Tomography-based determination of Nusselt number correlation for the porous volumetric solar receiver with different geometrical parameters

Pore-scale numerical models of the porous volumetric solar receiver are established in this paper. By using the X-ray computed tomography and the imaging processing techniques, models of porous media with different geometrical parameters are reconstructed. The conjugate heat transfer process in the porous volumetric solar receiver is solved based on the direct pore-scale numerical simulation. The turbulent effect of fluid flow inside porous geometry is considered by the Shear-Stress Transport k-ω model and the absorbed solar energy is simulated by following the Beer's law. The results present that the inlet velocity and the geometrical parameters influence the thermal performance of the porous volumetric solar receiver. Larger inlet velocity tends to enhance the convective heat transfer between fluid and solid phases meanwhile decreases noticeably the overall temperature. Receiver with larger porosity is preferred because it limits the reflection losses. The Nusselt number increases as the porosity becomes larger. As a result, the general correlation of Nusselt number for the porous volumetric solar receiver is derived as a function of porosity and Reynolds number. This correlation is applicable with the porosity ranging from 0.74 to 0.89 and the pore Reynolds number ranging from 3 to 233.