Analysis of a combined trilateral cycle - organic Rankine cycle (TLC-ORC) system for waste heat recovery

A combined Trilateral Cycle-Organic Rankine Cycle (TLC-ORC) system for waste heat recovery is proposed in this paper in order to obtain a better matching performance between the heat source and working fluid. Working fluid selection including Cyclohexane, Toluene, Benzene and water for the high temperature cycle is analyzed based on thermodynamic model under different evaporating temperature of high temperature cycle and low temperature cycle. Results show that Toluene has the best performance among the studied four high temperature working fluid. The net power output, thermal efficiency and exergy efficiency increases with Tevap,HT or Tevap,LT increasing at any a high temperature working fluid. The maximum net power output 11.3 kW, thermal efficiency 24.2% and exergy efficiency 63.2% are achieved by Toluene at Tevap,HT =530 K and Tevap,LT =373 K at the same time. It is also found that evaporator 1 has the largest exergy destruction while condenser 1 has the smallest one among all the components. Meanwhile, the condenser 2 has the lowest exergy efficiency while condenser 1 has the highest one. These results show us the direction to optimize the system parameters to improve the total efficiency of the whole system.