| Heat pump,as a typical energy cascade heating method,has been widely used in life and industry.But the traditional heat pump uses freon and other working medium as refrigerant,aggravating the earth’s greenhouse effect and causing great damage to the ozone layer.As the refrigerant of heat pump system,natural working medium carbon dioxide has no pollution to the environment and high heat exchange efficiency.Based across critical CO2 heat pump water-water system as the research object,through the thermodynamic analysis of the CO2 heat pump system,using the lumped parameter method,established across critical CO2 heat pump system of air cooler,evaporator,compressor and other key equipment simulation model,through the relationship of the equipment import and export,the steady state simulation model of heat pump system is established.In the process of simulation,EES(Engineering Equation Solver),as a software for solving Engineering equations,has built-in a large number of mathematical and thermodynamic functions,providing a quick and convenient method for solving Engineering thermodynamic fluid mechanics,heat transfer and other problems.In this paper,EES software is used to analyze and calculate the thermal cycle of the transcritical CO2 heat pump system,MATLAB software is used to write the system simulation program,and REFPROP software is used to obtain the physical properties of working media.Through calculation results,the paper analyzes the system input parameters:freezing water inlet temperature of cooling water pressure changes will affect the performance of the system,provide a basis for practical system design and on the basis of simulation analysis and calculation,this paper has carried on the structure across critical CO2 heat pump system design and equipment selection,system structure and equipment parameters were determined.In the design process of heat exchanger,based on the pinch point analysis,the minimum pinch point temperature along the process of heat transfer between working medium and water was found,and the heat transfer area of related heat exchanger was determined,which provided a method and basis for the design and optimization of heat transfer equipment of trans-critical CO2 heat pump system. |
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