A type-302 stainless steel tube of inner and outer diameters Di = 25 mm and Do = 29 mm, respectively, is used in a cross

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A type-302 stainless steel tube of inner and outer diameters Di
= 25 mm and Do = 29 mm, respectively, is used in a cross-flow heat
exchanger. The fouling factors, Rf″, for the inner and outer
surfaces are estimated to be 0.0004 and 0.0002 m2 · K/W,
respectively. The inner fluid is water (65 Celcius degree) with 0.5
m/s of velocity. The crossflow fluid is air at 10 Celcius degree
with 12 m/s of velocity (a) Determine the overall heat
transfer coefficient based on the outside area of the tube, Uo.
Compare the thermal resistances due to convection, tube wall
conduction, and fouling. (ii) Calculate heat transfer between two
fluids when air velocity is varied between 10 m/s and 18
m/s.