Question

Atmospheric air at a pressure of 1 atm and dry bulb temperature of 28 C has a wet-bulb temperature of 20 C.

Using the psychrometric chart, determine:

(a) the relative humidity,

(b) the humidity ratio,

(c) the enthalpy,

(d) the dew-point temperature, and

(e) the water vapor pressure.

Answer 1

a)
`\phi = 48\%`, b)
`\omega = 0.012\,(kg\,H_(2)O)/(kg\,Air)`, c)
`h = 58\,(kJ)/(kg\,Air)`, d)
`T = 17^(\textdegree)C`, e)
`P_(v) = 1.831\,kPa`

Step-by-step explanation:

a) The relative humidity is given by the intersection of the dry bulb and wet bulb temperatures:

`\phi = 48\%`

b) The humidity ratio is:

`\omega = 0.012\,(kg\,H_(2)O)/(kg\,Air)`

c) The enthalpy is:

`h = 58\,(kJ)/(kg\,Air)`

d) The dew-point temperature is:

`T = 17^(\textdegree)C`

e) The water vapor pressure is the product of the relative humidity and the saturation pressure evaluated at dry bulb temperature:

`P_(v) = \phi \cdot P_(sat)`

`P_(v) = 0.48\cdot (3.816\,kPa)`

`P_(v) = 1.831\,kPa`