Problem Description

The problem to be considered is illustrated in Figure  6.1, showing a simple two-dimensional section of a headlamp construction. The key components to be included are the bulb, reflector, baffle, lens, and housing. For simplicity, the heat output will only be considered from the bulb surface rather than the filament of the bulb. The radiant load from the bulb will cover all thermal radiation - this includes visible (light) as well as infra-red radiation.

The ambient conditions to be considered are quiescent air at 20C. Heat exchange between the lamp and the surroundings will occur by conduction, convection and radiation. The rear reflector is assumed to be well insulated and heat losses will be ignored. The purpose of the baffle is to shield the lens from direct radiation. Both the reflector and baffle are made from polished metal having a low emissivity and mirror-like finish; their combined effect should distribute the light and heat from the bulb across the lens. The lens is made from glass and has a refractive index of 1.5.

Figure 6.1: Schematic of the Problem