EFFECT OF DISC-BLADE INTERCEPTING ANGLE ON MIXING PERFORMANCE IN A MULTIPHASE STIRRED VESSEL

L, Huiwen.; Ghotli, R. Afshar; Shah, R. S. S. Raja Ehsan; Raman, A.A.A.

doi:10.1590/0104-6632.20190362s20180268

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Fluid Dynamics, Heat and Mass Transfer • Braz. J. Chem. Eng. 36 (2) • Apr-Jun 2019 • https://doi.org/10.1590/0104-6632.20190362s20180268 copy

EFFECT OF DISC-BLADE INTERCEPTING ANGLE ON MIXING PERFORMANCE IN A MULTIPHASE STIRRED VESSEL

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The impeller geometry is a determining factor for mixing efficiency in a stirred vessel. In this study, the effect of disc-blade intercepting angle on power number, just suspended speed and mass transfer coefficient was investigated in a multiphase system under turbulent conditions. The impellers used in this study were fabricated with 3D printing. The interactions between the experimental parameters were analysed using Response Surface Methodology (RSM). The impeller power number was found to have a linear positive relation with disc-blade intercepting angle from 30° to 90°. Beyond 90°, the impeller power number became lower with increment in the disc-blade intercepting angle. The results confirmed better suspension efficiency in the angle range of 50° to 120° in 5 wt% solid suspensions. The lowest specific power requirement (Ɛjs) at just suspension condition was observed in the angle range of 30° to 80°. The highest mass transfer coefficient was obtained for the impellers with disc-blade intercepting angle in the middle range. Two models were established on power number and mass transfer coefficient for various disc-blade intercepting angles. The study confirmed that the hydrodynamic and mass transfer performance of disc blade impellers could be maximized by changing the disc-blade intercepting angle for a selected system.

Keywords:
Disc-blade intercepting angle; Power number; Just suspended speed; Mass transfer coefficient; RSM

Parameter	Dimension
Vessel Diameter, T	0.2 m
Number of baffles	4
Baffle Width	T/10
Impeller Diameter, D	T/3
Impeller Clearance, C	T/3
Sparger Diameter, Ds	0.8 D
Sparger Clearance, Cs	T/6
Liquid Height, H	T

Variables	Code	Coded variable level
Variables	Code	-1	0	1
Disc-blade intercepting angle (°)	X₁	30	90	150
Reynolds number (×10⁴)	X₂	1.70	4.10	6.60
Superficial gas velocity (mm/s)	X₃	1	2	3

Run	Type	Disc-blade intercepting angle, X₁	Reynolds number, X₂ (×10^-4)	Power number, Y₁
1	Center	90	4.10	5.86
2	Axial	150	4.10	1.19
3	Factorial	150	1.70	0.87
4	Center	90	4.10	5.93
5	Factorial	30	1.70	0.87
6	Center	90	4.10	5.93
7	Center	90	4.10	5.86
8	Axial	90	6.60	5.96
9	Center	90	4.10	5.86
10	Factorial	30	6.60	1.47
11	Axial	90	1.70	3.92
12	Axial	30	4.10	1.32
13	Factorial	150	6.60	1.31

Run	Type	Disc-blade Intercepting angle, X₁	Superficial gas velocity, X₃	k_La (s^-1), Y₂
1	Factorial	150	3	0.0073
2	Center	90	2	0.0106
3	Center	90	2	0.0114
4	Factorial	30	1	0.0042
5	Factorial	30	3	0.0087
6	Axial	30	2	0.0065
7	Factorial	150	1	0.0050
8	Center	90	2	0.0115
9	Center	90	2	0.0112
10	Center	90	2	0.0122
11	Axial	90	3	0.0141
12	Axial	150	2	0.0065
13	Axial	90	1	0.0076

Source	Sum of squares	Degree of freedom	Mean of square	F-value	p-Value (Prob>F)	Remarks
Model	66.29	5	13.26	74.60	<0.0001	Significant
X₁	6.346×10^-3	1	6.346×10	0.036	0.8555
X₂	0.87	1	0.87	4.89	0.0626
X₁²	49.55	1	49.55	278.82	<0.0001
X₂²	0.87	1	0.87	4.89	0.0626
X₁X₂	6.345×10^-3	1	6.345×10^-3	0.036	0.8555
Residual	1.24	7	0.18
Lack of fit	1.24	3	0.41	280.76	<0.001
Pure error	5.88×10^-3	4	1.47×10^-3
Cor total	67.53	12
R-squared	0.9816

Source	Sum of squares	Degree of freedom	Mean of square	F-value	p-Value Prob>F	Remarks
Model	1.075x10^-4	5	2.150x10^-5	32.46	0.0001	Significant
X₃	2.948x10^-5	1	2.948x10^-5	44.51	0.0003
X₁	6.000x10^-8	1	6.000x10^-8	0.091	0.7722
X₃2	3.795x10^-7	1	3.795x10^-7	0.57	0.4738
X₁2	6.155x10^-5	1	6.155x10^-5	92.93	<0.0001
X₃X₁	1.210x10^-6	1	1.210x10^-6	1.83	0.2185
Residual	4.636x10^-6	7	6.623x10^-7
Lack of fit	3.308x10^-6	3	1.103x10^-6	3.32	0.1382
Pure error	1.328x10^-6	4	3.320x10^-7
Cor total	1.121x10^-6	12
R-squared	0.9587

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[1] * Corresponding author: R. Afshar Ghotli - E-mail: afsharghotli_reza@yahoo.com