Cooling Tower Calculator

This calculator computes the two fundamental temperature metrics used to describe cooling tower performance -- Cooling Range (Hot Water Temperature minus Cold Water Temperature, the amount of heat rejected) and Cooling Approach (Cold Water Temperature minus Wet Bulb Temperature, how close the tower gets the water to the theoretical limit set by ambient wet- bulb conditions). A smaller Approach means a more effective tower, since the wet-bulb temperature is the coldest a cooling tower can ever bring water to -- it can never cool below ambient wet-bulb temperature regardless of size. The Merkel Number (KaV/L) reported here is a simplified Range/Approach-based surrogate for the real Merkel heat-and-mass-transfer integral used in cooling tower thermal design -- it is NOT computed from the entered Water Flow Rate and Air Flow Rate; those two inputs are instead used to size Evaporation Rate and Makeup Water below, and only confirm the tower actually has a liquid and a gas stream to exchange heat between (a full Merkel calculation would also need the tower's actual L/G ratio and fill characteristic curve, which this simplified estimate does not model). A higher value here indicates a larger Cooling Range relative to Approach.

Evaporation Rate is estimated from the field guideline that roughly 1% of circulating water flow evaporates per 10°F (about 5.6°C) of cooling range -- since Cooling Range is computed in °C, it is converted to an equivalent °F temperature difference (multiplied by 1.8, with no +32 offset, because this is a delta not an absolute temperature) before the per-10°F coefficient is applied -- since evaporative cooling is the primary heat-rejection mechanism in a wet cooling tower. Makeup Water Required sums three water losses that must be continuously replaced: the estimated Evaporation Rate, drift loss (droplets carried out with the exhaust air, approximated at 0.1% of circulating flow), and blowdown (water deliberately discharged to control dissolved-solids concentration, approximated here as one-third of the evaporation rate). Air Flow Rate itself only needs to be positive: it confirms the tower actually has a gas stream to exchange heat with, but its magnitude has no further bearing on Cooling Range, Cooling Approach, Merkel Number, Evaporation Rate, or Makeup Water Required, all of which are driven by Water Flow Rate and the entered temperatures instead.