Turbulent thermal-magneto convection in a teardrop-shaped dimpled tube: An experimental and numerical study

Abstract

In this study, the forced convection properties of teardrop-shaped dimpled fins, Fe 3 O 4 /H 2 O ferrofluid, and constant magnetic field parameters were investigated numerically and experimentally. The study consists of two parts. In the first part, a numerical simulation was conducted, incorporating all relevant parameters, and the results were analyzed. In the second part, the experimental setup was completed for the scenario that yields the highest performance evaluation criterion value, as determined from the numerical results. The Reynolds number (10000≤ Re ≤ 50000), the size of the teardrop-shaped dimple ( BTD , MTD and STD ), dimples distance (30≤ P ≤ 50), constant heat flux ( qʺ = 20 kW/m2), ferrofluid concentration ratio (0.0≤ φ vol. ≤2.0) and the constant magnetic field strength applied at x/D = 20 location (0 T ≤ B 0 ≤ 0.3 T) were studied experimentally and numerically. The findings showed that the DT9 case increased the thermal performance change by 36.18 % compared to the smooth tube. The highest heat transfer rate occurred in the magnetic field strength B 0 = 0.3 T. The magnetic field strength caused an improvement in heat transfer of 5.12 % and 7.32 % in the Nusselt number, respectively, in the numerical and experimental results. The highest PEC was obtained by using φ vol. = 2.0 % Fe3O4/H2O nanofluid in case DT9 ( STD , P = 50 mm) at Re = 10000 and B 0 = 0.3 T, with a contribution of 32.45 % compared to the smooth tube. The compound effect amounts of teardrop-shaped dimples, ferrofluid, and constant magnetic field were obtained numerically and experimentally as 55.41 % and 55.37 % in Nusselt number, while obtained as 29.15 % and 32.45 % in PEC , respectively, compared to a smooth tube, using H2O and the absence of a constant magnetic field.