There are two terms you need to understand if you want to sound somewhat competent when describing a tower’s performance: Approach and Range.
Range is the temperature difference between the inlet water and the outlet water.
The formula is EWT (95℉) – LWT(85℉) = Range (10℉)
The higher the range, the more efficient the tower.
Approach is the difference between the outlet water temperature and the entering air wet bulb temperature.
The Higher the approach the less efficient the tower.
The formula is LWT (85℉) – WBT (78℉) = Approach (7℉)