Effect of radiation heat transfer on the performance of high temperature heat exchanger, (3)

In the heat exchangers using high temperature gas as working fluid, such as the heat exchangers for high temperature gas-cooled reactors and the recuperators for waste heat recovery, the acceleration of heat transfer can be achieved by the effective utilization of radiation heat transfer. In this study, heat transfer phenomena were investigated under the conditions that non-radiative air flowed through the annular channel of a double-walled pipe, the outer pipe was insulated, and the inner pipe was heated with constant heat flux, so that the result can be applied to the flow around the circular fuel rods of high temperature gas-cooled reactors, because in annular flow, the comparison of the theory and the experiment is relatively easy, and the clarification of the phenomena can be made accurately. The temperature distribution in the direction of flow and the effect of the emissivity of surfaces measured were compared with the results of approximate calculation or numerical calculation. Also the emissivity of various surfaces was measured, and the surface with the emissivity close to 1 was studied. The effect of emissivity on the promotion of heat transfer by solid radiation was examined experimentally and theoretically. The temperature of the outer pipe was raised by the solid radiation from the inner pipe, and heat was transferred to air also from the outer pipe. (Kako, I.)