Recent advances of nanofluids application in helical coiled tube heat exchanger: A comprehensive review

Abstract This review presents a comprehensive evaluation of recent developments in the use of nanofluids to enhance the thermal performance of helical coiled tube heat exchangers (HCTHEs). While widely employed in industrial applications, HCTHEs face limitations when operating with conventional heat transfer fluids. The analysis synthesizes experimental and numerical studies on various nanofluids, including carbon nanotubes (MWCNT, SWCNT), SiO 2 , ZnO, Al 2 O 3 , Ag, Fe 3 O 4 , TiO 2 , and hybrid formulations, with volume fractions ( ϕ ) ranging from 0.05% to 8%. Findings reveal notable enhancements in heat transfer coefficient ( h ) and Nusselt number (Nu); for example, 0.6% MWCNT/water at Dean number (De) of 1400 improved h by 30%, 0.21% carbon black/water increased thermal convection by 40.7%, and 0.5% MWCNT/water boosted Nu by 65%. Hybrid nanofluids, such as CuO–TiO 2 /water, achieved up to 12% additional gains. These improvements often incurred higher pressure drops (Δ P ), reaching 47.35% for 0.5% MWCNT/water. Challenges include nanoparticle stability, cost, and the trade‐off between heat transfer enhancement and Δ P . The review concludes that nanofluids hold strong potential for HCTHE optimization, but optimal ϕ and geometry are critical for balancing performance and feasibility. Future research should focus on scalability, long‐term stability, and economic viability for industrial implementation.