Performance Analysis And Experiment Study On Air-cooled Heat Pump With Partial Condensing Heat Recovery

With the development of the society and the energy consumption, energy-saving, environmental protection and the sustainable development have become an important topic in today’s society urgently to be solved. At present, about 43% to 70% energy is lost in the form of waste heat and the condensing heat of the air conditioning system accounts for a significant proportion. The condensing heat of air conditioning system usually reaches 1.15 to 1.3 times of refrigerating capacity. The condensing waste heat released into the atmosphere causes great a waste of the resources, and contributes to the greenhouse effect. We can recycle the heat to make hot water, and it has a very high energy conservation value. Added with a heat recovery system in the original heat pump air conditioning system, the air-cooled heat pump with partial condensing heat recovery does not need to make big changes to the original system, which can improve the comprehensive energy efficiency of the system. Therefore, the study has a good theoretical value and practical significance.Experimental and theoretical researches are carried out on the performance of air-cooled heat pump water chiller-heater module units with partial heat reclamation system whose rated refrigerating or heating amount is 45 kW.These experiments are realized on the prototype under the condition of the nominal working condition of refrigeration(the ambient temperature is 35℃, the water temperature is 7℃)and the nominal working condition of heating(the ambient temperature is 7℃, the water temperature is 45℃).During the testing,the water flow rates of the used side and the heat recovery side of two kinds of working condition are fixed, and the variance characteristics of operating parameters and system performance of refrigeration and heating are studied and analyzed of the prototype under the two kinds of working condition getting the hot water of 45℃and 50℃respectively. The mainly parameters of the prototype include : cooling capacity/heating capacity, heat recovery, the compressor suction/exhaust pressure, the compressor suction/exhaust temperature, temperature before and after the throttling,COP and so on.As the cooling air volume reduces, the results show that the refrigeration COPA varies from-10.55% to 1.09% in nominal working condition of refrigeration with hot water of 45℃comparing with no heat recovery situation. The refrigeration COPA is decreased by 0.32 and the comprehensive performance coefficient COPW is rises by 0.31. The refrigeration COPA varies from 3.64%to 12.73% with the hot water of 50℃comparing with no heat recovery situation, and the refrigeration COPA is decreased by 0.25 and the comprehensive performance coefficient COPW is rises by 0.17.The COPA decreases 2.44% to 4.68% when the temperature rises from 45℃to 50℃ with single and double fans. With the increase of water temperature of the nominal heating condition, the heating COPa also gradually improves, but the heating COPa decreases 10.96% to 21.58% comparing with no heat recovery situation and the COPa increases 4.42% with the temperature rising from 45℃to 50℃.The hot water efficiency COPr is extremely low in winter, and the COPr declines10% to15% with the temperature rising from 45℃to 50℃.The comprehensive performance coefficient COPw of the nominal working condition of heating declines, but the COPw already reache 3.28 and 3.09 of 45℃ and 50℃, which are much higher than the heating COPa of 2.49 and 2.60 of the same temperature.Experimental researches are carried out on the performance of air-cooled heat pump water chiller-heater module units with partial heat reclamation system whose rated refrigerating or heating amount is 45 kW. These experiments are realized on the prototype under the condition of nominal heating condition and nominal cooling condition. During the testing, the water flow rates of the used side and the heat recovery side of two kinds of working condition are fixed,and the variance characteristics of operating parameters and system performance are studied and analyzed after opening heat recovery function of the prototype under the two kinds of working condition getting the hot water of 45℃ and 50℃ respectively. Comparing with no heat recovery situation, the results shows that the refrigeration COPA varies from-10.55% to 1.09%and 3.64%to 12.73% respectively for leaving heating water of 45℃ and 50℃ and the heat recovery integrated COPW reaches 3.38 to 3.69 and 2.98 to 3.15 in nominal cooling condition. The COPA decreases 2.44% to 4.68% when the temperature rises from 45℃to 50℃ with single and double fans. In nominal heating condition, the heating COPa decreases 10.96% to 21.58% comparing with no heat recovery situation and the COPa increases 4.42% with the temperature rising from 45℃to 50℃. The COPw reaches 3.28 and 3.09.From the above, the COPA of the nominal working condition of refrigeration declines. With the recycling of the condensing heat of the system, the comprehensive performance coefficient COPW increases greatly, much higher than the refrigeration COPA. The COPA of nominal working condition of refrigeration can reach the energy efficiency of level 5 of the national standard of GB19577-2004 when CC≤50kW and COP≥2.4.The COPA can meet the requirements of air-cooled heat pump units in the engineering practice. In the nominal working condition of heating, the prototype can satisfy the indoor heating and hot water. At the same time, the heating capacity and the heating COPa both decline, but the comprehensive performance coefficient COPw is much higher than the heating COPa of the same temperature. The energy efficiency of the prototype is improved. Above all, after adding the heat recovery system in the original heat pump air conditioning system, the comprehensive performance coefficients of the prototype under the condition of nominal cooling and heating condition are improved, which has a certain significance in energy saving.