Heat transfer in a dual wavy wall squared enclosure saturated by non-Newtonian fluid: a numerical investigation of mixed convection and application to concentrated solar power collectors (CSPC)

In this research paper, the two-dimensional mixed convection heat transfer through a square, wavy walled enclosure adopted from a novel Concentrated Solar Power collector configuration with undulations in the left and right walls is investigated numerically. The left wall is subjected to a constant high temperature, while the right wall has a variable low temperature that depends on a sinusoidal function of dimensionless length. The horizontal top and bottom sides are kept adiabatic and non-slipped walls. The enclosure is saturated with non-Newtonian fluid that can be either shear thinning or shear thickening. The numerical computations are performed using COMSOL Multiphysics. The effects of important parameters on streamlines, isotherms, velocity contours, and Nusselt numbers are introduced through plots, tables, and graphs. Solar energy systems, particularly solar thermal collectors, often require efficient heat transfer mechanisms. The wavy wall design of our work can enhance heat transfer by inducing more heat transfer enhancement and increasing the surface area for heat exchange. The results reveal that by increasing the Richardson number, the fluid mixing improves and the velocity increases along the enclosure walls for the shear-thinning case. Moreover, this study highlights that the highest values of local Nusselt numbers are obtained at Richardson number, Ri = 10 for both left and right sides of the enclosure at power-law index n = 0.6. Moreover, the velocity increases as Re and Ri increase and the recirculation zone grows as Re increases. This novel geometry enhances the surface area and fluid mixing, making it more applicable to optimizing heat transfer in practical applications like CSP collectors.