Air Cooled Heat Exchanger Profile

Working Principle

An air cooled heat exchanger is commonly referred to as an air cooler, which uses air as a coolant and can be utilized as either a cooler or a condenser. The air cooler is mainly composed of a tube bundle, a bracket, and a fan.

The hot fluid flows inside the tubes while the air blows across the outside of the tube bundle. Due to the large volume of ventilation required for heat exchange and the relatively low air pressure, axial flow ventilators (typically installed on the top of the equipment) are predominantly used. The type and material of the tube bundle have a significant influence on the performance of the air cooler. Because the heat transfer coefficient on the air side is small, fins are frequently added to the tubes to increase the heat transfer area, enhance fluid turbulence, and reduce thermal resistance. Consequently, most air cooled heat exchangers utilize finned tubes. These coolers typically employ a bare tube with an outer diameter of 25 mm, a low finned tube with a fin height of 12.5 mm, or a high finned tube with a fin height of 16 mm. The fins are generally made of a material with high thermal conductivity (most commonly aluminum) and are wound or embedded onto the bare tube. To further enhance the heat transfer effect of the air cooler, water can be sprayed into the inlet air for humidification. This not only reduces the air temperature but also increases the overall heat transfer coefficient.

The use of air cooled heat exchangers can save a significant amount of industrial water, reduce environmental pollution, and lower infrastructure costs. Especially in water-scarce areas, replacing water cooling systems with air cooling can effectively alleviate the challenges of insufficient water resources.

Main Components and Materials

The air cooled heat exchanger is mainly composed of three parts: the frame, the tube bundle, and the ventilator.

Framework

The frame is a rigid structural component used to support and connect the main components, such as the tube bundle box and the fan of the air cooler. It directs the flow of the guide air and provides convenience for the operation and maintenance of the equipment. The frame is constructed from national standard galvanized steel or stainless steel, utilizing professional welding processes to ensure a long service life.

Tube Bundle

Tube bundle boxes include heat transfer tubes, tube boxes, side beams, and cross beams. They can be arranged in three basic forms: horizontal, vertical, and tilted (herringbone). The horizontal arrangement provides a large heat transfer area, uniform air distribution, and optimal heat transfer efficiency. The tilted arrangement positions the ventilator in the central space of the herringbone for a compact structure. The vertical arrangement offers the minimal footprint.

The heat transfer finned tube is the core element of the air cooler, directly affecting equipment performance through its form and material. The base pipe can be manufactured from carbon steel, copper, aluminum, or stainless steel. Fin material is determined by the operating environment and manufacturing process, predominantly utilizing industrial pure aluminum. Copper or stainless steel are applied in scenarios demanding high corrosion protection or specific manufacturing conditions. Basic forms of finned tubes include: set type, winding type, rolling type, welding type, elliptical tube type, insert type, turbulent flow type, spoke type, slotted form, and corrugated form. The tube box structure mainly features flange type, pipe plug type, and manifold pipe type. Generally, the flange type is utilized for medium and low pressure, while the pipe plug and manifold types are reserved for high pressure.

Fan

Low-speed, hermetically sealed motors feature extra-wide blades. The fan comprises aluminum blades and a steel wheel hub, characterized by low wind resistance, high air volume, low noise, high efficiency, and reliable performance.

The EC motor features a direct-axis drive with IP55 protection and Class F insulation, ensuring reliable long-term operation in humid and hot environments with smooth performance. It achieves ultra-high energy efficiency up to IE5, delivering exceptional energy-saving capabilities. It is equipped with maintenance-free bearings featuring a 60,000-hour service life and an insulated bearing system to prevent shaft current damage. Through static and dynamic testing during production, noise is minimized while meeting the required heat exchange performance. The EC fan system maintains high static efficiency even at low speeds.

Advantages and Disadvantages of Air Cooled Heat Exchangers

Advantages

• Large heat dissipation area, conserving energy and water resources.

• Resistant to clogging, prevents heat transfer degradation due to scaling, and maintains a low corrosion rate.

• Modular design facilitates straightforward installation, maintenance, and future expansion.

• Integrates seamlessly with other equipment to provide a comprehensive total cooling solution.

Disadvantages

• Occupies a substantial spatial footprint.

• Cooling intensity is lower compared to water-cooled systems.

• Surface ash accumulation negatively impacts heat transfer efficiency.

Fields of Application

• Water-scarce and arid regions, significantly reducing water consumption and operational costs.

• Areas with abundant electricity (e.g., wind power, hydropower, tidal energy, nuclear power facilities) where the substantial power consumption of the fan motors required for high-volume dry operation is viable.

• Projects requiring an effluent temperature more than 10 degrees higher than the ambient temperature.