| A piston-and-cylinder device with a free-floating piston contains saturated water vapor at 225oC. Heat is
lost from the water to the surroundings which are at 25oC. |
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| Eventually, all of the water has condensed and the cylinder contains saturated liquid water
at 225oC. Is this process internally reversible? Reversible? Irreversible? Explain your answer. |
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| Read : |
What can be said about
this case of heat transfer process for (a) isothermal cooling of the water and (b) contact between 225oC and 25oC surroundings? |
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| Given: |
Tw |
225 |
oC |
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Find: |
Internally Reversible
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Reversible ? |
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Tsurr |
25 |
oC |
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Explain. |
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| Diagram: |
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| Assumptions: |
1 - |
The system is the water in the piston-and-cylinder assembly. |
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2 - |
The system undergoes a constant-temperature process from saturated vapor to saturated liquid. |
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/ Data / Solve: |
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No equations
are needed to resolve this problem. |
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There are no equations to solve. |
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| Verify: |
None of the
assumptions made can be verified with the given information. |
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| Answers : |
Since the temperature is constant during the process, the pressure also remains constant. As shown by the
T-V Diagram, the
process is a sequence
of equilibrium states,
and thus is internally reversible. |
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| The process is
not reversible because there is a
significant irreversibility in the surroundings. The spontaneous heat transfer taking
place between the water at 225oC and the surroundings at 25oC is irreversible. |
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