RESUMO

This work presents the theoretical and experimental study of a water phase-change solar collector. This solar collector is comprised of two contiguous sections of which one is filled with paraffin (40−42)°C and the other with water; this type of solar collector uses the combined storage of heat by water and paraffin. With a low thermal conductivity, the performances of solid paraffin are improved considerably by its semi-transparency in the vicinity of the melting point (40−42)°C, it becomes transparent in the liquid phase and while becoming solid during the night, it limits the thermal losses of stored water, thus water is preserved at the melting point of paraffin (40−42)°C. The experimental results show that the average water temperature reached 48°C at 5 p.m. and the thermal efficiency reaches 50% during four operating hours. A one-dimensional mathematical model based on the enthalpy formulation is applied to the system. It correctly describes the performance of the solar collector by predicting the changes of the temperature in paraffin and stored water. This model takes into account natural convection in molten paraffin. A water phase-change solar collector has a rate of recovery of about 10% to 50% which is higher than that of a slab of about 10% to 15%.