Question

Atmospheric air at 1 atm has a dry-bulb temperature of 20°C and a wet-bulb temperature of 15°C. Determine the dew point temperature

Answer 1

The dew point temperature is 11.65°C

Step-by-step explanation:

Dew point temperature formula is given as follows;

From the modified Apjohn equation, we have;

`P_v = P'_v -(1.8 * p (t - t'))/(2700)`

Which gives;

The saturation vapor pressure at 15°C = 1.705 kPa

`P'_v` = 1.705 kPa

p = 101.325 kPa

`P_v` = 1.705 - 1.8*101.325*(20 - 15)/2700 = 1.36725 kPa

The dew point temperature is the steam saturation temperature at 1.36725 kPa

= 6.9696 + (17.4953 - 6.9696)*(0.0136725 - 0.01)/(0.02 - 0.01) = 10.84°C by approximation calculation from steam tables and 284.8 K = 11.65°C from Wolfram Alpha.