The role of cooling towers

        The waste heat generated in industrial production or refrigeration processes generally needs to be dissipated by cooling water. A certain amount of water is drawn from natural water bodies such as rivers, lakes, and seas as cooling water. The cooling process equipment absorbs waste heat to raise the water temperature, and then discharges it into rivers, lakes, and seas. This cooling method is called direct cooling. When direct current cooling conditions are not available, a cooling tower is needed for cooling.

        The function of a cooling tower is to exchange heat between the cooling water carrying waste heat and the air inside the tower, allowing waste heat to be transmitted to the air and dispersed into the atmosphere.

        Taking a thermal power plant as an example, the boiler will heat water into high-temperature and high-pressure steam, driving the steam turbine to work and generate electricity from the generator. The exhaust steam after being powered by the steam turbine is discharged into the condenser, where it exchanges heat with the cooling water and condenses into water, which is then pumped back to the boiler for recycling. During this thermal cycle process; The waste heat from the exhaust steam is transferred to the cooling water in the condenser, causing the water temperature to rise. The cooling water carrying the waste heat is transferred to the air in the cooling tower, and discharged into the atmosphere from the tower outlet. The cooled water in the cooling tower becomes low-temperature water, which is then fed back into the condenser by the water pump for recycling. The former cycle is the circulation of water in the boiler, while the latter cycle is the circulation of cooling water. Cooling towers are also widely used in other industrial sectors such as petroleum, chemical, and steel.

        One of the heat exchange methods between water and air in a cooling tower is that the air flowing through the surface of the water comes into direct contact with the water, and through contact heat transfer and evaporation heat dissipation, the heat in the water is transferred to the air. This cooling method is called a wet cooling tower (referred to as a wet tower). The heat exchange efficiency of a wet tower is high, and the maximum temperature at which water is cooled is the wet bulb temperature of air. However, water is lost due to evaporation; Evaporation also increases the salinity of the circulating cooling water. In order to stabilize the water quality, it is necessary to discharge a portion of the water with higher salinity; Wind blowing can also cause water loss. The loss of these water must be continuously replenished with sufficient new water, therefore, the wet tower needs to have a source of make-up water.

        In areas with water scarcity and difficulties in replenishing water; Only dry cooling towers (referred to as dry towers or air cooling towers) can be used. Heat exchange between air and water (as well as air and exhaust steam) in the dry tower; It transfers heat from the water or exhaust steam inside the radiator surface, which is composed of metal tubes, to the air flowing outside the radiator. The heat exchange efficiency of a dry tower is lower than that of a wet tower, and the maximum cooling temperature is the dry bulb temperature of the air.