Numerical and statistical analysis of hybrid nanofluid impact on finned shell and coil heat exchanger performance

This numerical study meticulously investigates the thermo-hydraulic performance of a novel shell-and-double -coil heat exchanger augmented with 100 annular fins on its external surface, operating under laminar flow conditions. A three-dimensional computational fluid dynamics (CFD) approach was employed to comprehensively evaluate the system's efficiency with pure water, SiC-CNT/Water, and CuO-ZnO/Water nano-hybrid fluids. The findings reveal a significant enhancement in heat transfer performance when utilizing both the finned geometry and nano-hybrid fluids. Specifically, at a Reynolds number of 2000, the finned configuration with SiC-CNT/Water nano-hybrid fluid exhibited a heat transfer coefficient of approximately 780 W/(m².K) and an average Nusselt number of around 26.5, markedly outperforming pure water and the unfinned system. The presence of annular fins alone resulted in a substantial increase in convective heat transfer; for instance, at Re = 500, the finned configuration using pure water showed a Nusselt number approximately 69% higher than the unfinned coil.Further analysis explored the impact of SiC-CNT nanoparticle volume concentration. Increasing the concentration from ϕ =0.3% to ϕ =0.7% in SiC-CNT/Water further boosted the heat transfer coefficient, demonstrating improvements of up to 9.8% in Nusselt number (at Re=1500) compared to lower concentrations. This enhancement is primarily attributed to the increased thermal conductivity of the nanofluid and the intensified micro-convection induced by the Brownian motion of nanoparticles, which effectively thin and disrupt the thermal boundary layer. While the pressure drop incrementally increased with higher nanoparticle concentrations and the presence of fins, for example, rising from 105 Pa for the unfinned case at Re=2000 to over 165 Pa for finned configurations, the overall thermal performance (PEC) showed significant net benefits. The Performance Evaluation Criterion (PEC) analysis demonstrated the superior overall efficiency of the enhanced configurations. At Re = 1500, the finned system utilizing SiC-CNT/Water at ϕ =0.7% achieved a PEC of approximately 2.28, representing an impressive 128% enhancement compared to the unfinned baseline. This study underscores the substantial advantages of employing finned double-helical-coil heat exchangers with optimized nano-hybrid fluids for improved thermal management and energy efficiency in various industrial applications.