Evaporation Loss in a Cooling Tower

Quantifies the heat removed from a cooling tower by evaporating a small fraction of the recirculating water.

$$Q_{evap}=m_{evap}\times h_{fg}$$

Variables

Symbol	Meaning	Unit
$Q_{evap}$	Heat removed by evaporation	BTU/min
$m_{evap}$	Mass of water evaporated	lb/min
$h_{fg}$	Latent heat of vaporization (about 970 for water)	BTU/lb

Worked example

A tower recirculating 1,000 gpm (8,340 lb/min) evaporating 1% loses 83.4 lb/min. Q_evap = 83.4 lb/min x 970 BTU/lb = about 81,000 BTU/min.

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Part of The Blueprint of Water