Performance analysis of Heat Pump Water Heating System with Cascade Utilization of Waste Heat from Wastewater

摘要

Wastewater heat pump water heater (WHPWH) can be used to recover waste heat from industrial orrndomestic wastewater with high efficiency. In this study, a WHPWH system was proposed and itsrnperformance was theoretical analyzed. The proposed system includes a preheating heat exchanger and arnwater source heat pump. The fresh water is preheated by wastewater then heated to the desired temperaturernby water source heat pump. Thus, the waste heat of wastewater can be cascaded recovered throughrnpreheating the fresh water and being the heat source of the heat pump. A thermodynamic model wasrndeveloped to evaluate and optimize the performance of the proposed WHPWH. The energetic analysis wasrncarried out to investigate the influences of the temperature of the wastewater, the inlet and the outletrntemperatures of fresh water. The results were compared to the system which only uses wastewater tornpreheating or as heat source of heat pump, and showed a significantly higher waste heat utilization rate.