The closed cooling tower (also called evaporative air cooler or closed cooling tower) is to place the tube heat exchanger in the tower, and ensure the cooling effect through the heat exchange of circulating air, spray water and circulating water. At present, there are many forms of this kind of cooling equipment, which are characterized by spraying water outside the partition heat exchanger and forced ventilation. The heat is transferred from the cooled fluid in the partition heat exchanger to the spray water outside the wall through the wall, and then to the air through the forced convection between the spray water and the air. The heat transfer from the spray water to the air is mainly composed of the latent heat of evaporation and the sensible heat exchange between the spray water and the air. Advantages of the closed cooling tower: Because the closed cooling tower is fully closed for circulating cooling, there is no phenomenon that sundries enter the cooling pipeline system, thus causing pipeline blockage; Soft water is circulated for cooling, and no scale is generated at high temperature, which causes scaling of cooling pipeline system; Small floor space, no need to dig the pool, easy to locate, save water and reduce energy consumption; Double cooling mode of air cooling, evaporation and heat absorption is adopted, which has high cooling efficiency; Can directly cool water, oil, alcohol, quenching liquid, salt water and chemical liquid, etc., with no loss of medium and stable composition; Because of the closed cycle, the medium is not affected by the environment and will not pollute the environment; The pressure loss of cooling water is less than that of open cooling tower. However, there are also some small shortcomings: because a large number of copper coils with high heat exchange performance are used, the price of closed cooling towers is generally higher; If properly maintained, in the long run, the total project cost will be equal to or slightly higher than that of the open cooling tower due to its energy-saving and consumption-reducing characteristics, longer service life and stable cooling performance. The temperature in the northern region is low in winter, and if effective anti-freezing measures are not taken, it may cause local freezing crack of the cooler.