Paritian

Engineering

Evaporative Cooler Calculator (Outlet Air Temperature)

Temperature of the air leaving a direct evaporative cooler from the outdoor temperature, humidity and the effectiveness of the wet media.

Results

Air temperature leaving the cooler 23.6 °C
Temperature drop 11.4 °C
Wet-bulb temperature 20.8 °C
How it changes
Air temperature leaving the coolerRelative humidity 5 – 95. Air temperature leaving the cooler: 17.6459 → 34.4678Air temperature leaving the cooler152025303520406080Relative humidity (%)

The dashed line marks the value you entered.

What this tool does

A direct evaporative cooler can never cool the air below its wet-bulb temperature; its effectiveness says what share of the gap between air and wet-bulb it closes, and wetted-pad media typically reach roughly 70–90 %. So the dryer the air, the bigger the gap and the bigger the cooling: 35 °C air at 25 % humidity drops by well over 10 °C, while at 70 % humidity the same cooler gains only a few degrees. The air also leaves more humid, so the room needs an opening to let it out.

Formula

T_out = T − ε × (T − Tw) (Tw = wet-bulb temperature by Stull's formula, ε = effectiveness)

Variables

SymbolMeaningUnit
tTemperature°C
rhRelative humidity%
efCooler effectiveness (saturation efficiency)%
TOAir temperature leaving the cooler°C
DRTemperature drop°C
TWWet-bulb temperature°C

Worked example

  • Temperature35 °C
  • Relative humidity25 %
  • Cooler effectiveness (saturation efficiency)80 %
  • Air temperature leaving the cooler23.6 °C
  • Temperature drop11.4 °C
  • Wet-bulb temperature20.8 °C

Limitations

  • The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
  • The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.