Enhancement analysis of turbulent flow and heat transfer of supercritical CO_2 in a static mixer with three helical blades

摘要

Supercritical CO_2 has excellent flow and heat transfer characteristics, but studies are lacking on the heat transfer characteristics of static mixers using it as a working medium. To obtain the heat transfer enhancement mechanism of supercritical CO_2 within static mixers with three helical blades (TKSM), the flow and heat transfer characteristics of supercritical CO_2 in horizontal and vertically upward of TKSM were determined by three-dimensional steady-state numerical simulation at Re=7,900-22,385, respectively. With other parameters fixed, lower heat flux, inlet temperature, operating pressure, or higher mass flow corresponds to higher heat transfer coefficients (h). The orthogonal test revealed that mass flow has the greatest effect on heat transfer. Besides, the results showed that the comprehensive performance evaluation criteria (PEC) of TKSM were 1.18-1.64 times and 1.25-1.47 times of Kenics static mixer (KSM) in two different states. Considering the local deterioration of the horizontal flow, the vertically upward flow was recommended with uniform temperature distributions. Compared with the horizontal flow, the heat transfer capacity of TKSM in the upward flow increases by 92.64%-119.63%, whereas the buoyancy effect decreases by 99.83%- 99.97%.