Experimental investigation on convective heat transfer of Shear-thinning fluids by elastic turbulence in a serpentine channel

•Local heat transfer performance by elastic turbulence is investigated experimentally.•Flow visualization by elastic turbulence is performed and analyzed.•A three-stage pressure drop profile with flowrates and Reynolds number is identified.•A non-linear profile of friction factor is revealed for polymer solutions.•Local h exhibits a non-linear behavior at high polymer concentrations.•Nu increases with Wi due to the coupling of shear-thinning influence and EI effects. Elastic turbulence has shown great potential to enhance heat transfer performance at the microscale. Most of the studies, however, have only considered global convective heat transfer performance along curvilinear channels, despite that the intensity of the chaotic flow varies along the streamline, leading to different local heat transfer characteristics. This work systematically investigated the local convective heat transfer performance by elastic turbulence of a shear-thinning fluid in a serpentine channel. The flow visualization along the serpentine channel was obtained and analyzed to show the existence of elastic instability and elastic turbulence. Significantenhancement of mixing was observed with the increase of polymer concentration and bulk flowrate. The variations of pressure drop, heat transfer coefficients and Nusselt numbers along the serpentine channel were analyzed to reveal local characteristics of elastic turbulence. A three-stage pressure drop profile was identified due to the variations of viscosity and elastic turbulence intensity at different flowrates and Reynolds numbers. A non-linear heat transfer performance, which increased with the increase of polymer concentrations, was observed. These are mainly attributed to the increasing intensity of elastic instability, resulting from the balance between normal stresses and streamline curvatures. A large increase of Nusselt number versus Weissenberg number was also revealed due to the coupling of shear-thinning behavior and elastic instability effects.