Mesh independency study for an unglazed transpired solar collector

Transpired solar collectors have been widely studied during the last 30 years by experimental, mathematical, and numerical approaches. However, numerical approaches have been frequently simplified because of insufficient computing power. Transpired solar collectors are complex to analyze via numerical simulation mainly due to a difference in scale between the very small holes on the absorber plate and the entire collector size. Thereby, the aim of this paper is to analyze the independency of high-resolution meshes for a longitudinal slice of an entire transpired solar collector and to determine a proper geometrical discretization leading to a good accuracy of the numerical results in a reasonable computing time. This study has shown the importance of the mesh size and refinement in order to capture the thermal and flow characteristics inside unglazed transpired solar air collectors. The obtained results highlight the fact that even with the lowest size of mesh the outlet temperature and temperature variation inside the solar collector is despite everything close to the finest mesh. Thus, for global analysis of a simple solar collector a coarse mesh could be sufficient. However, an increase in the mesh size it has an influence on the temperature and velocity profiles behind the perforated absorber plate.