Wet-bulb temperature

The cooling limit temperature, measured as the wet-bulb temperature is the lowest temperature that can be achieved by direct evaporative cooling. Here is the release of water a wet surface with the water absorption capacity of the surrounding atmosphere in balance. Due to the evaporative cooling, the cooling limit temperature is a function of the relative humidity below the air temperature. The temperature reduction is all the greater, the drier the surrounding air. Conversely, it can be determined from the temperature difference, the humidity.

The rate of the wet bulb temperature ( tF) by a psychrometric measurement with a thermometer, which is provided with a moistened cloth or cotton wool coating ( psychrometer or Aspirationspsychrometer ).

In this measurement, the wet bulb is well ventilated, so that makes her no boundary layer in which the ambient air wearing a locally higher vapor fraction. The cooling limit temperature ( except for a relative humidity of 100% ) is higher than the temperature of dew point.

Relevant the cooling limit temperature anywhere in large amounts of liquid is evaporated. The cooling effect can be a desired goal (eg, evaporative cooling, water injection, wet cooling) or a side effect (eg in drying systems, convection ).