Wet Bulb Dry Bulb Chart

The following tables calculate dew point and relative humidity based on the observed wet bulb and dry bulb temperatures and the elevation at the site of the observation.

Wet bulb dry bulb chart.

At lower humidity the wet bulb temperature is lower than dry bulb temperature because of evaporative cooling. Dry bulb temperature ranging 20 o f to 120 o f. 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. These can be calculated automatically using wildland fire rh calculator apps for ios and android available for free.

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. Barometric pressure 29 921 inches of mercury. Combining the dry bulb and wet bulb temperature in a psychrometric diagram or mollier chart gives the state of the humid air. The psychrometric chart below is made for standard atmospheric conditions.

Dry bulb temperature is 30 0 c and wet bulb temperature is 25 0 c. 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. This equality occurs at only in air become saturated. By definition wet bulb temperature is the lowest temperaturea portion of air can acquire by evaporative cooling only.

Constant dry bulb temperatures appear as vertical lines in the psychrometric chart or horizontal lines in the mollier diagram. Wet bulb temperature axis on psychrometric chart wet bulb temperature axis is highlighted in following figure. Calculate the relative humidity. The state of air with dry bulb temperature 75of and wet bulb temperature 62 5of can be visualized in the psychrometric chart as indicated below.

The relative humidity is approximately 50 the humidity ratio is approximately 65 grainsh2o lbdry air relative humidity temperature in fahrenheit. English imperial units with wet bulb and dry bulb temperature and relative humidity. With enthalpy units in btu lb. Wet bulb temperature is lower than dry bulb temperature or equal to the dry bulb temperature.