Working principle of cooling tower: A cooling tower is a device that uses the contact of water and air to dissipate waste heat generated in industry or refrigeration and air conditioning through evaporation. The basic principle is that dry (low enthalpy) air enters the cooling tower from the intake network after being pumped by the fan; High temperature water molecules with high partial pressure of saturated steam flow to air with low pressure, and hot and humid (high enthalpy) water is sprayed into the tower from the water seeding system. When water droplets come into contact with air, on the one hand, due to the direct heat transfer between air and water, on the other hand, due to the pressure difference between the water vapor surface and air, evaporation occurs under the action of pressure. Currently, in order to remove the latent heat of evaporation, the heat in the water is taken away, which is called evaporation heat transfer, so as to achieve the purpose of cooling. The working process of the cooling tower: Take the working process of a circular countercurrent cooling tower as an example: the hot water in the main machine room passes through the pipes, transverse throats, curved throats, and central throats at a certain pressure through a pump to circulate water pressure into the water distribution system of the cooling tower, and evenly sprinkles water onto the filler through the small holes in the water distribution pipe; Dry air with low Han value enters the tower from the bottom through the air inlet network under the action of a fan. When hot water flows through the surface of the filler, a water film is formed to exchange heat with the air. Hot air with high humidity and high Han value is extracted from the top, and cooling water drips into the bottom basin and flows into the host through the outlet pipe. Generally, the air entering the tower is dry and low wet bulb temperature air. There is a significant difference in the concentration and kinetic energy pressure of water molecules between water and air. When the fan is running, under the effect of static pressure in the tower, water molecules continuously evaporate into the air and become water vapor molecules. The average kinetic energy of the remaining water molecules will decrease, resulting in a decrease in the temperature of circulating water. From the above analysis, it can be seen that evaporative cooling has nothing to do with the temperature of the air (commonly referred to as the dry bulb temperature) being lower or higher than the water temperature. As long as water molecules can continuously evaporate into the air, the water temperature will decrease. However, the evaporation of water into the air does not continue indefinitely. When the air in contact with water is not saturated, water molecules continuously evaporate into the air. However, when the air on the water vapor contact surface reaches saturation, the water molecules do not evaporate, but are in a dynamic equilibrium state. The number of water molecules evaporated is equal to the number of water molecules returned from the air to the water, and the temperature of the water remains constant. It can be seen that the drier the air in contact with water, the easier it is for evaporation to occur, and the easier it is for the water temperature to decrease.
Key words: cold water tower