How to do cooling tower tonnage calculation?

Well, please study the following formula and explanation.

The following design data is required for cooling tower tonnage calculations.

- Flow rate in GPM
- Range of cooling in °F (T1-T2) [ Also known as Delta T ]

**Cooling tower tonnage calculation**

There are two ways to calculate tonnage

- Cooling tower tonnage = GPM/3 (only when the temperature difference is 10 F), otherwise please follow
- Cooling tower tonnage = GPM* Delta T *500 (constant) /15000

Now you may ask, how 500 came? here in formula

Because there are, 8.33 (Pounds in gallon) * 1 (water specific heat) * 60 (mins)

When we run above calculation, we would get 499.8.

Hence 500 = 499.8, used in cooling tower tonnage calculation

**How to calculate design heat load of cooling tower?**

Heat load (BTU/hr) = GPM X 500 X Range (T1-T2) °F

If the range of cooling or heat load, one of the other factors are known. Then can be calculated using this following formula.

- GPM = Heat load ( BTU/hr) / 500 X Range (T1-T2) °F
- Range of cooling = Heat load ( BTU/hr) / 500 X GPM

Heat load is directly proportional to the range of the cooling tower.

Once you get the heat load of cooling tower, then can easily calculate cooling tower tonnage.

**How many BTU per ton of cooling ?**

1 ton = 15000 BTU

So, we can use formula like this.

**Cooling tower tonnage calculation formula**

Cooling tower tonnage = GPM X 500 X Range (T1-T2) °F / 15000

The result is tons of cooling capacity for cooling tower.

500 is a “fluid factor”, it’s based on water as we using water as heat transfer fluid in cooling towers.

The fluid factor is derived by using the weight of a gallon of water, which is 8.33 lbs. then multiply weight of water by specific heat of water, which is 1.To convert it in hr multiply it to 60 ( minutes/ hour)

**Fluid factor calculation for cooling capacity**

8.33 X 1 X 60 = 499.8

Round figure 500

Hence we use 500 as a fluid factor for cooling tower tonnage calculation. or to calculate the heat load of the cooling tower.

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