Relative Humidity Chart Dry Bulb Wet Bulb

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.

Relative humidity chart dry bulb wet bulb.

When dry bulb temperature and wet bulb temperature are known we can determine the relative humidity absolute humidity and enthalpy. When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. Relative humidity table or relative humidity chart step 1. 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.

Now we are going to learn two of those axis dry bulb temperature and wet bulb temperature. 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. Chart shows dry bulb temperature td in rows and difference between td tw in columns. Lines of constant wet bulb temperatures run diagonally from.

When we know dry bulb temperature and wet bulb temperature. Example the state of air in the psychrometric chart. Two independent intensive properties are required to completely specify the state of air in the psychrometric chart. The relative humidity is approximately 50 the humidity ratio is approximately 65 grains h2o lb dry air.

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. By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only. Properties of atmospheric air such as the dry bulb temperature the wet bulb temperature the dew point temperature the specific humidity the relative humidity specific enthalpy and specific volume are discussed in relation to the psychrometric chart below. Relative humidity temperature in.

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 wbt is the temperature read by a thermometer covered in water soaked cloth wet bulb thermometer over which air is passed. Dry bulb temperature tells the actual room temperature. Substract wet bulb temperature from the dry bulb temperature i e.

Note down the dry bulb temperature td and wet bulb temperature tw. 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.