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Lecture 5 PES Su 2011 annotated

# Lecture 5 PES Su 2011 annotated - ME 200 Thermodynamics I...

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ME 200: Thermodynamics I Lecture 5: Expansion/Compression Work, other Examples of Work Prof. Sojka Summer 2011

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2 In this Lecture … Expansion/compression (boundary work) Other examples of work
3 Types of Mechanical Work Moving a system boundary Rotating shaft Stretched spring Stretching an elastic solid bar Stretching a liquid film Accelerating a body Raising a body

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4 Moving Boundary Work Fdx W = δ = 2 1 s s s d F W = 2 1 s s s d F W pA F = dV Adx = pdV W = δ = 2 1 V V pdV W
5 Moving Boundary Work δ W = pdV means W cannot be computed until we know how p depends on V (i.e., we know the path or process ). MOVING BOUNDARY WORK IS NOT A PROPERTY.

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6 Moving Boundary Work Polytropic Process For an ideal gas C pV n = n and C are constants ( 29 n T T mR W - - = 1 1 2 = 1 2 ln V V pV W n 1 n = 1 n CV p - = n V p V p V pd W - - = = 1 1 1 2 2 2 1
7 Shaft Work Fds W = δ = 2 1 s s s d F W θ τ d Fds = θ τ δ d W = t W = τϖ τϖ = W & τ – torque ω – angular velocity (rad/s)

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