ISSN Print: 1049-0787
ISSN Online: 2375-0294
Indexed in
COMPLEX HEAT TRANSFER PROCESSES IN HEAT-GENERATING HORIZONTAL FLUID LAYERS
ABSTRAKT
The behavior of heat-generating horizontal fluid layers has been of important concern in geophysics, astrophysics, chemical engineering, combustion theory, nuclear technology, and nuclear reactor safety analysis. Previous studies of this class of problems, however, have focused only on certain particular heat transfer aspects of the layers. As a result, they do not appear to be closely connected nor do they provide a complete description of the overall physical picture. In this paper, the various heat transfer processes in horizontal fluid layers with different heat-generation properties are reviewed and presented systematically. These include laminar convection in the post-stability regime, steady and transient turbulent convection, and combined natural convection and radiation in horizontal fluid layers with volumetric energy sources that can be either uniform and constant, time-dependent, or temperature-dependent. Also included in this review is the case of a horizontal fluid layer heated internally and from below. Particular attentions are given to physical modeling that facilitates the solution procedures.
Owing to the fact that the instability-driven flows in horizontal fluid layers are fundamentally different than the wall-bounded turbulent shear flows, the conventional approach such as the κ-ε turbulence model cannot be directly applied to the case of turbulent convection in horizontal layers. Alternative methods based on the boundary layer-dominant aspect of turbulent flows are found to be more effective and reliable. According to these methods, the various heat transfer processes in heat-generating horizontal fluid layers are governed by either a system of parabolic partial differential equations or a system of non-linear ordinary differential equations. The latter can be readily solved by a standard numerical technique whereas the former can be solved by the method of collocation or finite difference. The validity of the boundary layer-dominant aspect under the strong influence of internal thermal radiation is critically examined. Whenever possible, comparison of the various physical models with experimental results is indicated.