Question

Problem 5: The temperature of air flowing through a 25-cm-diameter duct whose inner walls are at 320° C is to be measured using a thermocouple soldered in a cylindrical steel well of 1.2-cm OD with an oxidized exterior, as shown in the accompanying sketch. The air flows normal to the cylinder at a mass velocity of 17,600 kg/h m1 . If the temperature indicated by the thermocouple is 200°C, estimate the actual temperature of the air Air 17,600 kg/h m2 1.2 om 25 cm

Answer 1

ob lem Apply-the, enre)T balance to the thermo ou thu cho Yea vecton tom the thermo Couple wall ow e A vection Boltzmann Cons tantis Inol ce enpevator emh %, the text book, Thermal Conauctivity 150- 200

beni at 200 obtato emissoonldlised steel frem oppandix table 7, by perties 아 soUds rn the tert book PA Hire , A- fg area of low Sub O 820

Find the Reynolds number by uringtte e =2417-216 on teeross number c for Nusret Nt, s. CeeoTr(%).ar take the volve of- n19 o 31 ince dorendtl number s mater than on Take mand nvalues from table Re7.216 Sub 0137 or n,o6 for m, and o2b forc pms sub 2чт-216 for Ro ,o71 for pr, on o for prs