Performance improvement of photovoltaic/thermal systems by using twisted tapes in the coolant tubes with different cross-section patterns

A numerical technique is applied to study the efficacy of integrating twisted tapes to the collector of Photovoltaic/Thermal (PV/T) units on the system performance when the tubes with different cross-sections are used. Hence, computational fluid dynamics is employed to evaluate PV/T systems with and without twisted tapes when using cylindrical, rectangular, and triangular patterns for the tube cross-section. The effect of employing twisted tapes with various pitch-to-width ratios ( Y D ) of 3, 4 and 5 is evaluated. The impact of the total inlet mass flow rate ranging from 25 to 150 L h r is also studied. To analyze the system performance the evaluation of energy and exergy is performed. The results demonstrated that the triangular pattern is the optimum pattern for the tube cross-section without twisted tapes. However, inserting a twisted tape makes the cylindrical tube superior to other designs from electrical and thermal aspects. A collector employing a cylindrical tube with and without a twisted tape could increase the module's electrical efficiency by 7.2 and 9%, respectively. Also, it was observed that integrating twisted tape with the lowest value of pitch-to-width ratio could decrease the surface temperature by 3.2 and 17.55 K compared to the systems with cylindrical tubes and PV alone.