ISSN:0149-5720    

DOI:10.1080/10407788708913540

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Natural convective motion within a three-dimensional rectangular enclosure is numerically simulated using a time-split finite-element method. Differential heating from either the side or bottom surface is examined for Rayleigh numbers of 104and 105with a Prandtl number of 1.0. The time-dependent primitive equations of motion are solved using a form of the SIMPLE algorithm. Linear basis functions are used with a dissipation parameter based on a Petrov-Galerkin procedure. A simple tridiagonal solver is used to obtain the solution to the matrix set of equations. Three-dimensional stereographic images of the results are displayed.

ISSN:0149-5720    

DOI:10.1080/10407788708913541

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In this work the applicability of the combined bulk convection and gradient transport hypotheses for modeling turbulent diffusion is investigated. The resulting model equation, namely the one-equation model, is solved for free-shear flows by an implicit finite-difference method. Results indicate that significant improvements over previous models can be achieved with this new formulation of turbulent diffusion for both heat and momentum transport.

ISSN:0149-5720    

DOI:10.1080/10407788708913542

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Natural convection and heat transfer in a vertical air slot partitioned by corrugated plates have been analyzed by the finite-element method to investigate the heat transfer characteristics as an insulating wall. The modified Galerkin method was used for the formulation. The computations were performed for the Prandtl number 0.7 in the Rayleigh number range from 103to 106. Two thermal boundary conditions were considered for the partition plate: the conduction case and the no-thickness case. In the case of no thickness, radiation heat flux was included in the heat balance on the partition plate. The radiation effect was examined for a wide range of emissivities. The heat transfer performance was compared with that for the flat partition plate case. Both convection and radiation heat transfer rates for the corrugated partition plate are less than those for the flat partition plate.

ISSN:0149-5720    

DOI:10.1080/10407788708913543

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The unsteady natural convection flow in a square cavity at high Rayleigh numbers Ra = 107and 2 × 107, has been treated by using a spline method of fractional steps in each coordinate direction. The essential features of this method are that in each computation step the problem is treated as a one-dimensional case and in the implicit form, and only one tridiagonal matrix system is evaluated. In general, it is not necessary to evaluate the first and second derivatives, and additional boundary conditions are not required. Hence the computer time can be shortened and the storage requirement reduced. The technique represents an improvement over the spline-alternating direction implicit method. Numerical results have been obtained at high Rayleigh numbers. The main features of the transient flow from zero conditions are in good agreement with the theoretical predictions [1, 2]. The steady-state results have been compared with accurate solutions presented recently for Ra = 107.

ISSN:0149-5720    

DOI:10.1080/10407788708913544

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A numerical model was developed to study the effectiveness of superheated steam, humid air, and dry air as dehydration media for wedge-shaped food products. Superheated steam had slightly higher surface friction loss than humid air and dry air except at lower free-stream temperatures. Superheated steam also exhibited higher heat transfer rates than the other fluids. The combined effect of these two characteristics was the existence of an inversion point in dehydration rate. The inversion point was the temperature at which evaporation rates for the fluids were approximately equal. The inversion points for different wedge angles were observed at approximately 275°C. The evaporation rates were greater for superheated steam than for dry air or humid air when the fluid temperature was above the inversion point. However, the evaporation rates were less for superheated steam than for dry air or humid air when the temperature was below the inversion point.

ISSN:0149-5720    

DOI:10.1080/10407788708913545

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor