Heat-transfer in a tube to sodium-potassium alloy and to mercury

Abstract

The existing experimental data on heat transfer to liquid metals often do not agree with each other, nor with theoretical values. The reasons for the discrepancies have so far not been clear. From the present work we can draw the conclusion that the main reason for the discrepancies is the thermal resistance that exists at the boundary between the heat-transfer surface and the liquid metal. We have come to this conclusion after measuring the heat-transfer coefficient to liquid metal by two methods: measuring the temperature distribution in the stream of liquid and measuring the temperature of the wall. The temperature distribution in the stream agreed with the distribution calculated from Lyon's equation. It was found that contamination of the sodium-potassium alloy by oxygen leads to a decrease of the heat-transfer coefficient. The results of experiments carried out in the absence of contact thermal resistance at the boundary between the wall and the liquid metal are in agreement with the results of Isakoff and Drew, and also with those of Brown, Amstead, and Short. The present paper contains a description of the experimental apparatus and of the tube section and thermocouple with which the temperature distribution in the stream of liquid metal was measured.