Reversible%20&%20Irreversible%20Processes

Reversible%20&%20Irreversible%20Processes - Internal...

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1 Reversible & Irreversible Processes Reversible Process A process that, once having taken place, can be reversed and in doing so leaves no change in either the system or the surroundings Net work and net heat transfer must be zero A reversible process is an ideal that we never achieve – all processes are irreversible
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2 Why do we study reversible processes? They are ideals that we can shoot for. They are standards to which we can compare different processes. Irreversibilities Irreversibilities are what cause a process to be irreversible ± Friction ± Unrestrained expansion ± Heat transfer through a finite temperature difference ± Mixing of different substances ± Others (chemical reactions, inelastic deformation of solids, electric resistance, hysteresis effects)
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3 Internal vs. External Irreversibilities External irreversibilities occur outside the system you’re looking at.
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Unformatted text preview: Internal irreversibilities occur inside the system youre looking at. A totally reversible system is internally & externally reversible. Example 1 A gas in an insulated tank is separated from an evacuated region by a membrane. The membrane is removed and the gas expands. Internally or externally reversible? Or neither? 4 Example 2 Which heat transfer process is irreversible? If the system is the piston, is the irreversibility internal or external? Control Volume Boundary Temperature=T Carnot Cycle (1824) A reversible cycle to which we compare all other cycles; an ideal to shoot for Four processes: Reversible isothermal expansion Reversible adiabatic expansion Reversible isothermal compression Reversible adiabatic compression Will we ever achieve this cycle in real life?...
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This note was uploaded on 04/15/2008 for the course ME 113 taught by Professor Usaxena during the Spring '07 term at San Jose State University .

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Reversible%20&%20Irreversible%20Processes - Internal...

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