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ME410-2_HW7_FALL2010_Solutions

# ME410-2_HW7_FALL2010_Solutions - ME [email protected] Name...

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Unformatted text preview: ME 410-2 @LUTMN Name: Homework #7 (due October 25, 2010) Homework Format 1. 2. 3. “899% 1. Use this page as a cover sheet. One problem per page. Always state what is given, your assumptions, provide a sketch, and analysis. Circle your answer. Include units. Write legibly. No late homework accepted. Work independently. Use paper with four straight edges. Staple together your work. A fine wire of diameter D is positioned across a passage to determine ﬂow velocity from heat transfer characteristics. Current is passed through the wire to heat it, and the heat is dissipated to the ﬂowing ﬂuid by convection. The resistance of the wire is determined from electrical measurements, and the temperature is known from the resistance. a. For a ﬂuid of arbitrary Prandtl number, develop an expression for its velocity in terms of the difference between the temperature of the wire and the free stream temperature of the ﬂuid. b. What is the velocity of an airstream at 1 atm and 25°C, if a wire of 0.5 mm diameter achieves a temperature of 40°C while dissipating 35 W/m? Water at 20°C ﬂows over a 20-mm diameter sphere with a velocity of 3 m/s. The surface of the sphere is at 60°C. What is the drag force on the sphere? What is the rate of heat transfer from the sphere? A thermocouple junction is inserted in a large duct to measure the temperature of hot gaSes ﬂowing through the duct. The thermocouple junction is in the shape of a 2-mm diameter sphere with a surface emissivity of 0.6. If the gas velocity and temperature are 3 m/s and 500°C, respectively, what temperature will be indicated by the thermocouple if the duct temperature is 200°C? The gas may be assumed to have the properties of atmospheric air. What temperature will be indicated by the thermocouple if the gas pressure is doubled and all other conditions remain the same? Duo)f TS Thermaawp‘c duru‘lion Problem 3 Pracst ' 1. (ha/ow: Tempemac é Hem 05\$?an \m m meg as IOLWé-‘zee n Fmb: C4.) EXPQéQSlom F02 FLU.» VELbCVN 00812 unQé) (kg) Vewcﬁy cg: anagram F’on PRéSLRIBéO amotmg Scmml c Q‘Ssomprwms: as. ) \Samwmm 1/0126) wéeu'cetsm- mommm Papa-mes; gm (TwamQJIaM‘): D=\537§10"’W375) human. ﬁt) Pa my; PM. (E. 233,1a’rm3) Pr = mos.” Amwaycgmc rams 0F Hem msverz P612 um'c LENG'IH x5 %/= (33) e I; (mag—T») 60144414 } Fan/n THE '25:“: Kit-103mg- Rebirth)!” bump} Frag ﬁrs) Héwctz QSSummé (103<Pe0< wasl C= 6.29} m:a.£ Fm mus. 7,4. \ Heme A“ — V ~ ’35 w/m 1&1? xto‘mz/s' ~ (5. 6267. bum-«)0 .25 (ontf'ﬂﬂ‘io 45)? 5xw‘4m W: szsl T0 vEQnW Tue HSgU‘MPTHN of m:— (Zfawee- ) Cchum’Té- ﬁe g LD: (Wﬂls) (9610:?“ _= 3074 \Asmmm is 0 V \s,% 110'“ wzls Com-am WW Noumea “we 6H,: gamma) WATER (11.»g 213K), {3: qw WM,” -= no“ . I —; ‘ n. ) r, '00) ' LS"? Klo"' us/m'z NO FROM p\L , C n o g ace H.__..,.. _. (QJM‘n-l- mg ggmauDS-gﬂ Sumoﬁ'ﬁ'iv 191' 1146 "F966 - “W Wmmae .. ' _. «Qt-6:33.13: (9‘3" k‘a’mglﬁmfs) (mg _ . I M ﬂJ-QQT? my" Nuslm1__ ' g; "—4 ‘T JW-ms Beam me wunKéR 861mm mn'r onam 3. Kmaww bxqmewz 3“ EMKS‘U‘W 0F 9; Mmocouwa (maxim 61490560 To HOT 6H€é§ e? 926566660 vewcx‘w Am Tam parama- FLapwcs‘“ Maven, F} Doc-c 0F mesa—lam eueFGce TEMQ/flﬂ‘fuﬂé FWD: («5 meMonmrs Qeﬁowué Foe 66: Wt ﬂTwerWe/mc {onessueéj (b) mmcwﬂa 2690mm» wﬁé’N 698 Wessan xS acumen, Scaemmlc: gases .4 ﬂow rams " a “‘3' gee-mac me TaGKOdC’AV33mIS .—-——J T Jch-EaaQ m awn (or 2%..) W” ASSWW‘NS: S-S-J Jucumaw \s qusev-oaw) DUCT. W5 73 Lavage ENCLOSURE (+3061 JUNCTION) Née‘uGIEHE ﬂea-z togg ﬂy C'awOuC‘Tlm «Mona-k *mémo-cwﬁa WC) Gag mopwleg 0F 3le ) felF‘éc’z gas XSQHQUiOQ P€ofém\é\$: Qua (13': 773K) bdrm) 2 12 =?o.smr"bm"/sj kcom'm “92) M 2* 3 6x703, WWLWS‘T (a) ware/ram en,ch «5mwa am J‘DNCTLUN SmaPﬁcé * 4 warm) 2 am CT“. ~Ts“) y Méexechc me vnrcmeu': movemv Cowl-(mafiaN (WW/1‘3 41 AM) who _ _ > _ em: 29 a my, V 90.5%" Wis 34% WHITNEYL Cmriwnwm FWL B SPWE ewes \ .141 ’/z 213 0.4 w M. = [2+ [0.40453 \$0.0b (74kg) 1(0‘795’) leLbrﬁ—R 0K We 7‘33 ‘ 1'3: law 34,11": 3 [7.4.4473 Mun mam ‘MM MD ma gounm b Axummb \Qu. (Jammie; m‘gerz _ mama“ awsrmw wax-1 n can/Nae, IN PeeSSueA ‘t P 3v 2 bull-L. 4- V BY i 2 who Hen-Ce 0 P, BY '2 5“:th (2,: =14ﬁ. ! 3 "C a ...
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