Wet Bulb Dew Point Chart

Combining the dry bulb and wet bulb temperature in a psychrometric diagram or mollier chart gives the state of the humid air.

Wet bulb dew point chart.

This script will determine the relative humidity from the entered dry and wet bulb temperatures data. 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. For the saturated air the dry bulb temperature the wet bulb temperature and dew point temperature are same. The dew point temperature of air depends upon its mositure content.

If the supply air leaving the system is at 55 f dry bulb and 53 f wet bulb we see from the chart that the dew point is 51 5 f. Higher the mositure content of the air higher is the dew point temperature. 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. Lines of constant wet bulb temperatures run diagonally from the upper left to the lower right in the psychrometric chart.

Enter the two different temperatures. Looking at the psychrometric chart we see the dew point is 55 f. Dew point temperature tdp. By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only.

The dew point lines traverse the chart as horizontal lines. The coil of the air conditioner is at 45 f so the system will condense water from the air. Dew point and wet bulb temperatures are very important in indicating the state of the humid 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.

At 100 relative humidity the wet bulb temperature is equal to the air temperature dry bulb temperature. Therefore the change on the chart is down and to the right. These can be calculated automatically using wildland fire rh calculator apps for ios and android available for free. What this tells you is that dew point does not change as the dry bulb temperature varies.

The dry bulb wet bulb and dew point temperatures are important to determine the state of humid air. The key difference between dewpoint and wet bulb temperature is that dewpoint temperature is the temperature to which we should cool the air to saturate the air with water vapor whereas wet bulb temperature is the temperature that we get from a moistened thermometer bulb that is exposed to air flow. At lower humidity the wet bulb temperature is lower than dry bulb temperature because of evaporative cooling.