A long steel pipe carries hot oil at 180∘C through a factory hall whose air temperature is 30∘C. The pipe is painted dull black on its outer surface and is supported horizontally on brackets well above the floor so that air can circulate freely around it.
(i) Identify and explain the sequence of heat transfer modes by which thermal energy travels
(a) from the hot oil to the inner wall of the pipe,
(b) across the thickness of the steel wall,
(c) from the outer wall to the surrounding air,
(d) from the pipe-air interface to distant objects in the hall.
(ii) If the pipe were instead polished to a shiny finish, discuss qualitatively how each of the modes mentioned in part (i) would be affected and what overall change you would expect in the rate of heat loss from the pipe.