Wet Bulb Dry Bulb

At 100 relative humidity the wet bulb temperature is equal to the air temperature dry bulb temperature.

Wet bulb dry bulb.

At lower humidity the wet bulb temperature is lower than dry bulb temperature because of evaporative cooling. When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only. The uncovered thermometer measures dry bulb temperature while the one covered with wet cloth measures wet bulb temeprature.

It is therefore measured by wrapping a wet wick around the bulb of a thermometer and the measured temperature corresponds to the wet bulb temperature. Since both the thermometers are placed side by side the mositure from wet wick may affect the readings of dry bulb thermometer to avoid this the wet bulb thermometer is placed at the lower level. Combining the dry bulb and wet bulb temperature in a psychrometric diagram or mollier chart gives the state of the humid air. The wet bulb temperature is always lower than the dry bulb temperature but will be identical with 100 relative humidity the air is at the saturation line.

Wet bulb temperature is the lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure. The knowledge of only two of these values is enough to determine the state of the moist air including the content of water vapor and the sensible and latent energy enthalpy in the air. The wet bulb temperature wbt is the temperature read by a thermometer covered in water soaked cloth wet bulb thermometer over which air is passed. Relative humidity is measured using a device called a sling psychrometer this consists of 2 side by side conventional thermometers one of which the wet bulb thermometer has a wetted wick placed at the bottom the other the dry bulb thermometer has no wetted wick.