Experimental results on local heat transfer coefficient inside a rectangular channel with chevron-shaped ribs

Abstract

A non-intrusive measurement technique of the heat transfer coefficient field, based on IR-thermography, is applied on a 12-mm-height rectangular channel of 1:10 aspect ratio, whose lower surface is enhanced by chevron-shaped square-cross-section ribs. The channel is operated at imposed heat flux while forced-air flows for Reynolds numbers ranging from 700 to 8000. In particular, the technique uses local temperature measurements to retrieve the radiative heat flux with a three-wavelength-band model for partially transparent enclosures, and the conductive flux towards the backside with a FEM model, which allow an edge-to-edge estimation of the local convective heat transfer. The resulting local Nusselt number maps are presented and compared to data obtained operating both at fixed temperature and inside a channel with flat surfaces.

Forced air flow through a rectangular channel with 3D turbulence enhancers: visualization of flow structures by laser sheet scattering

“…The research group of the ThermALab laboratory, at Politecnico di Milano, has been carrying out fundamental research on this topic, both with experiments [6], by measuring the global and local convective heat flux in ribbed channels, and CFD simulations [7], aimed at reproducing with good enough accuracy the experimental data. The next stage of this work is to use the methods developed during previous research projects in conjunction with optimization techniques, to find suitable geometries of turbulence enhancers to further increase the heat transfer efficiency.…”