Newtonian and Shear-thinning Taylor flow heat transfer in wavy micro-tubes: a numerical study

In the present study, the two-phase gas–liquid convective heat transfer is numerically studied inside uniformly heated wavy micro-tubes in the Taylor flow regime. Both Newtonian and Shear-thinning rheological behavior for the liquid phase are considered. The volume of fluid method is employed to capture the gas–liquid interface throughout the flow domain and a numerical flow solver based on the well-known finite volume method on a structured grid is adopted here. The effect of wavy wall amplitude and wavelength is comprehensively investigated on the overall shape of the gas bubbles, liquid film thickness, overall pressure drop, wall temperature profile and average Nusselt number. A proper thermal performance factor is introduced to determine the optimum wavy geometry with the best heat transfer performance. It is shown that using wavy micro-tubes yields 27% heat transfer enhancement for the Taylor flow. Moreover, an additional 8–20% heat transfer enhancement can be achieved inside a wavy micro-tube using shear-thinning liquids obtained by adding carbon nanotubes to pure water in the Taylor flow regime.