Evaporative Cooling Calculator - HVAC Calculator Toolbox

About this calculator This calculator evaluates indirect or direct evaporative cooler performance at specific entering air conditions. It determines leaving dry bulb and wet bulb temperatures, cooling effectiveness, and face velocity across the media. Use it to size evaporative cooling equipment or to verify performance at design conditions in dry climates where evaporative cooling is effective.

Use when You need to evaluate evaporative cooler performance at specific entering conditions.

Variables

Entering DB Entering dry bulb temperature °FEntering WB Entering wet bulb temperature °FCFM Airflow in cubic feet per minuteFace Area Media face area in square feetAltitude Elevation above sea level in feetMedia Type Celdek or standard evaporative media

Entering Dry Bulb (°F)

Entering air dry bulb temperature

Entering Wet Bulb (°F)

Entering air wet bulb temperature

CFM

Cubic feet per minute of airflow

Face Area (sq ft)

Pad face area in square feet

Altitude (ft)

Site elevation above sea level

Celdek Media90% effectiveness

Standard Media70% effectiveness

Media Type

Leaving DB (°F) —

Leaving WB (°F) —

ΔT (°F) —

Leaving RH (%) —

Face Velocity (FPM) —

What is evaporative cooling?

Evaporative cooling is an energy-efficient cooling method that lowers air temperature by evaporating water into the airstream. As water evaporates, it absorbs heat from the surrounding air, reducing the dry bulb temperature while increasing humidity. The effectiveness of evaporative cooling depends on the wet bulb depression—the difference between the entering dry bulb and wet bulb temperatures. In direct evaporative coolers, the theoretical maximum cooling approaches the entering wet bulb temperature. Effectiveness ratings of 85–95% are typical for well-designed media. Evaporative cooling is most effective in hot, dry climates where the wet bulb depression is large. In arid regions such as the American Southwest, direct evaporative coolers can reduce air temperature by 15–25°F while using 60–80% less energy than mechanical refrigeration. Indirect evaporative systems provide cooling without adding moisture to the supply air.

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