Study On Indoor Thermal Response And Comfort Zone Under The Influence Of Solar Radiation In Winter

With the large-area application of French windows and glass curtain walls,the solar radiation entering the room through the envelope structure has increased significantly.Current studies have shown that solar radiation has a significant effect on the human thermal sensation.ASHRAE Standard-55,2017 gave a mean radiation temperature calculation method.However,there were still many problems worth exploring further,such as the change of heat transfer characteristics of the local and the whole body under the influence of solar radiation;the comfort zone based on the equivalent temperature and the standard effective temperature;whether the unsatisfactory rate of radiation asymmetry <5 % which was considered as a criterion for thermal comfort applies to indoor thermal environments under the influence of solar radiation.Therefore,this paper develops the study of human thermal response under the influence of solar radiation,quantitatively studies the influence of solar radiation on indoor thermal environment parameters,physiological parameters and heat transfer characteristics,and explores the change of comfort zone under direct sunlight conditions.Firstly,the theoretical calculation method of thermal environment evaluation parameters(mean radiant temperature,plane radiant temperature,radiation temperature asymmetry)under the influence of solar radiation has been studied;ECOTECT software was used to simulate the dynamic changes of solar spot in the test room,and the thermal comfort experiment of human body in winter was designed.Four kinds of possible solar radiation exposure in office environment were studied,including,not directly irradiating the human body,irradiating part of the leg,irradiating the "part of the upper + leg",irradiating the "part of the upper + leg + head".The thermal environment parameters and the human skin temperature were collected,and the questionnaire was conducted at the same time.By SPSS and Origin software,paired sample T test,covariance analysis and principal component regression model were used to analyze the subjective response of human body under four different solar radiation exposures.Using MATLAB,the local and overall comfort zones of human body based on equivalent temperature were calculated,and the displacement of comfort zones based on standard effective temperature was determined.Through field experiments,the changes of the mean radiant temperature and the plane radiant temperature under solar radiation conditions were quantitatively studied,and the radiation temperature asymmetry was calculated.The result revealed that the maximum asymmetry was as high as 22.15?.By studying the subjective thermal sensation,thermal comfort,thermal expectation and sweating sensation of human body under different experimental conditions,we could see that there were significant differences in thermal sensation of human body at different experimental stages.This difference was mainly due to the different irradiation areas of solar radiation.Solar radiation can significantly improve the thermal sensation of human body without causing thermal discomfort.At the same time,the influence weights of different parts on the overall thermal sensation at different experimental stages were calculated.In order to ensure the objectivity of the analysis results,skin temperature was taken as the main physiological parameter for analysis.The results showed that different areas of human surface irradiated by solar radiation could increase skin temperature in varying degrees.According to skin temperature,air temperature and humidity,and mean radiation temperature,the convective,radiative and evaporative heat transfer of different body parts and the whole in different experimental stages were obtained.Through the analysis of their corresponding changes,it is found that the convective heat transfer in the exposed part decreases from the stage where the solar radiation does not directly irradiate the human body to irradiating the "part of the upper + leg + head",while that in the clothing part was contrary to its regular pattern,the radiative heat transfer decreases continuously and the evaporative heat transfer increases gradually.Total heat loss was calculated,the relationship between the proportion of heat loss to total heat loss and thermal perception were studied.The results showed that with the increase of human body area irradiated by the sun,the total heat dissipation decreased,the overall thermal perception increased,and the heat transfer ratio of convective,radiation and evaporation had a good linear relationship with thermal perception.Then,the comfort zone of A,B and C grades of different parts of human body based on equivalent temperature and the comfort zone deviation based on standard effective temperature were calculated.It is found that the solar radiation makes the difference between the comfort zones of the left and right sides of the human body based on the equivalent temperature.The neutral temperature of the left part that can be directly irradiated by solar radiation was lower than the right side,and the comfort zone was narrow.Compared with no direct sunlight,the upper and lower temperature of the comfort zone based on the standard effective temperature decreased and became narrower.It can be seen from the above analysis that,in winter,the rational use of solar radiation could make the human body warm locally,achieve thermal neutrality,and would not cause human thermal discomfort.Achieving the same thermal sensation as the actual situation was equivalent to increasing the temperature in a uniform stable environment.Therefore,making full use of solar radiation could improve human thermal comfort and reduce air conditioning energy consumption.