Determining the optimal pinch point temperature difference of evaporator for waste heat recovery

From the perspective of exergy recovery, the pinch point temperature difference (PPTD) of evaporator for waste heat recovery has been optimized by exergo-economic principle using the annual net profit per transferred heat load as objective function. And for comparison, another criterion, the annual total cost per transferred heat load from the view of exergy destruction, is introduced. Taking organic fluid R600a as an example, the effects of thermodynamic and economic parameters on the optimal PPTD are examined. It is found that the optimal PPTD is closely related to the total investment costs of evaporator. Different trends on the optimal PPTD are provided with the variations of thermodynamic and economic parameters. And the flow exergy loss has little impact on the optimal PPTD of evaporator. The optimal PPTD from the perspective of exergy recovery is larger than that from the view of exergy destruction.