Development of a novel solar system incorporating a heat pipe within a porous enclosure for simulating paraffin melting

In current work, a new design of a heat pipe solar collector coupled with a parabolic reflector is numerically analyzed to boost the overall efficiency. The design incorporates several advanced thermal management strategies aimed at improving both heat transfer and energy storage capabilities. The region surrounding the heat pipe inside the evacuated tube is filled with paraffin (RT31), which serves as a phase change material (PCM) and is reinforced with MWCNT nanoparticles to boost its thermal conductivity and accelerate the melting process. In the condenser section, water mixed with hybrid nanoparticles (Ag-MoS₂) is employed as the working fluid to significantly enhance convective heat transfer. Moreover, porous metallic foam is embedded within the PCM zone to further improve heat diffusion and reduce melting time. The thermophysical characteristics of the mixtures are incorporated through User-Defined Functions (UDFs), whereas the radiative heat transfer within the evacuated zone is also considered. The outputs reveal that the inclusion of the parabolic reflector notably increases the temperature of the heat pipe, paraffin, and water zones by approximately 31.62%, 31.43%, and 11.82%, respectively. The liquid fraction of the PCM in structure equipped with the reflector is about 2.897 times greater than that of the conventional system, demonstrating a significant improvement in melting performance. Furthermore, as the operating time increases from 10 to 40 min, the temperatures of the heat pipe, paraffin, and water zones rise by 23.77%, 24.97%, and 9.18%, respectively. When all enhancement techniques-including the reflector, hybrid nanoparticles, and porous foam-are combined, the system achieves remarkable temperature increases of 8.81%, 23.61%, and 27.18% for the water, PCM, and heat pipe zones, respectively, with the PCM liquid fraction reaching 3.247 times that of the base design. Overall, this integrated configuration demonstrates a significant advancement over conventional heat pipe solar systems by coupling optical concentration, nanomaterial enhancement, and porous media conduction within a single structure. The results highlight the strong potential of this design for improving solar thermal efficiency, accelerating energy storage, and promoting sustainable energy utilization.