The working principle of a cooling tower

Cooling towers are devices that dissipate waste heat generated in industrial processes or refrigeration 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 high saturated steam partial pressure flow towards the lower-pressure air. Wet (high enthalpy) water is sprinkled into the tower from the spray system. When water droplets come into contact with the air, on 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, removing heat from the water, thus achieving the purpose 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, a horizontal throat, a curved throat, and a central throat 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 air with low enthalpy is drawn into the tower from the bottom inlet grille by the fan. When the hot water flows over the packing material, it forms a water film and exchanges heat with the air, the high humidity, high enthalpy hot air is extracted from the top, and the cooled water drips into the basin, then flows into the main unit through the outlet pipe. Generally, the air entering the tower is dry and has 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 is running, under the action of the static pressure inside the tower, water molecules evaporate into the air continuously, becoming vapor molecules, and 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 (usually referred to as dry bulb temperature) is lower or higher than the water temperature, as long as water molecules can evaporate into the air continuously, the water temperature will decrease. However, the evaporation of water into the air will not continue indefinitely. When the air in contact with the water is unsaturated, water molecules continue to evaporate into the air, but when the air on the water-vapor contact surface reaches saturation, water molecules cannot evaporate out and remain in a dynamic equilibrium state. The number of water molecules evaporated into the air is equal to the number of water molecules returning to the water from the air, and the water temperature remains constant. It can be seen from this that the drier the air in contact with the water, the easier the evaporation occurs, and the easier the water temperature is to decrease.

Cooling Tower Categories

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: According to the flow direction of hot water and air, there are counterflow cooling towers, crossflow (cross-current) cooling towers, and mixed flow cooling towers.

Four, Cooling towers are divided by usage into general-purpose, industrial, and high-temperature models.

Five: Classified by noise level into standard cooling towers, low-noise cooling towers, ultra-low-noise cooling towers, and super-quiet cooling towers.

Cooling tower applications

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 dispersing it into the atmosphere. For example, 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 heat to the air in the cooling tower, which is exhausted into the atmosphere through the wind tunnel. The cooling tower is widely used in 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.