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 (YD) of 3, 4 and 5 is evaluated. The impact of the total inlet mass flow rate ranging from 25 to 150 Lhr 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 crosssection 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.