Performance characteristics and working fluid selection for low-temperature binary-flashing cycle

In this paper, the performance characteristics of a low-temperature thermal energy driven binary-flashing cycle (BFC) for power generation have been investigated. Also, the potentials of nine working fluids, including R245fa, R1233zd(E), R1234yf, R1234ze, R1234ze(Z), R600, R600a, R601 and R601a used in the BFC are comparably examined. Results show that, there exists an optimum vapor generation temperature that makes the BFC obtain the best thermodynamic performance. Also, an optimum flashing temperature exists for maximum net power output, while an increase in the flashing temperature always leads to the thermal efficiency and second law efficiency increasing as well as the total exergy destruction rate and cooling water mass flow rate needed decreasing. With the BFC operating at optimum vapor generation temperature and flashing temperature, the heat source temperature always offers positive contribution on the BFC performance. Besides, the thermodynamic performance of the BFC as well as its optimum parameters has a strong connection with the critical temperature of working fluids in general. The higher the critical temperature of working fluids is, the better the BFC performance will be. Therefore, among the working fluids examined, R601 with the highest critical temperature should be recommended as working fluid for the BFC.