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

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.