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Huibo Meng,Yunjuan Yao,Yanfang Yu,Bowen Shi,Pengcheng Ding 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.1
Supercritical CO2 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 CO2 within static mixers with three helical blades (TKSM), the flow and heat transfer characteristics of supercritical CO2 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%.
Numerical analysis of thermal dynamics and mixing performance in the blade-type static mixers
Yanfang Yu,Yaxin Chen,Huibo Meng,Yunjuan Yao,Dongzhou Liu,Jianhua Wu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.7
The turbulent thermal dynamics and mixing performance of kenics static mixer (KSM), lightnin static mixer (LSM) and Q-type static mixer (QSM) were numerically simulated with uniform heat flux within the range of Reynolds numbers (Re) between 6000 and 30000. The numerical predictions of Nusselt number (Nu) and friction coefficient (f) in KSM were well consistent with the experimental data. The dean vortices, thermal resistance, entropy generation and field synergy were fully analyzed to obtain the enhancement mechanism of heat transfer performance. The synergy performance between temperature gradient and flow field firstly decreased and then increased and are superior to that of KSM with increasing Re. With the same Re, the entropy generation rates of LSM are 0.93-0.94 times that of QSM. LSM is a better alternative consideration for convection mixing and heat transfer enhancement. Two new relationships between Nu and f under different dimensionless uniform heat flux are obtained.