Experimental and Numerical Investigation of Laminar Flow and Heat Transfer Characteristics in Helically Coiled Micro-Channels

Helically coiled micro-channels have become highly effective elements in compact heat exchanger systems because of their intrinsic capacity to enhance heat transmission while preserving a smaller system size. In micro-scale flows, the interplay of curvature and confinement produces intricate secondary flow patterns that markedly modify standard laminar behavior. This paper conducts a thorough experimental and numerical analysis of the laminar flow and heat transfer properties of helically coiled micro-channels, emphasizing the impact of curvature-induced centrifugal forces and geometric design parameters. Micro-channel specimens with varying coil diameters, pitch values, and hydraulic diameters were constructed and evaluated under steady-state conditions across a spectrum of Reynolds numbers (Re) pertinent to actual microfluidic applications. Experimental measurements of pressure drop, outlet temperature fluctuations, and local heat transfer coefficients were obtained and confirmed against comprehensive Computational Fluid Dynamics (CFD) simulations employing a three-dimensional finite-volume methodology. The numerical model integrates exact boundary conditions and grid refinement to effectively resolve secondary Dean vortices, hence improving mixing inside the thermal boundary layer. Results indicate a continuous increase in the Nusselt number compared to straight micro-channels, with the degree of enhancement significantly influenced by the Dean number, curvature ratio, and thermal boundary conditions. The study examines performance trade-offs by connecting friction factor data with heat transfer enhancement to assess thermohydraulic efficiency. The results offer significant design insights, affirming that helical micro-channel designs can greatly enhance heat dissipation efficiency without incurring high pumping power costs. This study enhances the formulation of reliable predictive correlations for laminar flow in coiled micro-scale geometries and promotes the application of high-performance cooling technologies in burgeoning sectors like microelectronics thermal management, biomedical engineering, and renewable energy systems.