Abstract:City sewage,which is an excellent low temperature heat source,has the characteristic of being relatively stable in temperature,cool in summer and warm in winter and a promising energy-saving prospect.A sewage source heat pump is constructed;the secondary effluent from the sewage plant is employed as the heat source.Based on this,the effect of the flow rate of the sewage side on the system COP under the cooling condition is studied in experiments,along with the flow rate and inlet temperature of the user side.Built on the tests data,system COP is fitted.The results show that system COP is slowly increased with the user side inlet temperature,but markedly increases with the flow rate of the sewage side and user side.The COP fitting result can well present the system actual operation with an average error of only 3.35%.