Apipe of outside diameter 200 mm is lagged with an insulating material of thermal conductivity 0.06 w m k-1 and thickness 75 mm. the pipe carries a process fluid at a temperature of 300 °c and the average temperature of the outer surface of the lagging is 45 °c (a) estimate the rate of heat loss per metre length of pipe. (b) explain why the thermal resistance of the pipe wall can be ignored.