Thermal analysis of an Archimedean spiral-shaped circular piped heat exchanger with nano-fluids using simulation

• Numerical evaluation is performed on an Archimedean spiral shaped circular piped heat exchanger. • More spiral turns resulted in higher Dean Number ( De ) with the generation of significant secondary flow offsetting the adverse pressure gradient effects. • The h and the Nu increased by almost 20% and 30%, respectively, by the combined effects of spiral turns and nanoparticle. • The spiral configuration provides ∼ 8.2 times more heat transfer surface area per unit footprint length than the linear exchanger. This research investigates the thermal-hydraulic characteristics of an Archimedean spiral shaped circular piped heat exchanger with different number of turns ( N ) using ZnO/water nanofluids using finite element method. Conventional heat transfer fluids and straight-tube geometries face limitations due to low thermal conductivity and inefficient flow patterns. To address this, we explore the synergistic effect of geometric modification and nanofluid enhancement. The simulation model solves fluid flow and heat transfer equations under non-isothermal conditions for linear and spiral models with different N across a laminar flow regime with Reynolds number ( Re ) varying from 350 to 650. The results demonstrate that the spiral geometry induces secondary flows (Dean vortices), whose strength, quantified by the Dean number ( De ), increases with the N due to a decreasing radius of curvature. This improves fluid mixing, thins the thermal boundary layer, and improves the heat transfer rate than linear ones. More turns resulted in smaller radii of curvature (tighter spiral) and the Dean Number ( De) reached ∼ 70 for N = 2 and as high as ∼ 130 for N = 5 at Re = 650, showing the generation of secondary flow. Overall, the heat transfer coefficient ( h ) and Nusselt Number ( Nu ) improved by almost 20% and 30%, respectively, indicating that both change in heat exchanger geometry and nanoparticle concentration significantly affected the thermal performance, leading to substantial improvements in heat transfer rates. The performance evaluation criterion (PEC) reached ∼3.95, confirming the design's superiority offsetting the adverse pressure gradient effects. The spiral configuration provided more heat transfer surface part per unit footprint length than the linear exchanger and thus suitable for compact footprint thermal applications.