experimental characterization of gas-liquid column: effect of nozzle orientation and pressure by...
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Experimental Characterization of Gas-Liquid Column:
Effect of nozzle orientation and pressure
by Peter Spicka
CHEMICAL REACTION ENGINEERING LABORATORY
CREL group regular meeting, November 26th
Objective
• Study the sparger nozzle orientation effect on gas hold-up, liquid velocity and turbulence in gas-liquid column
• Only few data, i.e. liquid velocity and gas holdup, available in the literature for churn-turbulent flow regime
• CARPT and CT techniques allow relatively accurate acquisition of needed data
• Different pressures and UGS can be covered
• Additional experimental database for CFD simulations can be created
Motivation
Experiment• 6.375” stainless steel column• Cross-sparger, two nozzle
orientations: facing upward and downward
• Air-water system• Dynamic height maintained at 11 D• Pressure: 1 bar and 4 bars• UGS= 5 cm/s (only CT) and 20 cm/s
CARPT setup• Typical setup, 30 detectors• Only photo peak acquisition• 50 Hz sampling frequencyCT setup• 5 detectors, 7 projections per view• 4 axial levels: 2.5D; 3.5D; 5.5D; and
9D• 20 Hz sampling frequency
Supporting plate
CROSS SPARGER SIDE VIEW
.5"
1.0"1.0"
.5"
.75"
.5"
Nozzle, d=0.1"
gas deflector
Detector alignment and calibrationCT CARPT
Angular Symmetry Check
0
100
200
300
400
500
600
700
-10 -5 0 5 10
Angle [o]
Co
un
t
Counts
Dis
tan
ce[c
m]
0 50 100 150 2000
20
40
60
80
100
CalibrationSpline
DETECTOR 1
x [cm]
y[c
m]
-10 -8 -6 -4 -2 0 2 4 6 8 10-10
-8
-6
-4
-2
0
2
4
6
8
10
1 cm
1 bar, NozzleD
0
0.1
0.2
0.3
0.4
0.5
0 200 400 600 800 1000
E [mV]
dI/d
E1st det.
2nd det.
3 per. Mov.Avg. (1st det.)3 per. Mov.Avg. (2nd det.)
CT ResultsEffect of Nozzle Orientation- Global View
Gas holdup at UGS=20 cm/s and p=1 bar nozzles facing downward nozzles facing upward
-10
1r/R
2
4
6
8
x/D
0.400.360.320.280.240.200.160.120.080.040.00
Gas Holdup
-10
1r/R
2
4
6
8
x/D
0.400.360.320.280.240.200.160.120.080.040.00
Gas Holdup•Bubbles formed from nozzles facing upward are smaller increased hold-up
•Similar behavior was found for all the studied regimes
CT ResultsEffect of Nozzle Orientation and Pressure
Gas holdup profilesUGS=5 cm/s UGS=20 cm/s
Nozzle orientation
•particularly pronounced at high pressure and high UGS in the sparger zone
•diminishes with axial position
•Pressure
•Typical increase of gas holdup magnitude
r/R
0 0.25 0.5 0.75 10
0.2
0.4
0.6
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
r/R
0 0.25 0.5 0.75 10
0.2
0.4
0.6
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
r/R
0 0.25 0.5 0.75 10
0.1
0.2
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=5.5
r/R
0 0.25 0.5 0.75 10
0.2
0.4
0.6
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=5.5
r/R
0 0.25 0.5 0.75 10
0.1
0.2
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
r/R
0 0.25 0.5 0.75 10
0.1
0.2
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
CARPT ResultsLiquid velocity
•Steeper velocity profiles observed at high pressure higher bubble momentum
•However, effect of nozzle orientation on liquid velocity is visible only at near-sparger region
Axial velocity profiles Radial velocity profiles
r/R
UR
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0-0.10
-0.05
0.00
0.05
0.10
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
r/R
UR
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0-0.10
-0.05
0.00
0.05
0.10
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=5.5
r/RU
R[m
/s]
0.0 0.2 0.4 0.6 0.8 1.0-0.10
-0.05
0.00
0.05
0.10
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
r/R
UX
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0
-0.4
-0.2
0.0
0.2
0.4
0.61 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
r/R
UX
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0
-0.4
-0.2
0.0
0.2
0.4
0.61 bar ND4 bars ND1 bar NU4 bars NU
x/D=5.5
r/R
UX
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0
-0.4
-0.2
0.0
0.2
0.4
0.61 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
Liquid velocity calculation
• CARPT processing algorithm considers uniform time step
• However, relatively large amount of data is excluded from calculation (25% and more)
Comparison with Boon Cheng’s data
r/R
UX
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0
-0.4
-0.2
0.0
0.2
0.4
0.6ND nonunif. time stepNU nonunif. time stepND unif. time stepNU unif. time step
x/D=2.5
• Time step is non uniform
• Calculated velocity will be biased towards higher values
r/R
UX
[m/s
]
0.0 0.2 0.4 0.6 0.8 1.0
-0.4
-0.2
0.0
0.2
0.4
0.6 nonunif. t step UGS=20 cm/sunif. t step UGS=20 cm/sPP UGS=30 cm/s
x/D=2.5
Nozzles facing down Nozzles facing upp= 1 bar p = 4 bars p = 1 bar p = 4 bars
CARPT ResultsTurbulent kinetic energy
• Turbulent kinetic energy is higher for nozzles pointing downward and at higher pressure
• Nozzle effect is significant mainly at low pressure
• Significant effect of bubble-induced turbulence
-50
5
-50
5r [cm]
50
100
150
x[c
m]
0.600.540.480.420.360.300.240.180.120.060.00
k [m2/s2]
-50
5
-50
5r [cm]
50
100
150
x[c
m]
0.600.540.480.420.360.300.240.180.120.060.00
k [m2/s2]
-50
5
-50
5r [cm]
50
100
150
x[c
m]
0.600.540.480.420.360.300.240.180.120.060.00
k [m2/s2]
-50
5
-50
5r [cm]
50
100
150
x[c
m]
0.600.540.480.420.360.300.240.180.120.060.00
k [m2/s2]
CARPT ResultsReynolds stresses
• u’xu’x are approximately 2.5 x higher than u’ru’r and they are weakly coupled
• Magnitude of u’xu’x is comparable with the corresponding mean velocities
• Highly anisotropic flow !
r/R
u' ru
' r[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=5.5
r/R
u' xu
' x[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=5.5
r/R
u' xu
' x[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
r/R
u' xu
' x[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
r/R
u' ru
' r[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
r/R
u' ru
' r[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
r/R
u' xu
' r[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.00
0.05
0.10
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=2.5
r/R
u' xu
' r[m
2/s
2]
0.0 0.2 0.4 0.6 0.8 1.00.00
0.05
0.10
1 bar ND4 bars ND1 bar NU4 bars NU
x/D=9.0
Concluding Remarks
Nozzle orientation• Significant effect on gas holdup and turbulent kinetic
energy mainly near the column bottom
• More pronounced at high UGS and high pressure
• Effect on liquid velocity profiles is less significant• Uncertainty in magnitude of turbulent parameters
due to gas holdup fluctuations
Outlook for future
Filtering• Elimination of gas holdup fluctuations from CARPT data
CFD• Examination of nozzle orientation effect in churn-turbulent
regime