Lecture 15 Notes - EGN 3353C Fluid Mechanics Lecture 15 We...

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EGN 3353C Fluid Mechanics Lou Cattafesta MAE Dept. University of Florida Lecture 15 ± We will now apply the Reynolds Transport Theorem (RTT) to the Conservation of Energy ± Conservation of Energy for a system N N rate of work rate of heat done on system added to system system dE QW dt += ± ± where N N N 2 internal potential energy/mass kinetic energy/mass energy/mass 2 ; system system system M Ee d m V ug z ed e ρ ⎛⎞ ⎜⎟ ++ ⎝⎠ == = ∫∫ ± Heat Transfer Rate Q ± o units of power = energy / time o positive if there is heat transfer rate to the system o if Q ± =0 during a process Æ adiabatic Æ not the same as a constant temperature isothermal process ± Rate of Work W ± o units of power = energy / time = W o positive as shown if there is work done on the system ² e.g., compressor or fan or pump o negative as shown if there is work done by the system ² e.g., turbine or engine
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EGN 3353C Fluid Mechanics Lou Cattafesta MAE Dept. University of Florida o Various types of work ± Viscous Æ work done by viscous shear forces on system boundary usually small compared to other contributions examples where it is not small include overcoming viscous drag on a (1) airplane at cruise and (2) in turbomachinery ± Other Æ electric, magnetic, etc. (system dependent) ± Shaft Æ work transmitted by a rotating shaft (e.g., turbomachinery) N N N N 2 rad 1 rev 1 r torque rad s ev s 2 shaft n T T W π ω == ± ± ± Pressure Æ work done by pressure forces on system boundary e.g., gas being compressed in cylinder pressure pres pist n ue o sr Pd ds dW W d PA PAV dt dt
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This note was uploaded on 08/17/2011 for the course EGN 3353C taught by Professor Lear during the Spring '07 term at University of Florida.

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Lecture 15 Notes - EGN 3353C Fluid Mechanics Lecture 15 We...

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