Sizing a cooling tower accurately is an incredibly important part of a facilities’ cooling system design. Having a cooling tower that is too small could mean hotter living temperatures, delayed production, and system efficiency problems. The dimensions and capacity (heat load measured in BTU) that it will have need to be tailored to the specific needs your facility has for a tower.
Generally, large towers cool more than smaller towers. You want to choose a tower size that meets your cooling needs efficiently, not oversized with unnecessary capacity or undersized with insufficient capacity. The chart below describes the general idea of each measurement as it relates to cooling tower size.
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Heat Load: |
Wet Bulb Temperature: Lowest temperature it can reach from evaporation. | Range: Amount of heat removed from the system. |
Approach: Temperature difference between cooled water and wet bulb temperature. | |
| Larger tower | Outputs more BTU. | High temperature require larger size. | Larger range. | Larger approach temperature. |
| Smaller tower | Outputs less BTU. | Low temperature requires smaller size. | Smaller range. | Smaller approach temperature. |
For professional help regarding cooling tower efficiency, sizing, treatment, and more contact us here.
Larger cooling towers have more air flowing through the tower. This, in turn, leads to better cooling. Larger cooling towers cost more to construct and maintain so it is necessary to consider various factors to determine how large of a tower is needed for your situation.
A large facility or a processing application that needs a lot of heat expelled will need a larger tower. However, it is important to choose the right size as installing an oversized cooling tower is leads to uncessary:
Additionally, it should be tailored to your specific industry. Whether that is residential hvac, health care, or industrial manufacturing, each one has different needs for the function of its cooling tower.
78°F is an example of a normal wet bulb temperature for a cooling tower. The wet bulb temperature indicates how much water the temperature of the air that is coming into the tower can hold. To measure wet bulb temperature you use a specific wet bulb thermometer, the units it is measured in is Tw. This will measure the lowest temperature water can be in a cooling tower and still evaporate. Due to this, it is highly dependent on the outside of facility’s climate. Humid areas will allow for more moisture and result in lower levels of evaporative cooling.
Range is a useful measurement for indicating the amount of cooling that took place. It is the measurement of the water temperature entering the heat exchanger minus the water temperature leaving the heat exchanger. Thermometers (thermocouples) are installed into the pipes on both ends to take this measurement. The incoming water is hot (HWT) and the outbound water is cold (CWT).
Formula: Range= HWT-CTW
Head load describes the amount of heat a cooling tower can remove in an hour. It is often measured in BTU, British thermal unit. Directly related to this is GPM, gallons per minute, describes the amount of water volume that can pass through the cooling tower process. Essentially, the larger the surface area material and the larger the amount of cool water passing through, the larger the amount of cooling that can occur.
This can be calculated using the aforementioned factors. To calculate this you need to find out your gallons per minute as well. Volume will be in gallons and time will be in seconds when calculating GPM.
Formula: Gallons Per Minute (GPM)= Volume/Time
Formula: Head Load Capacity= GPM*500*Range
Lastly, the approach is an essential factor that affects size. Approach measures the difference between the cold water entering the basin temperature and the wet bulb temperature. Lower approach temperatures generally require a bigger tower, however, it is important to consider all of the factors.
Formula: CWT-WBT
The other factors are inversely related to tower size. If the wet bulb temperature, approach, or range is not constant, then one of those increasing while the others are constant would mean a smaller size tower is needed. Additionally, size is not the only important factor when choosing a cooling tower. It is important to choose the correct type of cooling tower.
Ultimately, sizing a cooling tower correctly will result in higher efficiency, lower maintenance, and lower installation costs. For sizing a cooling tower and maintaining it properly, it is important to work with a company that has experience in your local climate and your specific industry. Chardon Labs knows what it takes to design and maintain a cooling tower system. For expert cooling tower assistance please reach out.
