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# Assign7-2 - Problem Statement 44 An insulated...

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Problem Statement: 44 An insulated piston-cylinder device contains 0.050 0.8 MPa. The refigerant is now allowed to expand in a reversible manner until to pressure drops to 0.4 MPa. Determine: a) The final temperature in the cylinder b) The work done by the refrigerant Schematic: Assumptions/Approximations: The kinetic and potential energy changes are negligible The cylinder is well-insulated and thus heat transfer is negligible The thermal energy stored in the cylinder itself is negligible The process is stated to be reversible Physical Laws: Properties/Sources: State P (kPa) u (kJ/kg) s (kJ/kg*K) 1 800.000 0.02562 246.79 0.918350 2 8.91 400.000 232.91 63.62 235.07 0.918350 0.247610 0.926900 Calculation: 1.95 kg Reasoning/Verification/Discussion: 98.74% None needed 232.91 kJ/kg -27.08 27.08 kJ m 3 of saturated Refrigerant-134a vapor at m = V/v 1 u 2 = u f + x 2 *(u g - u f ) x 2 = (s 2 - s f )/(s g - s f ) -W OUT = m*(u 2 - u 1 ) T ( o C) v (m 3 /kg) v f (m 3 /kg) v g (m 3 /kg) u f (kJ/kg) u g (kJ/kg) s f (kJ/kg*K)s

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Assign7-2 - Problem Statement 44 An insulated...

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