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Test4_Solution - Name MI Page U3 NE 37203 Intro Fluid...

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Unformatted text preview: Name: MI??? Page U3 NE 37203 Intro Fluid Thermo Eng — Spring 2008 Test #4 (April 7?, 08:05 — 08:55 am, open textbook only) You do not need to follow any specific procedure. Use a hand-held calculator. Use mar ins to write down our derivations clearl Z, 61M 02965621, ,4: Eff/(Io ¥0yhz Problem 1. (50 pt) Water (p=1000 kgIm3 anO-sfmz) flows til/{7 @323 [<- through a horizontal pipe at a rate of l kgf s. The pipe 15 made of Galvanized iron, and its diameter and length are 0.1 m and 2 m, respectively. Assume the flow is fully developed. (i) (10 pt) Calculate the average velocity of water through the pipe. Answer: 0 ‘ l2} [mfs] m H: 8V6? Ac. 1/ ”’4 —.— L a ' : o. m: 6‘3 ‘ p/lo @1331? 1090 g} 0.!“ (ii) (10 pt) Calculate the Reynolds number and determine whether the flow is laminar or turbulent. Answer: ’lV’LL“ L0” t /%£b1 fl: [oooXo.12?Xol: l (#SXlO >2300 M g fiXJDfié’ -—————-*———""‘ (iii) (10 pt) What is the fiction factor of the pipe? 0. Olly Answer: Fifi” He‘d/1 Owl— E/DQ o-llXIOJflM: 000:5 la 30,... 0.0215 6 ..-. lrd xro Web .. 6 I. Name: . £1 (7" Page 2x3 (iv) (10 pt) Determine the pressure drop through the pipe. -3 Answer: 3‘ ¢€7f X lo [kPa] _ . 2v“ .. i; 9 Alba-:Xh“ Faffizg ._j(‘ Dzla/ 2 00219 2 J—Iaao 0l371=3452ttla 0! .2 (v) (10 pt} What is the required pump power in order to restore the gessure drop? Pl '3 F7” PF) Answer: 3 ‘ (/6?le [kW] \ - A r 8 F (’3 _ 3, @531 x1615 414/ _—._-—.— I‘ — W€W& Co :7/ M d‘ J"! Problem 2. (20 pt) Air (p: .17kgfm3 and ,u =1.85x10_5 N-sfrnz) flows over a flat plate with a velocity 2 mfs. (i) (10 pt) At a location x=1 m from the leading edge of the plate, determine whether the boundary layer is laminar or turbulent. Answer: jay” {in 0-4 (Vac: flL : H7 xxx:- —= L25X/0j It tn " f/M 5’ 0 (bf/of “—9 «652M009!» Name: goal/tab”? Page 33 (ii) (10 pt) What is the boundary layer thickness at x=1m from the leading edge? .._'J.—- Answer: l ~ 6‘ {Al/O [In] I ‘- Va“ #1 st“ (foo-:- QTY/:1“- é/W "J“ H was pal/(loam Problem 3. (30 pt) Hot gases inside a room are separated from the ambient air by a 5-cm-thick glass window. Under the steady-state condition, the inner and outer surface temperatures of the window are 100 °C and 40 °C, respectively. The thermal conductivity of glass is 1.4 me-K. (i) (10 pt) What is the heat loss through the window that is 1 m by 3 m on a side? 3799—”? Answer: [W] 9:0“ —- C Magma = MH’ #993- 0'-°§‘hv1 (ii) (20 pt) If the ambient air temperature is 25 °C, what is its convection heat transfer coefficient? Neglect the radiation heat transfer between the window and surroundings. Answer: l K 2/! [WImZ-K] ...
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