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Unformatted text preview: CENG 101A HOMEWORK # 3 D.MILLER FALL 2009 10/8/09 Due : Thursday, Read : Chapter 6 (again  especially the example Bernoulli applications) and Chapter 7 10/15/09, by 5pm at 380 EBU II, or earlier in class. Problems : 6.7 (assume P =Patm at fan exit) ; 6.27 ; 6.30 (a only ) ; 6.31 (find Q and P B only  not the time to fall 3ft); 6.32 (head loss h L is the internal energy change due to viscous dissipation see Ex 4) Selected 6.7 : Q ~ 1 . 5 m 3 /s , Power ~ 350 watts ~ 0 . 5 hp ( Answers ( ~ means close to, +/ 50% ): note 1 hp = 746 watts) ; 6.27 : h ~ 2" Hg ; 6.30(a ): h ~ 1.5 cm H 2 O ; 6.31: Q ~ 1.5 ft 3 /s , h B = (P B / g) ~ 20 ft of water or P B ~ 9 psi ; 6.32: Q ~ 0.05 ft 3 /s Comments on Chapter 6 : Chapter 6 is an important chapter and deals with the 1 st Law of Thermodynamics written for control volumes. The general CV equation, 610 , forms the basis for much of your courses in engineering thermodynamics. I would only add that we usually always select a CV such that there is no sh ear work term, W /dt, which is easy since it requires viscous shear forces on a moving surface. In this fluids course all that you are expected to learn from this requires viscous shear forces on a moving surface....
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 Spring '07
 Krashinov

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