NEWS CENTER
Oasis Iceberg
11
2024
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07
How to correctly select a closed cooling tower!
1. Closed cooling towers are classified according to the type of fan used: induced-draft closed cooling towers and forced-draft closed cooling towers. The fans can be either axial-flow or centrifugal-type. In induced-draft towers, the coil is positioned on the suction side of the fan, creating negative pressure inside the tower, which helps maintain a lower water evaporation temperature. Additionally, the airflow passing through the coil is more uniform, leading to better heat transfer performance. However, this design places the fan directly in contact with moist air, resulting in relatively harsh operating conditions. Currently, most closed cooling towers utilize this configuration. In contrast, forced-draft closed cooling towers have the coil located on the discharge side of the fan, causing positive pressure within the tower. While the airflow distribution isn’t as even as in induced-draft systems—and thus heat transfer efficiency is slightly lower—this setup offers improved working conditions for the fan.
1. Closed cooling towers are classified according to fan type: induced-draft closed cooling towers and forced-draft closed cooling towers.
Fans can be either axial-flow or centrifugal-type. In induced-draft systems, the coil is positioned on the suction side of the fan, creating negative pressure within the tower, which helps maintain a lower water evaporation temperature. Additionally, the airflow passing through the coil becomes more uniform, enhancing heat transfer efficiency. However, this design has a drawback: the fan operates in a humid air stream, leading to relatively harsh working conditions. Currently, most closed-circuit cooling towers utilize this configuration. In contrast, forced-draft closed-circuit cooling towers place the coil on the discharge side of the fan, resulting in positive pressure inside the tower. While airflow distribution isn’t as even as in the induced-draft system—and thus heat transfer performance is slightly less efficient—the fan itself benefits from better operating conditions.
2. Closed cooling towers can be classified into two types based on whether or not they have packing inside the tower: packed-type closed cooling towers and packed-plus-coil-type closed cooling towers.
The fillerless closed cooling tower has no packing inside, offering the advantage of being suitable for cooling high-temperature water. However, it features a large tower volume, heavy weight load, and relatively lower efficiency. To prevent water vapor convection from causing scaling at the bottom of the coil heat exchange tubes—and also to enhance the water-vapor heat transfer surface—a patented elliptical-tube coil design has been developed.
3. Closed cooling towers can be classified according to the relative orientation of water flow and airflow into counterflow, crossflow, and hybrid (also referred to as mixed-flow) closed cooling towers.
A. The reverse-flow closed cooling tower features bottom-mounted, counterflow air intake, which alternates with the downward-sprayed water—creating saturated, hot, moist air through the countercurrent interaction of air and water. Heat is expelled via a top-mounted fan, while condensed moisture is captured by a specially designed dehydrator and returned to the collection tank for recycling. Notably, the internal space is free of pre-cooling packing materials, leaving more room to maximize the unit’s heat dissipation area per coil. This compact design occupies minimal floor space, making it particularly well-suited for cooling fluids with lower temperatures or small temperature differences.
B. Cross-flow closed cooling tower with lateral air intake! The coil primarily relies on sensible heat conduction for cooling. A key feature of this operating principle is its ability to significantly inhibit scale formation on the outer wall of the coil. It’s especially well-suited for cooling high-temperature fluids or fluids with large temperature differences.
C. The composite-flow closed cooling tower is named after the way its spray water mixes with the direction of the hot air. The spray water flows downward, while the air splits into two streams: one portion of cool air moves downward, and the other enters horizontally from the side. This air then crosses paths with the falling spray water as it passes through the packing material, effectively transferring heat and reducing the temperature of the spray water.
4. Closed cooling towers are classified according to their shell material: galvanized steel plate closed cooling towers, aluminized-zinc coated plate closed cooling towers, stainless steel closed cooling towers, and FRP (fiberglass reinforced plastic) closed cooling towers, among others.
5. Classified by heat exchanger material, they include: copper-tube closed cooling towers, stainless steel-tube closed cooling towers, carbon steel-tube closed cooling towers, titanium-tube closed cooling towers, and aluminum-tube closed cooling towers, among others.
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