In winters, human bodies shiver, so we insulate ourselves by wearing woolen clothes. A boiler in operation doesn’t shiver to maintain its internal energy, even if it did, it would have been highly undesirable keeping in mind the impacts of vibration in a system. Ambient temp being extremely low, so the temperature difference between human body and ambient is large. This enhances the heat transfer between them, this woolen insulation helps in reducing this heat rejection to the atmosphere and in the end we feel warm. The Same condition applies to the steam boilers . Combustion in the furnace and the flow of the flue gases in the Boiler Shell tubes heat up their respective surface areas leading to steam generation or hot water heating. But some part of this heat also gets conducted away to the surface of the Boiler shell . Now the Boiler shell gets heated up and is ready to transfer this heat to the surroundings. The situation be...