Experimental Research On Operating Characteristics Of R32 Air Source Heat Pump Water Chiller-heater Unit In Winter And Summer Operating Conditions

With the phase-out of R22,finding suitable alternative refrigerants has become an urgent task.Because R32 has good environmental protection characteristic and favorable thermal properties,it has gradually been accepted as an alternative refrigerant for R22 in the industrial and commercial fields.At present the biggest obstacle to R32 application is its high exhaust temperature.In order to solve this problem,a new type of R32 air source heat pump chiller-heater unit is proposed in this paper.By means of vapor injection and liquid injection,the exhaust temperature is reduced and the performance of this unit is improved under bad working conditions.Based on the climate characteristics of the hot summer and cold winter areas and related design specifications,the nominal working conditions of this unit is determined,and the thermodynamic cycle is calculated.Then,detailed selection design of compressor,water-side heat exchange system,wind-side heat exchange system,throttling device and auxiliary equipment of this unit are carried out,the experimental prototype is developed and the experimental platform is built.Finally,through the experimental tests under various environmental conditions and outlet water temperatures in winter and summer,the dynamic operation characteristics of the unit and the influence of the vapor injection and liquid injection on the unit's performance are studied.The experimental results show that:Under cooling conditions,this unit's cooling capacity and COP decrease as the outdoor ambient temperature rises,while the power increases with the increase of the outdoor ambient temperature.Meanwhile,the exhaust pressure and exhaust temperature of this unit gradually increase,and the suction pressure and suction temperature change little.When the temperature of the outlet water increases,this unit's cooling capacity and COP gradually increase and the power rises slightly.Meanwhile,the exhaust pressure and exhaust temperature,the suction pressure and suction temperature of this unit are gradually increasing,and the compression ratio is continuously decreasing.Under high temperature conditions,the vapor injection and liquid injection both can effectively reduce the high exhaust temperature of this unit in time,thus ensure safe,reliable and stable operation of this unit.However,when using liquid injection,the cooling effect lasts longer and the extent of temperature reduction is larger.Within 80 seconds,the exhaust temperature can be reduced by 16?.Under heating conditions,the heating capacity,power,and COP of this unit gradually increase with the increase of the outdoor ambient temperature.When the temperature of the outlet water increases,the heating capacity and COP of this unit gradually decrease,while the power of this unit gradually increases.At the same time,the discharge pressure and exhaust temperature of this unit gradually increase,while the suction pressure and suction temperature changes little.Under low temperature conditions or frosting conditions,the use of the vapor injection can effectively reduce the high exhaust temperature of this unit in time.Within 90 seconds,the exhaust temperature can be reduced by 8?,thus ensure safe,reliable and stable operation of this unit.At the same time,the vapor injection can also improve the heating performance of this unit and increase the heating capacity by about 9.0%.This paper studies the operating characteristics of R32 air source heat pump water chiller-heater unit in winter and summer operating conditions,and explores the methods of reducing the high exhaust temperature.Thus,reliable experimental data and reference for the development and performance improvement of the R32 air source heat pump water chiller-heater unit.