Simulation And Experimental Study Of Carbon Dioxide Heat Pump Water Heater System Based On MATLAB

As a new generation of hot water production equipment,CO₂ transcritical heat pump water heater has very significant advantages in energy saving,environmental protection and high efficiency,but the characteristics of CO₂ fluid in the supercritical area are highly variable and the system operating pressure is high,which increase difficulty in system design and optimization of the CO₂ heat pump water heater.Therefore,this paper has done the following work for a CO₂ heat pump water heater:?1?The steady-state mathematical model for each component of CO₂ transcritical cycle is established in MATLAB with reference to the modeling method of traditional heat pump system,based on which,the system simulation model is established in SIMULINK platform;?2?In the environmental simulation enthalpy laboratory,test and analyze the operating parameters such as consumed power and heat capacity of the unit at different ambient temperatures and different effluent temperatures;The calculation accuracy is improved by correcting the parameters of the model according to the test data and the correlation between leakage heat coefficient of the compressor,the outlet water temperature and the ambient temperature is obtained by fitting method;?3?The heat transfer characteristics of the gas cooler and the influence of heat transfer area when the high temperature water of unit is discharged and the influence of the size of internal heat exchanger?IHE?on the operating parameters under certain working conditions is analyzed by using the component and system simulation model,respectively.After the above-mentioned staged work,the following conclusions were drawn:The deterioration of heat transfer characteristics in the gas cooler when the high temperature water of unit is discharged is mainly due to the influence of the supercritical CO₂ fluid physical properties and the change of water mass flow,which can be mitigated by increasing the heat transfer area but the effect is limited;When considering throttling loss under specific conditions,IHE has the best heat exchange area to minimize the throttling loss,maximum heat capacity and maximum system energy efficiency ratio of unit.