The working principle of a cooling tower
Cooling towers are equipment that dissipates waste heat generated in industrial processes or refrigeration and air conditioning systems by utilizing the contact between water and air through evaporation.
The basic principle is:
Dry (low enthalpy) air, after being drawn by the fan, enters the cooling tower through the air intake mesh; high-temperature water molecules with a large saturated steam partial pressure flow towards the lower-pressure air. Wet (high enthalpy) water is sprinkled into the tower from the sprinkling system. When water droplets come into contact with the air, on the one hand, due to direct heat transfer between the air and the water, and on the other hand, due to the pressure difference between the water vapor surface and the air, evaporation occurs under the pressure, carrying away the latent heat of evaporation and removing heat from the water, thereby achieving the purpose of cooling.
Cooling tower operation process:
The working process of a circular counterflow cooling tower, for example: Hot water is pumped from the machine room at a certain pressure through pipes, lateral channels, bends, and the central channel to the spray system inside the cooling tower. Water is then evenly sprinkled onto the fill material through small holes in the spray pipes; dry, low enthalpy air is drawn into the tower from the bottom air intake by the fan. As the hot water flows over the fill material, a water film forms and heat exchange occurs with the air, resulting in the extraction of high humidity, high enthalpy air from the top. The cooled water drops into the basin and flows into the main unit via the outlet pipe. Generally, the air entering the tower is dry with a low wet bulb temperature, and there is a significant difference in water molecule concentration and kinetic pressure between the water and air. When the fan operates, under the influence of static pressure within the tower, water molecules continuously evaporate into the air, becoming vapor molecules, thereby reducing the average kinetic energy of the remaining water molecules, leading to a decrease in the circulating water temperature. From this analysis, it is evident that evaporative cooling is not related to whether the air temperature (commonly referred to as the dry bulb temperature) is below or above the water temperature; as long as water molecules continue to 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 the water is unsaturated, water molecules continue to evaporate, but when the air on the water vapor interface becomes saturated, water molecules cannot evaporate further and reach a dynamic equilibrium state. The number of water molecules evaporating equals the number of water molecules returning to the water from the air, and the water temperature remains constant. It is clear that the drier the air in contact with the water, the easier evaporation occurs, and the water temperature is more likely to drop.
Cooling Tower Classification
One, classified by ventilation methods, there are natural ventilation cooling towers, mechanical ventilation cooling towers, and mixed ventilation cooling towers.
Two: Categorically divided by the contact method between hot water and air, there are wet cooling towers, dry cooling towers, and dry-wet cooling towers.
Three: There are counterflow cooling towers, crossflow (cross-current) cooling towers, and mixed flow cooling towers, categorized by the flow direction of hot water and air.
Four: General air conditioning cooling towers, industrial cooling towers, and high-temperature cooling towers.
Five, classified by noise level into standard cooling towers, low-noise cooling towers, ultra-low-noise cooling towers, and ultra-quiet cooling towers.
Application Range of Cooling Towers
Waste heat generated during industrial production or refrigeration processes is typically transferred away using cooling water. The function of a cooling tower is to exchange heat between the cooling water carrying the waste heat and the air inside the tower, transferring the waste heat to the air and dissipating it into the atmosphere. For instance, in a power plant, the boiler heats water into high-pressure steam, which drives the turbine to generate electricity. After the turbine has done its work, the exhaust steam enters the condenser, where it exchanges heat with the cooling water and condenses into water, which is then pumped back to the boiler for recirculation. During this process, the waste heat from the exhaust steam is transferred to the cooling water, causing the water temperature to rise. The cooling water carrying the waste heat then transfers the heat to the air in the cooling tower, which is then exhausted into the atmosphere through the air duct. The cooling tower is widely used in various fields, primarily in air conditioning cooling systems, refrigeration series, injection molding, leather processing, foaming, power generation, steam turbines, aluminum profile processing, air compressors, and industrial water cooling. The most common applications are in air conditioning cooling, refrigeration, and plastic chemical industries.
