Relative Humidity
Find the relative humidity (%) if the actual air temperature is 21.5°C and the wet-bulb temperature is 15°C.
![](/img/v3/ae11ad33-59a9-461f-b7f7-5c31ab60dd86.png)
Expand Hint
Properties of an air-water vapor mixture at a fixed pressure are given in graphical form on a psychrometric chart as provided in problem statement. When the system pressure is 1 atm, an ideal-gas mixture is assumed.
![](/img/v3/3d007b1a-1473-4e90-9abd-79b8b8b404b6.png)
Hint 2
![](/img/v3/882178d2-d7d6-4c87-b5a2-c4b3e2fda4ee.png)
Properties of an air-water vapor mixture at a fixed pressure are given in graphical form on a psychrometric chart as provided in problem statement. When the system pressure is 1 atm, an ideal-gas mixture is assumed.
![](/img/v3/a3e2163c-5eb1-4d03-ac40-155360316d0c.png)
In the psychrometric chart, let’s find where the 21.5°C dry bulb temperature (the temperature of air measured by a thermometer freely exposed to air) intersects with the 15°C wet-bulb temperature (2). The relative humidity curve that crosses this intersection is what the problem is asking for (3).
![](/img/v3/d6f53647-64ce-4159-9e58-db99dcb37e3d.png)
The relative humidity is 50%.
50%
Time Analysis
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Similar Problems from FE Sub Section: Psychrometric Charts
258. Dew Point
618. Wet Bulb Temp
623. Dew Point Temp
Similar Problems from FE Section: Psychrometric
258. Dew Point
618. Wet Bulb Temp
623. Dew Point Temp