Experimental and numerical investigation of turbulent flow and heat transfer characteristics in the Komax static mixer

Abstract

The turbulent flow and heat transfer characteristics in the Komax static mixer are experimentally and numerically investigated in the range of Reynolds number (Re) from 2640 to 17600. The vortex evolution, Nusselt number (Nu), Darcy friction factor (f), PEC, field synergy principle and power spectrum in the Komax are evaluated based on that in Ross LPD, respectively. The Computational Fluid Dynamics (CFD) predictions of Nu and f based on SST k-ω model from ANSYS Fluent have a good agreement with the experimental results. The magnitudes of longitudinal vortices and swirl intensity in Komax are larger than those of Ross LPD. The synergy performance between velocity and temperature fields in Komax is better than that in Ross LPD due to the Dean Vortex gradually induced and weakened by the Komax inserts. The Komax static mixer has an obvious superiority in heat transfer and could enhance Nu higher than Ross by 46.7%‒49.6% at the cost of friction factor increasing 2.80‒4.37 times. Considering the PEC of both static mixers greater than 1, the Komax insert are recommended for Re<5280 and Ross LPD would be a good alternative due to much lower pressure drop for Re ≥ 5280. Based on the uniform heat flux experiments, the empirical correlations of Nu and f in both static mixers are established with the prediction errors less than ±6.20%. Turbulent kinetic energy and turbulent dissipation rate are used to evaluate the mesoscopic and microscopic mixing performance. The power spectrum and scaling relationship of outlet pressure pulsation signals are evaluated to reveal the turbulent chaotic performance which could help to enhance the mass and heat transfer. The scale relationship between power spectrum and pressure pulsation frequency satisfies power function attenuation.