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Computational Simulation of Mixing Performance in the Circulating Jet Mixing Tank

  • Yan-Fang Yu , Xiu-Hui Jiang , Hui-Bo Meng EMAIL logo , Jian-Hua Wu , Zong-Yong Wang und Wei Wang
Veröffentlicht/Copyright: 3. März 2016
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Abstract

Computational fluid dynamics (CFD) was used to investigate the turbulent mixing performance in a vertical CJT in the range of Re=3,668−18,342. Energy source of hot water was centrally placed just below the top of the tank and temperature instead of concentration measurements were used to quantify mixing performance. The 95 % criterion for temperature equilibrium was employed to evaluate the local mixing degree, and the global mixing performance was evaluated based on the ratio of well-mixed volume to total fluid volume. It was obviously observed from the axial distributions of t95 % that the macro-mixing times decreased slightly for z/H < 0.6 and a deep downward trends appeared with the increase of z/H with given r/R. The macro-mixing time in the jet mixing boundary layer were uniform which were a little longer than those in the bulk zones below z/H=0.5 and decreased sharply by 37.5−87.5 % than that in the bulk zone above z/H=0.5. The values of 95 % mixing time increased with the increase of r/R. The global t95 % decreased with the increasing Reynolds number, and a power correlation between the global t95 % values and Re was proposed. With the increasing logarithm of mixing time, the logarithm of segregation intensity rapidly decreased linearly in the slopes from –0.996 to –0.955. The segmentation intensity first decreased then increased with the increasing values of θ.

Award Identifier / Grant number: “Nos. 21476142, 21306115 and 21106086”

Funding statement: Science Foundation for Doctorate Research of the Liaoning Science and Technology Bureau of China (Grant / Award Number: “No. 20131090”); Program for Liaoning Excellent Talents in University (Grant / Award Number: “No. LR2015051”); Liaoning BaiQianWan Talents Program (Grant / Award Number: “No. 2013921047”); Science and Technology Research Project of Education Department of Liaoning Province (Grant / Award Number: “No. L2013164”); National Natural Science Foundation of China (Grant / Award Number: “Nos. 21476142, 21306115 and 21106086”); Natural Science Foundation of the Liaoning Science and Technology Bureau of China (Grant / Award Number: “No. 2015020148”)

Acknowledgments

The authors acknowledge the financial support from the National Natural Science Foundation of China (Nos. 21476142, 21306115 and 21106086), the Program for Liaoning Excellent Talents in University (No. LR2015051), the Natural Science Foundation of the Liaoning Science and Technology Bureau of China (No. 2015020148), the Science Foundation for Doctorate Research of the Liaoning Science and Technology Bureau of China (No. 20131090), and Liaoning BaiQianWan Talents Program (No. 2013921047). We also thank the referees for their enlightening remarks which helped us both in English and in depth to improve the quality of the paper. Conflict of interest: The authors have declared no conflict of interest.

Nomenclature

c

[kg m−3] instantaneous concentration

[kg m−3] final mean tracer concentration

dj

[m] diameter of the jet nozzles

H

[m] tank height

Is

[−] intensity of segregation

Mb

[kg] liquid mass of the bulk zone

Mt

[kg] liquid mass of the tracer

N0

[−] the number of jet nozzles

p

[Pa] pressure

q

[W · m−2] sub-grid scale heat flux

Q

[m3h−1] volumetric flow rate

R

[m] tank radius

Re

[−] jet Reynolds number

t95 %

[s] mixing time

T1–31

[−] measurement points of temperature

V

[m3] volume of a computational cell

ūi

[m · s−1] mean velocity component

w

[m] width of rectangle outlets

xi

[m] coordinate component

Greek symbols

θ

[°] circumferential angle of polar coordinate

Θ

[K] instantaneous temperature of the bulk liquid

Θi

[K] initial temperature of the energy resource

Θm

[K] final equilibrium value of temperature

Θ0

[K] initial temperature of the bulk liquid

μ

[Pa · s] viscosity

νt

[m2s−1] eddy viscosity

ρ

[kg m−3] density

σij

[N · m−3] the stress tensor

τij

[N · m−2] the sub-grid scale stress

ϑ

[−] dimensionless temperature

ϑ̄

[−] average dimensionless temperature

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Published Online: 2016-3-3
Published in Print: 2016-4-1

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Heruntergeladen am 16.11.2025 von https://www.degruyterbrill.com/document/doi/10.1515/ijcre-2015-0185/pdf?lang=de
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