This Demonstration investigates radiation between two surfaces (shown in green and black) that are approximated as blackbodies. Blackbodies lose energy as a result of emission, but all incident radiation is absorbed. The blackbodies are maintained at a constant temperature by using electric heaters; otherwise, their energy would radiate away to the surroundings. You can choose between three arrangements: two parallel plates, two perpendicular walls, or two parallel cylinders. The view factor is calculated, along with the rate at which radiation leaves the green surface and is intercepted by the black surface. You can change distance parameters for each scenario, and the resulting arrangement is shown inside the plot, which shows the rate of heat transfer as a function of the temperature of the green surface.
The view factor, , is defined as the fraction of the radiation leaving the green surface that is intercepted by the black surface. The different view factors for each situation are shown below. Let be the rate of heat transfer from the green surface to the black surface.