Heat transfer of a Stirling engine for waste heat recovery application from internal combustion engines

This work analyzes the performances of a Stirling engine for waste heat recovery from the exhaust gas of internal combustion engines. Both experimental and numerical approaches were used. Experimental tests have been carried out on a research Stirling engine coupled to compression ignition engine by a thermally insulate pipe and a cap. Three configurations of coupling have been analyzed. Then, a three-dimensional numerical model has been developed by the authors to deepen the heat transfer between exhaust gas and working gas in the Stirling engine. The cap-heater system has been studied as a shell-and-tube heat exchanger. Experimental results have been set as boundary condition values for the cap, whereas for the heater, pressure and velocity have been evaluated using a 1D adiabatic model properly modified according to Stirling engine configuration. Velocity fields and temperature distribution inside the cap and heater have been analyzed, remarking that the layout of the heat exchanger becomes important for system efficiency. The method presented in this work could be useful to improve in wider terms the coupling between Stirling engine and internal combustion engines.