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A piston-cylinder contains 1 kg of liquid water at 300 kPa, 20°C. Initially the piston floats, with a maximum enclosed volume of 0.002 m3 if the piston touches the stops. Now heat is added so that the final pressure is 600 kPa. Find the work in the process.

A piston-cylinder contains 1 kg of liquid water at 300 kPa, 20°C. Initially the piston floats, with a maximum enclosed volume of 0.002 m3 if the piston touches the stops. Now heat is added so that the final pressure is 600 kPa. Find the work in the process. Correct Answer 0.30 kJ

State 1: Compressed liquid v = vf(20) = 0.001002 m3/kg v(stop) = 0.002 m3/kg , 300 kPa v2 = v(stop) = 0.002 m3/kg and V = 0.002 m3 Work is done while piston moves at P(lift) = constant = 300 kPa 1W2 = ∫ P dV = m*P(lift)*(v2 -v1) = 1 × 300(0.002 − 0.001002) = 0.30 kJ.

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