Experimental Study On The Optimization Of The ASHP With Phase Change Heat Storage Evaporator

The air source heat pump(ASHP)with refrigeration in summer and heating in winter,has the advantages of energy conservation and environmental protection,widely used in the area of the Yangtze River.ASHP was applied in the north and there was a series of problems such as operating conditions deteriorate for compressor,insufficient heating capacity at low temperatures.Therefore,a new ASHP with heat storage evaporator using phase change material was developed by our research team,whose performance at low temperatures was greatly improved.However,the regenerative heat exchanger was slow,less heat storage within a limited time and couldn't meet the heating needs,especially at low temperatures.It must be optimized.The optimization of the phase change heat storage material.The original composite heat storage material made by 86.8%Na2S4·10H20?7%sawdust?4%borax?2%CMC?0.2%HMP and a certain amount of NaCl was optimized by 80%Na2SO4·10H2O+20%Na2HPO4·12HO.It had the advantages of large phase change latent heat,phase change temperature stability,stability and reproducibility.The optimization of the accumulator structure.The original accumulator with double spiral coil(light pipe)was replaced by rectangular finned spiral tube heat exchanger structure.It optimized the fin structure and enhanced heat transfer.In addition,the position of store liquid machine and exothermic throttle valve were optimized.The experimental results showed that the optimized ASHP with phase change heat storage evaporator had the advantages of reasonable exhaust temperature and pressure,and significantly shortened thermal storage time.The regenerative shortest time was 3h and for a maximum of 7.2h under ambient temperatures were running 15? and-2?,compared with before optimization shortened 6h and 8h,respectively.When inlet temperature of cooling water was 45?,it could ensure normal heating user demands and heating COP up to 1.75 under the ultra-low temperature environment of-30?.When cooling water inlet was 40 ?,the condensing temperature and compressor pressure ratio decreased and regenerative time has been extended.But the compressor power was reduced and users basically unchanged for the heat,the heating COP is up to 1.89 under the ambient temperature was of-30?.The ASHP with phase change heat storage evaporator could adapt to continuous changes in the ambient temperature under the coldest day of winter operating conditions.Under the conditions of the average day temperature was-2? and the heat storage period for 10h,the system worked 8.7h to meet the low-temperature heat for the time period of 14h.The optimized ASHP with phase change heat storage evaporator could be safely operated at different ambient temperatures and high thermal storage efficiency,to achieve a good combination of heat pump technology and storage technology.It met the heating requirements of the user cryogenic environment and providing the technical basis for the promotion of the northern cold regions.