Effect of Phase Change Materials Integration on the Thermal Performance of a Parabolic Trough Collector

摘要

In this paper, a parabolic trough collector (PTC) is studied, and its thermal performance is compared to that of an integrated collector storage solar water heater (ICSSWH). The effect of the concentration technology is so investigated using computational fluid dynamics (CFD) simulations. Results show that the PTC presents higher useful heat and, consequently, higher water temperature relative to the ICSSWH. It is also shown that its main disadvantage is its fast temperature drop and, thus, its high night losses. This drawback can be limited by covering the storage tank with a particular material layer. Phase change materials (PCM) are so introduced, and a PTC in which the storage tank is covered with a PCM layer is studied. Three different materials, respectively, durene, methyl bromobenzoate, and octatricontane, and three PCM radiuses, respectively, 0.03, 0.04, and 0.04 m, are considered. Simulation results show that the latent heat storage unit presents better thermal performance than the sensible one. Concerning the phase change, it is noted that for methyl bromobenzoate, the melting temperature that is relatively the highest in comparison with other PCM is not reached, and the phase change does not occur. The thermal behavior is similar to that in the sensible unit in which the water temperature increases, reaches its maximum value, and decreases next. However, for the other PCM, the melting temperature is reached, and the solid/liquid transition occurs. We notice that in an isothermal behavior during all this period and even after its end, the water temperature decreases very slightly during the rest of the night. Durene can be so selected as the most appropriate PCM for this PTC's design relative to octatricontane as it allows higher useful heat and lower night losses. The effect of the PCM's radius shows that the best performance corresponds to the lowest value, which is 0.03 m.