Question

12) The thin-walled square duct/conduit (0.02m x 0.02 m x 20 m, W x H x L) below is subject to an isoflux boundary condition around the periphery. Using the illustration and properties below, what is the maximum surface temperature on the inside of the square duct/conduit? (30 Points) Tmo Internal Fluid Property Value Pr 6400 k. 0.145 W/(m-K) р 884.1 kg/m² μ 0.486 Pa-sec с 1909 J/(kg-K) Um 0.5 m/sec Tmi 300 K Tmo 305 K Tmi

Answer 1

Hydraulic diameter =18.11 Nu for constant heat fure Solution Dna de Ac te (0.02X0.02) 0.02m P 2(0.02 +0.02) 88 4. lx 0.5X 0.02 flow use Heat transfer DHB, 8th edition by CP Kothandaraman Section 2.5 pg fig Nul h= Nuk Reynold's number Re = su Dh M Re <2300 0.486 es laminar 3 & pgr no. 128 no. 127 = 3.608 2o 3.608 x o-145 0.026 W/m2K Heat supplied to fluid from tube wall = energy absorbed by in Cp (T2-T,) = mcp (Tmp - Tmi) feuid Area A= 2 Co-02 +0.02) XL = 2 (6.02+0.02) × 20 = 1.6 m2 ATlm = 0,- Oz Es-Tm. i)-(Ts - Tm, o) HA Atem en vor In (Ts - Tm. i) fo (Ts-Tmio) m = sau = 88 kol (0.02x0.02)x0.5 m = 0.1768 kgle mil 27°C 75-300) - (Ts - 305) 0-1768 x 1909 X (305-300) 0.0268 1.6x In As-300 TS-305 1.000 123 2 (Ts - 2305h Ts 300 1-2626 X10 = 5.6375943 Š 1.000126[Ts - 32] - E5-27) TS = 32X1.000126-27 0.000126 s = 39714.5c