Changes Of Thermal Resistance Of Multilayer Clothing At Different Activity Levels And Their Effects On Thermal Sensation

Humans spend most of their time indoors,and the thermal comfort of indoor environments is attracting widespread attention.Studies have shown that factors affecting human thermal comfort can be divided into environmental factors and individual factors.Environmental factors include ambient temperature,relative humidity,air flow rate and average radiant temperature.Individual factors include human body metabolic rate and clothing thermal resistance.Prof.Fanger of the Technical University of Denmark analyzed 1,300 subjects with thermal sensation,and finally published the heat balance equation and the predicted mean vote PMV(Predirected Mean Vote)in 1970,combined with the seven-level classification method of thermal sensory level proposed by ASHRAE,when four environmental factors and two individual factors are determined,the human body heat sensation can be predicted.The heat balance equation does not take into account the thermal resistance of the garment in the actual state of the human body,only set the thermal resistance of the garment according to different clothing combinations,for the multi-layer garment,the thermal resistance of the single garment is superimposed.With the diversity of clothing styles,especially the habit of multi-layer clothing in China,the heat and moisture transfer process of clothing is not a simple superposition of the thermal resistance of a single piece of clothing.The actual thermal resistance of clothing is affected by environmental factors and activity levels,at this point,considering the thermal resistance of the garment as a fixed value can no longer meet the needs of thermal comfort research.In addition,in the PMV,a fixed metabolic rate value is given for a certain activity state,but the actual metabolic rate of the human body has individual differences,and is affected by environmental factors,the metabolic rate,which is simply based on the activity level,leads to a bias in the thermal sensory prediction.This paper first discusses the different calculation methods of garment thermal resistance.Then,when experimentally studying the different environmental temperature and activity level,the actual thermal resistance of the garment under the multi-layered clothing state is analyzed,and its influence on thermal sensation is analyzed.The test subjects used three kinds of dressing methods in the constant temperature and humidity climate laboratory,the activities were static sitting,standing and walking,and measured physiological parameters such as metabolic rate,skin surface temperature and sensible heat loss on human skin surface.Analyze the changes in thermal resistance and metabolic rate of garments through MATLAB,Origin and SPSS.Studies have shown that when the activity level is certain,the thermal resistance of the garment increases as the ambient temperature increases;when the ambient temperature is constant,the activity level increases and the thermal resistance of the garment decreases.In the study of metabolic rate,it was found that the ambient temperature was too high or too low,which led to an increase in metabolic rate.As the activity level increased,the metabolic rate increased.On this basis,the thermal resistance of clothing under different calculation methods is analyzed,and combined with measured metabolic rate,and the corresponding PMV is calculated.Compared with the actual thermal sensation voting of the human body,it is found that the difference between the two is large.In addition,the MATLAB programming is used to calculate the PMV and the standard effective temperature SET* respectively,and the human body thermal sensation evaluation prediction under different environmental temperature,activity level and clothing mode is obtained,and then compared with the actual thermal sensation voting TSV.It is found that the thermal sensation prediction calculated from the thermal resistance and metabolic rate of the clothing according to the thermal comfort standard has a large deviation from the actual thermal sensation voting TSV.and the linearity with the standard effective temperature SET* is poor.This article corrects the comfort zone.The study found that using the holistic method to calculate the thermal resistance of the garment,the calculated thermal sensation is higher than the actual thermal sensation vote TSV.Therefore,this paper proposes a method for calculating the thermal resistance of clothing considering the coverage of clothing.The predicted thermal sensation is in good agreement with the actual thermal sensation TSV.Therefore,the influence of clothing coverage on the surface coverage of the human body is considered when calculating the thermal resistance of the garment.