Experimental Study On Performance Of Heat Pump System Driven With Compound Energy

Building energy consumption accounts for more than30%of the total energyconsumption in our society, building energy conservation has become the focus areasof the national energy saving. Increasing the proportion of renewable energy in thebuilding energy consumption is an important measure of the building energy saving.Air source heat pump （ASHP）, the solar assisted heat pump （SAHP） and other heatpump systems, at the present stage, have been applied in the construction universally.However, the low temperatures in winter in most parts of northern region of China, andthe low density and intermittency of solar energy, the application of the conventionalheat pump system has become a huge restriction. Therefore, the development of thenew heat pump system of cost-efficient, stable performance and applying to the vastterritory is becoming an effective way to solve this problem.Solar energy, air thermal energy can be universally accessed, which are two kindsof renewable energy with large amount of resources. In order to give full play to theadvantages of air source heat pump and solar assisted heat pump and make up for theirlackness respectively, a multi-complementary heat pump （CEHP） system wasresearched and developed and the experimentally performance was studied. Themulti-complementary heat pump system integrated with vacuum tube solar waterheaters and air source heat pump, a finned air heat exchanger and a immersive coil heatexchanger adapted in parallel arrangement to form the evaporator of the heat pumpsystem, the condenser is used in the same immersive coil type, composed of capillarytube as throttling device, with circulation work of the compressor, achieved the heattransfer and conversion. Endothermic heat source of heat pump system can be the heatcarried by the air, also can come from the hot water collected by the vacuum tube solarcollector device, the low-temperature floor radiant heating and interior fan coil arearranged in parallel connection as the heating ends of the system. At normal state theair thermal energy is a prior heat source, the heat collected by solar collector device isa second prior heat source. The system has independent mode of operation of the airsource heat pump, mode of united operation of solar water-air source heat pump,independent mode of operation of the water source heat pump, can achieved heating（water）, cooling and other functions by switching operation modes according tooutdoor environmental conditions and user needs. In order to study the heating performance of heat pump system with compoundenergy under specific environment to particular mode in cold and dry area, draw up areasonable switching program of operation mode for the winter heating conditions andconduct a comprehensive evaluation of the benefit of the system. The followingresearches are made in this subject:1. According to the structure of the target room, their respective layout end ofheating and cooling was slected, and a heat pump system with compound energy wasdesigned for the winter indoor and outdoor environmental conditions.2. In the specific outdoor environment, the heating performance of the threemodes of operation of the system was studied experimentally. The heating performanceparameters of the system with independent mode of operation of the air source heatpump, mode of united operation of solar water-air source heat pump and independentmode of operation of the water source heat pump was calculated, which include theheating capacity of the system, heat pump coefficient of performance (COP_hp), thesystem coefficient of performance (COP_sys) and the instantaneous status of condensing,eavporating pressure and temperature, the flow rate of heating water, powerconsumption of compressor and heat pump unit and so on.3. According to the heating performance of heat pump system basing onexperimental data and the analysis results from theoretical models of heat load, theswitching program among the three operation modes for different environmentalconditions was concluded.4. The conclusion of optimization to the operating conditions for the CEHPsystem in winter is as follows: when the outdoor temperature ranges from0to5℃and the system works with dual heat sources, the water source with low temperaturemaintained at the temperature range of10to15℃, now the COP_hpis up to2.19andthe COP_sysis up to1.86, the average heating capacity of the system can be maintainedaround3500W; when the outdoor temperature ranges from-5to0℃and the systemworks with dual heat sources, the water source with low temperature maintained at thetemperature range of15to25℃, now the COP_hpis up to2.17and the COP_sysis up to1.82, the average heating capacity of the system can be maintained above3300W.5. Basing on the thermodynamics theory the exergy analysis for CEHP system wasconducted. The results of exergy analysis show that the exergy efficiency of the systemin dual-source model is significantly higher than a single air source model. From theenergy economy point of view, the system should run as much as possible with thedual-source model, and the energy conversing efficiency of the system maintains a high level, the exergy efficiency of the system is up to0.3429.The innovation in this subject is that a heat pump system with compound energywas designed, and the performance of this system is initially revealed.The renewable energy of extensively available in natural environment such assolar energy, air thermal energy was effectively combined in heat pump systemdeveloped in this subject，the heating load in winter and air conditioning load insummer in cold northern regions and the annual domestic hot water demand weremeeted at the same time, and the serious problems such as the poor heatingperformance and low stability in operation existed in air source heat pump and solarassisted heat pump under bad conditions in winter were initially solved out.