Transient one dimensional heat transfer in a composite medium of two materials exposed to radiant heat flux has been investigated. The end faces of the composite were considered to be losing heat energy by natural convection and radiation. The principle variables studied were the temperature at steady state and the time required to attain the steady state with and without the contribution of loss by radiation. It was observed that neglecting the loss of energy by radiation from the face receiving the radiant heat flux introduced an error in the absolute steady state temperature of that face as high as 48% for the dimensionless heat flux (qL1/k1t) at 20.0 and an error in the time required for the attainment of steady state by as much as 33%. These errors became 9.3% and 6% respectively for (qL1/k1t) at 5.0. The investigation further showed that when the ratio of surface temperature (absolute) to the ambient air temperature (absolute) exceeds 1.4 or when dimensionless heat flux exceeds 5.0, loss of energy by radiation can no longer be ignored. The results also indicated that steady state is attained more rapidly if the radiant flux is increased as could be expected from physical reasoning. Finite difference technique was used to solve the governing differential equations with nonlinear boundary conditions. A computer program was written to solve the resulting algebraic equations and temperatures were calculated for two different values of dimensionless radiant flux, emissivity, width ratio and the ratio of thermal diffusivity.
Department, Program, or Center
Mechanical Engineering (KGCOE)
Mackar, Ripujit, "Unsteady State Heat Transfer in a Composite Medium Exposed to Radiant Heat Energy" (1970). Thesis. Rochester Institute of Technology. Accessed from
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