Research On Dynamic Thermal Comfort Of Human Body During Intermittent Exercise

In recent years,our country has enhanced the national physique and promoted the sports industry consumption to the height of national strategy,which greatly promotes the development of China’s fitness industry.However,in the face of a large number of sports consumers,the construction of sports related infrastructure in China is still lagging behind: the current thermal comfort evaluation standards in China mainly focus on the sitting state of office buildings,which is difficult to provide reference for the thermal comfort of human body in sports state.China’s current standards do not put forward specific control scope for the design of environmental parameters of sports venues.However,the recommended values of relevant foreign standards are far lower than the summer air conditioning temperature(26 ℃)in China.Blindly following will bring huge energy consumption load and economic burden of air conditioning,which does not meet the demand of energy saving in China.In addition,in real life,most of people’s activities are intermittent exercise;however,most of the related research on thermal comfort tends to focus on steady-state continuous exercise.During intermittent exercise,the effect of metabolic rate dynamic change on human physiology and subjective response is quite different from that in steady state,but there is still a lack of systematic research and formation of evaluation and prediction model and corresponding design guidance.Therefore,this study is to improve the thermal comfort and environmental quality of indoor sports personnel as the theme,and try to explore the characteristics of metabolic rate changes and thermal response under intermittent exercise state,in order to save building energy consumption and obtain the threshold value of human comfortable thermal environment parameters under gymnasium exercise state,so as to provide reference for the thermal environment evaluation of indoor sports venues.In this study,the indoor physical environment parameters(air temperature,relative humidity,air flow rate,average radiation temperature,etc.)were controlled by the artificial climate chamber system,and the physiological parameters such as metabolic rate,skin temperature,skin moisture,heart rate and skin blood flow of the subjects were measured at the same time The subjective questionnaire voting results(thermal sensation,thermal comfort and thermal acceptability)of the subjects under various working conditions were collected,and the dynamic thermal comfort of the human body under intermittent movement was analyzed.The results show that: 1(1)From the point of view of physiological parameters,metabolic rate,heart rate,average skin temperature,skin wetness and blood flow of forearm skin all show an obvious "ladder" trend with exercise,that is,the trend is increasing in the exercise stage,and decreasing in the rest stage until reaching the steady value.Among them,the average skin temperature range of 40 min continuous exercise is larger than that of the other two intermittent periods;compared with 10 min and 20 min intermittent periods,the skin moisture of continuous exercise stage is basically larger,while the skin moisture of rest stage is basically smaller.(2)From the perspective of subjective reaction,the lower the temperature,the lower the voting value of thermal sensation in the rest stage,which can even reach-1(slightly cool)in the rest stage at 20 ℃;except for the 20 ℃ condition,the voting values of other thermal comfort and thermal acceptability are basically similar,and are at a higher level;in terms of local thermal sensation,the four parts tend to be the same,and the sweating amount of the head is the most Many.The fatigue range of continuous motion is larger than that of 10 min and 20 min intermittent condition.Among them,the lowest value of thermal comfort voting appears in 20 minutes of exercise,which may be due to the short duration of 10 minutes of exercise,and the high thermal comfort of the subjects in a short time;while 40 minutes of continuous exercise is longer,the sensitivity of the subjects to temperature is reduced,and the thermal regulation has fatigue effect.Therefore,the thermal demand of the people who exercise for 20 minutes or so should be paid more attention to.(3)After analyzing the physiological response characteristics under intermittent and continuous exercise,it is found that the metabolic rate change rate under continuous exercise is greatly affected by temperature;when the exercise begins,the change rule of metabolic rate change rate is basically consistent with the change rule of heart rate,but after the end of exercise,the change of heart rate in the rapid decline stage is faster than that of metabolic rate,and in the slow decline stage The results show that the change rate of skin temperature is slower than that of metabolic rate;the maximum value of average skin temperature change rate of 40 min continuous exercise in the exercise phase is basically less than that of the other two working conditions,while the maximum value of average skin temperature change rate of the three in the rest phase is basically close;under all working conditions,the change rate of skin moisture in the rest phase is basically less than that in the exercise phase,and the skin is moist The absolute value of degree change rate basically shows a trend of increasing with the decrease of intermittent exercise duration;however,there is no significant difference in the change rate of blood flow under the three temperature conditions,but they also show a trend of decreasing with the increase of intermittent exercise duration;this shows that the longer the intermittent exercise duration is,the slower the response speed of human blood flow becomes,which affects the average skin temperature and skin moisture Long time exercise may bring "thermal regulation fatigue effect" to human body temperature regulation system,resulting in slow response of human body temperature self regulation system,which is not conducive to timely adjustment of human body heat balance.(4)In this study,the correlation between average skin temperature and thermal sensation,skin moisture and thermal comfort is not strong;thermal sensation and thermal comfort show a good quadratic polynomial relationship under three temperature conditions,indicating that the duration of intermittent exercise has no effect on the relationship between thermal sensation and thermal comfort.(5)According to the iso-8996 standard,there are some differences between the predicted metabolic rate distribution and the measured value.When the care rate is greater than 130 BPM,the two distribution values are close,while the care rate is less than 130 bpm The measured value of BPM is generally lower than that of iso-8996standard;according to the equation provided by Zhang,the estimated metabolic rate value is higher than that of iso-8996 standard and the measured value,which obviously overestimates the metabolic rate of ordinary men under the same heart rate;two prediction equations are obtained by dividing the distribution of heart rate and metabolic rate according to the exercise and rest stages,and can be used for the actual generation Application of metabolic rate prediction.(6)Whether it is intermittent or continuous exercise,the predicted value of PMV for human skin temperature deviation is relatively large;and the predicted value of skin temperature based on two node model is significantly higher than the measured value in this study;in addition,the two node model may overestimate the response ability of human skin temperature,and underestimate the impact of environmental temperature on human skin temperature;the predicted value of skin temperature based on two node model is significantly higher than the measured value There is even a 1-2 minute delay in the temperature change compared with the measured change.(7)In this study,we found that the traditional method of calculating neutral temperature by regression of average thermal sensation voting value and air temperature is not scientific enough,because it underestimates the acceptable range of thermal sensation of sports people.In this study,the most unfavorable thermal comfort value corresponding to each intermittent working condition is selected,and the relationship between the most unfavorable thermal comfort voting value and air temperature is calculated respectively.Taking the people whose heat demand is the most difficult to meet for 20 minutes as the object,the most suitable temperature parameter for sports buildings is 24.4 ℃,which indicates the temperature of previous gym research Most of the settings are not reasonable(either too high or too low);for sports buildings,this parameter can meet the heat demand of most of the sports crowd,and is conducive to building energy efficiency.