Why is the temperature of human body around 37 degrees?

The normal body temperature of the human body is around 37℃. But this does not mean that people are most comfortable when they keep the temperature of 37℃ in clothes or houses. Because the heat generated by human metabolism must be radiated at a certain speed. If the ambient temperature is too high, the heat can't be dissipated and accumulated in the body, people will feel very uncomfortable. At this time, the human body will excrete a lot of sweat and reduce the body temperature by evaporation and heat dissipation. Only when the temperature is lower than the body temperature can the body's heat be freely emitted. However, when the temperature is too low, the heat is dissipated too quickly, which exceeds the normal heat dissipation speed of the human body, and the human body will feel cold again. At this time, it is necessary to wear appropriate warm clothes to prevent the heat of the human body from radiating outward.

Upper and lower limits of comfort temperature According to experiments at home and abroad, the most comfortable temperature for people is 19-24℃ in summer and 17-22℃ in winter. The human body always keeps its body temperature constant. When the ambient temperature exceeds the upper limit of comfortable temperature, people will feel hot, and when it exceeds 37℃, people will feel extremely hot. The upper limit of temperature that people can tolerate is 52℃. On the contrary, when the ambient temperature is lower than the lower limit of comfortable temperature, people will feel cold and cold; If it is below 0℃, it will feel cold. For people who are generally engaged in outdoor activities and wear appropriate clothes, the lower limit of tolerable temperature is about MINUS 34℃.

I feel that temperature is also related to wind speed and humidity. It is not comprehensive to talk about cold and heat only from the level of temperature. In fact, the so-called cold and hot are human feelings, which are not exactly the same as the actual temperature. Perceived temperature is not only related to air temperature, but also related to wind speed and humidity. For example, it rains in the south in winter, which makes people feel cold. When the wind blows in the north, I feel biting cold. Before the arrival of typhoon or rainstorm in summer, because the temperature is higher than the body temperature, the temperature plays a heating role on the human body, and people can only maintain the body temperature balance by sweating and consuming calories. If the air humidity is high at this time and the sweat does not volatilize, the human body will feel sultry and abnormal. If the cool breeze in Xulaili accelerates the release of human heat at this moment, the human body will feel cool immediately. All these show that when we talk about cold and heat, we can't ignore the role of wind and humidity.

Wind and humidity play an important role in sensing temperature. One can enhance the convective heat transfer of human body, and the other can accelerate the evaporation of air, which also affects the heat dissipation efficiency of sweat. The effect of the two is different, because the temperature is higher than the skin temperature or lower than the skin temperature. When the air temperature is higher than the skin temperature, the function of wind is to heat the human body through convection on the one hand, and to enhance evaporation on the other hand, thus improving the heat dissipation efficiency. For example, when there is hot air blowing in summer, because sweat evaporates quickly, although it feels dry and hot, it is not stuffy. On the contrary, when the temperature is lower than the skin temperature in winter, the convection heat transfer is faster and the heat dissipation efficiency is higher, so at the same temperature, the human body will feel colder when there is wind. The influence of humidity on human body is mainly that it determines the heat dissipation efficiency of sweat. In the comfortable temperature range, the influence of humidity is not obvious, but at high temperature, with the increase of temperature and humidity, the influence becomes more and more obvious. This is because when the humidity is high, the skin is completely moist. At this time, the evaporation rate and the heat dissipation it produces only depend on the evaporation of air.