Psychrometrics and Wet-Bulb Temperature: Cooling Tower Performance Limits

Wet-bulb temperature (TWB) is a key parameter in cooling tower performance, defining the theoretical lower limit for water cooling in a conventional evaporative cooling tower. Understanding the relationship between air temperature and humidity is therefore essential when evaluating industrial cooling systems.

On a psychrometric chart, dry-bulb temperature (TDB) and wet-bulb temperature (TWB) become equal at 100% relative humidity, when the air is saturated.

A conventional evaporative cooling tower cannot cool its outlet water below the wet-bulb temperature of the entering air. In practical operation, the outlet water temperature remains above this theoretical limit.