A thermo-mechanical model for shape memory alloy–based crank heat engines

A thermo-mechanical model to simulate the mechanical response of a shape memory alloy heat engine has been developed. In such a kind of engine, the thermally induced shape recovery capabilities of shape memory alloys are exploited to obtain mechanical work from low-grade energies, such as warm wastewater, geothermal, and solar sources. As a consequence, these engines represent simple and environmentally friendly solutions, and several architectures have been proposed in the last years. However, none of these devices has been industrialized, mainly due to the lack of robust design tools as well as to several technological and economic issues. To this aim, a simple semi-empirical numerical model has been developed to analyze the mechanical response of a shape memory alloy–based crank heat engine. In particular, the engine output characteristics (e.g. torque, specific power, efficiency) have been studied as a function of several geometrical configurations (e.g. dimensions, number of cranks) as well as of different thermo-physical properties of the heating and cooling thermal sources.