Evaluation And Analysis Of Thermal Comfort On Vehicle HVAC

The comfort requirement of driving is increasing higher and higher, and itchanges from the past cool in summer and warm in winter to meet the need fordifferent body parts, air conditioning zoning and all season comfort. Human thermalcomfort evaluation develops from temperature, humidity and wind velocity evaluationto a comprehensive evaluation which integrated environmental factors, clothingfactors and even physiological factors. Therefore, it’s very important to researchadvanced thermal comfort evaluation method and explore more potential air supplysystem. This is the main direction of energy saving for automotive air conditioning.Based on the requirement of thermal comfort for cabin, this paper summarizedthe thermal comfort evaluation under non-uniform thermal environment, proposedprecise evaluation method of human thermal comfort——the Fixed weighted PMValgorithm and thermal comfort deviation AEQTwhich based on EquivalentTemperature EQT. The Fixed weighted PMV algorithm divided the human body intothree zones, and set up the mathematical relationship of the local PMV and the overallPMV. This evaluation divided thermal sensation into seven stages which changedfrom-3to+3.The thermal comfort deviation AEQTwhich based on EquivalentTemperature EQT measured the deviated degree of the human thermal comfort andcomfort ideal value. The value of AEQTranged from-1to+1, the higher the value thebetter comfort. The thermal sensation was within the comfort range when AEQT≥0; itwas the ideal value when AEQT=1; it was outside the comfort range when AEQT<0.This paper applicated the thermal comfort evaluation index into CFD simulationcalculations, evaluated the dynamic thermal comfort during the cooling process,analyzed and researched the thermal comfort of the cabin by CFD software, andcompared the influence of different air inlet temperature and different cycle mode onthe human thermal comfort. The results showed that the impact of different air inlet temperature on AEQTand weighted PMV was great. The weighted PMV will increaseby0.288and AEQTwill reduce by0.074when the air inlet temperature rises1℃,which leading to produce a hot thermal sensation. What’s more, the impact on coolingtime was greater which showed exponential growth when the air inlet temperaturerose.This paper optimized the cabin airflow field based on meeting the uniformhuman thermal comfort level, analyzed the thermal comfort and energy saving effectof several optimized designs. The results show that the lateral air supply mode willnot only help to improve the occupant thermal comfort, and reached a goodtemperature stratification which reduced the air conditioning load and energyconsumption. Its energy-saving efficiency coefficient reached98.73%which4.93%higher than the original model. Based on a certain condition, the evaporator coolingload will be reduced by10.4%under outer cycle mode and reduced by26.48%underinner cycle mode. This paper provided a realization method for low-power and highcomfort development needs of automotive air conditioning.