Design Calculating Model And Simulation Analysis Of Sewage-source Heat Pump With Direct Heat Exchange System

Sewage-source heat pump system can supply heating, refrigeration and hot water for building which use urban sewage as low heat source. The available-sewage source heat pump systems are mainly direct heat exchange system and indirect heat exchange system. Sewage-source heat pump with direct heat exchange system has higher COP, EER and thermodynamic degree of perfection compared to sewage-source heat pump with indirect heat exchange system. Sewage-source heat pump with direct heat exchange system has become the main developing direction of sewage-source heat pump system.According to the characteristics of sewage-source heat pump with direct heat exchange system, heat pump should take the mode of refrigerant reversing to realize the heating and cooling switching. Sewage-side heat exchanger of heat pump is condenser under refrigeration condition and evaporator under heating condition, using-side heat exchanger of heat pump is evaporator under refrigeration condition and condenser under heating condition. The structure of sewage-side heat exchanger is floating-head, shell-and-tube heat exchanger which is convenient to dirt removal and the tube is high efficiency type which can enhance heat transfer for condensing and evaporating.Then, according to the relative standards this dissertation designs sewage-side heat exchanger and using-side heat exchanger in detail, then have a model selection of compressor and electronic expansion valve. Based the mathematical model establishing of sewage-side heat exchanger, using-side heat exchanger, compressor and electronic expansion valve, this dissertation compiles simulation programs of these four parts and the whole unit.Using the simulation programs, this dissertation calculates the performance parameters of sewage-source heat pump under heating condition and refrigeration condition respectively. Then this dissertation analyzes the effect of variation of heat exchanger area, fouling thermal resistance, sewage flow rate, sewage inlet temperature, part load rate on the heat pump under heating condition and refrigeration condition respectively.