Apparatus:
Natural Convection Apparatus - a metal cylinder fitted vertically in a wooden rectangular duct which is open at the top and the bottom (Fig 1). An electric heater is provided in the vertical cylinder, which heats the surface of the cylinder. Heat is lost from the cylinder to the surrounding air by natural convection, because the air in contact with the cylinder gets heated and becomes less dense, causing it to rise. This in turn creates a continuous flow of air upward in the duct. The temperature at the various locations on the surface of the vertical cylinder and in the incoming and outgoing air is monitored with thermocouples. The duct is made of wood because it is a poor conductor, so not much heat will transfer from the air to the duct. Thus the duct will enhance air flow without introducing another convective surface.