The working principle of a cooling tower
Cooling towers are devices that utilize the contact between water and air to dissipate waste heat generated in industrial processes or refrigeration and air conditioning systems through the process of evaporation.
The basic principle is:
Dry (low enthalpy) air, after being drawn by the fan, enters the cooling tower through the air intake network; high-temperature water molecules with a high saturated steam partial pressure flow towards the lower-pressure air. Wet (high enthalpy) water is sprinkled into the tower through the spray system. When water droplets come into contact with the air, evaporation occurs due to both direct heat transfer between the air and the water droplets and the pressure difference between the water vapor surface and the air, driven by the pressure. This process carries away the latent heat of evaporation, removing heat from the water, thereby achieving the goal of cooling.
Cooling tower operation process:
The operation process of a circular counterflow cooling tower, for example: Hot water is pumped from the machine room at a certain pressure through pipes, cross pipes, bend pipes, and central pipes to the spray system of the cooling tower. The water is evenly sprayed onto the packing 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 packing material, a water film is formed for heat exchange with the air. The high humidity, high enthalpy hot air is then extracted from the top. The cooled water drops into the basin and flows into the main unit through the outlet pipe. Generally, the air entering the tower is dry with a low wet-bulb temperature, and there is a significant difference in the concentration of water molecules 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. The average kinetic energy of the remaining water molecules decreases, thereby lowering the temperature of the circulating water. From the above analysis, it can be seen that the evaporation cooling is not related to whether the air temperature (commonly referred to as dry-bulb temperature) is 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 the water is unsaturated, water molecules continuously evaporate into the air. But when the air on the water-vapor interface reaches saturation, water molecules cannot evaporate further and are in a state of dynamic equilibrium. The number of water molecules evaporated equals the number of water molecules returning to the water from the air, and the water temperature remains constant. It can be concluded that the drier the air in contact with the water, the easier the evaporation process, and the easier it is to lower the water temperature.
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 direction of hot water and air flow.
Four: General air conditioner cooling towers, industrial cooling towers, and high-temperature cooling towers.
Five, divided into standard cooling towers, low-noise cooling towers, ultra-low-noise cooling towers, and ultra-quiet cooling towers according to noise levels.
Application Range of Cooling Towers
Waste heat generated during industrial production or refrigeration processes is typically transferred away using cooling water. The role of a cooling tower is to facilitate heat exchange between the cooling water carrying the waste heat and the air within 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's 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 released into the atmosphere through the wind tunnel. The cooling tower is widely used in various fields such as air conditioning cooling systems, refrigeration series, injection molding, leather making, 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.
