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A piston cylinder contains 3 kg of air at 20°C and 300 kPa. It is now heated up in a constant pressure process to 600 K. Find the heat transfer.

A piston cylinder contains 3 kg of air at 20°C and 300 kPa. It is now heated up in a constant pressure process to 600 K. Find the heat transfer. Correct Answer 941 kJ

Ideal gas: PV = mRT P2V2 = mRT2 thus V2 = mRT2 / P2 = 3×0.287×600 / 300 = 1.722 m^3 Process: P = constant, 1W2 = ⌠ PdV = P (V2 – V1) = 300 (1.722 – 0.8413) = 264.2 kJ U2 – U1 = 1Q2 – 1W2 = m(u2 – u1) 1Q2 = U2 – U1 + 1W2 = 3(435.097 – 209.45) + 264.2 = 941 kJ.

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