Experimental Research And Economic Analysis Of The R507A/R134a Air Source Heat Pump

With the development of national economy,the demand for energy is growing and environmental pollution problems are becoming more and more important.Energy conservation and environmental protection have become significant themes of social civilization and sustainable development.As a kind of energy saving and efficient hot water technology,air source heat pump gets great favor of people.It is known as” the fourth generation of water heaters”.However,the air source heat pump has the problems of frequent start-stop,high exhaust temperature and low heat production and other issues in the low temperature environment which limit its further promotion.Aiming at the problems of air source heat pump existing in the low temperature environment,an air source heat pump hot water system with single stage / cascade double mode operation is put forward based on the analysis of the current situation of scholars at home and abroad.Based on the theory of refrigeration cycle,thermal performance under single-stage operating mode in which R507 A and R134 a are used as refrigerants is analyzed in ideal conditions.Comparing with the R507 A,in the same working condition,the air source heat pump system adopting R134 a as the circulating quality in single-stage operation mode has higher heating coefficient and the system can operate under lower condensing pressure.By applying the principles of refrigeration,heat transfer,engineering thermodynamics and related empirical formulas,the mathematical model of compressor,condenser,evaporator,throttle valve and condensing evaporator is established respectively.According to the internal relation between them,the single-stage air source heat pump system and the compound air source heat pump system are simulated.Research shows that in low temperature environment,the heating coefficient of the cascade heat pump system is higher than single stage heat pump system.With the increase of the temperature of the environment,and the increased rate of the single stage heat pump heating coefficient faster than cascade heat pump system.Aiming at maximum COP,when the condensation temperature is 60?,the best switching evaporation temperature of single stage mode and cascade type operation mode is 7?.The operating characteristics of the heat pump system change witch the out water temperature and the external environment temperature during the whole year are analyzed in the single stage and cascade operation mode.The changing law of some parameters such as heating capacity,power input,mass flow,suction and discharge pressure,discharge temperature,pressure ratio,etc has been obtained.The simulation results and experimental results are compared and the simulation results are consistent with the experimental results.Combining with the feature of the climate of xiangtan region,When the water temperature of 55?,annual comprehensive energy efficiency ratio of the heat pump system is 3.496?Comparing the air source heat pump with the common gas water heater,solar water heater and electric water heater of the market,when the daily water consumption of households is 240 L,the annual carbon dioxide emissions will be reduced by 426.62 kg,417.67 kg and 2702.24 kg and the annual operating expenses decreased by 29.8%,46.5.9% and 75.4% respectively during the whole year.