1. CHEMICAL REACTION ENGINEERING LABORATORY
Experimental Characterization of Gas-Liquid Column:
Effect of nozzle orientation and pressure
by Peter Spicka
CHEMICAL REACTION ENGINEERING LABORATORY

2. Objectives
Effect of nozzle orientation on gas hold-up and liquid velocity field
studied at different pressures and UGS
future comparison with Sandia’s experiments
additional experimental database for CFD simulations
Secondary goals
effect of wavelet filtering on turbulence properties
mastering both the CT and the CARPT technique

3. 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
CT setup
5 detectors, 7 projections per view
4 axial levels: 2.5D; 3.5D; 5.5D; and 9D 1”

4. Gas holdup at UGS=20 cm/s and p=1 bar
CT Results
Effect of Nozzle Orientation- Global View
Gas holdup at UGS=20 cm/s and p=1 bar
nozzles facing downward nozzles facing upward
Bubbles formed from nozzles facing upward are smaller Þ increased hold-up
Similar behavior was found for all the studied regimes

5. Gas holdup at UGS=20 cm/s and p=1 bar
CT Results
Effect of Nozzle Orientation and Pressure
Gas holdup at UGS=20 cm/s and p=1 bar
UGS=5 cm/s UGS=20 cm/s
Effect of nozzle orientation
particularly pronounced at high pressure and high UGS
diminishes with axial position

6. CARPT Results Liquid velocity & turb. kinetic energy profiles
Indication of steeper axial velocity profiles for nozzles facing upward
However, effect of nozzle orientation on liquid velocity is inconclusive !
Turbulent kinetic energy is higher for nozzles pointing downward at both pressures

7. CARPT Results Reynolds stresses Highly anisotropic flow !
UGS=20 cm/s , p = 1 bar
nozzles pointing down nozzles pointing up
Highly anisotropic flow !
However, the magnitude of Reynolds stresses is most likely overestimated. If typical UB~0.6 m/s and u’=O(UB) then u’u’ should be about 0.4 m2/s2 !
Þ hold-up fluctuations ?

8. Remarks: Wavelet Filtering Azimuthal velocity UF computed by:
Devanathan
Rados
Cartesian components
UGS=20 cm/s , p = 4 bar
nozzles pointing down
Magnitude of Reynolds stresses is only slightly affected by wavelet filtering
In some cases, qualitatively different profiles !

9. Concluding Remarks Outlook for future Nozzle orientation CARPT data
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 inconclusive
CARPT data
Overestimation of turbulent parameters due to gas holdup fluctuations
Wavelet filtering slightly reduces Reynolds stresses but provides qualitatively different results
Outlook for future
Filtering
Elimination of gas holdup fluctuations from CARPT data
CFD
Examination of lift forces and bubble-induced turbulence models in churn-turbulent regime and 3D column