摘要:

A new control volume-based finite-element method for the solution of heat, mass, and momentum transfer equations is presented. As compared with other similar methods, the new feature of the proposed method lies in the choice of the particular shape function that accounts explicitly for the source terms in the transport equations. The use of such a shape function for interpolating the velocity components while discretizing the continuity equation leads, very naturally, to a consistent equal-order formulation that permits velocity and pressure to be computed at all the grid points in the domain. The method is applied to a number of test problems, and in all cases the results are found to be more accurate than those obtained by its predecessors.

ISSN:0149-5720    

DOI:10.1080/10407788608913477

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This paper addresses the problem of unsteady, flux-driven, fully developed forced convection in general periodic configurations, in which globed conservation properties are used to uniquely determine the proper form for developed thermal profiles. A numerical implementation of the problem is formulated using the isoparametric spectral element method, a high-order (exponentially convergent) finite-element technique for solution of the unsteady incompressible Navier-Stokes and energy equations. As the problem statement requires global energy balance, special emphasis is placed on proper treatment of the convective terms so as to ensure conservation of thermal energy in the appropriate discrete sense. The technique is applied to several test problems, including steady-periodic flow in grooved channels and steady flow past cylindrical obstructions, to indicate the stability, accuracy, and generality of the formulation.

ISSN:0149-5720    

DOI:10.1080/10407788608913478

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Complementary numerical and experimental studies were made of the heat transfer characteristics of a hydrodynamicaUy developed turbulent flow passing through a flat rectangular duct. One, of the principal walls of the duct was maintained at a uniform temperature different from the fluid inlet temperature, while the other walls of the duct were adiabanc. Results were obtained for the local, quasi-local, and average Nusselt numbers in the thermal entrance region and for the fully developed Nusselt number. Both heal and mass transfer versions of the problem were investigated. Excellent agreement prevailed between the experimentally and numerically determined quasi-local Sherwood numbers at a succession of axial stations in the mass transfer entrance region, thereby establishing the analytical model and the numerical solution method. Heat transfer results for airflow were obtained from the numerical solutions for Reynolds numbers between 10,000 and 100,000. It was found that away from the immediate neighborhood of the onset of heating the Reynolds number dependence of the local Nusselt number was virtually the same at all axial stations. The one-sided heating condition gave rise to relatively long thermal entrance lengths.

ISSN:0149-5720    

DOI:10.1080/10407788608913479

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Natural convection between horizontal plates heated from below was computed by using a finite-element method based on a second-order approximation, and the average Nusselt number was extrapolated to zero element size. This process of extrapolation was required to obtain good agreement with the experimental data. Even when a second-order approximation was used for all of the variables, such an extrapolation was found to be necessary. This behaviour was further confirmed for natural convection in a square channel heated on one sidewall and cooled on the opposing one. Sample calculations for these two cases suggest, contrary to prior assertions and implications, that extrapolation or the equivalent is essential to eliminate numerical error and thereby obtain reliable results even with higher-order finite-element formulations.

ISSN:0149-5720    

DOI:10.1080/10407788608913480

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Results are presented for the heat flux and the intensity of temperature fluctuations, obtained by solving a modification of the forced-convection equation in which a mixing length profile is imposed on the spanwise and longitudinal average of the temperature field for points lying outside the wall region. The results for steady turbulent flow are shown to be in reasonably good agreement with the available experimental data. Results for unsteady turbulent flow, which indicate that the heat flux exhibits a strong phase dependence, are also given.

ISSN:0149-5720    

DOI:10.1080/10407788608913481

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A direct-contact heat transfer process in a two-phase (gas-liquid) flow is formulated, and the solution of the two-point boundary-value problem (with Danckwerts-type initial condition) is given. Simulations are performed for a low Peclet number flow and high-pressure coal liquefaction preheater. The simulations show that direct-contact heat exchangers can be considered as an alternative to conventional heat exchangers.

ISSN:0149-5720    

DOI:10.1080/10407788608913482

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A numerical method that allows accurate simulation of counterflow thermal regenerators in which condensation and evaporation can occur is described. By way of an example, it is shown to be convergent, stable, and able to preserve energy and mass balances to acceptable accuracies. By careful choice of finite-difference mesh size, a high degree of precision in the results can be obtained, but slightly high computer processing times result.

ISSN:0149-5720    

DOI:10.1080/10407788608913483

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor