Air flows at 85 Β°C through a copper pipe with an internal diameter of 6 cm and a thickness of
0.4 cm, where it is externally heated by water at 130 Β°C. On the external surfaces of the pipe,
a scale with a thickness of 0.2 cm is formed. Take the thermal conductivity of the copper pipe
as ππππππππππππππ = 384 ππ/ππ.πΎπΎ and of the scale as πππ π π π π π π π π π = 1.75 ππ/ππ.πΎπΎ and the convective
coefficient of the inside surface as βππ = 221 ππ/ππ2.πΎπΎ and outside surface as
βππ = 3605 ππ/ππ2.πΎπΎ. Calculate the overall heat transfer coefficient on the outside area basis,
the water to air heat transfer and the temperature drop across the scale deposit. Figure 1
below shows a schematic representation of the copper pipe