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Cooling Towers: Energy-Saving Strategies

Key Points
  • Cooling towers use evaporation to transfer heat from water to air and send it into the atmosphere.
  • A regular maintenance program can save on energy costs by improving overall system efficiency.
  • Maintenance includes regular component adjustments and annual system cleaning and inspection.

Cooling towersCooling towers are widely used in chillers, air conditioning systems and process cooling equipment. Regular inspection, cleaning and testing of key components will increase the lifespan of equipment while improving system performance and efficiency.  

How cooling towers work

A cooling tower is a specialized heat exchanger, which uses evaporation to transfer waste heat from water to air, and then rejects it into the atmosphere. There are two types of cooling towers:

  • Open exposes the hot water directly to the atmosphere where the heat is removed through evaporation. The remaining cooled water is recirculated to the chiller.
  • Closed circulates the hot water through tubes within the tower. Water is sprayed on the tubes to reduce the temperature of the hot water inside. Air-cooled towers only blow air across coolant-filled tubes.

Open cooling tower systems include several major components:

  • Condenser pump delivers hot water to the top of the cooling tower through distribution piping.
  • Heat transfer medium, which is typically arranged in thin plastic sheets or as splash bars supported by a grid pattern, evaporates and cools the hot water flowing from the condenser.
  • Fan system generates airflow through the heat transfer medium, which increases the rate of evaporation and the cooling capacity of the system.
  • Cold water collection basin at the bottom of the tower gathers cool water after it has passed through the heat transfer medium.

Energy-saving maintenance strategies

Improper cooling tower maintenance can result in warmer cooling water and increased condenser temperatures. This reduces cooling tower efficiency, wasting energy and increasing costs. The following maintenance practices and procedures can help keep your system operating at peak performance.

Regularly:

  • Perform an overall visual inspection to ensure all equipment is operating properly and safety systems are in place.
  • Test water samples for proper concentrations of dissolved solids and chemistry. Adjust blowdown and chemicals as necessary.
  • Read conductivity and flow meters to identify problems. Keep a record of make-up water and blowdown quantities, conductivity and cycles of concentration. Monitor trends to spot deterioration in performance.
  • Check water sprinkler heads for proper rotation and spray patterns.
  • Clean water filters and basin strainers.
  • Inspect the tower structure for loose fill, algae buildup, failed connections, leaks and more.
  • Operate the make-up water float switch manually to ensure proper operation.
  • Check motor supports and fan blades for excessive wear and secure fastening.
  • Test motors, fans and pumps for excessive vibration and adjust, or repair, as needed.
  • Inspect the bearings and make sure they're lubricated following manufacturer's recommendations.
  • Align motor couplings to allow for efficient torque transfer.
  • Check drift eliminators and louvers for scale buildup, and to make sure they're positioned properly.

Annually:

  • Clean the tower. Remove all dust, scale and algae from the tower basin, as well as the fill and spray nozzles.
  • Inspect the bearings and drive belts for wear. Adjust, repair or replace as necessary.
For detailed information on cooling tower components and ways to improve water and energy efficiency, see Cooling Towers from the U.S. Department of Energy.

Image source: U.S. Department of Energy