What is the Difference Between Dewpoint and Wet Bulb Temperature?

The main difference between dew point and wet bulb temperature lies in their definitions and the processes involved in their determination:

1. Dew Point Temperature: This is the temperature at which air becomes saturated with moisture, leading to the condensation of water vapor into liquid water (dew). It is the temperature at which the air can no longer hold all of the moisture in the form of water vapor, causing the moisture to condense into liquid water when the air temperature is dropped. The dew point is always lower than the dry bulb temperature and is identical to 100% relative humidity (the air is at the saturation line).
2. Wet Bulb Temperature: This is the lowest temperature to which air can be cooled by evaporating water into it, with the process bringing the air to saturation. The wet bulb temperature is always between the dry bulb temperature and the dew point temperature. It is influenced by both the air temperature and moisture content, and it can be measured by using a thermometer with the bulb wrapped in wet muslin.

In summary, the dew point temperature is the temperature at which air becomes saturated and condenses moisture, while the wet bulb temperature is the lowest temperature that air can reach through the process of evaporating water into it. The wet bulb temperature always falls between the air temperature and the dew point temperature.

Comparative Table: Dewpoint vs Wet Bulb Temperature

The difference between dew point and wet bulb temperature depends on the humidity of the air. The wet bulb temperature is always lower than the dry bulb temperature but can be identical in some cases. Here is a summary of the differences between dew point and wet bulb temperature:

To determine the state of humid air, knowledge of only two of these values (Tdb, Tws, and Tdp) is enough. The relationship between these temperatures can be visualized using a psychrometric chart or Mollier diagram, where lines of constant wet bulb temperatures run diagonally from the upper left to the lower right.