Performance enhancement of an evacuated tubes solar collector using Forchheimer’s saturated porous media with embedded nanofluid

Abstract

The evacuated tube solar collector is a proper choice for converting solar energy into heat since it is efficient, practical, and cost-effective. In the current study, the role of nanofluid in porous medium was numerically investigated to improve the performance of a solar collector model and the potential to store energy. The governing equations for the suggested model were solved analytically in the fully developed region using the Forchheimer model. The investigation of the impact on temperature fluctuation in the solar collector was done by considering several factors such as medium porosity, pore diameter, nanoparticles with respect to the solid volume ratio, system pressure, and conduit radius. The governing equations for the entrance region were expressed in a non-dimensional form and solved using the finite difference method (FDM), with the resulting non-dimensional differential equation solved using MATLAB software. Various parameters, such as Prantel number (Pr) and fluid velocity, were examined, and the findings were shown in various diagrams. For the fully developed region, an analytical solution was obtained, and the findings were presented using the Mathematica® software. The results demonstrate that utilizing nanofluid and porous media improves the performance of the evacuated tube when compared to sole use of water. It was found that the temperature difference across the solar tube was enhanced by 10%–20%. In addition to that, the performance of the evacuated tube solar collector showed around 10% enhancement in the obtained temperature difference in cold months, when nanofluids were added. Also, the comparison between nanofluids using Forchheimer model shows that the best nanofluid was AL2O3. The best results had a significant effect on the solid volume fraction rate of nanoparticles in nanofluids obtained at low Reynolds and Prandtl numbers. Where the higher the fraction, the higher the heat transfer, the higher the resulted temperature.