Economic Analysis Of Cascade Air Source Heat Pump Pressurized Domestic Hot Water System Operation

In winter in severe cold regions,when using conventional air source heat pumps to provide domestic hot water,it is often difficult to operate,and electric heating is required to assist in operation.Compared with conventional air source heat pumps,cascade air source heat pumps can not only operate normally in severe cold areas,but also provide high-temperature hot water above 70℃,providing higher sanitation conditions for water.In this paper,MATLAB software is used to construct the R134 a single-stage compressed air source heat pump pressurized domestic hot water system,the R410 A single-stage compressed air source heat pump pressurized domestic hot water system and the R134a/R410 A cascade air source heat pump pressurized domestic hot water system.Some parameters were analyzed and compared under steady-state conditions,and the optimal intermediate temperature of the R134a/R410 A cascade air source heat pump was fitted.Taking Xi’an and Shenyang as the research objects,the COP and operating power consumption costs of different systems in different cities were compared and analyzed,and the economy of R134a/R410 A cascade air source heat pump pressurized domestic hot water system and R134 a single-stage compressed air source heat pump pressurized domestic hot water system in Shenyang was further explored.The following conclusions are drawn:(1)Under steady-state conditions,when the evaporation temperature is-19℃,the performance coefficient of the cascade air source heat pump system has obvious advantages compared with the single-stage compressed air source heat pump system.When the evaporation temperature is 25℃,the coefficient of performance of the cascade air source heat pump system has no obvious advantage.In general,the cascade air source heat pump system has a large temperature range of high and low temperature heat sources,and can produce high temperature hot water while ensuring the coefficient of performance.Compared with the single-stage compressed air source heat pump system,it has certain advantages.(2)Under unsteady conditions,for Xi’an City,when the initial water temperatures of the water tanks are 40℃ and 45℃ respectively,the R134a/R410 A cascade air source heat pump pressurized domestic hot water system with a water storage temperature of 75℃compare with the R134 a single-stage compressed air source heat pump with electric heating pressurized domestic hot water system with a water storage temperature of 60℃,the annual average COP is 6.15% and 4.24% lower,and the annual operating power consumption is 5.77% and 3.97% higher respectively.For Shenyang City,when the initial water temperature of the water tank is 40℃ and 45℃ respectively,the R134a/R410 A cascade air source heat pump pressurized domestic hot water system with a water storage temperature of 75℃ compare with the R134 a single-stage compressed air source heat pump with electric heating pressurized domestic hot water system,the annual average COP is 25.32% and 28.77% higher,and the annual operating power consumption cost is21.16% and 22.93% lower respectively.It can be seen that the colder the climate,the more the cascade air source heat pump pressurized domestic hot water system should be used.(3)In Shenyang city,for the R134a/R410 A cascade air source heat pump pressurized domestic hot water system with a water storage temperature of 75℃ and the R134 a single-stage compressed air source heat pump with electric heating pressurized domestic hot water system with a water storage temperature of 60℃,the comparative analysis of the economics shows that: when the initial water temperatures of the water tanks are 40°C and 45℃ respectively,the R134a/R410 A cascade air source heat pump pressurized domestic hot water system with a water storage temperature of 75℃ compare with the R134 a single-stage compressed air source heat pump with electric heating pressurized domestic hot water system with a water storage temperature of 60℃,the annual cost and present value of the cost are reduced by 16.88% and 22.04% respectively.It can be seen that the R134a/R410 A cascade air source heat pump pressurized domestic hot water system with a water storage temperature of 75℃ is more economical in operation and is more suitable in Shenyang.