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Modern Engineering Thermodynamics

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CHAPTER 4<br />

The First Law of <strong>Thermodynamics</strong><br />

and Energy Transport Mechanisms<br />

CONTENTS<br />

4.1 Introducción (Introduction). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100<br />

4.2 Emmy Noether and the Conservation Laws of Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100<br />

4.3 The First Law of <strong>Thermodynamics</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101<br />

4.4 Energy Transport Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104<br />

4.5 Point and Path Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107<br />

4.6 Mechanical Work Modes of Energy Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108<br />

4.6.1 Moving System Boundary Work ..................................................109<br />

4.6.2 Rotating Shaft Work ...........................................................112<br />

4.6.3 Elastic Work .................................................................114<br />

4.6.4 Surface Tension Work ..........................................................115<br />

4.7 Nonmechanical Work Modes of Energy Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116<br />

4.7.1 Electrical Current Flow Work ....................................................117<br />

4.7.2 Electrical Polarization Work .....................................................118<br />

4.7.3 Magnetic Work ...............................................................120<br />

4.7.4 Chemical Work ...............................................................122<br />

4.7.5 Mechanochemical Work ........................................................123<br />

4.8 Power Modes of Energy Transport. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124<br />

4.9 Work Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124<br />

4.10 The Local Equilibrium Postulate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126<br />

4.11 The State Postulate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127<br />

4.12 Heat Modes of Energy Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127<br />

4.13 Heat Transfer Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128<br />

4.13.1 Conduction .................................................................128<br />

4.13.2 Convection .................................................................129<br />

4.13.3 Radiation ...................................................................129<br />

4.14 A Thermodynamic Problem Solving Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130<br />

4.15 How to Write a <strong>Thermodynamics</strong> Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134<br />

A. Select the working equations and unknowns ..........................................135<br />

B. Write a short story that contains all the information needed to solve the problem ..............135<br />

C. Solve the problem in the forward direction ............................................135<br />

Now Let us Write a <strong>Thermodynamics</strong> Problem ...........................................136<br />

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138<br />

<strong>Modern</strong> <strong>Engineering</strong> <strong>Thermodynamics</strong>. DOI: 10.1016/B978-0-12-374996-3.00004-X<br />

© 2011 Elsevier Inc. All rights reserved. 99

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