1 Chapter 12 Noel de Nevers – Gas – Liquid Flows Fall 2008 Why is it important? Table 1: Classification of Gas‐Liquid Equipment (In most of these the liquid is the continuous phase) 2‐Phase Flows Heat Exchangers with a change of phase Gas‐Liquid Contactors (no reaction) Chemical Reactors 2‐phase and multiphase • Petroleum reservoir with recovered gas and liquid in line • CO2 Pressurized pub taps • Bubbles in Guinness Style Beers • Carburetor • Drip Coffee Maker • Thermosiphon • Reboiler • Boilers • Condensors • Distillation • Gas absorption in a packed column • Fermentors • Waste/Chemical treatment lagoons • Hydrogenation • Oxidation • Partial Oxidation • Chlorination • Hydration • Hydroformylation • Organic Synthesis: alkylations, alkoxylations, aminations, carbonylations Several lists of 2‐phase and multiphase reactions are given in the text by W.‐D. Deckwer. 1 Figure 1: Typical Drip Style Coffee Machine How does the liquid flow uphill without a pump? How much liquid is boiled? leaching and filtration Condenser and Distributor heat transfer tubular heater with two-phase flow one-way valve Coffee Beans bypass lever timer, switch thermal fuses, and digital display AC Power thermal switch no-drip valve
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Chapter 12 Noel de Nevers – Gas – Liquid Flows Fall 2008
Why is it important?
Table 1: Classification of Gas‐Liquid Equipment (In most of these the liquid is the continuous phase)
2‐Phase Flows Heat Exchangers with a change of phase
Gas‐Liquid Contactors (no reaction)
Chemical Reactors 2‐phase and multiphase
• Petroleum reservoir with recovered gas and liquid in line
Several lists of 2‐phase and multiphase reactions are given in the text by W.‐D. Deckwer.1
Figure 1: Typical Drip Style Coffee Machine
How does the liquid flow uphill without a pump?
How much liquid is boiled?
leaching andfiltration
C ondenser and D istributor
heat transfer
tubular heaterw ith tw o-phase flow
one-w ay valve
C offee B eans
bypass lever
tim er, sw itchtherm al fuses, and dig ital display
AC Pow ertherm al sw itch
no-drip valve
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Figure 2: Rowan Distillation Column with Thermosiphon Reboiler
Figure 3: Depiction of a Thermosiphon (or Thermosyphon) Reboiler1
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Intellectual Property: US Patent 4832968
Foam production Shear-induced nucleation
Tiny Hole 0.061 cm diameter - laser-bored
Material Polypropylene
Manufacturing Blow molding
Volume of liquid 15 ml
Gas mixture for pressurization N2 (2% v/v), CO
2 (150% v/v), supersaturated
Pasteurization After sealing, 60°C, 15-20 min
Show Movie of Tank‐Type Gas‐Liquid System –
Visual Mixing2,3
Gas Dispersion Movie
Drop Breakup Movie
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Gas‐Sparged Chemical/Waste Treatment Systems
Gas Plumes in Lagoon from work of Dr. Gephardt4
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Figure 4: Multiplume Flow Regime5
Figure 5: Macroscale Fluid Flow Pattern
What do we need to know to design these systems?
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Figure 6: Flow Mapping for Horizontal Pipe Flow from Denn6
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Figure 7: Rise Velocity of Air Bubbles in Water at 20°C7
Part 1 ended here with references
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Bubble Column: Volumetric Mass Transfer Coefficients
Figure 8: Volumetric mass Transfer Coefficients as a function of gas velocity in Bubble Column water‐air systems.1 Equation
plotted is by Akita and Yoshida. The units of
The equation plotted in Figure 8
D0.6
D
.
⁄. (1)
An approximate equation for gas holdup
or .
(2)
Substituting gives
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. .
(3)
Liquid‐Liquid Dispersions in various systems
Figure 9: Relation of drop sizes in agitated systems using a Local Power per unit mass2,8 The local power for an agitated system is defined as the power input into the fluid divided by the mass within ½ of the swept out volume of the impeller. (e.g. swept out volume D⁄2 ) where D is the impeller Diameter and W is the impeller blade width
.
(4)
The value of is between 0.5 and 1.0.
1 Deckwer, W. –D., Bubble Column Reactors, John Wiley and Sons, New York, 1992. 2 Paul, E. D. V. A. Atiemo-Obeng, and S. M. Kresta, “Introduction of the Handbook of Industrial Mixing”, Wiley,
2004. 3 Visual Mixing CD by S. Kresta and K. Boyle included with the text by Paul, E. D. V. A. Atiemo-Obeng, and S. M.
Kresta, “Handbook of Industrial Mixing”, Wiley, 2004 4 Otero, Z., J.N. Tilton, T.W.F. Russell, “Some observations on flow patterns in tank‐type systems International Journal of Multiphase Flow,” 11(4), July‐August 1985, Pages 583‐589. 5 Russell, T. W. Fraser, A. S. Robinson, N. J. Wagner, “Mass and Heat Transfer: Analysis of Mass contactors and Heat Exchangers, Cambridge University Press, 2008 6 Denn, M. M. Process Fluid Mechanics, Prentice‐Hall, Inc. Englewood Cliffs, NJ 1980. 7 Clift, R., J. R. Grace, M. E. Weber, “Bubbles, Drops and Particles,” Academic Press, Inc. Boston, 1978. 8 Davies, J. T., “A Physical Interpretation of Drop Sizes in Homogenizers and Agitated Tanks, Including the Dispersion of Viscous Oils.” Chemical Engineering Science, 42(7) pp1671‐1676 (1987)