Experimental study of heat transfer performance of compact wavy channel with nanofluids as the coolant medium: Real time non-intrusive measurements

Abstract

Abstract Heat transfer performance of nanofluids in the context of corrugated compact channels has been experimentally investigated through real-time, non-intrusive diagnostic technique. The corrugated channel (dimensions: 50\u202fmm (length)\u202f×\u202f10\u202fmm (width)\u202f×\u202f4\u202fmm (depth); hydraulic diameter of 5.7\u202fmm) comprises of two horizontal wavy plates aligned in an in-phase configuration. Amplitude and period of the wavy plates have been kept constant. Experiments have been performed with varying concentrations of Al2O3/water-based nanofluids for Re\u202f=\u202f350–1000. For reference, experiments have also been conducted using water as the base fluid and a plane channel with the same hydraulic diameter as that of the corrugated channel. Convective field has been mapped using a Mach-Zehnder interferometer. Results have been qualitatively as well as quantitatively interpreted to characterize the heat transfer performance of nanofluids as the coolant medium. Interferograms recorded under infinite fringe setting mode captured the phenomena of flow detachment and re-attachment at the wavy sections of the corrugated channel and their dependence on nanofluids concentration. Thermal boundary layer profiles at such sections are seen to be locally perturbed due to flow detachment and its subsequent attachment to the principal wall of the channel. Quantitative data retrieved through the wedge fringe setting interferograms revealed a clear enhancement in heat transfer coefficient for the combination of nanofluids and corrugated channel in comparison with that achieved through water in the plane and/or corrugated channel. For any given Re and channel configuration, the heat transfer coefficient is seen to increase with increasing concentration of dilute nanofluids. For the wavy channel, an enhancement of ≈37% in heat transfer rates with 0.02% volume concentration of nanofluids is achieved at Re\u202f=\u202f350 in comparison to the plane channel at the similar levels of nanoparticles volume concentration.