Cooling Tower Airflow Calculator
Airflow and evaporation for a cooling tower.
Enter your values
ⓘ Live results
Results
- Heat rejected
- 3,000,000 BTU/h
- In tons
- 250
- Airflow
- 55,556 CFM
- Evaporation
- 6 gpm
- Makeup with 3 cycles
- 9 gpm
Quick answer
Cooling tower airflow is set by the heat rejected and the enthalpy rise of the air passing through the fill.
CFM ≈ heat rejected / (4.5 x enthalpy rise)
How to use the Cooling Tower Airflow Calculator
- 1Enter the condenser water flow and the range you need across the tower.
- 2Use 10-14 Btu/lb enthalpy rise for a typical induced draft tower.
- 3Add blowdown to evaporation to size makeup water.
Worked example
Using the values the calculator loads with:
Inputs
- Water flow600 gpm
- Range (in - out)10 °F
- Air enthalpy rise12 Btu/lb
Results
- Heat rejected3,000,000 BTU/h
- In tons250
- Airflow55,556 CFM
- Evaporation6 gpm
- Makeup with 3 cycles9 gpm
Frequently asked questions
What is approach?
The gap between leaving water temperature and ambient wet bulb — a 5°F approach tower is much larger than a 10°F one.
Cycles of concentration?
Higher cycles save water but need better chemical treatment to avoid scale.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.