Summer design wet bulb temperature represents the humidity level coinciding with peak summer dry bulb temperature, used to calculate latent cooling loads and total cooling capacity requirements. Unlike relative humidity percentage, wet bulb directly indicates the combined effect of temperature and moisture content on cooling system performance.
Technical Characteristics
Summer design wet bulb values appear alongside design dry bulb temperatures in ASHRAE tables, typically 5-15°F lower than coincident dry bulb temperature depending on regional climate. Wet bulb temperature indicates the lowest temperature achievable through evaporative cooling, directly affecting cooling tower performance and dehumidification requirements. The difference between dry bulb and wet bulb (called dry bulb depression) varies by location, from 10-12°F in humid regions to 25-35°F in arid climates.
Load Calculation Impact
Latent cooling loads, representing moisture removal rather than sensible temperature reduction, depend directly on design wet bulb temperature. Systems must be sized for both sensible (dry bulb dependent) and latent (wet bulb dependent) cooling capacity. Humidity control becomes critical in applications like data centers and laboratories where design wet bulb temperatures guide dehumidification equipment selection.