Heating Transfer Characteristics Analysis on the Flooded Refrigerant Evaporator Using Untreated Sewage Heat Energy

Abstract

Sewage evaporator is the critical component which affects the performance of the direct sewage source heat pump unit. The sewage directly flows into the evaporator and exchanges heat with the refrigerant. The performance of sewage evaporator is different from the general water source heat pump units because of the characteristic of sewage. This paper developed a theoretical model with sewage FRE distribution parameters based on some reasonable simplifications, and this model was applied to predict the performance of some sewage evaporator and analyze the influence of different tubes and pass arrangements and different sewage inlet temperature and flux on evaporator performance. The results show that there is little effect on the sewage FRE performance with different pass arrangement. The evaporator heat exchange increases linearly with the rise of sewage inlet temperature when the sewage flux and refrigerant inlet conditions are fixed. The evaporator heat exchange and flow resistance increase with the sewage flux raises when the sewage inlet temperature and refrigerant inlet conditions are constant. In addition, the change extent of heat exchange is similar to that of the flux change.