lecture_2011_09_06

# lecture_2011_09_06 - Michigan State University Mechanical...

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Harold Schock, Michigan State University Michigan State University Michigan State University Mechanical Engineering Mechanical Engineering FALL 2011 - ME 444 FALL 2011 - ME 444 First Law Analysis of Reacting Systems First Law Analysis of Reacting Systems Harold Schock Harold Schock

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Harold Schock, Michigan State University First Law Analysis of Reacting Systems First Law Analysis of Reacting Systems For a SSSF process, the First Law yields Q c.v. +H R =W c.v. +H P or on a per mole basis e e P . v . c i i R . v . c h n W h n Q + = +
Harold Schock, Michigan State University First Law Analysis of Reacting Systems, continued Us Usually 1 kmole of fuel is chosen as the base for the solution. Usually, the substances that comprise the products and the reactants are not at 0.1MPa and 25 ° C. One must develop methods to relate the state of initial and final conditions to the enthalpy of formation, which is given for molecules @ 0.1 MPa and 25 ° C.

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Harold Schock, Michigan State University Finding the Change In Enthalpy for Gases Finding the Change In Enthalpy for Gases 1) Assume I.G. behavior between 0.1MPa and 25 ° C and the given state If I.G. h=h(T) only Use an equation for CP o Use tabulated data as a function T (which assumes ideal gas behavior) , 298 o o t superscrip h enthalpy at 0.1MPa Use one of the following:
Harold Schock, Michigan State University Change in Enthalpy (continued) 2) If a real substance table is available, h can be found directly from the tables. For example liquid water. 3) If deviation from I.G. behavior is significant, but tables are not available Generalized Charts h

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Harold Schock, Michigan State University Thus, in general, for a SSSF process involving a chemical reaction and negligible KE and PE changes, First Law can be written as: e o f e P . v . c i o f i R . v . c ) h h ( n W ) h h ( n Q + + = + + Change in Enthalpy (continued)
Harold Schock, Michigan State University Some Examples Some Examples Example 5.1 Example 5.1 Calculate the enthalpy of water (on a kmole

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## This note was uploaded on 01/29/2012 for the course ME 444 taught by Professor Staff during the Fall '08 term at Michigan State University.

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lecture_2011_09_06 - Michigan State University Mechanical...

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