Heat transfer enhancement in tubular heater of Stirling engine for waste heat recovery from flue gas using steel wool

Experimental tests were performed on a pilot Stirling engine used for waste heat recovery from flue gas to assess approaches to effectively enhance heat transfer within its tubular heater. For these tests, the heat transfer coefficient of flue gas was measured for the original heater and then after it had been filled with heat-resistant steel wool. The experimental results show that the steel wool effectively enhanced the combined heat transfer coefficient on the outer surface of heater tubes; as the porosity of the steel wool was decreased, the combined heat transfer coefficient continued to increase but at a successively slower rate. These results provide an approach for heat transfer enhancement from high temperature flue gas for tubular heat exchangers, and contribute to design optimization of a tubular heater in a Stirling engine.