Modifying the Surface of Twisted Tapes With a Hydrophobic Coating to Enhance Their Performance in Parabolic Trough Solar Collector

Twisted tapes are widely recognized as an effective passive method to enhance heat transfer in parabolic trough solar collectors. However, a major drawback is the substantial pressure drop caused by the high friction between the fluid flow and the tape surface. This study introduces hydrophobic twisted tapes as a solution to reduce pressure drop while sustaining enhanced heat transfer. A variety of twisted tapes with differing widths and twist ratios were fabricated and tested experimentally under laminar and turbulent flow regimes, focusing on pressure drop, efficiency, and performance index. The results demonstrate that hydrophobic twisted tapes can elevate the performance index from below one to above one. At the flow rate of 50 Lph, the performance index of the twisted tape with a hydrophobic surface increased by 125%. It was observed that increasing the tape width and reducing the twist ratio led to higher pressure drop, improved efficiency, and a better performance index. Additionally, the study compared the performance of twisted tapes with fixed versus variable widths. Experimental findings revealed that twisted tapes with variable widths exhibit superior performance compared to those with fixed widths. At a flow rate of 50 Lph, the performance index of the variable width twisted tape with a hydrophobic surface increased by 143%.