A cooling tower is a specialised heat exchanger in which air and water are brought into direct contact with each other in order to reduce the water's temperature. As this occurs, a small volume of water is evaporated, reducing the temperature of the water being circulated through the tower.

Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature.

Hot water, which is usually caused by air conditioning condensers or other industrial processes, is pumped through pipes directly into the cooling tower. Cooling tower nozzles are used to spray the water onto to the “fill media”, which slows the water flow down and exposes the maximum amount of water surface area possible for the best air-water contact. The water is exposed to air as it flows throughout the cooling tower. The air is being pulled by an motor-driven electric “cooling tower fan”.

When the air and water come together, a small volume of water evaporates, creating an action of cooling. The colder water gets pumped back to the process/equipment that absorbs heat or the condenser. It repeats the loop over and over again to constantly cool down the heated equipment or condensers.

TYPES OF COOLING TOWERS

Not all towers are suitable for all applications. Cooling towers are designed and manufactured in several types, with numerous sizes available. Understanding the various types, along with their advantages and limitations, is important when determining the right tower for use.

1. Crossflow Cooling Towers

In crossflow cooling tower systems the water vertically flows through the fill media while the air horizontally flows across the falling water. That’s why they call it “crossflow” because the air and water cross paths or flows. Because of the crossing of flows, the air doesn’t need to pass through the distribution system. This permits the use of hot water flow via gravity and distribution basins on the top of the tower right above the fill media. The basins are a standard of crossflow cooling towers and are applied on all units.

1. Counterflow Cooling Towers

In counterflow cooling tower system processes, the air vertically flows upwards, counter to the water flow in the fill media. Due to the air flowing vertically, it’s not possible to use the basin’s gravity-flow like in crossflow towers. As a substitute, these towers use pressurized spray systems, usually pipe-type, to spray the water on top of the fill media. The pipes and cooling tower nozzles are usually spread farther apart so they will not restrict any air flow.

1. Forced Draft & Induced Draft Cooling Towers

Cooling tower fans are used on induced draft cooling towers to pull air up through the fill media.

On forced draft cooling towers, the air is pushed/forced by blowers at the bottom of the air inlet louver.

1. Natural draft Cooling Towers

The natural draft cooling towers are used in the same way as the forced draft cooling towers for removing low-potential heat generated in the production process. The cooling principle is the same, but the fan unit is missing here since heat is removed from the cooling tower using a natural draft/flow of air.

It offers the following advantages :

• power saving (no power consumption to induce air flow- no fan)
• environmentally friendly
• no mechanical noise (no fan)
• safety of operation
• no recirculation as the plume is rejected at high level
• limited plot area
• limited maintenance
• high longevity (generally more than plant life expectancy)