Study On Cooling Load Calculation And System Cooling Capacity Checking Model Of Passenger Car Air Conditioning

On the one hand,the automobile air conditioning system affects the thermal comfort of occupants,on the other hand,it also seriously affects the energy consumption of automobiles.Nowadays,automobile cooling load and cooling capacity of air conditioning system have become important issues concerned by automobile manufacturers and researchers.There are two current air conditioning vehicle cooling test standards in China’s automobile industry,"Automobile air conditioning vehicle cooling performance Test Method" and "Automobile air conditioning refrigeration system performance road test method";In the industry,the widely used methods for the calculation of automotive cooling load are mainly occupant estimation method and model estimation method,which all rely on the experience of designers to estimate.Therefore,it is necessary to calculate automobile cooling load reasonably and accurately and determine the cooling capacity of air-conditioning system.In this paper,the domestic and foreign literatures are reviewed from the aspects of the cooling load of the vehicle under stable conditions,the drying of the vehicle and the thermal environment in the vehicle cabin during the cooling and cooling process.It is found that there are some studies on the calculation of the cooling load of the vehicle and the selection of the cooling capacity of the compressor,and they are all focused on the stable conditions.However,after vehicle exposure to the sun in subtropical areas,a great amount of cooling is needed to cool down the waste heat,and this part of the load calculation is relatively rare.In addition,at present,the selection of cooling load and compressor and other air conditioning equipment under stable conditions in the automotive industry mostly adopts empirical estimation method,and the accuracy is questioned to a certain extent.Therefore,this paper proposes to use the cooling load coefficient method in buildings to calculate hourly cooling load in typical summer days under stable working conditions,and uses the prediction model of cabin air temperature in the cooling process to check the cooling capacity of automobile air conditioning system,thus forming a relatively complete method to determine the cooling capacity of automobile air conditioning system.Firstly,the automobile air conditioning system is briefly introduced,including its air transport mode,control system,refrigerant and system components.Secondly,the calculation of hourly cooling load is theoretically analyzed by referring to the cooling load coefficient method in building.Then,based on the law of conservation of energy for drying and refrigeration cooling process in the theoretical analysis,established sun car and car cabin air temperature prediction model,refrigeration cooling process by the process of car refrigeration cooling time can get the initial conditions,and the refrigeration cooling process in the cabin air temperature prediction model for automotive air conditioning system of cold quantity check.Finally,the variation of cabin air temperature during drying and cooling in Beijing,Shanghai,Guangzhou and Lhasa was analyzed by theoretical model.Then,the sun experiment and cooling experiment were designed respectively to test the thermal environment parameters in the car cabin,and the experimental content and experimental process were introduced in detail.It is found that the change of air temperature in the cabin meets the exponential function.The linear regression equation between the air temperature in the cabin and the drying time in the drying process and the linear regression equation between the air temperature in the cabin and the cooling time in the cooling process are obtained.The results are consistent with the theoretical model of air temperature change in cabin during drying and cooling.Finally,the software of vehicle load calculation is compiled.Based on the software,the calculation and analysis of the experimental model are carried out,and the cooling load calculation and system cooling capacity checking are introduced in detail.The influence of vehicle direction and speed on cooling load is analyzed in detail and it is concluded that the influence of vehicle direction is not as great as the influence of building orientation on the room.Speed only affects the convective heat transfer coefficient of the car envelope,but has little influence on its heat transfer coefficient,so the influence on the cooling load of the car can be ignored.