lec 8 - Steady state assumptions and simplifications Time...

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Lec 8 Mass Balances, Energy Balances and Applications to Conversion Devices. Review of mass balance Conservation of energy for a control volume Energy balance can be expressed in terms of beginning and end states or in terms of flow rates
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Work for a control volume has two parts: Work due to the flow. ..… and everything else. 1-D Flow form of the control volume energy rate balance + + + - + + + + + = e e e e e e i i i i i i cv cv cv z g V v p u m z g V v p u m W Q dt dE 2 2 2 2 &
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Steady-state form for the mass and energy balances Steady state mass balance: = e e i i m m Steady state energy balance:
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Unformatted text preview: Steady state assumptions and simplifications Time averaged energy, mass flow rates, heat transfer rates, work rates, pressures, temperatures, etc are constant. cv Q & may be neglected when: cv W & is neglected when: KE and PE are dropped when: Application of Mass and Energy Balances to Devices Nozzles and Diffusers nozzle cross sectional area of flow passage narrows in so that the flow velocity increases. diffuser cross section area increases, the velocity decreases...
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This note was uploaded on 10/05/2011 for the course ME 2124 taught by Professor Uzgoren during the Spring '08 term at Virginia Tech.

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lec 8 - Steady state assumptions and simplifications Time...

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