HEAT TRANSFER BY COMBINED WALL CONDUCTION, NATURAL CONVECTION AND RADIATION THROUGH A RECTANGULAR SOLID WITH A CAVITY
Abstract
This study is concerned with the effects of wall conduction and radiation heat exchange between surfaces on laminar natural convection heat transfer in a two-dimensional rectangular solid with a cavity. To this end, theoretical and experimental studies were conducted. The theoretical studies involved development of a comprehensive model to predict the temperature fields in both the solid and the fluid filled cavity and the flow field in the cavity. Two outside walls are insulated and two others are maintained at constant, but different temperatures. The conservation equations of mass, vorticity and energy are solved numerically using finite-difference methods. The study examines two problems: (1) conjugate heat transfer with heat conduction in the wall and natural convection in the cavity, and (2) combined convection and radiation exchange in the cavity. Extensive parametric heat transfer calculations have been performed for modified Rayleigh number ranging from 10('4) to 10('7). The results show that the total heat transfer through the structure is strongly dependent on the thermophysical properties of the wall, the aspect ratio of the cavity, the porosity, the radiation number and other factors. Experiments were performed in the laboratory by using a Mach-Zehnder interferometer as a diagnostic tool for determining the temperature distribution in the fluid (air) occupying the cavity. Temperature distributions in the fluid were measured by an interferometer, and thermocouples were used to measure the temperatures in the solid walls (Lexan). In addition to boundary condition heating from one vertical side of the cavity and cooling from the opposite vertical wall, two other configurations in which the solid is heated from the bottom and the top have been studied. Excellent agreement has been obtained between the data and predictions for the temperatures of the solid wall, but the agreement was less favorable one for the temperatures in the fluid.
Degree
Ph.D.
Subject Area
Mechanical engineering
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