Simulation-Based Analysis of Additively Manufactured Printed Circuit Heat Exchangers

Abstract

Compact heat exchangers often incorporate semicircular flow channels in thermal processing applications involving viscous media. However, due to manufacturing constraints, these channels may have semielliptical shapes. With small hydraulic diameters and relatively large length-to-diameter ratios (L/dh), these channels typically experience laminar flows that are fully developed hydrodynamically and thermally. Initially, we investigated fully developed laminar flow and heat transfer in a straight, circular, smooth duct subjected to constant heat flux using FLUENT. The accuracy of the solutions was validated by calculating the Fanning friction factor, Nusselt number, and Colburn factor. Subsequently, we extended our analysis to include three-dimensional, periodic straight and sinusoidal ducts with semielliptical cross-sections of varying aspect ratios. Employing Computational Fluid Dynamics (CFD) with FLUENT, we examined the impact of Reynolds number (50 ≤ Re ≤ 500) and aspect ratio for straight ducts and amplitude-to-wavelength ratio (A/L=0.3 & 0.5) for sinusoidal channels (with L/D=4.5) on heat transfer enhancement and pressure drop. We studied velocity and temperature fields, Fanning friction, Colburn, and goodness factors. Notably, the interruption of boundary layers near solid surfaces, replaced by fluid from the core, increases temperature gradients, leading to higher overall heat transfer coefficients and pressure drop penalties in sinusoidal ducts than in straight ducts. Finally, we established correlations between Fanning friction factor, Colburn factor, Reynolds number, and geometrical parameters for the analysed configurations.