Comparison of direct and indirect sewage source heat pump systems

Describes the specific forms of the two systems, and analyses the difference of heat transfer area of evaporator when evaporation temperature of two systems is equal and the difference of evaporation temperature when heat transfer area of evaporator of two systems is equal. Compares their economic effects, operating energy consumption and reliability. The results show that for the equal evaporation temperature, the heat transfer area of the sewage heat exchanger in an indirect system is 3-5 times as large as that of evaporator, and the heat transfer area of evaporator in the direct system is 0.4-0.7 times larger than that of the indirect system; for the equal heat transfer area of evaporators, the evaporation temperature of direct system is 3-4 ℃ lower than that of the indirect system; the investment of direct system is not really lower than that of indirect system, its energy consumption is lower at most by 4% to 5%, and it is unreliable.