The air cooler uses air as the coolant and can be used as a cooler or a condenser. The air cooler is mainly composed of tube bundles, brackets and fans. The hot fluid of the air cooler flows inside the tubes, and the air blows through the outside of the tube bundle. Due to the large amount of ventilation required for heat exchange and the low wind pressure, axial fans are often used (see fluid conveying machinery). The type and material of the air cooler tube bundle have a great influence on the performance of the air cooler. Because the heat transfer coefficient of the air side is small, fins are often added outside the tube to increase the heat transfer area and fluid turbulence, and reduce thermal resistance. Most air coolers use radial fins. Air coolers usually use light tubes with an outer diameter of 25mm, low-fin tubes with a fin height of 12.5mm, and high-fin tubes with a fin height of 16mm. The fins are generally made of materials with high thermal conductivity (aluminum is commonly used), wound or inlaid on the light pipe. In order to strengthen the heat transfer effect of the air cooler, water can be sprayed in the inlet air for humidification. This not only reduces the air temperature, but also increases the heat transfer coefficient. The use of air coolers can save a lot of industrial water, reduce environmental pollution, and reduce infrastructure costs. Especially in water-scarce areas, replacing water-cooling with air-cooling can alleviate the contradiction of water shortage.