Research On The Influence Of Temperature Step Change On Human Thermal Response

In recent years,extreme weather such as high temperature and extreme cold occurs more and more frequently around the world.Due to the operation of indoor heating equipment and air conditioning equipment,the air temperature of people’s daily life and office can mostly be kept at neutral temperature.Therefore,when people enter the indoor environment of neutral temperature from the outdoor environment of extreme weather such as high temperature and extreme cold,or from the indoor environment of neutral temperature into the outdoor environment of high temperature,extremely cold and other extreme weather,it is bound to experience a large abrupt change in environmental temperature;In addition,there is also a large temperature difference between the airconditioned environment in public transport in winter and summer and the natural environment outside.People frequently come and go in the air conditioning environment and outdoor natural environment,the large change of temperature will have a strong impact on human thermal comfort,and even affect human health.Therefore,it is necessary to conduct in-depth exploration on the thermal response rule and the change rule of thermal load of human body under the circumstance of large temperature difference abrupt change of environmental temperature,further explain the mechanism of human body perception to the dynamic environment of temperature abrupt change by human heat load analysis,and try to establish the thermal sensation prediction model of human body in the dynamic environment of temperature step change,so as to enrich and develop the dynamic thermal comfort theory.In this study,12 males and 12 females were selected from Xi ’an University of Architecture and Technology in September and December 2020 and March and June 2021,and a total of 24 subjects were selected to carry out neutral → hot(cold)→ neutral roundtrip temperature mutation experiment.Nine temperature mutation processes corresponding to three seasons(summer(26 ℃-30/35/40/45 ℃-26 ℃),transition(24 ℃-15/20 ℃-24 ℃)and winter(20 ℃-(-10)/0/10 ℃-26 ℃)were created by artificial climate chamber,a total of 216 tests were made in the experiment.During the experiment,subjective response(thermal sensation,thermal comfort,thermal acceptability,thermal preference)and physiological response(skin temperature,skin wetness)parameters of subjects’ whole body and 16 local parts were collected,and environmental parameters during the experiment were continuously measured.The precise measurement of human physiological parameters and physical environment parameters combined with human thermal balance equation can accurately calculate the change law of human body thermal load during the experiment,and then the thermal response of human body under the dynamic environment of temperature change is analyzed.The research findings in this paper are as follows:(1)The physiological reaction and subjective reaction of human body changed dynamically in the dynamic environment of temperature sudden change,and the phenomenon of mental advance and thermal asymmetry appeared in the experiment.(2)The sensitivity of human body to hot and cold stimuli varies in different seasons.Different parts of the human body respond differently to cold and hot stimuli.To the change of ambient temperature,the local response of the human body is slower than that of the whole body,and the response range is smaller.In summer and winter,local air conditioning can be used to supply air to sensitive parts of human body,so as to enhance human thermal comfort.(3)The phenomenon of " cold sensation overshooting " occurs in the abrupt change from hot to neutral environment.The reason for the cold sensation is that at the moment when the subjects enter the neutral environment from the high temperature environment,the skin temperature is much higher than the air temperature,and the sweating amount also reaches the maximum,which leads to the maximum convection heat dissipation,radiation heat dissipation and skin heat dissipation between the human body and the environment,and the heat dissipation of the human body is much greater than the heat production.As the body’s thermoregulation system kicks in,the body’s cold sensation gradually disappears.(4)By analyzing the relationship between human skin temperature and its rate of change and human thermal sensation,the mean skin temperature and its rate of change were combined to predict human body thermal sensation in the dynamic environment of temperature change,and then a thermal sensation prediction model based on skin temperature was obtained.(5)By analyzing the relationship between human heat load,skin temperature and its rate of change and human thermal sensation,combining human thermal load and average skin temperature to predict human body thermal sensation in dynamic environment of temperature change,a thermal sensation prediction model based on thermal load was obtained.(6)By comparing the prediction performance of PMV model,skin temperaturebased thermal sensation prediction model and thermal load-based thermal sensation prediction model under the condition of sudden temperature change,it is found that the prediction model with thermal load has better performance.