1Lesson 6, Geof Silcox, Chemical Engineering, University of UtahII. Energy and the First Law of ThermodynamicsA. Generic Statement of the First Law for a Closed System⎟⎟⎠⎞⎜⎜⎝⎛−⎟⎟⎠⎞⎜⎜⎝⎛=⎟⎟⎟⎠⎞⎜⎜⎜⎝⎛systemleavesenergyratesystementersenergyratesystemwithinenergyofchangeofrateTimeSystemNo massenters orleaves.HeatWorkoutinsystemEEE−=∆systeminoutdEEEdt=−±±Rate form of energy balance:Integrated form of energy balance:∆Esystem+ ∆Esurroundings= 0Note:(4-12)(4-11)Lesson 6, Geof Silcox, Chemical Engineering, University of UtahII. Energy and the First Law of ThermodynamicsB. Specific Statement of First Law for a Closed System1. Energy is conserved.2. Energy can cross the boundary of a closed system by only two mechanisms: heat transfer and work transfer.3. The change in energy of a closed system is equal to the net heat transferred to the system minus the net work performed by the system (4-17).21V()2EmummgzkJ=++)kJ(WQEnet,outnet,in−=∆21V2kJeugzkg⎛⎞=++⎜⎟⎝⎠,,(kJ/kg)in netout neteqw∆=−,,(kJ/kg)in netout netdeqwδδ=−Energy per unit mass:in,netout ,netdEQW(kJ )δδ=−The differential form of (4-17):/and/wWmqQ m==Total energy:
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