Numerical laminar forced convection modelling in a ceramic and concrete solar collector with non-circular duct

Abstract

The paper presents simulations of laminar forced convection in non-circular piping of flat solar collectors made of ceramics or concrete, which are characterized by a low thermal conduction coefficient. The cross-sections of piping in the shape of a regular polygonal, elliptic, superellipse (Lamé curve) and Cassini oval were used for the calculations. In order to perform the simulation, a simplified two-dimensional model of laminar forced convection in a straight axis duct was used and the issue of H2 (constant axial wall heat flux with uniform peripheral wall heat flux) for materials with low thermal conductivity was applied. The calculations were made using the boundary element method (BEM) in a calculation program written by Fortran by the author. In the work, the number of Poiseuille, Nusselt and dimensionless parameters for the evaluation of heat exchangers such as the area goodness factor and the volume goodness factor were determined in the function of characteristic geometrical parameters of the assumed cross-sectional shapes of the flat solar collector piping.