Experimental Research Of A Two-stage Air-source Heat Pump For Residential Heating

With the rapid development of economy and the accelerating speed of the urbanization process,the urban residential heating energy consumption is increasing with time,which will greatly affect the normal operation of the national econmy development.In order to acquire a new heating mode that is able to save energy and protect the environment,the subject is become more and more important.An air source heat pump system is a sort of highly efficient, energy saving and environmental heating mode,which is very suitable for the energy situation of our country,climatic characteristics and enviornment requirement and is also easy to achieve the household heat metering.The system has been widely applied to the south region of Changjiang River in China.But there are some shortages of air source heat pump systems in low temperature environment,such as high compression ratio,low efficiency,high discharge tempreture for compressors and low heating capacity.In this paper,in order to make the system operate efficiently in low temperature,we make the two-stage compression cycle apply to an air source heat pump system,analyze the theory of the system and do some experimental research.Based on the Comparison of different kinds of the two-stage compression cycle,it is found that the two-stage compression cycle with incomplete inter cooling can be used in the air source heat pump system for low temperature climate as a more ideal way of two-stage compression cycle,which have advantages of lower exhaust temperature,higher COP and so on.We calculate the detailed parameters of the cycle in different conditions.It is shown that in system of fixed compressor volume the feeding vapor decreases with evaporation temperature increasing,which is almost zero when the evaporation temperature is at 10℃, and the input power of the compressors rises with evaporation temperature increasing,which is decreased in the system of unfixed compressor volume.We have developed an experimental prototype of an air source heat pump heating system which is adapted to the low-temperature environment.The experimental prototype has two kinds of operation mode,which are sigle-stage and two-stage compression cycles.The two modes can be automatically converted.Through experimental testing in various conditions, we get the optimum filling refrigerant that is about 4.5kg and the transition temperature is 0℃in experimental condition.Experimental results show that,at -20℃ambient temperature and at -50℃condensing temperature,the heating power is 4.65kW,the COP is 2.01 and the discharge tempreture for compressor is lower than 100℃.In this paper,we take for an actual residential in Dalian and use DeST-h software to simulate the heating system.Through the simulation results,we get the average COP that equals 2.508 and the running cost for heating is 8.42yuan/m~2.The operation cost is 1/2～2/3 lower than that of other heating types.