The effect of thermal capacitance and phase change on outside plant enclosures

The use of heat storage materials in outside plant (OSP) enclosures to reduce internal temperatures is examined. A simple thermal analog model is used to represent the heat flow in an enclosure that contains a thin envelope of phase change material (PCM). From this model, two sets of equations are developed for the internal and the PCM temperatures. The first set defines temperatures when the PCM is in a sensible-heat-storage mode, in which it acts as a simple thermal capacitor, and the second set defines temperatures when the PCM is in its latent-heat-storage mode. Exact solutions are obtained for both modes when the daily outside temperature and solar load are modeled by sinusoidal functions