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Mass transfer enhancement in a two-phase flow electrochemical reactor
Materials Today: Proceedings xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Mass transfer enhancement in a two-phase flow electrochemical reactor M. Vijay a, G.V.S. Sarma b, D.U.S.L. Deepthi b, K.V. Ramesh b,⇑ a b
Department of Chemical Engineering, CUTM, Paralakhemundi 761200, India Department of Chemical Engineering, Andhra University, Visakhapatnam 530003, India
a r t i c l e
i n f o
Article history: Received 24 August 2019 Received in revised form 18 November 2019 Accepted 21 November 2019 Available online xxxx Keywords: Mass transfer coefficient Gas–liquid flow Limiting current Augmentation Turbulent promoter
a b s t r a c t Experimental investigations were carried out to determine the possible levels of augmentation in mass transfer coefficient in gas–liquid flow system using a string of inverted cones. It is noticed that the mass transfer coefficient nearly doubled due to insertion of this promoter. Studies revealed that gas velocity, liquid velocity, pitch and rod diameter have no effect on mass transfer coefficient. The mass transfer coefficient increased with base diameter of cone. An empirical correlation is also obtained to predict mass transfer coefficient. Ó 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the First International Conference on Recent Advances in Materials and Manufacturing 2019.
1. Introduction The design engineer has to face upheaval task in the present survival of the fittest days. In order to meet the competent economic criteria, the design of process equipment essentially requires high rates of heat and mass transfer, effective operation and better control. These objectives can be achieved with the help of appropriate augmentation technique in bubble columns with concurrent upward flow of gas and liquid. As per the literature survey, less number of studies [1–6] is available in achieving high rates mass transfer. Table 1 shows relevant studies carried out so far in this direction. Therefore it was found that no relevant research has been reported on mass transfer augmentation in gas liquid flow systems with string of inverted cones as internal. The range of variables studied in the present experiment is provided in Table 2. 2. Experimental Schematic diagram shown in Fig. 1 essentially represents the features of the experimental setup. Two-phase upward flow is employed in this investigation. Nitrogen is used as gas phase and the liquid phase is an electrolyte (ferro-ferri redox system). Cones arranged on a central rod as shown in Fig. 2 essentially acted as promoter internal. Limiting current is measured at electrodes fixed ⇑ Corresponding author. E-mail address: [email protected] (K.V. Ramesh).
in the test section using an electric circuit shown in Fig. 3. Reduction of ferricyanide is considered in the present case according to following reaction equation:
Fe(CN)6 3 + e ! Fe(CN)6 4
ð1Þ
From limiting current, using Eq. (2) mass transfer coefficient is known.
kL ¼
iL zFAC 0
ð2Þ
3. Results and discussion Fig. 4 shows augmentation in average mass transfer coefficient (kL,avg) for three flow systems: (i) liquid flow in pipe (Plot A), (ii) gas–liquid flow in pipe (Plot B) and (iii) gas–liquid flow with inverted cone promoter element (Plot C). Plots B and C were obtained with superficial gas velocity maintained at 2.34 cm/s. Plot A presents kL,avg data obtained from Lin et al [7] for empty conduit flow and plot B for the gas–liquid flow in empty conduit which is in agreement with Ramesh et al [1]. Plot C consists of the present experimental mass transfer coefficient data in gas–liquid flow system with inverted cone promoter. Examination of plots A and B reveals that the addition of gas yielded an enhancement in kL,avg at lower liquid velocity end upto 5 fold and as the liquid velocity goes on increasing, the enhancement gradually decreased and finally reached 2 fold on the higher velocity end within the range of liquid velocities chosen for the present investigation. Plot C gives
https://doi.org/10.1016/j.matpr.2019.11.258 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the First International Conference on Recent Advances in Materials and Manufacturing 2019.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
2
M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
Nomenclature A C0 Dc dc dr F iL kL P Ug UL X Z
surface area of electrode [m2] concentration [kmol/m3] diameter of test section [m] cone diameter [m] rod diameter [m] Faraday constant [C/mol] limiting current [A] mass transfer coefficient [m/s] pitch [m] superficial gas velocity [m/s] superficial liquid velocity [m/s] longitudinal distance [m] number of electrons
Greek Symbols h = half-apex angle of cone [degree] lL = electrolyte viscosity [kg/m s] qL = electrolyte density [kg/m3] Dimensionless groups = Colburn j-factor =UkLL Sc2=3 jD
Table 1 Earlier investigations on using turbulent promoters in gas–liquid flow systems.
l
Sc
= Schmidt number =q DL c L
Re
= Reynolds number =qL DlC U L L
Table 2 Variables and their ranges considered in the present work.
S.No.
Reference
Promoter employed
S.No.
Variable
Range
1 2 3 4 5 6
Ramesh et al [1] Sarma et al [2] Suresh et al [3] Subramanyam et al [4] Rama Prasad et al [5] Rohini Kumar et al [6]
Helicoidal tape on a rod String of discs String of hourglass elements Twisted tapes String of inclined discs String of spheres
1 2 3 4 5 6 7
Velocity of gas, Ug Velocity of liquid, UL Promoter rod diameter, dr Pitch, p Diameter of base of the cone, dc Half apex angle of cone, h Reynolds number, Re
0.014–0.074 m/s 0.0468–0.234 m/s 0.6, 1.0, 1.3 cm 5.0, 7.0, 10.0 cm 3.0, 4.0, 5.0 cm 30, 45, 60° 3725–22723
Fig. 1. Schematic representing experimental unit.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
the magnitudes of augmentation in mass transfer coefficient in two-phase gas–liquid upflow bubble column due to the introduction of inverted cone promoter were upto 100 percent (Plots C and B). One can reason that the inverted cone promoter elements yielded significant augmentation of mass transfer rates. In this investigation, with gas–liquid upflow bubble columns, the fluids flow upward in the test section in the presence of inverted cone promoter element. Along the length of the test section, changes in flow area are noticed due to the appearance of a sequence of contractions and expansions. Thus varied turbulent intensity occurs in the longitudinal direction in the test section which leads to fluctuating mass transfer coefficient value in the flow direction. As expected, a close examination of Fig. 5 reveals that, with inverted cone promoter element, the fluctuation fell within ±21%. In the present study data on kL,avg were obtained in a gas–liquid upflow bubble column containing inverted cone promoter {p = 5 cm; dr = 1 cm; dc = 4 cm; h = 45°} at three constant different gas velocities and shown in Fig. 6. The superficial gas velocities
3
employed were 0.014, 0.0234 and 0.0374 m/s respectively. It is clearly seen from the plots that both the liquid and gas velocities have not exhibited any noticeable influence on kL,avg. Because the overall turbulence resulting due to the combined effect of gas flow, liquid flow and promoter assembly was very large so that the additional turbulence generated out of the variations in gas and liquid velocities was insignificant. This reason is also supported by the plots of Fig. 7 which were obtained for constant liquid velocities viz., 0.0935, 0.1217 and 0.1498 m/s. Fig. 8 shows kL,avg obtained for the case of an inverted cone promoter element {dr = 1 cm; dc = 4 cm; h = 45°} against gas velocity for the pitch values of 5, 7 and 10 cm when superficial liquid velocity is maintained at a constant value of 0.121 m/s. A close examination of the plots of this graph reveals that pitch had only marginal influence of kL,avg. It can be reasoned that as the fluid electrolyte moves past the inverted cone element, at leading edge, the fluid has stream line flow and at the trailing edge there appears nearly stagnant liquid pocket. Therefore, the influence of the pitch was not seen in the present case. Fig. 9 shows kL,avg obtained for the inverted cone pro-
Fig. 2. Inverted cone promoter variations.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 3. Schematic diagram of the circuit.
1e-4
C
kL, avg [m/s]
B
1e-5
1e-6 0.07
A
0.1
0.15
0.2
0.3
UL [m/s] Fig. 4. Augmentation of mass transfer coefficient.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
moter element {p = 7 cm; dr = 1 cm; h = 45°} for the cone diameter being 3, 4 and 5 cm. A close inspection of this graph indicates that higher kL,avg values were realized for highest cone diameter and as the cone diameter was increased the kL,avg values increased. This trend is also conspicuous from the inset. Fig. 10 shows the kL,avg data obtained for the case of an inverted cone promoter element {p = 7 cm; dr = 1 cm; dc = 4 cm} for half apex-angles of 30, 45 and 60° . A close examination of this diagram indicates that the cone angle has exhibited no noticeable influence on kL,avg. The reason can be attributed to the streamlined nature of the inverted cone in the flow direction. Therefore, there is no influence exercised by the cone angle on kL,avg. There is no effect of rod diameter on kL,avg. The entire data on kL,avg were correlated with Coulburn j-factor, Reynolds num-
ber and geometrical parameters of the promoter element. The following correlation equation is obtained based on least squares regression analysis with an average deviation of 10.68 percent and a standard deviation of 13.97 percent. The correlation obtained is shown in Fig. 11.
jD ¼ 189:6ðReL Þ0:95
dc Dc
0:1 ð3Þ
4. Conclusions The improvements in mass transfer coefficients due to inverted cone promoters in bubble column were up to 100%.The mass
0.00012 0.00010
Average=5.22 x 10-5m/s
UL[m/s] Ug [m/s] p[cm] dr[cm] dc[cm] 0.0936
0.00008
kL [m/s]
plot
0.0140
5.0
1.0
[degrees]
4.0
45
0.00006 0.00004 -5
Min =4.45 x 10 m/s
0.00002
-5
Max =6.33 x 10 m/s
0.00000 0.0
0.1
0.2 Axial Distance, X [m]
0.3
0.4
Fig. 5. Longitudinal variation of mass transfer coefficient.
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
2e-5
Ug [m/s] 0.0140 0.0234 0.0374
1e-5 0.08 0.09 0.1
0.15
0.2
0.3
UL [m/s] Fig. 6. Effect of liquid velocity.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
Ug [m/s] 2e-5
0.0935 0.1217 0.1498
1e-5 0.01
0.02
0.04
0.06
0.08
0.1
0.05 0.06
0.08
0.1
Ug [m/s] Fig. 7. Effect of gas velocity.
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
2e-5
pitch [cm] 5 7 10
1e-5 0.01
0.02
0.03
0.04
Ug [m/s] Fig. 8. Effect of pitch.
transfer coefficient varied along the length of the test section in the flow direction and the fluctuations were within ±20% for inverted cone promoter elements employed in the present study. Variation in the mass transfer coefficients due to variations in liquid and gas
velocities, pitch, half apex angle and rod diameter in the presence of string of inverted cones is insignificant. In the presence of inverted cone promoter, an increase in cone diameter caused an increase in mass transfer coefficient.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
1e-4 8e-5
kL,avg [m/s]
6e-5 C B A
4e-5
1e-4
kL [m/s]
2e-5 cone diameter [cm] plot 3 4 5 1e-5 0.04
A B C
0.06
4e-5 2e-5 1e-5 2
0.08
0.1
3 4 5 6 cone diameter [cm]
0.15
0.2
0.3
0.15
0.2
0.3
UL [m/s] Fig. 9. Effect of base dia of cone.
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
2e-5
cone angle [degrees] 30 45 60
1e-5 0.04
0.06
0.08
0.1 UL [m/s]
Fig. 10. Effect of half apex angle of cone.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
1
jD(dc/Dc)-0.1
0.1
0.01
0.001 1e+3
1e+4
1e+5
ReL Fig. 11. Correlation plot.
CRediT authorship contribution statement
References
M. Vijay: Investigation, Resources, Visualization, Writing - original draft. G.V.S. Sarma: Supervision, Data curation, Project administration. D.U.S.L. Deepthi: Software, Validation, Formal analysis. K.V. Ramesh: Conceptualization, Writing - review & editing.
[1] K.V. Ramesh, G.M.J. Raju, M.S.N. Murty, C.B. Sarma, Ind. Chem. Eng. 51 (2009) 215–227. [2] G.V.S. Sarma, M.S.N. Murty, K.V. Ramesh, G.M.J. Raju, J. Energy Heat Mass Transf. 33 (2011) 233–249. [3] S. Suresh, M.S.N. Murty, B. Srinivas, K.V. Ramesh, J. Instn. Eng. Ind. Ser. E 94 (2013) 91–96. [4] Subramanyam BS, Murty MSN, Babu BS, Ramesh KV. in: Proceedings of ICACE TKMCE ’14, October 16-18, Kollam, India. pp.82-85 (2014). [5] B.S.G. Ramaprasad, B.N. Rao, K.A. Kumar, K.V. Ramesh, Chem. Technol. Ind. J. 11 (5) (2016) 1–9. [6] P.R. Kumar, K.A. Kumar, P. Venkateswarlu, K.V. Ramesh, Am. J. Heat Mass Transf. 3 (2016) 225–237. [7] C.S. Lin, E.B. Denton, H.S. Gaskill, C.L. Putnam, Ind. Eng. Chem. 43 (1951) 2136– 2143.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Mass transfer enhancement in a two-phase flow electrochemical reactor M. Vijay a, G.V.S. Sarma b, D.U.S.L. Deepthi b, K.V. Ramesh b,⇑ a b
Department of Chemical Engineering, CUTM, Paralakhemundi 761200, India Department of Chemical Engineering, Andhra University, Visakhapatnam 530003, India
a r t i c l e
i n f o
Article history: Received 24 August 2019 Received in revised form 18 November 2019 Accepted 21 November 2019 Available online xxxx Keywords: Mass transfer coefficient Gas–liquid flow Limiting current Augmentation Turbulent promoter
a b s t r a c t Experimental investigations were carried out to determine the possible levels of augmentation in mass transfer coefficient in gas–liquid flow system using a string of inverted cones. It is noticed that the mass transfer coefficient nearly doubled due to insertion of this promoter. Studies revealed that gas velocity, liquid velocity, pitch and rod diameter have no effect on mass transfer coefficient. The mass transfer coefficient increased with base diameter of cone. An empirical correlation is also obtained to predict mass transfer coefficient. Ó 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the First International Conference on Recent Advances in Materials and Manufacturing 2019.
1. Introduction The design engineer has to face upheaval task in the present survival of the fittest days. In order to meet the competent economic criteria, the design of process equipment essentially requires high rates of heat and mass transfer, effective operation and better control. These objectives can be achieved with the help of appropriate augmentation technique in bubble columns with concurrent upward flow of gas and liquid. As per the literature survey, less number of studies [1–6] is available in achieving high rates mass transfer. Table 1 shows relevant studies carried out so far in this direction. Therefore it was found that no relevant research has been reported on mass transfer augmentation in gas liquid flow systems with string of inverted cones as internal. The range of variables studied in the present experiment is provided in Table 2. 2. Experimental Schematic diagram shown in Fig. 1 essentially represents the features of the experimental setup. Two-phase upward flow is employed in this investigation. Nitrogen is used as gas phase and the liquid phase is an electrolyte (ferro-ferri redox system). Cones arranged on a central rod as shown in Fig. 2 essentially acted as promoter internal. Limiting current is measured at electrodes fixed ⇑ Corresponding author. E-mail address: [email protected] (K.V. Ramesh).
in the test section using an electric circuit shown in Fig. 3. Reduction of ferricyanide is considered in the present case according to following reaction equation:
Fe(CN)6 3 + e ! Fe(CN)6 4
ð1Þ
From limiting current, using Eq. (2) mass transfer coefficient is known.
kL ¼
iL zFAC 0
ð2Þ
3. Results and discussion Fig. 4 shows augmentation in average mass transfer coefficient (kL,avg) for three flow systems: (i) liquid flow in pipe (Plot A), (ii) gas–liquid flow in pipe (Plot B) and (iii) gas–liquid flow with inverted cone promoter element (Plot C). Plots B and C were obtained with superficial gas velocity maintained at 2.34 cm/s. Plot A presents kL,avg data obtained from Lin et al [7] for empty conduit flow and plot B for the gas–liquid flow in empty conduit which is in agreement with Ramesh et al [1]. Plot C consists of the present experimental mass transfer coefficient data in gas–liquid flow system with inverted cone promoter. Examination of plots A and B reveals that the addition of gas yielded an enhancement in kL,avg at lower liquid velocity end upto 5 fold and as the liquid velocity goes on increasing, the enhancement gradually decreased and finally reached 2 fold on the higher velocity end within the range of liquid velocities chosen for the present investigation. Plot C gives
https://doi.org/10.1016/j.matpr.2019.11.258 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the First International Conference on Recent Advances in Materials and Manufacturing 2019.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
2
M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
Nomenclature A C0 Dc dc dr F iL kL P Ug UL X Z
surface area of electrode [m2] concentration [kmol/m3] diameter of test section [m] cone diameter [m] rod diameter [m] Faraday constant [C/mol] limiting current [A] mass transfer coefficient [m/s] pitch [m] superficial gas velocity [m/s] superficial liquid velocity [m/s] longitudinal distance [m] number of electrons
Greek Symbols h = half-apex angle of cone [degree] lL = electrolyte viscosity [kg/m s] qL = electrolyte density [kg/m3] Dimensionless groups = Colburn j-factor =UkLL Sc2=3 jD
Table 1 Earlier investigations on using turbulent promoters in gas–liquid flow systems.
l
Sc
= Schmidt number =q DL c L
Re
= Reynolds number =qL DlC U L L
Table 2 Variables and their ranges considered in the present work.
S.No.
Reference
Promoter employed
S.No.
Variable
Range
1 2 3 4 5 6
Ramesh et al [1] Sarma et al [2] Suresh et al [3] Subramanyam et al [4] Rama Prasad et al [5] Rohini Kumar et al [6]
Helicoidal tape on a rod String of discs String of hourglass elements Twisted tapes String of inclined discs String of spheres
1 2 3 4 5 6 7
Velocity of gas, Ug Velocity of liquid, UL Promoter rod diameter, dr Pitch, p Diameter of base of the cone, dc Half apex angle of cone, h Reynolds number, Re
0.014–0.074 m/s 0.0468–0.234 m/s 0.6, 1.0, 1.3 cm 5.0, 7.0, 10.0 cm 3.0, 4.0, 5.0 cm 30, 45, 60° 3725–22723
Fig. 1. Schematic representing experimental unit.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
the magnitudes of augmentation in mass transfer coefficient in two-phase gas–liquid upflow bubble column due to the introduction of inverted cone promoter were upto 100 percent (Plots C and B). One can reason that the inverted cone promoter elements yielded significant augmentation of mass transfer rates. In this investigation, with gas–liquid upflow bubble columns, the fluids flow upward in the test section in the presence of inverted cone promoter element. Along the length of the test section, changes in flow area are noticed due to the appearance of a sequence of contractions and expansions. Thus varied turbulent intensity occurs in the longitudinal direction in the test section which leads to fluctuating mass transfer coefficient value in the flow direction. As expected, a close examination of Fig. 5 reveals that, with inverted cone promoter element, the fluctuation fell within ±21%. In the present study data on kL,avg were obtained in a gas–liquid upflow bubble column containing inverted cone promoter {p = 5 cm; dr = 1 cm; dc = 4 cm; h = 45°} at three constant different gas velocities and shown in Fig. 6. The superficial gas velocities
3
employed were 0.014, 0.0234 and 0.0374 m/s respectively. It is clearly seen from the plots that both the liquid and gas velocities have not exhibited any noticeable influence on kL,avg. Because the overall turbulence resulting due to the combined effect of gas flow, liquid flow and promoter assembly was very large so that the additional turbulence generated out of the variations in gas and liquid velocities was insignificant. This reason is also supported by the plots of Fig. 7 which were obtained for constant liquid velocities viz., 0.0935, 0.1217 and 0.1498 m/s. Fig. 8 shows kL,avg obtained for the case of an inverted cone promoter element {dr = 1 cm; dc = 4 cm; h = 45°} against gas velocity for the pitch values of 5, 7 and 10 cm when superficial liquid velocity is maintained at a constant value of 0.121 m/s. A close examination of the plots of this graph reveals that pitch had only marginal influence of kL,avg. It can be reasoned that as the fluid electrolyte moves past the inverted cone element, at leading edge, the fluid has stream line flow and at the trailing edge there appears nearly stagnant liquid pocket. Therefore, the influence of the pitch was not seen in the present case. Fig. 9 shows kL,avg obtained for the inverted cone pro-
Fig. 2. Inverted cone promoter variations.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 3. Schematic diagram of the circuit.
1e-4
C
kL, avg [m/s]
B
1e-5
1e-6 0.07
A
0.1
0.15
0.2
0.3
UL [m/s] Fig. 4. Augmentation of mass transfer coefficient.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
moter element {p = 7 cm; dr = 1 cm; h = 45°} for the cone diameter being 3, 4 and 5 cm. A close inspection of this graph indicates that higher kL,avg values were realized for highest cone diameter and as the cone diameter was increased the kL,avg values increased. This trend is also conspicuous from the inset. Fig. 10 shows the kL,avg data obtained for the case of an inverted cone promoter element {p = 7 cm; dr = 1 cm; dc = 4 cm} for half apex-angles of 30, 45 and 60° . A close examination of this diagram indicates that the cone angle has exhibited no noticeable influence on kL,avg. The reason can be attributed to the streamlined nature of the inverted cone in the flow direction. Therefore, there is no influence exercised by the cone angle on kL,avg. There is no effect of rod diameter on kL,avg. The entire data on kL,avg were correlated with Coulburn j-factor, Reynolds num-
ber and geometrical parameters of the promoter element. The following correlation equation is obtained based on least squares regression analysis with an average deviation of 10.68 percent and a standard deviation of 13.97 percent. The correlation obtained is shown in Fig. 11.
jD ¼ 189:6ðReL Þ0:95
dc Dc
0:1 ð3Þ
4. Conclusions The improvements in mass transfer coefficients due to inverted cone promoters in bubble column were up to 100%.The mass
0.00012 0.00010
Average=5.22 x 10-5m/s
UL[m/s] Ug [m/s] p[cm] dr[cm] dc[cm] 0.0936
0.00008
kL [m/s]
plot
0.0140
5.0
1.0
[degrees]
4.0
45
0.00006 0.00004 -5
Min =4.45 x 10 m/s
0.00002
-5
Max =6.33 x 10 m/s
0.00000 0.0
0.1
0.2 Axial Distance, X [m]
0.3
0.4
Fig. 5. Longitudinal variation of mass transfer coefficient.
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
2e-5
Ug [m/s] 0.0140 0.0234 0.0374
1e-5 0.08 0.09 0.1
0.15
0.2
0.3
UL [m/s] Fig. 6. Effect of liquid velocity.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
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M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
Ug [m/s] 2e-5
0.0935 0.1217 0.1498
1e-5 0.01
0.02
0.04
0.06
0.08
0.1
0.05 0.06
0.08
0.1
Ug [m/s] Fig. 7. Effect of gas velocity.
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
2e-5
pitch [cm] 5 7 10
1e-5 0.01
0.02
0.03
0.04
Ug [m/s] Fig. 8. Effect of pitch.
transfer coefficient varied along the length of the test section in the flow direction and the fluctuations were within ±20% for inverted cone promoter elements employed in the present study. Variation in the mass transfer coefficients due to variations in liquid and gas
velocities, pitch, half apex angle and rod diameter in the presence of string of inverted cones is insignificant. In the presence of inverted cone promoter, an increase in cone diameter caused an increase in mass transfer coefficient.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
7
M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
1e-4 8e-5
kL,avg [m/s]
6e-5 C B A
4e-5
1e-4
kL [m/s]
2e-5 cone diameter [cm] plot 3 4 5 1e-5 0.04
A B C
0.06
4e-5 2e-5 1e-5 2
0.08
0.1
3 4 5 6 cone diameter [cm]
0.15
0.2
0.3
0.15
0.2
0.3
UL [m/s] Fig. 9. Effect of base dia of cone.
1e-4 8e-5
kL,avg [m/s]
6e-5
4e-5
2e-5
cone angle [degrees] 30 45 60
1e-5 0.04
0.06
0.08
0.1 UL [m/s]
Fig. 10. Effect of half apex angle of cone.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258
8
M. Vijay et al. / Materials Today: Proceedings xxx (xxxx) xxx
1
jD(dc/Dc)-0.1
0.1
0.01
0.001 1e+3
1e+4
1e+5
ReL Fig. 11. Correlation plot.
CRediT authorship contribution statement
References
M. Vijay: Investigation, Resources, Visualization, Writing - original draft. G.V.S. Sarma: Supervision, Data curation, Project administration. D.U.S.L. Deepthi: Software, Validation, Formal analysis. K.V. Ramesh: Conceptualization, Writing - review & editing.
[1] K.V. Ramesh, G.M.J. Raju, M.S.N. Murty, C.B. Sarma, Ind. Chem. Eng. 51 (2009) 215–227. [2] G.V.S. Sarma, M.S.N. Murty, K.V. Ramesh, G.M.J. Raju, J. Energy Heat Mass Transf. 33 (2011) 233–249. [3] S. Suresh, M.S.N. Murty, B. Srinivas, K.V. Ramesh, J. Instn. Eng. Ind. Ser. E 94 (2013) 91–96. [4] Subramanyam BS, Murty MSN, Babu BS, Ramesh KV. in: Proceedings of ICACE TKMCE ’14, October 16-18, Kollam, India. pp.82-85 (2014). [5] B.S.G. Ramaprasad, B.N. Rao, K.A. Kumar, K.V. Ramesh, Chem. Technol. Ind. J. 11 (5) (2016) 1–9. [6] P.R. Kumar, K.A. Kumar, P. Venkateswarlu, K.V. Ramesh, Am. J. Heat Mass Transf. 3 (2016) 225–237. [7] C.S. Lin, E.B. Denton, H.S. Gaskill, C.L. Putnam, Ind. Eng. Chem. 43 (1951) 2136– 2143.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Please cite this article as: M. Vijay, G. V. S. Sarma, D. U. S. L. Deepthi et al., Mass transfer enhancement in a two-phase flow electrochemical reactor, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.258