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Thermodynamics
Entropy & Second Law
GATE 2011
Medium

For the same adiabatic flow set-up (station P: 150 kPa, 350 K; cp=1.005 kJ/kgK, R=0.287 kJ/kgK), if the pressure at station Q is 50 kPa, the change in entropy (sQ - sP) in kJ/kgK is

  • A-0.155
  • B0
  • 0.160
  • D0.355

Explanation

Δs = cp·ln(TQ/TP) - R·ln(PQ/PP) = 1.005×ln(300/350) - 0.287×ln(50/150) = 1.005×(-0.15415) - 0.287×(-1.0986) = -0.15493 + 0.3153 ≈ 0.160 kJ/kgK.

Source: GATE ME 2011 (2011)

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