BOILING AND CONDENSATION HEAT TRANSFER COEFFICIENTS FOR A DOWTHERM-A CHARGED HEAT PIPE HEAT EXCHANGER

Abstract

This paper reports on the experimental determination of the boiling and condensation heat transfer coefficients for the working fluid of a novel heat pipe heat exchanger at high operating temperatures. This technology is of importance in the high-temperature gas cooled nuclear power and process heat industries as it eliminates the probability of tritium finding its way into the product stream. The high temperature wor king fluid used to evaluate the heat pipe heat exchanger was Dowtherm-A, a special high temperature eutectic mixture of 26.5% diphenyl and 73.5% diphenyl oxide. A specially designed experimental heat pipe heat exchanger was built using a hot gas stream of up to 600 °C as the heating stream and col d water as the cooling stream. The basic features of the design are given. The experimental model is used as a proof of concept and to validate the theoretical heat transfer modeling analyses. Existing heat transfer coefficients correlations were considered; they include the Rohsenow, Stephan and Abdelsalam, Gorenflo, and Kutateladze correlations. None of these correlations gave satisfactory results and as such experimentally determined boiling and condensation correlations were determined and which gave reasonable results.