Effects of heating/cooling-water temperatures on output power characteristics of forced cooling pulley-type SMA heat-engine

Abstract

In this research, the effects of heating/cooling water temperatures of a heat engine on the output characteristics of the forced cooling pulley-type SMA heat-engine is investigated for the purpose of operating temperature optimization of the engine. The engine output increases almost linearly as the heating water temperature (T_H) rises. On the other hand, the engine output shows a gradual decrease as the temperature of SMA element during cooling (T_SMA) rises to 321.4 K and then an abrupt decrease when the T_SMA = 322.7 K. Thermal cycling tests under constrained strain conditions for the SMA element were carried out to investigate the effect of heating/cooling temperatures to generation stress (Δσ) and reaction velocity (V_R) of the SMA element. In result, Δσ increases gradually with the increase of T_H. Besides, V_R increases almost linearly as T_H increases. This result suggests that the increase of engine output as T_H increases is mainly due to the increase of the V_R. Meanwhile, V_R increases gradually with the increase of T_SMA. Besides, Δσ increases as T_SMA rise up to 318 K, above which it decreases rapidly. From these results, it may be concluded that the contributing factor to the engine output is the variation of Δσ and V_R with the variation of T_SMA.