Elastic turbulence has shown great potential to improve mixing and heat transfer performance. Most of the studies, however, are focused on the mixing behaviour, heat transfer characteristics induced by elastic turbulence are still not well established. This work investigates systematically the flow and heat transfer performance by elastic turbulence in a swirling flow region. The heat transfer enhancements in the bulk fluid and between the fluid and the wall are characterised by the effective thermal conductivity and the Nusselt number, respectively. The variations of statistical properties, such as probability distribution functions and spectra profiles are analysed for the characterization of elastic turbulence. The results indicate that viscoelastic fluid intensifies the heat transfer performance with gradually increasing swirling velocity, and a six-times enhancement comparing to the Newtonian fluid at the maximum given swirling velocity is obtained. Particularly, the statistical properties imply that the flow is still in the transition regime to elastic turbulence at Wi = 5.5.

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. Significant enhancement of mixing was observed with the increase of polymer concentration and bulk flowrate, suggesting the occurrence of elastic instability and elastic turbulence. 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.

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This is a repository copy of Effects of rheological properties on heat transfer enhancements by elastic instability in von-Karman swirling flow.

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