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HW6 spring 2011 solutions

# HW6 spring 2011 solutions - CHEG 2313 Thermo I HW#6 Spring...

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CHEG 2313 Thermo I HW#6 Spring 2011 Due Wednesday, March 9, 2011 by 5pm. 1. A process produces power by expanding 1.3 kg/s of steam from 500C and 3.5 MPa to 250C and 3000 kPa. A breakdown in insulation around the process allows a heat loss of 30 kJ per kg of steam. a) How much power can be produced from this process? (5 pts) - system: process - start with mass balance – since steady state M M M out in = = - next energy balance . . 1 2 . 2 2 2 W Q gh H M gh M U dt d k K k k + + + + = + + = ν ν - steady state and no kinetic or potential energy changes - reduced energy balance . . 2 1 . 0 W Q H H M + + - = - determine enthalpy values from steam tables ( 29 kg kJ MPa C H 9 . 3450 5 . 3 , 500 ˆ 1 = ( 29 kg kJ MPa C H 8 . 2855 3 , 250 ˆ 2 = - solve for work ( 29 kW s kJ W s kg kg kJ kg kJ s kg Q H H M W 6 . 734 6 . 734 3 . 1 30 9 . 3450 8 . 2855 3 . 1 . . 1 2 . . - = - = - - - = - - = b) If the heat is being transferred at 350°C, is this process possible? (5 pts) - entropy equation gen k k S T Q S M dt dS + + = . - steady state - reduced entropy eqn gen S T Q S S M + + - = .

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HW6 spring 2011 solutions - CHEG 2313 Thermo I HW#6 Spring...

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