# Problem 4-1 - Example 4-1 Nitrogen is compressed in a...

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Example 4-1 Nitrogen is compressed in a piston-cylinder assembly from an initial temperature of 15°C and pressure of 98 kPa to a final temperature of 180°C and pressure of 410 kPa. The mass of nitrogen is 9.17 x 10 -4 kg. If the process is adiabatic, a) find the entropy generated. b) What would the final pressure be if the process were isentropic? (the final temperature remains at 180°C) Solution: a) An entropy balance gives: 2 21 1 gen Q SS S T δ −= + The process is adiabatic, so gen S =− 1 kJ entropy(N2, 98, 15) 6.81 kg K sP T == = = 2 kJ entropy(N2, 410, 180) 6.85 kg K T = = () 4 kJ 9.17 10 kg 6.85 6.81 kg K gen Sm s s 5 kJ J 4.32 10 0.0432 KK gen S = b) If the process were isentropic, then

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1 2 2 11 k k s P T TP ⎛⎞ = ⎜⎟ ⎝⎠ Evaluate specific heats at the average temperature, which is
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Problem 4-1 - Example 4-1 Nitrogen is compressed in a...

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