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Thermodynamics
First Law of Thermodynamics
GATE 2013
Medium

The pressure, dry bulb temperature and relative humidity of air in a room are 1 bar, 30°C and 70%, respectively. Given that the saturated steam pressure at 30°C is 4.25 kPa, the specific humidity of the room air in kg water vapour/kg dry air is

  • A0.0083
  • B0.0101
  • 0.0191
  • D0.0232

Explanation

Vapor pressure Pv = φ·Psat = 0.7×4.25 = 2.975 kPa. Specific humidity ω = 0.622·Pv/(P−Pv) = 0.622×2.975/(100−2.975) = 1.8504/97.025 ≈ 0.0191.

Source: GATE ME 2013 (Booklet Code A) (2013)

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