Characteristics Research And Energy Consumption Simulation Of R134a/CO₂ Cascade Air Source Heat Pump System

Winter heating in severe cold regions of China is one of the issues concerned by people's livelihood.Traditional heating methods cannot meet the requirements of current"energy conservation and emission reduction"policies due to their high energy consumption and large pollution.Therefore,the research on energy-saving and environment-friendly heating methods has become one of the current key directions.Based on the above background,this paper presents a R134a/CO₂ cascade air source heat pump system suitable for low-temperature environment,which is environmentally friendly and reliable.Through numerical calculation,experimental verification and simulation analysis,the cycle and operation characteristics of the system are studied,and the following results are obtained:?1?By analyzing the development status of the cascade air source heat pump industry and related technologies,and comparing the properties of refrigerants,the paper puts forward the cycle of R134a/CO₂ cascade heat pump;?2?The circulation mathematical model of R134a/CO₂ cascade air source heat pump is constructed,and the circulation characteristics are analyzed by numerical method.It is found that the optimal intermediate temperature maximize the circulation COP when the temperature of high and low-temperature heat source is constant.With the decrease of high-temperature condensation temperature,low-temperature evaporation temperature and intermediate heat transfer temperature difference,the circulation COP increase and the refrigerants flow rate of high and low-temperature grade decreases;According to actual engineering needs,calculate the key state parameters of R134a/CO₂ cascade heat pump cycle under-12?;?3?The R134a/CO₂ cascade air source heat pump prototype experimental system is built,and variable condition performance test was carried.The experimental results showed that with the decrease of ambient temperature,the COP and the heat capacity of the system decrease,the pressure ratio of the high and low-temperature compressor increases,the outlet temperature of the condensing side of the intermediate heat exchanger decreases,and the pressure loss of the condensing side of the intermediate heat exchanger increases;?4?TRNSYS simulation software was used to calculate the annual energy consumption of the R134a/CO2 cascade air source heat pump heating system,and through economic analysis,it is found that the system meets the requirements for use in cold regions,and the average temperature in winter has a great influence on the parameter index.When the simulated city is changed from Beijing to Harbin,the heating demand increases by 209.9%and the energy consumption increase by 221.8%.Meanwhile,the resource consumption and pollution emission of the air source heat pump heating system are lower than that of the traditional coal heating method.