Work out cooling tower capacity instantly with clear inputs, formula shown and shareable results.
Tower duty is the water-side heat load, GPM x range x 500. Tower tons are quoted as 15,000 BTU/h rather than 12,000 because a tower also rejects compressor heat. Range is how far the water is cooled; approach is how close the cold water gets to the wet bulb, and it is the approach that governs tower size and cost.
Heat rejected
BTU/h = GPM x range x 500, range = hot - cold water temperature
Tower tons
Tower tons = BTU/h / 15000; approach = cold water - wet bulb
BTU/h = GPM x range x 500, range = hot - cold water temperature. Tower duty is the water-side heat load, GPM x range x 500.
Evaporative cooling drives water toward the wet bulb temperature asymptotically. A design approach below about 5 °F needs a disproportionately large tower.
This calculator takes 4 inputs: Circulating water flow, Hot water temperature in, Cold water temperature out, Design wet bulb. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.