Study On Performance Of Medium And High Temperature Working Fluid Used In Water Source Heat Pump Units

The research on medium and high temperature heat pumps can bring huge energy saving and environmental protection benefits.As the environmental problems become more and more serious,traditional working fluids are facing obsolescence because of their destructive effects on the environment,which limits the development of medium and high temperature heat pump technology.This article aims to find a new type of working fluid with ODP of 0,low GWP and good thermal performance.The selected working fluid is analyzed theoretically,experimentally and through simulation.This paper first screened out three new working fluids,namely XP140,R417 A,and NC004(R134a: R1234ze(E): R32 = 40%: 30%: 30%).The three working fluids were analyzed under the principles of environmental properties,thermal properties,and safety.The ODP values of the three working fluids are all 0,of which the GWP value of NC004 is lower and the harm to the environment is smaller.Then,preliminary analysis of R417 A and NC004 is performed through theoretical calculations.The results show that NC004 performs well in the medium and high temperature region,and the system COP and heating capacity are higher than R417 A.Secondly,the performance parameters of the three working fluids were tested on a water source heat pump experimental bench.The experimental results show that the three working fluids all show a certain application potential under medium and high temperature conditions,Among them,XP140 has obvious advantages in exhaust pressure,but the parameters of COP and heating capacity are far from the other two working fluids.NC004 performance is relatively stable in the medium and high temperature region,while R417 A is slightly reduced.At the same time,the experiment also found that the superheat of the working medium can be reduced and the performance of the system can be improved by increasing the frequency of the compressor.Finally,a heat pump system simulation program was established,and the simulation accuracy of the model was found to be good through experimental verification.R417 A and NC004 were simulated under high-temperature conditions through the simulation model.The simulation results show that in the high temperature region,the working medium NC004 has better heating capacity than R417 A,but its high exhaust pressure will hinder its development in the high temperature condition,so if it needs to produce high temperature hot water,it needs to upgrade the pressure bearing capacity of the system compressor.The comprehensive analysis of the three methods shows that NC004 performs well in medium and high temperature areas and is environmentally friendly,and has the potential to be applied to medium and high temperature heat pumps.