Thermal Effect of Solar Irradiance on Decorative Tube-Shaped LED Lamps

The main purpose of this paper is to show that under the thermal effect of solar irradiance, the temperature of decorative tube-shaped light-emitting diode (LED) lamps can rise to values that can permanently destroy the lamps or cause a fire, regardless of whether the lamps are operating or not. The light diffuser of the considered LED lamp is made of two polycarbonate cylinders nested in each other. The considered problem is modeled analytically in MATLAB and numerically in COMSOL, and the data obtained analytically are used as inputs for the numerical model. The analytical model is based on empirical correlations for heat transfer, while the numerical model is based on the finite element method (FEM). Images taken by a thermal imaging camera are used as an experimental background. It is found that the outer hollow cylinder of the light diffuser behaves like a cylindrical solar concentrator, which in steady-state can raise the temperature of the inner solid cylinder of the light diffuser up to 218.2 °C.