Energy Transport by Combined Radiation and Conduction

Citation

Bell, Lon Edward (1968) Energy Transport by Combined Radiation and Conduction. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/1T27-2S89. https://resolver.caltech.edu/CaltechETD:etd-03262007-102306

Abstract

The problem of one-dimensional radiative and conductive heat transfer in a medium bounded by two infinite parallel walls is treated. The medium isotropically absorbs, scatters, and emits radiation. The walls absorb and reflect isotropically, and transmit diffusely. Thermal conductivity, as well as all radiative properties, are assumed independent of temperature and wavelength. Steady state solutions are sought. Approximate solutions are developed for the temperature distribution and the heat transfer rate. The temperature distribution is expanded in a power series in a dimensionless variable that is a measure of the ratio of radiative to conductive energy transport. The first two terms are retained in the expansion. This allows the radiation integrals that appear in the basic equations to be expressed in a simple, readily evaluated form. Values for the heat transfer rate and temperature distribution are computed and compared with those of other investigators, and the range of validity of the approximation is examined. The problem of two adjacent slabs with different optical properties is discussed. The analysis shows the interaction between the radiative and conductive transport mechanisms and displays the relative importance of each with changes in temperature. The problem of a coating of finite optical depth irradiated by an external source is also treated. The results indicate the conditions under which a coating may be characterized by an emissivity and the conditions under which it must be described in terms of its conductive and optical properties.

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