摘要:

In the present work a numerical simulation of the natural convection process in a chemically reacting packed bed has been carried out. The simulation has been based on a Galerkin method of finite element formulation. An investigation of the transient as well as steady state results is presented. The heat source term is represented by an Arrtnhius-type source term, which typically represents several zero-order chemical reactions in practice. The ensuing transient process of natural convection in the cavity is investigated, and the effect of the temperature of the not boundary on the heat removal capacity is also presented. The critical boundary temperature that will result in the thermal runaway inside the cavity was investigated, and the effect of the boundary temperature on the thermal explosion in the cavity was also analyzed. It was found that the flow field was symmetrical about the vertical centertine and the temperatures continued increasing away from the horizontal walls of the cavity, thus giving hot spots in regions removed from the horizontal boundaries of the cavity. The transient results provided some valuable information in terms of the times required for the evolution of the natural convection process in the cavity.

ISSN:1040-7782    

DOI:10.1080/10407789308902609

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A computational methodology is presented for solving natural convection dominated melting and resolidification of a phase change material around two horizontal cylindrical heat sources /sinks spaced vertically. A finite difference method with body-fitted coordinates is employed to handle the irregular boundaries, and a fixed grid enthalpy method is adopted for the phase change problem. Results show that the phase front during the melting and resolidification of the liquid from the upper cylinder is strongly affected by the surface temperature of the lower cylinder. Also, cyclic melting and freezing of the phase change material can result in complex shapes of the solid-liquid interfaces as well as in multiple phase fronts. The shapes of the melted and solidified regions depend on the imposed thermal boundary and the melting and freezing period.

ISSN:1040-7782    

DOI:10.1080/10407789308902610

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Thermal behavior of a liquid drop moving in an incompressible fluid of infinite extent is investigated numerically. Dynamical equations describing the temporal evolution of the flow and temperature fields of dispersed and continuous phases are solved by a hybrid spectral scheme in conjunction with the influence matrix technique to resolve the lack of vorticity boundary conditions. Both Chebyshev and Legendre polynomials are employed to expand the flow variables and temperature in the radial and angular directions, respectively. With the aid of the Galerkin and collocation methods, together with the first-order backward Euler time differencing, the governing partial differential equations reduce to a nonlinear system of algebraic equations. Numerical results reveal a discrepancy between quasi-steady and fully transient analyses at high Peclet numbers.

ISSN:1040-7782    

DOI:10.1080/10407789308902611

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A numerical method is presented for predicting radiation heat transfer from arbitrary bodies composed of numerous polygons. Each polygon is gray and has the comined characteristics of specular and diffuse surfaces. Both heat flux and temperature can be specified arbitrarily on the surfaces. A new concept of view factors was introduced for analyzing radiation heat transfer between specular and diffuse surfaces. A radiation ray tracing method was adopted for estimating the view factors, and efficient vector operation and parallel processing were achieved for a supercomputer. The accuracy of the method was checked in comparison with analytical solutions for a simple configuration, and the effect of specular reflectivity was investigated. As a numerical example, radiation heat transfer of a machine element and healer panels composed of 4388 polygons was demonstrated.

ISSN:1040-7782    

DOI:10.1080/10407789308902612

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper, laminar flow and heat transfer are investigated in the thermal entrance region of a curved elliptic duct. The elliptic duct is subjected to constant wall temperature. The solutions are numerically obtained by employing the control volume based, finite difference method via generation of a boundary-fitted coordinate system. The curvature ratio effect is also included in the formulation of the governing equations. Temperature distribution and local Nusselt numbers are obtained and presented graphically for various Prandtl numbers. Dean numbers, and minor- to major-axis ratios. It is observed that one-eyed isotherms appear in the process of temperature development. Effects of the Dean number and the Prandtl number on heat transfer are discussed in detail. Finally, the asymptotic Nusselt numbers art obtained. Furthermore, accuracy of the present calculations is validated by comparison with some published data available in the open literature. Excellent agreement has been obtained for all cases.

ISSN:1040-7782    

DOI:10.1080/10407789308902613

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This note was inspired by a paper published recently in this journal by T, S. Lee [I]. Here, results of calculations of the same problem are presented, which differ both qualitatively and quantitatively from those of Lee [I]. By using a series of systematically refined grids from 10 x 10 to 160 X 160 control volumes, a second-order discretization method, and an efficient multigrid algorithm, the convergence of the results toward grid independent solutions is demonstrated, and the errors are proven to negligibly small. Features of flows are discussed, and disagreements with results of Lee [I] are analyzed.

ISSN:1040-7782    

DOI:10.1080/10407789308902614

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method is developed for estimating natural convection heat transfer within enclosures for fluids where Pr → 0. The approach requires a coupled solution to Laplace's equation, describing the velocity field, and Poisson's equation, describing the temperature field. The method is used to calculate the heat transfer within a thermally driven cavity for Pr = 0.06, 0.01, and 0.001. The results obtained are in good agreement with accepted results.

ISSN:1040-7782    

DOI:10.1080/10407789308902615

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The present work consists of the comparative evaluation of the finite element method (FEM) and the finite difference method (FDM) for the analysis of free surface transport within a hollow ampule. The phenomenon of motion reversal of the five surfaces obtained earlier by the FDM is also analyzed by the FEM. It is found that the times at which the motion reversal occurs are independent of the applied pressure difference for any fixed dimension of the hollow ampule. Furthermore, it appears that the displacement of the inner and outer free surfaces varies linearly with the magnitude of the applied pressure difference. Finally, detailed comparative discussion is presented on the differences between the results obtained by FDM and FEM.

ISSN:1040-7782    

DOI:10.1080/10407789308902616

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor