ISSN:1040-7782    

DOI:10.1080/10407788908944675

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Transient melting of a subcooled vertical wall as a result of condensation of pure vapor at its saturation temperature is investigated analytically. Using a Nusselt-type analysis, the equations governing the laminar melt and condensate films are solved by a combination of analytical and numerical techniques. Three different situations are considered: First when the condensate and the melt are of the same species and melting of the solid occurs upon first contact with the vapor; second the same as the first but when the condensate and the melt are of different species; and third when the condensate and the melt are of different species but the initial wall contact temperature is below the melting temperature of the solid. The time to achieve a steady-state condition is also evaluated.

ISSN:1040-7782    

DOI:10.1080/10407788908944676

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A solution methodology is developed to obtain three-dimensional natural convection in a honeycomb enclosure with hexagonal end walls. The numerical methodology is based on an algebraic coordinate transformation technique, which maps the complex cross section onto a rectangle, coupled with a calculation procedure for fully elliptic three-dimensional flows. To the authors' knowledge this is the first three-dimensional numerical study of the problem. The results are obtained for laminar flow and for both conduction and adiabatic side wall thermal boundary conditions. The calculations are performed for Rayleigh numbers in the range of 103to 105, for a Prandtl number of 0.7, and for five values of the aspect ratio of the honeycomb enclosure. The average Nusselt number results are compared with the corresponding values for two-dimensional rectangular enclosures.

ISSN:1040-7782    

DOI:10.1080/10407788908944677

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A numerical study is presented for the combined forced and free convection in the entrance region of a horizontal annulus with radius ratio of 2. Results art presented for developing velocity profiles, temperature field, local pressure gradient, and the circumfer-entially averaged Nusselt number. These results reveal that the buoyancy-induced secondary flow has considerable influence on the fluid flow and heat transfer characteristics of the developing flow.

ISSN:1040-7782    

DOI:10.1080/10407788908944678

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A numerical model has been developed to study forced flaw and convection heat transfer over a circular cylinder in crossflow. Cases having either a constant heat flux or an isothermal wall are considered. It is assumed that the cylinder is placed in a fluid stream with uniform flow and without any free-stream disturbances. The formulation of the governing equations uses the stream function-vorticity approach along with a mapping transformation between the circular physical geometry and a rectangular computational regime. Solution techniques using the central difference and power law forms are compared. Results for air are obtained up to a Reynolds number of 3480, This is a significant improvement over previous work, which was successful only up to a Reynolds number of 200.

ISSN:1040-7782    

DOI:10.1080/10407788908944679

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A numerical procedure is demonstrated for the solution of moving convective boundary problems using a general finite element program and a stationary mesh. The proposed technique will allow for the modeling of various time- and temperature-dependent heat transfer coefficient profiles and removes the restriction of a constant convective boundary velocity from the solution. Quenching of a hot surface that occurs during rewetting is effectively modeled for the case of a step function heat transfer coefficient profile. The accuracy of the numerical scheme is examined by comparing the results with an analytical rewetting solution. A final example demonstrates the general capability of this finite element technique in modeling the effects of the nonlinear temperature dependency of the material thermal conductivity and heat capacity on the rewetting solution.

ISSN:1040-7782    

DOI:10.1080/10407788908944680

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The non-Darcian effects on transient conjugate natural convection-conduction heat transfer from a two-dimensional vertical plate fin embedded in a high-porosity medium are studied numerically. The coupled nonlinear partial differential equations for transient natural convection in the porous medium and transient heat conduction in the fin are solved numerically with a cubic spline collocation method. Numerical results for the heat transfer characteristics are presented for water and air at selected values of the convection-conduction parameter at different times. It is shown that the inertial effect on heat transfer characteristics is negligible at short times; its effect, however, becomes increasingly important at longer times. The time taken to reach steady state is longer for a fluid with a smaller Prandtl number and for a system with a smaller value of the convection-conduction parameter.

ISSN:1040-7782    

DOI:10.1080/10407788908944681

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor