ME 311 THERMODYNAMICS S. Masutani FALL 2007 CHAPTER 9 Gas Power CyclesChapter 8 focused on power systems in which the working fluid existed as either a liquid or a gas at different points in the cycle. The chief advantage of these vapor power systems lies in the fact that work required to pressurize a liquid (by the pump) << work performed during expansion of a gas (in a turbine) ⇒bwr is << 1. Early compressors were much less efficient than turbines; all-gas systems could not produce significant net power. Consider1 pump or compressor W&Q&2 2m&1m&1 Energy balance (SSSF)outflow = inflow QhhmWQhmWhm&&&&&&&−−=⇒++=)(1212For an internally reversible device: ∫=21TdsmQ&&(heat added) (note: if Qis taken to be heat lost from the system ⇒) &∫−=21TdsmQ&&The Gibbs equation yields ∫∫∫−−=⎟⎟⎠⎞⎜⎜⎝⎛−=⇒−=21122121)(vdpmhhmvdpdhmQvdpdhTds&&&&Substituting ∫∫=+−+−=21211221)()(vdpmvdpmhhmhhmW&&&&&
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