Evaporative (Swamp) Cooler Leaving Temperature
The supply-air temperature a direct-evaporative (swamp) cooler delivers.
Example
You enter
- Entering dry-bulb (°F) 95
- Entering wet-bulb (°F) 65
- Pad saturation effectiveness (0-1) 0.85
You get
- Leaving dry-bulb 69.5 F
- Temperature drop 25.5 F
Details, formula, and sources
T_out = T_db - saturation effectiveness x (T_db - T_wb). 95 F dry-bulb, 65 F wet-bulb, and an 85% pad give 69.5 F. The wet-bulb depression is the maximum possible drop, so a dry climate cools far more than a humid one; the process adds moisture (high leaving RH). Pad effectiveness ~0.80-0.90 rigid media, less for aspen. Direct single-stage only; the equipment data govern.
T_out = T_db - saturation_effectiveness x (T_db - T_wb); temp_drop = effectiveness x (T_db - T_wb); wet_bulb_depression = T_db - T_wb.
ASHRAE Fundamentals direct-evaporative (saturation) effectiveness relation, by name; classical psychrometrics.
The saturation-effectiveness relation is free in published engineering texts.
Estimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.
Field names used by the API: dry_bulb_F, wet_bulb_F, effectiveness, leaving_db_F, temp_drop_F
- Saturation effectiveness eff = (T_db - T_out)/(T_db - T_wb); user-entered, ~0.80-0.90 rigid mediaASHRAE / manufacturer rating
- Wet-bulb floor the leaving dry-bulb cannot fall below the entering wet-bulbpsychrometrics
- Direct single-stage adds moisture (constant wet-bulb line); indirect / two-stage is separatescope of this tile