A review of passive techniques, working fluid, and flow characteristics impacts on heat transfer, pressure drop, and friction factor in flow channels

• Published in: Journal of thermal analysis and calorimetry Vol. 150; no. 17; pp. 12983 - 13022
• Main Authors: Suwaed, Mahmood Sh, Turgut, Oguz, Abdulkarim, Ali Hussein
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 08.08.2025; Springer Nature B.V
• Subjects: Analytical Chemistry; Baffles; Channels; Chemistry; Chemistry and Materials Science; Energy consumption; Energy costs; Flow characteristics; Fluid flow; Friction factor; Heat transfer; Heat transfer coefficients; Inorganic Chemistry; Inserts; Laminar flow; Measurement Science and Instrumentation; Nanofluids; Nusselt number; Physical Chemistry; Polymer Sciences; Pressure drop; Reynolds number; Thermal conductivity; Tubes; Working fluids; Heat transfer enhancement; Nusselt number; Working fluid; Pressure drop; Flow channel inserts
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-025-14544-7

Among various enhancement techniques, passive methods such as rough surfaces, twisted tape inserts, and wire coils are widely utilized for their simplicity, low cost, and reliability. This review thoroughly analyzes studies on heat transfer augmentation, particularly on liquid working fluids, such as water and nanofluids, passive techniques such as twisted tapes and baffles, and the Reynolds number. The selected studies covered essential subjects such as using the inserts in channels, changing the working fluid, the variation of nanoparticles, and the impact of flow type. Studies highlight that twisted tape can enhance heat transfer rates by up to 13.8 times compared to plain tubes. And peripheral U-cut twisted tape inserts reveal Nusselt number up to 12.8 times higher in laminar flow than plain tubes, with a maximum thermal performance factor of 4.88. Other results indicate that nanofluids significantly increase heat transfer efficiency compared to pure fluids, with increased Nusselt number observed due to improved thermal conductivity and buoyancy effects at higher Reynolds numbers. Studies show that twisted tape inserts with nanofluids augment thermal performance by over 40%, reporting up to 30.4% improvements in the Nusselt number. Other studies show an 82% increase in heat transfer coefficient with holed tapes; however, the pressure drop rises by 8.7–10.02%. The study also identifies important future research directions. This study provides a valuable resource for researchers and designers seeking to maximize heat transfer efficiency while decreasing energy consumption and material costs.