Effect Of Local Electric Heating On Human Thermal Response In Cold Environment

People in many industries suffer from low temperatures working conditions.In order to reduce people’s discomfort in low temperatures,many scholars have conducted long-term research on personal cooling system.Among many kinds of individual heating equipment,electrically heated clothing has been widely used because it can improve human wear thermal comfort by supplying active heating,wear light and consume less energy.However,the current research on the optimal location of thermal stimulation and the effect of local thermal stimulation on the overall comfort of electrically heated clothing is not perfect.Therefore,explorative investigations on human responses were performed when single boby parts were thermally stimulated in cold environment,to analyze the thermal sensitivity of body parts.To provide reference for personalize heating design under cold environment.In order to explore the human responses to thermal stimulation of a boby parts,in a climate room with a temperature of 5℃,a heating plate was used to conduct thermal stimulation experiments on eight parts(front chest,upper back,abdomen,waist,elbow,knee,hand and soles).The changes of local and global thermal sensation,thermal comfort,thermal acceptability and skin temperature during thermal stimulation of different parts were analyzed.During the experiment,the subjects could adjust the temperature according to their own will.The results showed that local thermal stimulation could improve local skin temperature in this environment,but the improvement was limited.When each area reached comfort,local skin temperature remained stable at 39.1～39.7℃,and there was no obvious linear relationship between average skin temperature and overall thermal sensation.Local thermal stimulation can also significantly improve the overall thermal comfort of the human body.Different parts of the thermal stimulation have different effects on the overall,and the relieving effect of foot heating on the overall cold feeling is better than that of other parts.There is a good linear relationship between the overall thermal sensation,thermal comfort and thermal acceptability,and the overall thermal sensation can be used to predict the overall thermal comfort and thermal acceptability.The influence factor and the local radiative heat sensitivity were used to analyze the local thermal sensitivity,the results showed that the feet and upper back had the greatest influence on the overall thermal sensation,followed by the abdomen,waist and chest,and the elbows,knees and hands had the least influence.This indicates that except the feet,the influence of the heating on the trunk on the overall thermal sensation is greater than that of the limbs.The preferred heating temperature of each part was different.The preferred temperature of the trunk part was lower than that of the limbs part,and the preferred temperature of the hands and feet was the highest.In addition,the gender had an obvious effect on influence factors of local thermal on overall thermal sensation,men generally preferred lower heating temperature.In order to verify whether the local thermal sensitivity obtained in the local thermal stimulation experiment has scientific significance,eight sites were grouped for thermal stimulation(highly sensitive area was combined with upper back and feet,middle sensitive area was combined with waist and chest;Abdomen and waist,low sensitivity area is combined with knees and hands;Elbows and knees).Subjective evaluation and objective test results show that the combined heating effect of highly sensitive parts is better than that of medium sensitive parts,while the combined heating effect of low sensitive parts is the worst.Except for the low sensitive area,the combined heating effect is better than that of single heating site,which indicates that the conclusion of local thermal sensitivity is of scientific significance.Finally,through the analysis of energy consumption,it is found that the heating temperature is proportional to the energy consumption,and the heating of limbs consumes more energy than that of the trunk.In the selection of heating clothing parts,the upper back and other trunk parts should be selected first,the feet should be heated first for the limbs parts,and the heating temperature should not make the local skin temperature exceed 39.7℃.To sum up,this paper explores the influence law of local thermal stimulation on the overall thermal response from both subjective and objective perspectives,and analyzes the thermal sensitivity of the parts.The conclusions can provide theoretical basis for the construction of relevant thermal sensation models,and also have guiding significance for the parameter design of electric heating clothing.