Wet Bulb Dry Bulb Humidity

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

Wet bulb dry bulb humidity.

At lower humidity the wet bulb temperature is lower than dry bulb temperature because of evaporative cooling. 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 depression in wet bulb temperature allows the humidity to be calculated. The difference between these two temperatures is a measure of the humidity of the air.

Dry bulb temperature t db can be measured with a simple thermometer as shown above. Note that continuously air flow around the thermometer is important to evaporate. The higher the difference in these temperatures the lower is the humidity. 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.

A wet cloth is placed over the bulb of a thermometer and then air is blown over the cloth causing the water to evaporate. Since evaporation takes up heat the thermometer will cool to a lower temperature than a thermometer with a dry bulb at the same time and place. When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. At 100 relative humidity the wet bulb temperature is equal to the air temperature dry bulb temperature.

Air humidity can be estimated by measuring. 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. The dry bulb temperature is the ambient temperature.