Convective heat transfer enhancement in low Reynolds number flows with wavy walls

Abstract

The present work reports the analysis of combining low Reynolds number flows and channels with wall corrugation and the corresponding thermal exchange intensification achieved. The proposed model involves axial heat diffusion along the fluid and adiabatic regions both upstream and downstream to the corrugated heat transfer section, in light of the lower values of Reynolds numbers (and consequently Peclet numbers) that can be encountered in the present class of problems. Aimed at developing a fast and reliable methodology for optimization purposes, the related laminar velocity field is obtained by an approximate analytical solution valid for smooth corrugations and low Reynolds numbers, typical for instance of micro-channel configurations, locally satisfying the continuity equation. A hybrid numerical-analytical solution methodology for the energy equation is proposed, based on the Generalized Integral Transform Technique (GITT) in partial transformation mode for a transient formulation. The hybrid approach is first demonstrated for the case of a smooth parallel-plates channel situation, and the importance of axial heat conduction along the fluid is then illustrated. Heat transfer enhancement is analyzed in terms of the local Nusselt number and dimensionless bulk temperature along the heat transfer section. An illustrative sinusoidal corrugation shape is adopted and the influence of Reynolds number and corrugation geometric parameters is then discussed.