MEN 310 Exam 2 with Solution, Spring 2000

. Notre Dame University - Faculty of Engineering Mechanical Engineering Dep, © oe, TEST— MEN310 Heat Transfer} May 22, 2000 .A person is found dead at 5:00-p.m. in a room, whose temperature is 20°C. The _. temperature of the body. is measured to- be 22°C: when found, and the heat transfer: - “iq pp: coefficient is - estimated to be 8W/m”C. Modeling the body as 30-cm-diameter, 1.752m- * G ? long cylinder, and using the lumped system approach, -estimate the.time of death. Assume that the person was healthy before death and that the physical properties of the (2f" 7 body matemial are those of water at 37°C. Comment on the accuracy of the result. L . hee . The local atmospheric pressure at an altitude of 1500m is measured to be 85kPa(abs), An (io experiment is conducted at that altitude to determine the heat loss from a heated plate at constant temperature. The experiment consists ofan air stream at 20°C flowing with a velocity of 8m/s over a square flat plate (1.5mx1.5m) whose temperature is 135°C. The - same expciiment is conducted at sea level (p=latm) with an air stream at the same temperat:re and velocity. Which elevation is better to maximizing the heat loss from the Plate? Détermine the relative change in heat loss (with respect to sea level) between the two elevations in order to show the effect of surroundings conditions in convective heat transfer calculations. —_ 3. Dark. painted thick masonry walls called Trombe walls are commonly used on sunny side of passive solar houses to absorb solar energy, store it during the day, and release it to the home-during the night..The vertical :section of such a: wall (k=O7WarCa= . SHS 4,44x10° m/s) is sketched in the following figure with the required dimensions (in Taeter). : Outside Sun energy The well is initially at constant temperature of 20°C and subjected to constant temperature (20°C) on the inner side and constant heat flux (q=800W/m’) on the outer side. ; . Find the minimum number of time integration steps required to reach the temperature distribution in the wall after 1 hour using an explicit technique ead the mesh shown in the figure. Determine the temperature distribution after 2 time steps. Points: 1 (20%), 2 (30%) and 3 (50%). eepaeecn my Vee 44°C. boda BOwr ‘ Meewdin (tS m Reng cghandir, £4 “ P os 3353 Ke hod - ( hv) Coa at Kaec. ° Bx Bo tgi xt Laer AL- 20 LU Bprtnee oARaruce $84 chiawhens- nor SSiS4.2SIsee = 23,099 hewn. OE ody Ao Wd ~QA(VA)_ 3-5 _ gan (nat ccm. a of St) R fant 63 0. 9SZ on Whe <o.l TEL.: 950415 - TELEX: 20049 AQUALI LE- 8. 80106 -BEYROUTH- LUBAN i hee » A =[Soom K.P. OK (abd) Too = 20°C. a a ‘ . =a (Sx wt ole. —» Th 135420 9957 2350 be Bonfre % w e > f= = _ 49°C BW. Ip = 1as°c. Zz. ° Some expert | , Pe Lakin = I.olgeeio” fe L3-. 85000 ~ 0. B44dS tG/a- 28 F«359.5 - _ 21.009 ge, lo > Fz 2.97¥ xX107F Kha vee. hk. 0o-03003 Mfrs Pe. 0.644 Re = ie = 4 8864 xo” < S10 — Nu, =o. 332 Reo Pe? = ha * —h,, -4. gems Rw sae > Gs HA (Ta -Teo) = [2131.89 Walls = 9 isoom. TEL: 950415 . TELEX: 20049 AQUALI LE - B.P. 80106 -BEYROUTH - LIBAN frie = £0 132x108 2EF% 350.7 = |.oo $222 Koh) * Rey = 5, 82489 xl" > Sxtor —, pububet . <f- 5-85 —_ Na, = P-7 (0.037 Re £1) =ht ' a es a — — Ae tl, 4a24 Whee s|q: 2958 AKG Walt, A> Shs | | - Is #00 29931 me BY, A fhes a. = 1°) > /. (fersecs. | To, 3 2 ra} tw/ec oe ~ U qY¥ x(a” KC. i= 20°C : orn R & Nod. 0 et ip T, ~To 3q-8 -¢% -— ls Rie ° AT Rio 0.05 _ t 2 OdA <I4A ' off. Q. Ro 2.cS ; a fee _ _ pil _ Pp ~ — (H( i-kr)A @ BooA= PoV {, -~Te “AT ' - _Pt P “9 (UT, -1NTs @ 800 = O-txto gos 1. -Ts a4 2 “At —_ ae - pt oe aT, ~(QT, € Boo = 39443 1, al_® ~?P lo -_ — f {WAT [er 3 €0 | “ ( at) 1-14 pt ZO 344.43 = i TEL: 950415 - TELEX: 20049 AQUALI LE- 8.880106 -BEYROUTH- LIBAN AT <Aay ' 9: TA IMT + 41, - att, = tiezea2 Gh pel j af = AL [ “re + ['- Felaats 7, 1192-432 He2-452 LT < 56.206 see. Node dd: ae! ; pel? [aes < Ty th. - oy TL aT _ Ru A, AT Roz of Y= 464A , Cre od aiet.( at « oS) A a. + G4 i : it at TT, + 4.64% _ i647, = sto4z2 Roa “TT Bt 7! T _ 2 = AL [ener] [i Ui GEAE (44oAz 4 (St0.4t AL & (68.8% sec. _P ( t ~3.SA 7 corsa om P a-Ty L C,. 1, — is Ray = o-& 4 \ Ye. TEL.: 950415 - TELEX: 20049 AQUALI LE - 8.80106 -BEYROUTH - UBAN