Research On The Performance Of The Ejector-Compression Coupled Air-Source Heat Pump System Based On The Classified Utilization Of Solar Energy

As one of clean energy sources,solar energy has the advantages of huge energy,renewable,inexhaustible and so on,so it is widely used.However,due to the dispersibility and instability of solar energy,the utilization rate of solar energy is low at present,especially when the solar radiation intensity is low.So,improving the utilization rate when the solar radiation intensity is low has become the key to improve the utilization rate of solar energy.In order to make full use of solar energy of different intensities,this paper proposes a ejector-compression coupled air-source heat pump system based on the classified utilization of solar energy system.R134a was used as refrigerant,and the system performance was studied by establishing energy analysis mode and exergy analysis mode.The main research contents and conclusions are as follows:（1）The system sets five operation modes according to different outdoor temperature and different solar radiation intensity,describes the working principle of the five modes,and establishes the energy analysis mode and exergy analysis mode of each component of the system.The one-dimensional steady flow mode of ejector was established and the flow chart of ejector performance calculation was drawn.（2）The performance of the system in the mode of a solar driven boost ejector-cascade heat pump（mode4）is analyzed,the results show that,with the increase of evaporation temperature,the coefficient of mechanical properties COP_m,coefficient of thermal performance COP_hand coefficient of global performance COP_gof this mode are all increasing,while the heat capacity,exergy destruction and exergy efficiencyη_sys are increasing.With the increase of condensation temperature,the COP_mand COP_gof this mode decreased continuously,while COP_h,heat capacity andη_sys increased,and exergy destruction are increased slightly.With the increase of the intermediate condensation temperature,COP_m,COP_gandη_sys of this mode continue to rise,COP_hand heat capacity obviously decrease,exergy destruction are slightly decreases.With the temperature rising,COPm,heat capacity andη_syswere decreased,while COP_gand COP_hwere increased,and exergy destruction are decreased slightly.（3）Three kinds of heating methods of the mode of a solar energy+two stage compression heat pump is described,namely,the solar radiant heat is directly transferred to the condensing evaporator（OP1）,the solar radiant heat is directly transferred to the condenser（OP2）,and the solar radiant heat is transferred to the evaporator（OP3）,theoretical analysis of the shortcomings of OP3 way,The change of heat production,η_sys,COP_m,COP_gin OP1 and OP2 way under different outdoor temperature and different solar radiation intensity is calculated and analyzed.The results show that when the evaporation temperature increases from-25℃to 10℃and the solar radiation intensity increases from 200W/m²to 800W/m²,the COP_mand COP_gof OP2 way are higher than those of OP1 way,the heating capacity andη_sys of OP1 way is higher than that of OP2 way.When the evaporation temperature is-25℃and the solar radiation intensity is 400W/m²,600W/m²and 800W/m²respectively,compared with OP1 way,the heat capacity of OP2 way decreases by 8.30%at most,η_sys decreases by5.31%at most,COP_mincreases by 14.30%at least,COP_mincreases by 49.70%at most,COP_gincreases by 12.57%at least,and COP_gincreases by 29.31%at most.The OP2 way is better than other two modes when the evaporation temperature is-25℃to 10℃and the solar radiation intensity is 200W/m²to 800w/m².（4）The changes of heat capacity,COP_m,COP_gof the system in five modes under different outdoor temperature（evaporation temperature）,different indoor water supply temperature（condensation temperature）and different solar radiation intensity were studied.The study shows that when there is no outdoor solar radiation,the system runs in mode of single stage compression heat pump（mode1）and mode of double stage compression cascade heat pump（mode3）,in which mode1 is suitable for the case of high outdoor temperature（the corresponding outdoor temperature is also higher）,while mode3 is suitable for the case of low outdoor temperature.When there are outdoor solar radiation,the system with the mode of a solar energy+single stage compression heat pump（mode2）,the mode of a solar driven boost ejector-cascade heat pump（mode4）,the mode of a solar energy+two stage compression heat pump（mode5）operation,among them,the mode2 is suitable for the case of high outdoor temperature and high sun radiation intensity,the mode4 is suitable for the case of high outdoor temperature and low sun radiation intensity or low outdoor temperature and low sun radiation intensity,the mode5 is suitable for the case of low outdoor temperature and high sun radiation intensity,The operation strategy is as follows:1)When there is no solar radiation.When the condensation temperature is 35℃,mode1 is used for the evaporation temperature range of-8.8℃to 15℃,and mode3 is used for the evaporation temperature range of-25℃to-8.8℃.When the condensation temperature is 45℃,mode1 is used for the evaporation temperature range of 1.9℃to 15℃,and mode3 is used for the evaporation temperature range of-25℃to 1.9℃.When the condensation temperature is 55℃,mode1 is used for the evaporation temperature range of 8.7℃to 15℃,and mode3 is used for the evaporation temperature range of-25℃to 8.7℃.2)When there is solar radiation.When the condensation temperature is 35℃,mode2 is used for evaporation temperature range of 11.2℃to 15℃and solar radiation intensity range of 748W/m²to 800W/m²;mode4is used for evaporation temperature range of 11.2℃to 15℃and solar radiation intensity range of 200 W/m²to 748W/m²,mode4 also can used for evaporation temperature range of-25℃to 11.2℃and solar radiation intensity range of 200 W/m²to 800W/m².When the condensation temperature is 45℃,mode2 is used for evaporation temperature range is 3.5℃to 15℃,the solar radiation intensity range is 484W/m²to 800W/m²;mode4 is used for evaporation temperature range is 3.5℃to 15℃,the solar radiation intensity range is200W/m²to 484W/m²,mode4 also can used for evaporation temperature range is-25℃to3.5℃,the solar radiation intensity range is 200W/m²to 611W/m²;mode5 is used for evaporation temperature range is-25℃to 3.5℃,and the solar radiation intensity range is611W/m²to 800W/m².When the condensation temperature is 55℃,mode2 is used for evaporation temperature range is-2.1℃to 15℃,the solar radiation intensity range is 344W/m²to 800W/m²;mode4 is used for evaporation temperature range is-2.1℃to 15℃,the solar radiation intensity range is200W/m²to 344W/m²,mode4 also can used for evaporation temperature range is-25℃to-2.1℃,the solar radiation intensity range is 200W/m²to 434W/m²,mode5 is used for evaporation temperature ranges from-25℃to-2.1℃,and the solar radiation intensity ranges from 434W/m²to 800W/m².