Performance Optimization Of Mobile Air Conditioning Components And System

Energy saving and environment protection are two crucial issues in the global mobile air conditioning industry in the new century. The refrigerant alternative is one of the key contents of Kyoto Protocol. There are still a lot of arguments about the new alternative refrigerants which are researched. The mobile air conditioning (MAC) system using the refrigerant which global warming potential is larger than 150 assembled in the new car will be forbidden after 2011 by European Union. It is meaningful to improve the efficiency of the current R134a MAC to reduce carbon emission for the friendly environment. The purpose of this study is to survey the potential of energy efficiency improvement and carbon emission reduction of the enhanced MAC based on the components optimization using the simulation and experimental methods. The Total Equivalent Warming Impact (TEWI) is taken as the evaluation index of this study. The main contents and conclusions are included as the followings:1) The high precison system performance test bench is established for experimental studies including components test and system test. The optimization parameters of louver fin used in MAC heat exchangers are performed based on the Taguchi method. The potential of energy efficiency improvement of system COP (Coefficient of Performance, COP) based on the components optimization is studied using the vapor compression thermo-dynamic cycle analysis. The theoretical results indicate that the optimized evaporator and condenser can improve the system COP dramatically.2) The numerical models of normal parallel flow (PF) condenser and the sub-cooling PF condenser are set up using distributed parameter method and validated by numbers of experiments. The performance deviation compared with test data is within±5%. The experimental data of two components show that the system sub-cooling temperature with the sub-cooling PF condenser will be bigger than that of the traditional one and also improves system COP.3) The precious models of micro-channel parallel flow evaporator and laminated type evaporator are proposed and validated by numbers of experiments. The performance deviation compared with test data is within±5%. The experimental results of components performance of the two different type evaporators indicate that the micro-channel parallel flow evaporator is better in heat transfer than the laminated type evaporator. It also makes the system super-heat temperature stable.The refrigerant pass arrangement and the contact type between fin and micro-channel tube are optimized and tested.4) Based on the above two numerical models, a new simulation platform is built up for MAC system. Two optimized evaporator and condenser are designed on the level of system operation. The enhanced MAC system mainly consists of a sub-cooling parallel flow condenser, a micro-channel parallel flow evaporator (PFE), a fixed displacement compressor and a block TXV. The experiments show the enhanced system has a smaller refrigerant charge amount of about 50g than that of the baseline system. The enhanced system can supply a bigger cooling capacity and also has a higher system COP than that of the baseline system. The TEWI of the enhanced system is less than that of the baseline system by 125kgCO2 under the southwest condition of USA.5) A new displacement control strategy for externally-controlled variable displacement compressor is proposed based on in-car temperature, set temperature and evaporator surface temperature and so on. The analyses emphasize upon the variable displacement compressor system and fixed displacement system on the whole vehicle performance. The wind-tunnel test and on-road test results show that a remarkable character of this control strategy is to achieve energy saving through adjusting some control parameters which are set according to the control requirements.