Air Cooler

Product Overview
Air-cooled heat exchangers, commonly referred to as air coolers, use air as the cooling medium and can serve as both coolers and condensers. They are primarily composed of tube bundles, supports, and fans. In air-cooled heat exchangers, the hot fluid flows inside the tubes while air blows over the tube bundles externally. Due to the large ventilation volume required for heat exchange and low wind pressure, centrifugal fans are commonly used (see fluid conveyance machinery).
The type and material of the fins significantly affect the performance of air-cooled heat exchangers. Due to the low heat transfer coefficient on the air side, fins are often added to the tubes to increase the heat transfer area and fluid turbulence, thereby reducing thermal resistance. Most air-cooled heat exchangers use radial fins. Typically, they feature a smooth tube with an outer diameter of 25mm, a low fin tube with fins 12.5mm high, and a high fin tube with fins 16mm high. The fins are usually made of high thermal conductivity materials (commonly aluminum) and are wound or embedded onto the smooth tube. To enhance the heat transfer efficiency of the air-cooled heat exchangers, water can be sprayed into the incoming air to increase humidity. This not only lowers the air temperature but also increases the heat transfer coefficient. Using air-cooled heat exchangers can save a significant amount of industrial water, reduce environmental pollution, and lower construction costs. Particularly in water-scarce areas, replacing water cooling with air cooling can alleviate the contradiction of insufficient water resources.

Air Cooler Structure
The air cooler is mainly composed of three parts: the tube bundle, the fan, and the frame. The tube bundle includes heat transfer tubes, tube boxes, side beams, and cross beams. It can be arranged in three basic forms: horizontal, vertical, and sloped-roof (chevron). The horizontal arrangement offers a large heat transfer area, even air distribution, and good heat transfer performance. In the chevron arrangement, the fan is installed in the central space, occupying less floor space and having a compact structure. To compensate for the lower heat transfer coefficient on the air side, tubes with fins on the outer surface of the smooth tube are typically used. The finned tubes, as heat transfer tubes, can increase the heat transfer area. The finned tubes are layered and connected to the tube box at both ends using welding or胀接 methods. The number of rows of pipes usually ranges from 3 to 8. The tube bundle series can be as long as 12 meters. The outer diameter of the smooth tube is often 25 mm and 38 mm, with the fin height generally between 12 to 15 mm, and the width of the tube bundle between 100 to 3000 mm. The finned tube is a core component of the air cooler, and its form and material directly affect the equipment's performance. The tubes can be made of carbon steel, copper, aluminum, and stainless steel; the fin material is determined based on the application environment and manufacturing process, usually industrial pure aluminum, but copper or stainless steel may also be used in high corrosion resistance requirements or special manufacturing conditions. The fins can be arranged horizontally or vertically. The basic forms of finned tubes include: coiled fins, inserted fins, rolled fins, sleeve fins, welded fins, elliptical tube fins, and turbulent fins (including spoke-type, slotted, and wavy). The tube box structure mainly includes flanged type, pipe plug type, and collector tube type. The flanged type is generally used for medium and low pressure, while the latter two are used for high pressure. To accommodate the thermal expansion of the tube bundle, one end of the tube box is not fixed, allowing for displacement along the pipe length. The fan is usually an axial flow fan.

Ventilation Method
Ventilation is available in two methods: blowing and suction. ①Blowing type: Air first flows through the fan and then into the bundle. ②Suction type: Air first flows through the bundle and then into the fan. The former is more cost-effective in operation, generates beneficial turbulence for heat transfer, and is more commonly used. The latter ensures uniform airflow distribution,有利于 accurate temperature control, has less noise, and represents the direction of development. The outlet temperature of the hot fluid is primarily controlled by adjusting the airflow through the bundle, i.e., by adjusting the blade angle, fan speed, and the opening degree of the louvers. For fluids that are prone to condensation and freezing in winter, methods such as hot air recirculation or steam heating can be used to adjust the outlet temperature of the fluid.