| For the urban district heating system in the heating season,there is a problem that existed heating capacity cannot meet the requirements of most cities,especially for the supply and return water temperature has a very significant effect on the heat transmission and energy conservation.On account of the research background about current heating system and injector heat pump,this paper proposes an active heat exchanger(AHE)technology system which combines injector heat pump cycle and water-to-water heat exchanger.And the AHE locates at the part which is between secondary heat supply network and uptown pipelines inlets.It is applicable to heat user with low-temperature radiated heating system.In this study,we construct a prototype unit of the complete active heat exchanger in a small scale,and find that AHE can take use of the thermal energy step by step based on the different energy grades of the secondary heating network in the condition of a fixed 75? high temperature supply water as a heat source of injector heat pump.Based on the experimental data,the return water temperature of secondary heating network is in the range of 25?-30?,and the primary steam pressure is 0.23MPa-0.30 MPa which corresponding to a primary steam temperature range of 59?-66?.For the optimum condition,compression ratio is 1.571,the energy efficiency coefficient is 0.557,the entrainment ratio is 1.357.Based on the exergetic analysis of the AHE,we find the system exergetic efficiency range of 0.361-0.418,input exergy distribution ratio of water-to-water heat exchanger range of 0.689-0.735.Therefore,based on these analysis,we find that reducing the return water temperature of secondary heating network is an effective way to improve the expected energy saving effects,such as the decrease of secondary network flow and the water pump energy consumption,the increase of heating capacity and the possibility and path of heat recovery. |
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