit

Two different approaches, the finite-difference method coupled with the discrete-ordinate method (FDDO), and the direct-simulation Monte Carlo (DSMC) method, are used in the analysis of the flow of a rarefied gas from one reservoir to another through a two-dimensional slit. The cases considered are for hard vacuum downstream pressure, finite pressure ratios, and isobaric pressure with thermal diffusion, which are not well established in spite of the simplicity of the flow field. In the FDDO analysis, by employing the discrete-ordinate method, the Boltzmann equation simplified by a model collision integral is transformed to a set of partial differential equations which are continuous in physical space but are point functions in molecular velocity space. The set of partial differential equations are solved by means of a finite-difference approximation. In the DSMC analysis, three kinds of collision sampling techniques, the time counter (TC) method, the null collision (NC) method, and the no time counter (NTC) method, are used.

Convective heat transfer through boundary layers with arbitrary pressure gradient and non-isothermal surfaces

Abstract The solution method introduced by Chao and Cheema in their study of forced convection wedge flow with non-uniform surface temperature has been generalized to treat general two-dimensional and axisymmetric boundary-layer flows with non-uniform surface temperature. By the introduction of appropriate transformation variables, the equations for the temperature profile and the local wall heat flux can be expressed explicitly in terms of the Prandtl number and the wedge parameter for a step discontinuity in wall temperature. Numerical examples for an isothermal surface and for a wall temperature step change for a circular cylinder are given and are compared with values obtained from other formula available in the literature.

Thermal Contact Resistance in Vacuum

Similar or dissimilar materials thermal contact resistance in vacuum with negligible film effect, obtaining constriction resistance

Forced convection over rotating bodies with non-uniform surface temperature

Abstract An analytical method is developed for obtaining the temperature distribution and the rate of heat transfer in laminar boundary-layer forced convective flow over a rotating body of revolution having a step change in surface temperature. By using a special coordinate transformation and an appropriate series expansion of the temperature, the energy equation becomes expressible in terms of a set of partial differential equations which contain universal functions. These universal functions can be tabulated once and for all. Numerical examples are presented for an isothermal surface and for a surface which has a step discontinuity in temperature for the special cases of a rotating sphere and a rotating disk. These results are compared with values obtained from other formulas available in the literature.

A study of two limiting cases in convective and radiative heat transfer with nongray gases

Abstract A study is made for two optical limits in a convective and radiative heat-transfer process for nongray gases flowing in a circular tube having a constant uniform wall temperature. The governing energy equations which are valid for the optically thin and the large path length limits are obtained for fully developed laminar flow with a non-black wall. Numerical results for the temperature profiles, local conductive, radiative and total heat fluxes are obtained and the validity of these limiting cases is discussed.