Ouestion $5$ An uninsulated steam pipe passes through a room in which the air and walls are at $25^$C$.$ The outside diameter of the pipe is $70$mm and its surface temperature and emissivity are $250^$C and $0\mathrm{.}7$ respectively. What are the surface emissive power and irradiation? If the coefficient associated with free convection heat transfer from the surface to the air is $15$W $/$ m$^2$K$,$ what is the rate of heat loss from the surface per unit length of pipe?