Study Of The Average Velocity Of Airflow In The Intra-clothing Space Based On Multiple Factors

With the development of social economy,people pay more attention to thermal comfort.The main factors affecting thermal comfort include physiological factors,clothing thermal resistance,ambient air temperature,radiation temperature,wind speed and relative humidity.The research on human thermal comfort at home and abroad mostly focuses on the research on thermal comfort such as ambient temperature,relative humidity and clothing thermal insulation performance.Research on the influence of the internal space parameters between the inner surface of the clothing and the skin surface on the heat transfer and humidity exchange of the human body The micro-climate of the inner space is also the most direct factor affecting the thermal comfort of the human body.A good micro-space environment can make workers feel comfortable psychologically and physically.The flow velocity of the inner space of the clothing is the main factor affecting the convective heat transfer and evaporative heat transfer intensity between the skin surface,the inner surface of the clothing and the micro-space air.Therefore,it is very important to study the air flow velocity in the micro-space of human clothing to study the heat transfer intensity between the skin and the space in the clothing.This paper adopts the methods of theoretical analysis,real experiment and numerical simulation to carry out the theoretical analysis of human body-clothing-environment heat transfer,and the heat transfer intensity analysis between the human body and the microclimate inside the clothing.Research on the influence of spatial airflow velocity and the influence of human skin temperature;carry out numerical simulation of airflow velocity in the clothing space under different ambient temperature,metabolic rate,and inlet wind speed conditions,and explore the airflow velocity in different parts of the upper torso clothing space.The main conclusions reached are as follows:(1)When other factors did not change,with the increase of the ambient temperature,the average flow velocity in the inner space of the skin surface coat showed an increasing trend.The reason is that the increase of the ambient temperature causes the body temperature to rise,the amount of sweat increases,and the clothing sticks to the skin surface,resulting in a smaller circulation area between the skin and the inner surface of the clothing,which increases the average flow rate of the airflow in the clothing space.(2)Under the same ambient temperature and walking speed,the average flow velocity in the underclothing space of loose-fitting garments is the smallest,and the average flow velocity of tight-fitting garments is the highest.The reasons for the large average flow rate of air flow in the inner space of tight clothing are: one is the method of experimental measurement of average flow rate-the ratio of the straight-line distance of the smoke flowing from the lower part of the clothing to the upper neckline and the required time;the other is that the tight clothing is in the human spine area There is a local channel through which it takes the least amount of time for the released fumes to flow out.The reasons for the lower average flow rate of loose clothing may be: First,after the smoke enters the inner space of loose clothing,there is a process of diffusing to the entire space;second,the skin surface sweats,causing local clothing to adhere to the skin surface,especially the back area The clothing adheres to the clothes,changes the flue gas circulation channel,and increases the flow distance of the flue gas in the inner space of the clothing.(3)With the ambient temperature unchanged,as the walking speed increases,the average flow rate of the airflow in the inner space increases.The reason for this is that the movement of the human body causes the clothing to produce a stirring effect,which causes forced convection in the air layer inside the clothing.(4)The numerical simulation results show that the largest area of flow velocity in the clothing space is the waist,followed by the abdomen,chest and shoulders.The inlet air velocity has a linear positive correlation with the average velocity of the inner space.The wind speed has a great influence on the flow velocity in the micro space,and increasing the wind speed can improve the thermal comfort of the human body.