midterm2008Summer_solutions - 12-100 Propane is compressed...

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Unformatted text preview: 12-100 Propane is compressed in a steady-flow device. The entropy change and the specific work required for this compression are to be determined using the departure charts and treating the propane as an ideal gas with temperature variable specific heats.PropertiesThe properties of propane are (Table A-1, A-2a)K kJ/kg6794.1MPa,26.4K,370K,kJ/kg1885.kg/kmol,097.44crcr⋅===⋅==pcPTRMAnalysis(a) Using empirical correlation for the cpof propane as given in Table A-2c giveskJ/kmol440,49)373773(41074.31)373773(31072.15)373773(23048.)373773(04.4)(4)(3)(2)()()(4493352241423132212212213221ideal12in=-×+-×--+--=-+-+-+-=+++==-=--∫∫TTdTTcTTbTTadTdTcTbTadTchhwpThe work input per unit mass iskJ/kg1121===kg/kmol44.097kJ/kmol440,49ininMwwSimilarly, the entropy change is given byKkJ/kmol995.695004000ln)314.8()373773(31074.31)373773(21072.15)373773(3048.373773ln04.4ln)(3)(2)(lnlnln)(33922512313221221212122121221ideal12⋅=--×+-×--+-=--+-+-+=-+++=-=---∫∫PPRTTdTTcTTbTTaPPRdTdTcTbTaPPRdTTcssuuupThe entropy change per unit mass isKkJ/kg1.587⋅=⋅=-=-kg/kmol44.097KkJ/kmol995.69)()(ideal12ideal12Mssss(b) The enthalpy and entropy departures of propane at the specified states are determined from the generalized charts to be (Fig. A-29, A-30)0837....
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midterm2008Summer_solutions - 12-100 Propane is compressed...

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