me2322_lecture05

me2322_lecture05 - ME 2322 Engineering Thermodynamics I...

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ME 2322 Engineering Thermodynamics I Lecture 05, 01/24/08 Prof. Zhaoming He
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Chapter 2 • Introduce the concept of energy and define its various forms. • Define the concept of heat and the terminology associated with energy transfer by heat. • Define the concept of work, including electrical work and several forms of mechanical work. • Define several forms of mechanical work. • Introduce the energy balances, and mechanisms of energy transfer to or from a system. • Determine that a fluid flowing across a control surface of a control volume carries energy across the control surface. • Define energy conversion efficiencies.
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Mechanical Forms of Work • Work is related a force acting through a distance –W=F s • If F changes with displacement s – Force on boundary or a object – Boundary or a object must move • Work is associated with thermodynamics – System boundary moves (piston-cylinder device) – Entire system as a whole moves (car is running) = 2 1 Fds
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Shaft Work • Shaft work at torque T, unit N.m • Power, W=J/s () nT rn r T Fs W sh ππ 2 2 = = = T n W sh π 2 =
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• Spring (linear elastic) work from state 1 to 2: – Fdx=kxdx – k is spring constant – x is displacement ) ( 2 1 2 1 2 2 x x k W spring = Spring or Elastic Body
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Nonmechanical Form of Work -- Electric Work • When N coulombs of electrical charge move through a potential V, work is done: • Rate of work •T o t a l w o r k VN W e = VI W e = = 2 1 1 t e VIdt W
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This note was uploaded on 04/15/2008 for the course ME 2322 taught by Professor Oler during the Spring '06 term at Texas Tech.

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me2322_lecture05 - ME 2322 Engineering Thermodynamics I...

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