Lecture 3 Work

# Lecture 3 Work - Thermal and Fluids Engineering I Prof....

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Thermal and Fluids Engineering I Prof. Deborah A. Kaminski Lecture 3 – Work Definition of Work Work is a force through a distance Force and direction of motion Force and motion in not aligned the same direction In this course, we will only consider cases in which force and motion are in the same direction. Consider motion of a body traveling from x 1 to x 2 If the force is constant, the work done is () 21 WF x x =− If the force is a function of x , the work done is d = x Lecture 3 Page 1

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Thermal and Fluids Engineering I Prof. Deborah A. Kaminski Expansion or Compression Work Consider a quasi-equilibrium process – one which passes through a succession of equilibrium states. In a quasi- equilibrium expansion or contraction, the piston moves slowly compared to the speed with which the pressure equilibrates. WF d = x x WP A d = Adx dV = quasi-equilibrium d V = Units of Work SI 1 J = (1 N)(1 m) British 1 Btu = 778 ft·lbf Work is positive for expansion and negative for compression. Lecture 3 Page 2
Thermal and Fluids Engineering I Prof. Deborah A. Kaminski Use of EES Consider the ideal gas law in the form RT Pv M = The three properties in this equation are P vT In EES, functions to evaluate the ideal gas law are built into the program.

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## This note was uploaded on 04/06/2009 for the course ENGR 2250 taught by Professor Borca-tasciuc during the Spring '08 term at Rensselaer Polytechnic Institute.

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Lecture 3 Work - Thermal and Fluids Engineering I Prof....

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