Flow patterns multiphase

Multiphase Reactors. The overwhelming majority of industrial reactors are multiphase reactors. Some important reactor configurations are illustrated in Figures 3 and 4. The names presented are often employed, but are not the only ones used. The presence of more than one phase, whether or not it is flowing, confounds analyses of reactors and increases the multiplicity of reactor configurations. Gases, Hquids, and soHds each flow in characteristic fashions, either dispersed in other phases or separately. Flow patterns in these reactors are complex and phases rarely exhibit idealized plug-flow or weU-stirred flow behavior. 

Flow Regimes in Multiphase Reactors. Reactant contacting, product separations, rates of mass and heat transport, and ultimately reaction conversion and product yields are strong functions of the gas and Hquid flow patterns within the reactors. The nomenclature of commonly observed flow patterns or flow regimes reflects observed flow characteristics, ie, armular, bubbly, plug, slug, spray, stratified, and wavy. 

Weisman, J., Duncan, D Gibson, J. and Crawford, T. Inti. JL Multiphase Flow 5 (1979) 437-462. Effects of fluid properties and pipe diameter on two phase flow patterns in horizontal lines. 

Mandhane, J. M., Gregory, G. A. and Aziz, K. Inti. JL Multiphase Flow l (1974) 537-553, A flow pattern map for gas-liquid flow in horizontal pipes. 

Hetsroni G, Mosyak A, Pogrebnyak E, Yarin LP (2005c) Heat transfer in micro-channels comparison of experiments with theory and numerical results. Int J Heat Mass Transfer 48 5580-5601 Hetsroni G, Mosyak A, Segal Z, Pogrebnyak E (2003b) Two-phase flow patterns in parallel microchannels. Int J Multiphase Flow 29 341-360... 

Kawahara A, Chung PM, Kawaji M (2002) Investigation of two-phase flow pattern, void fraction and pressure drop in a micro-channel. Int J Multiphase Plow 28 1411-1435 Kawaji M (1999) Fluid mechanics aspects of two-phase flow Flow in other geometries. In Kand-likar SG, Shoji M, Dhir VK (eds) Handbook of phase change boiling and condensation. Taylor and Francis, Washington, DC, pp 205-259... 

Rezkallah KS (1996) Weber number based flow-pattern maps for liquid-gas flows at microgravity. Int J Multiphase Flow 22 1265-1270... 

Taitel Y, Bamea D, Dukler AE (1980) Modeling flow pattern transitions for steady upward gas-liquid flow in vertical tubes. AlChE J 26 345-354 Triplett KA, Ghiaasiaan SM, Adbel-Khalik SI, Sadowski DL (1999a) Gas-liquid two-phase flow in microchannels. Part 1 two-phase flow patterns. Int J Multiphase Flow 25 377-394 Triplett KA, Ghiaasiaan SM, Abdel-Khalik SI, LeMouel A, McCord BN (1999b) Gas-liquid two-phase flow in microchannels. Part 11 void fraction and pressure drop. Int J Multiphase Flow 25 395 10... 

Ungar EK, Cornwell JD (1992) Two-phase pressure drop of ammonia in small diameter horizontal tubes. In AIAA 17th Aerospace Ground Testing Conference, NashviUe, 6-8 July 1992 Wallis GB (1969) One dimensional two-phase flow. McGraw-Hfll, New York Yang CY, Shieh CC (2001) Flow pattern of air-water and two-phase R-134a in small circular tubes. Int J Multiphase Flow 27 1163-1177... 

Zhao L, Rezkallah KS (1993), Gas-hquid flow patterns at microgravity conditions. Int J Multiphase Flow 19 751-763... 

Zhao TS, Bi QC (2001a) Co-current air-water two-phase flow patterns in vertical triangular microchannels. Int J Multiphase Flow 27 765-782... 

Hetsroni G, Mosyak A, Segal Z, Pogrebnyak E (2003) Two-phase flow pattern in parallel microchannels. Int J Multiphase Flow 29 344-360... 

Steady-state reactors with non-ideal flow pattern. In fact, all reactors presented as reactors with ideal flow patterns show some non-idealities as already mentioned above. The deviation from the ideal state for multiphase reactors arises from the presence of phases with very different physical properties. 

Barnea, D., 1987, A Unified Model for Predicting Flow Pattern Transitions for the Whole Range of Pipe Inclinations, Int. J. Multiphase Flow 13 1. (3)... 

Salcudean, M., J. H. Chun, and D. C. Groeneveld, 1983a, Effect of Flow Obstructions on the Flow Pattern Transitions in Horizontal Two-Phase Flow, Int. J. Multiphase Flow, P( 1) 87. (3) Salcudean, M., D. C. Groeneveld, and L. Leung, 1983b, Effects of Flow Obstruction Geometry on Pressure Drops in Horizontal Air-Water Flow, Int. J. Multiphase Flow 9(l) 73-85. (3)... 

Multiphase copolymers, Ziegler-Natta catalysts for, 26 535, 537-540 Multiphase laminar flow patterning, in microfluidics, 26 961 Multiphase reactions, in microbial transformations, 16 412-414 Multi-phase reactors, 21 333-335 Multiphoton effects, in photochemical technology, 19 109... 

In some multiphase reactors, stirring with an impeller or the flow pattern caused by gravity will control the interfacial area. By suitably designing and positioning propellers and reactant injection orifices or by using static mixers, it is possible to provide very efficient breakup of hquids into drops and bubbles. A factor of two decrease in drop or bubble size means a factor of four increase in interfacial area. 

P. J. A. Kenis, R. F. Ismagilov, and G. M. Whitesides, Microfabrication inside capillaries using multiphase laminar flow patterning, Science 285, 83—85 (1999). 

The most reliable methods for fully developed gas/liquid flows use mechanistic models to predict flow pattern, and use different pressure drop and void fraction estimation procedures for each flow pattern. Such methods are too lengthy to include here, and are well suited to incorporation into computer programs commercial codes for gas/liquid pipeline flows are available. Some key references for mechanistic methods for flow pattern transitions and flow regime-specific pressure drop and void fraction methods include Taitel and Dukler (AIChEJ., 22,47-55 [1976]), Barnea, et al. (Int. J. Multiphase Flow, 6, 217-225 [1980]), Barnea (Int. J. Multiphase Flow, 12, 733-744 [1986]), Taitel, Barnea, and Dukler (AIChE J., 26, 345-354 [1980]), Wallis (One-dimensional Two-phase Flow, McGraw-Hill, New York, 1969), and Dukler and Hubbard (Ind. Eng. Chem. Fun-dam., 14, 337-347 [1975]). For preliminary or approximate calculations, flow pattern maps and flow regime-independent empirical correlations, are simpler and faster to use. Such methods for horizontal and vertical flows are provided in the following. 

P 49] CFD simulations were made for monitoring the flow patterns within a droplet which is generated at a concentric separation-layer micro mixer [39], Diffusion-convection equations of two user scalars have to be solved in addition to the corresponding equation for the volume fraction of the fluids within a multiphase CFD simulation. 

The flow regimes in capillaries have been investigated extensively, and the reported results provide a good basis for imderstanding the hydrodynamics of multiphase operation of monoliths. Figure 11 shows the well-known two-phase flow patterns observed in tubes (16,17). 

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