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Cooling Tower Fundamentals: Determine Cooling Tower Capacity and Size


How is cooling tower capacity and size calculated? There are many factors that can determine your cooling tower capacity and size requirements. These factors can be broken down between three main fundamentals to consider when designing a cooling tower. These fundamentals includes thermal design, project specifications, and structural design. Each of these areas impact the decisions made in cooling tower capacity, size and design.


The first step in cooling tower design is to thermally size a cooling tower. This means we determine how much cooling capacity is necessary at your facility. We determine the right amount of capacity by determining thermal requirements such as:>/p>

  • Water Flow Rate: The quantity of hot water entering the tower measured in gallons per minute (GPM)
  • Heat Load: The amount of heat to be removed by the circulating water. Heat load directly affects the sizing of your cooling tower. If the heat load determination is not accurate, a tower size that is too small or too large could be selected for your facilities required specifications.
  • Hot and Cold Water Temperatures: The temperatures of circulating water entering the tower (hot) and exiting the tower (cold).
  • Wet Bulb Temperature: The temperature of ambient air around the cooling tower as measured with a web bulb thermometer. This is the lowest possible temperature to which water can be cooled.
  • Percentage of Relative Humidity: Is the measurement of saturated air in a percentage.
  • Cooling Tower Approach: Is the temperature difference between the cold water leaving the cooling tower and the wet-bulb temperature. Generally, as cooling tower size increases the approach will decrease and Vis versa.
  • Fresh Water VS Salt Water: Depending on the type of water your facility will use in the thermal process, this will affect the amount of total dissolved solids in the circulating water therefore causing an increase in the water's concentration.
  • Drift Rate: The type of drift eliminator you choose will be manufactured between a .001% drift loss and a .0005% drift loss. The percentage of drift lost from your cooling tower will affect the cooling capacity.


Once your cooling capacity is determined, it's time to discuss individual project specifications. At this point we ask what specific requirements or restrictive parameters you might have. This includes

  • Any requirements for your total dissolved solids (g/kg)
  • If a certain amount of performance is required within space limitations.
  • Individual project requirements such as: Roof top construction, low noise requirements, plume abatement solutions, double wall construction, or water conservation.


Lastly, after calculating your cooling tower capacity, size and understanding custom project requirements, it is time to begin the design and engineering process to finalize your cooling tower performance and budget needs. This third and final step is to incorporate all of the environmental requirements into the structural design of your cooling tower. This includes:

  • The structural material that will be utilized: (type of Wood, FRP, or concrete)
  • Will the tower be constructed within a Fire zone or earthquake zone? Thus specific design solutions need to be considered such as site specific seismic analysis and design.
  • Concerns or requirements for water leaching
  • Geographical and site elevation

All of these specifications are a beginning base of knowledge to understand how cooling tower capacity, size and design are evaluated and engineered. Now you can calculate, size, design and price your own cooling tower with the DEPOT Design and Price Tool. Additionally we provide an opportunity for you schedule a Lunch and Learn for your team where cooling tower capacity and design requirements can be specifically discussed for your facilities operations.

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