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  • Notes
  • Comments & Questions
  • Exergy (Work Potential of Energy) is the maximum useful work possible during a process that brings the system into equilibrium with a heat reservoir, reaching maximum entropy.
  • Thedead state : the state when a system is in thermodynamicequilibrium with the environment
  • Surroundings are everything outside the system boundaries.
  • The immediate surroundings: the portion of the surroundings that is affected by the process.
  • Environment: the region beyond the immediate surroundings whoseproperties are not affected by the process at any point
  • Exergy: the useful work potential of the system at the specified state
  • Exergy of kinetic energy: the kinetic energy itself regardless of the temperature and pressure of the environment

$$x_{\mathrm{ke}}=\mathrm{ke}=\frac{V^{2}}{2} \quad(\mathrm{kJ} / \mathrm{kg})$$

  • Exergy of the potential energy: the potential energy itself regardless of the temperatureand pressure of the environment

$$x_{\mathrm{pe}}=\mathrm{pe}=g z$$

  • The surroundings work: the work done by or against thesurroundings during a process


  • The useful work: The difference between the actual work and the surroundings work


  • Reversible work: the maximum amount of useful workthat can be produced as a system undergoes a process between the specified initial and final states
  • irreversibility I : difference between the reversible work and the useful work

$$I=W_{\mathrm{rev}, \mathrm{out}}-W_{u, \mathrm{out}}$$ or $$I=W_{u, \mathrm{in}}-W_{\mathrm{rev} ; \mathrm{in}}$$

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