Simulation of a solar thermal system with a parabolic concentrator incorporating an evacuated tube system equipped with a new designed turbulator and hybrid nanofluid

This study explores a solar concentrated unit with a parabolic concentrator. The evacuated region between the glass and absorber is incorporated, and for modeling purposes, the discrete ordinates (DO) method is utilized. The working fluid contains a mixture of Syltherm 800 and hybrid nanoparticles (CNT + SiO₂). The heat flux absorbed by tube is derived from experimental work and applied as a heat source within the solid layer of the absorber. A new shape of turbulator is used to enhance the swirl flow, and turbulent flow is simulated. The influences of dispersing hybrid nanoparticles, inlet velocity (V_in), inlet temperature (T_in), and gravity force on the Darcy factor (f), convective heat transfer coefficient (h), and thermal efficiency (η) have been investigated. When hybrid nanoparticles utilize, the efficiency (η) increases by approximately 3.25% in the presence of a turbulator. Furthermore, the addition of nanoparticles significantly enhances the efficiency gains from the turbulator, with an improvement of about 46.65%. In the absence of a turbulator, as V_in increases, the values of η and “h” also increase by approximately 8.91% and 12.25%, respectively. When V_in is 0.06 m/s, the installation of a turbulator can increase η by about 8.54%. With the increase in T_in for the absorber pipe equipped with a turbulator, efficiency decreases by approximately 10.86%. For a conventional pipe, including the effect of gravity significantly enhances the performance, resulting in increase of approximately 67.54% in “h”, 98.14% in “f”, and 3.73% in (η). Additionally, the effectiveness of adding a turbulator on improving the efficiency diminishes when gravity is taken into account.