Increasing melting and solidification performances of a phase change material-based flat plate solar collector equipped with metal foams, nanoparticles, and wavy wall-Y-shaped surface

This paper presents solutions to improve the thermal performances of paraffin as a Phase Change Material (PCM) in solar flat-plate collector systems for domestic and industrial solar applications. These solutions are regarded as an effective way to solve the problem of energy supply and demand time delay. To address this issue, three different methods were proposed together or separately, namely using 10 PPIs aluminum foams with 0.92 or 0.95 porosity, various types of 5%wt nanoparticles, and modifications to the geometry in three different configurations: straight (Case A), wavy wall (Case B), and wavy wall-Y-shaped fin combinations (Case C). Because of melting, thermal energy is stored within the PCM during sun exposition; once the sun source is not available, thanks to the PCM solidification, thermal energy is released. Numerical predictions of phase change and temperature evolution are done – and extensively validated - by means of well-established approaches like enthalpy-porosity method, porous media approach, and nanoparticles single-phase homogeneous model. If comparisons are done with pure paraffin, it has been found that nano-powders in Case B and Case C reduce melting time by 18.15% and 40.70%, respectively. A reduction of 86.19% and 87.21% can be found if only metal foams, or nanoparticles with foams, are included. Furthermore, solidification time for Case C with nanoparticles and 0.95 or 0.92 porosity foams, in comparison with Case B-Pure paraffin, becomes lower of 84.49% and 89.18%, respectively. This suggests that metal foams play the most important role in improving cycling times in such applications, even if nanoparticles and wavy walls are helpful too. The heat storage rate has been found to be higher of an order of magnitude if both metal foam and nanoparticles are added to the paraffin in Case C.