MEN 310 Exam 2 MakeUp, Fall 1999

wad TEST (Make-Up) MENSI0 (Heat Transfer) January 05, 2000 \ A thick piece of ceramic material (k = 0.8 Whn'C, p =2700 kein c=08 75 Kif/kg’C) is initially ata uniform temperature of 20 °C. The ‘surface of the Material ‘ "is" suddenly exposed to a convection Surroundings.at 400 °C with h= 150W/m™C, "Determine the-time required for a point Idcated 25 tam. under the skin of the- material to reach steady state conditions ©" °° “oe . ‘2. Air at T.=20 °C flows with a velocity u.=10 m/s along a flat plate L~I m long ’ which is heated to a constant temperature of 100 °C Starting at a distance of 35 cm | Assume Re,=10°, "CISA rectangular carbon-steel bar of § om by 4em cross section (a=1x10% ms, : k=35 W/m°C) is initially at uniform temperature T=425 °C. Suddenly all its Surfaces are exposed to cooling by an air stream at T_=25 °C with a heat transfer coefficient h=100 W/m™C. By using an explicit finite difference scheme and mesh sizes 2 cm by 1 cm (Ax and Ay respectively), calculate the center temperature 10 s after the start of cooling. ee Points: 1 (25%), 2 (25%) and 3 (50%). eee 0:8 = BY xto Qos foo rhe of \ sar, aati | tof 0 OS ae eee TEL.: 950415 - TELEX: 20049 AQUALI LE - B.P. 80106 - BEYROUTH - LIBAN { if Ty, 2 Re. lo" |) Tap = 20°C ea J} Use lomfye te Le Img T. Pe 054 ofa? [pz foo X,- 0.35 \ fs {054 Cha? Pe 1994 H007 Ghaice GOT = S83K > fp gp o2k BUY Whee ; Pee toot , © oF 1.393 Re ~ 5,3029 KO < Ree, —> loner eee L ay! ep F:36—» & = 8 reo} 2)"] . 1.9026 L L ya) —, Spe Hehe PR? |i (xs) Of L - 5.9595 xIO7 om =| $9595 wn Se TEL.: 950415 - TELEX: 20049 AQUALI LE -B.P80I06 -BEYROUTH- UBAN ~~ whee we [Om KC jazieany Re as WAC Tre 425°C ys A Tre. 295°C 7 |e = loo wf sOCL [hem oe R _, fro KR NY fe oO _pe + dy Th - C. . hoo T, Rie | AL t o.o\ ; Ryo = a , Riea = 35 xo.01 joow o.c0F 1 keoxc C = Fev - Ry. 35xlO» o.chxo.005 x Gxt. ace =- . FVR Nede2 can C 1,5, 3, p) Nods 3 aes “! 7" la-\s + Ty Ts, + To -Ts Cc 3 7's “23 Ray Races . 8 av v . Rao- — , ot. & 4 {fa9.0.0f Siz. TEL.: 950415 - TELEX: 20049 AQUALI. LE - B.P. 80106 -BEYROUTH - LIBAN oe