The working principle of closed cooling tower is mainly based on wet cooling technology, and the cooling process is realized through internal and external circulation. The internal circulation system is connected with the target equipment to form a closed circulation system, and the circulation medium is soft water. The internal circulation cools the target equipment and takes the heat in the target equipment out to the cooling unit. The external circulation cools the cooling tower itself in the cooling tower, and does not contact the internal circulation water. It only exchanges heat and dissipates heat through the copper tube surface cooler in the cooling tower. The closed cooling tower can achieve energy saving by automatically controlling the operation of the motor according to the water temperature. In the spring and summer when the ambient temperature is high, two circulations need to run simultaneously. In the autumn and winter when the ambient temperature is not high, only one internal circulation is required in most cases1.
The internal circulation system, spray system and ventilation system of the closed cooling tower work together to achieve water cooling and heat transfer. The internal circulation system circulates the cooling medium inside the heat exchange tube bundle, exchanges heat with the water film formed by the spray water outside the tube, heats the water film on the outer wall, and the water film absorbs the latent heat of vaporization and evaporates into water vapor, thereby cooling the circulating medium in the tube bundle. The spray system sprays water outside the heat exchange tube bundle in the tower to form a thin layer of water film, which absorbs the heat inside the tube bundle, meets the thermal energy demand of the latent heat of vaporization, and evaporates into water vapor. The ventilation system uses the convection heat exchange mechanism. Low-temperature, dry air enters the cooling tower and first conducts convection heat exchange with the falling spray water to absorb part of the sensible heat. When passing through the heat exchange tube bundle, it takes away the evaporated water vapor and some small water droplets. After passing through the water collector with a special structure, the small water droplets hit the water collector due to inertia, and fall back to the surface of the heat exchange tube bundle by gravity or directly drip into the water tank for reuse, saving water resources2.
The advantages of closed cooling towers include effectively reducing water consumption, preventing pollution and scaling, and ensuring the normal operation of industrial production equipment3.