Relative Humidity Formula Dry Bulb Wet Bulb

By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only.

Relative humidity formula dry bulb wet bulb.

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. In of mercury mm of mercury millibars hpa. In of mercury mm of mercury millibars hpa. At 100 relative humidity the wet bulb temperature is equal to the air temperature dry bulb temperature.

At lower humidity the wet bulb temperature is lower than dry bulb temperature because of evaporative cooling. The dry bulb temperature is the ambient temperature. If the dry and wet bulb temperatures are set to the same value the calculator will show the saturation mixing ratio the amount of water in saturated air at that temperature. The dry bulb wet bulb and dew point temperatures are important to determine the state of humid air.

Enter your actual station pressure not the altimeter setting. Enter a temperature relative humidity and actual station pressure. It includes a dry bulb thermometer a wet bulb thermometer and a psychrometric chart a graph that plots the relationships between the dry and wet bulb temperature relative humidity and dew point at constant pressure. The difference between these two temperatures is a measure of the humidity of the air.

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. Enter your actual station pressure not the altimeter setting. Given the wet bulb temperature dry bulb temperature and ambient pressure the humidity of the air can be calculated as follows. The state of air with dry bulb temperature 75 o f and wet bulb temperature 62 5 o f can be visualized in the psychrometric chart as indicated below.

When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. The relative humidity is approximately 50 the humidity ratio is approximately 65 grains h2o lb dry air. The higher the difference in these temperatures the lower is the humidity.