A multi-objective optimal model was developed

in which the screening criteria include heat recovery efficiency and heat exchanger area per unit power output.The model was optimized using the simulated annealing algorithm for R123

R236ea

R245fa

R227ea and R600.The results show that the multi-objective optimization model can coordinate the relationship of different criteria and is better for system economy than that of a single screen criterion.At heat source temperature of 140℃

the optimal evaporation and condensation pressures using R123 are 0.69 MPa and 0.11 MPa

respectively.The optimal evaporation pressure increases with the condensing pressure.The velocity in tubes should be more than 0.5 m·s-1 and the optimal pinch point in evaporator is about 15℃.As the waste heat temperature increases

the optimal evaporation pressure increases.In the waste heat temperature range from 100℃ to 220℃

R123 is the best working fluid among the five working fluids.