What are the ways in which the human body dissipates heat

There are many ways for the human body to dissipate heat, but the main heat dissipation organ is the skin. Normally, heat can be dissipated through evaporation of sweat, and the body's heat can be taken away through urination and defecation. Usually, when dissipating heat, people will achieve the heat dissipation effect according to the changes in the surrounding environment. For example, lowering the temperature of the surrounding environment can achieve a good heat dissipation effect. So besides these, what other heat dissipation methods are there?

There are four main ways for the human body to dissipate heat: radiation, conduction, convection, and evaporation.

(1) Radiative heat dissipation: The heat of the body is dissipated to the surrounding objects with lower temperature in the form of heat rays, that is, dissipated into the low-temperature air, which is called radiative heat dissipation. This is the main heat dissipation method in quiet state and is affected by the ambient temperature. When the outside temperature is equal to or higher than body temperature, radiant heat dissipation becomes ineffective and body temperature rises. Heatstroke is a good example. In summer, people like to stay in cool places, which is the application of the principle of "radiant heat dissipation".

(2) Conduction heat dissipation: The heat deep inside the body is transferred to the skin on the surface of the human body by conduction, and then from the skin to clothes and other objects that are in direct contact with it. Since clothes and other items are poor conductors of heat and transfer heat very slowly, and the thermal conductivity of subcutaneous fat in the human body is low, the heat dissipated through conduction is very small. However, in hospitals, doctors often use ice caps, ice bags, etc. to physically cool down patients with high fever. This is also a form of conductive heat dissipation. Because water has a high conductivity, conductive heat dissipation has become one of the cooling methods frequently used in clinical practice.

(3) Convection heat dissipation: This is a special form of conduction heat dissipation that uses the continuous flow of air to dissipate body heat into the air. Convective heat dissipation is greatly affected by wind speed. For example, we all experience the coolness brought by a breeze under the scorching sun in summer. We can also use the principle of convection heat dissipation to undress patients with high fever, place them in well-ventilated rooms, or use electric fans (avoid direct blowing) to physically cool them down.

(4) Evaporative heat dissipation: This method can be used when the external temperature is equal to or higher than body temperature and heat cannot be dissipated by radiation, conduction, or convection. Normally, when 1 gram of water in the human body evaporates into water vapor, it absorbs about 2.5 kilojoules of heat, so a large amount of body heat can be taken away through the evaporation of sweat. Evaporative heat dissipation is a major way of dissipating heat. Although we usually do not feel obvious sweating, the human body can sweat 400-600 ml in 24 hours without realizing it, which is medically called inconspicuous sweat. Doctors also often use this mechanism to give high fever patients medication to reduce their temperature, such as giving them antipyretics. Antipyretic drugs all have a diaphoretic effect. After the patient sweats, the evaporation of sweat can take away a large amount of body heat, thereby achieving the purpose of reducing fever. The phenomenon of sweating, fever reduction and body cooling is something we often encounter.