water loss in cooling tower

A plant may have chillers, air conditioners or other process equipments. To cool these equipments we utilize Cooling towers so that the heat from circulating water can be dissipate to the ambient air. Cooling towers rejects heat from water to the environment through evaporation. Therefore, by design & architecture, cooling towers use significant amounts of water.

Thermal efficiency and longevity of any cooling tower and their equipments depend on the management of re-circulated water.

Water leaves from cooling tower system from one of following 4 ways:-

1. Evaporation : Evaporation is the primary and for most mechanism and functionality of the tower that transfers heat from the cooling tower system to the environment. 
2.  Drift: Drift is a small quantity of water may be carried from the tower as mist or small droplets. Drift loss is small compared to evaporation and is controlled through drift eliminators.
3. Blowdown: When water evaporates from the tower, dissolved solids such as calcium, magnesium, chloride, and silica remain in the re-circulating water. As more water evaporates, the concentration of dissolved solids increases. If the concentration gets too high, the solids can cause scale to form within the system. The dissolved solids can also lead to corrosion problems. The concentration of dissolved solids is controlled by removing a portion of the highly concentrated water and replacing it with fresh make-up water. Carefully monitoring and controlling the quantity of blow down provides the most significant opportunity to conserve water in cooling tower operations.
4. Basin leaks or overflows: Properly operated towers should not have leaks or overflows. Check float control equipment to ensure the basin level is being maintained properly, and check system valves to make sure there are no unaccounted for losses.

The sum of water that is lost from the tower must be replaced by make-up water:

Make-Up = Evaporation + Blowdown + Drift

A key parameter used to evaluate cooling tower operation is "cycle of concentration" sometimes referred to as cycle or concentration ratio. This is determined by calculating the ratio of the concentration of dissolved solids in the blow down water compared to the make-up water. Because dissolved solids enter the system in the make-up water and exit the system in the blow down water, the cycles of concentration are also approximately equal to the ratio of volume of make-up to blow down water.

Other loses are:

• Water drops carried off by airflow in the form of moist or drift.
• Drift release is not controlled
• Valve leak
• Drawndown/Draw-off

Get expert advice to help determine if a cooling tower required maintenance. Call us or mail us to have a discussion.

L K Chatuvedi
CEO - Wetpoint Aqua Equipments (P) Ltd
Manufacturer of all kind of Industrial Cooling Towers and Spares
Phone: +91-9302.214.784
Email: ceo@wetpointcoolingtowers.com