3. Steam moves through a horizontal pipe 2 in. O.D. The pipe with surface temperature at 120 C is in contact with air at 5C. The external heat transfer coefficient is 10 W/m2 K. a) Determine the rate of heat loss per unit length of the pipe from the steam to the air. b) The pipe is going to be insulated with a layer of glass wool (k = 0.4 W/m K). Calculate the critical radius of the insulation for the heat loss to decrease when the thickness is increased. c) Assuming the external heat transfer coefficient remains constant determine the rate of heat loss per unit length of the pipe if the insulation thickness is in. d) Calculate the temperature on the outside surface of the insulation. Tair = 5C Tair = 5 C Tsurface = 120C Tinterface = ? pipe no insulation 8 12 -insulation Tair =5C hot film pipe Tsteam =120C Turface. 19 with insulation