Study on influence of pinch temperature difference of evaporator on performance of ORC system

The design of the evaporator significantly impacts the efficiency of the ORC system. Two working fluids, R245fa and R134a, were selected, and Aspen HYSYS was employed to construct the ORC system. By manipulating the mixing ratio of the working fluids, the influence of evaporator sandwich temperature difference on system performance was explored. Additionally, an <i>F(X)</i> function was introduced to comprehensively evaluate system performance. Simulation results demonstrate that as the pinch point temperature difference in the evaporator increases, net output work gradually decreases while thermal efficiency and exergy efficiency initially increase before suddenly decreasing. Furthermore, a higher proportion of R134a in the mixture ratio leads to an associated increase in pinch point temperature difference. When using a 5:1 mixture ratio of R245fa and R134a, this configuration yields a smaller <i>F(X)</i> value indicating superior overall system performance; however, under any mixture ratio scenario considered here, <i>F(X)</i> exhibits a trend of initially decreasing followed by increasing.