Dry Bulb Wet Bulb Rh Chart

Relative humidity temperature in.

Dry bulb wet bulb rh chart. Altitude above sea level m. When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. Two independent intensive properties are required to completely specify the state of air in the psychrometric chart. Relative humidity table or relative humidity chart step 1.

Relative humidity dewpoint temp c results. 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. Note down the dry bulb temperature td and wet bulb temperature tw. 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.

The 100 percent relative humidity saturation line corresponds to the wet bulb and the dew point temperature scale line. By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only. Enter dry bulb temperature plus either wet bulb temp rh or dewpoint temp. Example the state of air in the psychrometric chart.

These can be calculated automatically using wildland fire rh calculator apps for ios and android available for free. The dry bulb wet bulb and dew point temperatures are important to determine the state of humid air. At 100 relative humidity the wet bulb temperature is equal to the air temperature dry bulb temperature. Specific volume m kg.

The line for zero percent relative humidity falls along the dry bulb temperature scale line figure 5. Partial vapour pressure pa. Substract wet bulb temperature from the dry bulb temperature i e. The relative humidity is approximately 50 the humidity ratio is approximately 65 grains h2o lb dry air.

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. Chart shows dry bulb temperature td in rows and difference between td tw in columns. To the upper right of the psychrometric chart. At lower humidity the wet bulb temperature is lower than dry bulb temperature because of evaporative cooling.

The versatility of the psychrometric chart lies in. 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. Wet bulb temp c. 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.

Determine cell where td.