Sustainability & Cooling Towers

Cooling towers are one of the best inventions for cooling application at a low cost using the natural air as cooling medium. Pharmaceutical facility widely uses this for HVAC application where it cools down the chiller condenser circulation water. In this process it uses mostly evaporative cooling where part of water gets evaporated while coming in contact with the air being induced in to the towers and heat get released from the incoming water.

Though there are various type of cooling towers based on application and economy, pharmaceuticals normally use induced draft cooling towers normally in FRP or metallic?? body construction having the plastic fills packing inside for efficient heat transfer or mixing of air and water. Though it is the one of the best ways to cool the water but it has certain drawback which affect the operation and maintenance cost of the facility. The issues faced by the operation for the cooling towers are as below.

1.????? ?Induced air to cooling tower create vacuum inside the cooling tower that tries to take all floating object in air surrounding the cooling towers. These foreign particles clog the packing materials inside and reduces the efficiency of the tower at the same time the fine particles that get mixed with water clogs the condenser and pipeline. As an effect it reduces the efficiency of chiller and require frequent shutdown for cleaning.

2.????? While the water gets evaporated giving required cooling to the water, it increases the tds and chloride level of water. If the pH, tds and chloride level are not monitored properly it could start the corrosion and erosion of condenser contact parts which at times led to leaking of tubes. Leaking tubes reduces the efficiency and effectiveness of chiller and a much costly affairs to detect and close the leaks.

3.????? To maintain the tds it is often recommended to go for continuous blowdown or periodic blow down which increases the water wastage and increase the chemical load to maintain the water quality. Chemicals are normally added to maintain water pH and biocides that limits the algae growth and control legionella growth.

4.????? Breakdown of cooling tower mostly due to blower/motor breakdown or clogging of packings. For critical application a standby is recommended.

Controlling the above three issues are a challenge for plant operation. Few conscious facility managements are operating with good engineering practices as tabulated below.

1.????? ?Close Circuit Operation:

This can be avoided in chiller circuit by introducing a Plate heat exchanger that separate the clean and dirty side with an approach difference of about 1 Degree Centigrade. This approach will improve the chiller efficiency and effectiveness also increases the life and reduces the maintenance cost chemical uses and water wastages. As a result, Chiller Reliability, operation cost and power saving improve substantially. The paybacks are normally in the range of 2 to 3 years. Alternatively, making a bigger cooling tower basin with dipped coil inside and tower water circulation to cool the water inside the coil also can be planned.

2.????? EC motor-based Fan:

With EC blower technology we can increase the no of fans instead of one to more based on the capacity requirement and controls the fan operation based on cooling tower out temperature. Implementing this we can improve the power consumption, vibration and noise level. The overall reliability of system improves and stand by cooling towers are not needed.