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R-22 is contained in a piston-cylinder, where the volume is 11 L when the piston hits the stops. The initial state is 150 kPa, −30°C with V=10 L. This system warms up to 15°C. Find the work done by R-22 during this process.

R-22 is contained in a piston-cylinder, where the volume is 11 L when the piston hits the stops. The initial state is 150 kPa, −30°C with V=10 L. This system warms up to 15°C. Find the work done by R-22 during this process. Correct Answer 0.15 kJ

Initially piston floats, V 3/kg; m = V/v = 0.010/0.1487 = 0.06725 kg now, P1a = 150 kPa, v = V(stop)/m and v1a = V/m = 0.011/0.06725 = 0.16357 m3/kg => T1a = -9°C & T2 = 15°C Since T2 > T1a then it follows that P2 > P1 and the piston is against stop. Work = ∫ P(ext) dV = P9ext)(V2 – V1) = 150(0.011 – 0.010) = 0.15 kJ.

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