Experimental Study of Heat Transfer Enhancement in Double-Pipe Heat Exchanger Integrated with Metal Foam Fins

Abstract

The influence of adding fins of copper foam on the characteristics of heat transfer in a double-pipe heat exchanger is investigated experimentally. The test rig consists of two concentric pipes (copper and Perspex) to form the required double-pipe heat exchanger. The metal foam fins of 40 PPI are made from copper and set at 30° angle with the tube entrance and are distributed in sections inside the annular gap around the inner copper tube to guide the fluid flow and to disturb its structure inside the annular gap. The Reynolds number range for air is from 616 to 2343, with a constant water volume flow rate (2 lpm) in these experiments. The inlet water temperature is controlled at three values (80 °C, 85 °C, and 90 °C). Both parallel and counterflows are examined in this study. The comparison is made between the two cases of with and without insertion of copper foam fins and between parallel and counterflow mode. Results show that the average heat transfer coefficient and the average Nusselt number are increased as the Reynolds number increased, and their largest values are obtained in case of copper foam fins insertion and for counterflow mode. The important finding is no significant pressure drop is found with the enhancement of heat transfer throughout the annular gap of heat exchanger. Results also showed that the effectiveness values are doubled in case of insertion of the copper foam fins. The counterflow pattern is the most efficient flow pattern than the parallel flow.