Question

A composite cylindrical wall is composed of 2 materials of thermal conductivity ka = 240 W/mK and kb = 20 W/mK, where interfacial contact resistance is negligible.

- Liquid pumped through the tube is at a temperature Tinf, i = 200 F and provides a convection coefficient hi = 450 W/m^2K at the inner surface of the composite pipe

-The outer surface is exposed to Tinf, o and provides a convection coefficient of ho = 20 W/m^2K

-A thermocouple between the two pipes (at r = r2) gives T2 = 180 F

- r1 = 0.25m, r2 = 0.31 m, r3 = 0.35 m

- Assume pipe length = 1 m

(A) Sketch (Clearly and neatly) the thermal resistance circuit of the system and express all resistances in terms of variables. Calculate all the resistances and provide their values and units.

(B) Calculate the heat transfer, q between the interface where r = r2 and the ambient air and provide the units.

(C) Obtain the outside free stream temperature Tinf,o

Answer 1