The friction between the gas and the liquid also generates heat, but the air flow increases the evaporation of water, so the water can absorb the heat. Friction between gases and solids can also generate heat. For example, meteors passing through the atmosphere can cause strong friction. Friction between liquids and solids also generates heat.
The friction above will generate heat, but remember that most of the earth's surface is covered in water. Such a large evaporation area must absorb a lot of heat. There are also many things on earth that need to absorb heat, such as cold-blooded animals. Additionally, when the earth rotates and faces the sun, the sun cannot shine at night and the temperature drops significantly.
There is friction between flowing molecules, resulting in mutual restraint. This is a characteristic lifluid definition, which is related to the fluidity of the liquid. We call it: viscosity. The mechanism of friction in a liquid: Inside the liquid, each molecule is surrounded by many other molecules. So, when a molecule moves from an equilibrium position to another direction, it is affected by the molecules in the direction in which it is moving. , and at the same time it is repelled by the molecules in the direction in which it is approaching. Generally, kinematic viscosity is used to characterize the viscosity of a fluid, the unit is m^2/s, which is a measure of the friction force during the time of fluid flow under the action of gravity . Temperature has the greatest impact on viscosity. Generally, kinematic viscosity is measured at a specific temperature and viscosity has nothing to do with liquid density. That is, comparing the kinematic viscosity between different liquidsmust be compared to the same temperature to be meaningful. For example, the viscosity of water is low, 1.004^(-6) m^2/s at 20°C; the viscosity of kerosene is high, 1.65*10^(-6) m^2/s at 20°C. . This shows that the friction between water molecules is less than the friction between kerosene molecules. Under other conditions being the same, water flows faster than kerosene. Is there friction between water? If so, will the water temperature be higher than that of the surrounding environment? In fact, this question should be asked: if the water temperature increases, will the friction decrease? water There is enormous friction between the molecules. When they flow, the water temperature increases. As the temperature increases, the thermal movement between molecules intensifies, the viscosity decreases, and the fluidity of the liquid increases, which is equivalent to reducing friction. Reference: “Penetration Testing”, Chapter 4 APenetrant Detection Agent: Penetrant Performance - Viscosity
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