Water Cooling Tower: Evaporative Technology in Industrial Heat Rejection

Devices that ensure the safe discharge of waste heat generated in industrial production processes and large-scale air conditioning systems into the atmosphere are called water cooling towers. These systems use the “evaporative cooling” principle to reduce water temperature. By allowing a small portion of the water intended for cooling to evaporate, the temperature of the remaining water is significantly lowered. While moisture-laden hot air is discharged into the atmosphere, the cooled water is reclaimed into the system, ensuring a sustainable cooling cycle.

Cooling Tower Operating Principle and Heat Transfer

Cooling towers are, thermodynamically, open heat exchangers. Hot water from the system is pulverized via nozzles at the top of the tower and trickles down. Meanwhile, air drawn into the tower by fans comes into contact with the water droplets. At this point where water and air meet, the water cools by transferring its heat to the air. While the air, whose humidity increases as a result of evaporation, is discharged into the atmosphere, the cooled water collects in the basin and is sent back to the process. [Image of evaporative cooling principle in a cooling tower] Key factors affecting heat transfer include:

• Fill: Increases the contact surface area between water and air to maximize heat transfer.
• Nozzles: Ensure the homogeneous distribution of water over the fill.
• Airflow Rate: The air velocity, controlled by fan power, directly determines the cooling capacity.
• Drift Eliminators: Prevent water loss by capturing water droplets that attempt to escape outside the tower with the air.

Tower Types: Open and Closed Circuit Systems

Cooling towers are divided into two main groups based on whether the cooled fluid comes into contact with the air:

• Open Circuit Cooling Towers: Water is in direct contact with the air. The water trickling over a labyrinth-like “fill” (film or splash fill) is cooled directly. The cost is lower, but the water is more susceptible to contamination.
• Closed Circuit Cooling Towers: The cooled liquid (water or glycol mixture) is inside a closed tube bundle (coil). Air cools the liquid inside the coil through the evaporation of external water sprayed onto the outer surface of the tubes. It is ideal for sensitive industrial processes where the fluid must not be contaminated.

Counterflow and Crossflow Designs

The direction of air and water movement relative to each other determines tower performance and maintenance possibilities:

• Counterflow: Air moves upward, in exactly the opposite direction of the water trickling downward. This design has the highest thermal efficiency.
• Crossflow: Air moves horizontally across the fill while water descends. Maintenance is easier, and the pressure drop at the air inlet is lower.

Difference Between Chiller and Cooling Tower

Although both are technologies used to reject heat in industrial cooling processes, the fundamental distinction lies in target temperature limits and operating methods. A chiller is a mechanical refrigeration machine containing a compressor and can lower water to +7°C or lower regardless of how high the ambient temperature is; electricity consumption is high, but water loss is minimal. In contrast, a cooling tower cools water by direct contact and evaporation with outside air and can only reduce the water temperature down to the ambient “wet bulb” value. In summary, a chiller provides very low and constant temperatures independent of outdoor air; a cooling tower is a heat rejection device that offers milder cooling depending on outdoor conditions, with low energy consumption but high water consumption.

Application Areas and Sectoral Applications

Fintherm cooling towers offer professional solutions wherever thermal loads must be managed accurately:

• Industrial Plants: Iron-steel, glass, plastic, and paper factories.
• Power Plants: Cooling of condensers and maintenance of the steam cycle.
• HVAC Systems: Central air conditioning systems for office buildings, hospitals, and shopping malls.
• Food Processing: Cooling of process water in pasteurization and freezing plants.
• Refineries: Evacuation of high heat loads in petrochemical processes.