Mass transfer in two-phase flow

Pohorecki, R. (2007) Effectiveness of interfacial area for mass transfer in two-phase flow in microreactors. Chem. Eng. ScL, 62 (22), 6495-6498. 

Pohorecld [59] investigated the effectiveness of the interfadal area for mass transfer in two-phase flow in an MSR. He developed criteria to avoid saturation of the liquid wall film in the case of physical absorption or liquid of the film for absorption with instantaneous chemical reaction ... 

In reviews of mass transfer in two-phase flow in microchannels, Kreutzer and coworkers [40, 41] noted that the Taylor flow regime is typically associated with the best gas-liquid mass transport because of the no-slip condition at the channel walls. The velocity gradient within the liquid slug promotes a chaotic mixing effect. The resultant continual refreshing of the two-phase interface provides a high driving force... 

A5. Anderson, J. D., Bollinger, R. E., and Lamb, D. E., Mass Transfer in Two Phase Annular Horizontal Flow. Presented at A.I.Ch.E. Natl. Meeting, Los Angeles, February, 1962. 

Moo-Young, M., Hirose, T., and Ali, S., Rheological effects on liquid phase mass transfer in two phase dispersions results for creeping flow, Proc. 5th Int. Congr. Rheol., p. 233, Kyoto, 1970. 

Limited experimental data for liquid-soUd mass transfer are available. Oliver and Hoon [47] measured heat transfer in two-phase flow in capillaries using very viscous liquids and hence with thick lubricating layers. The best data set is by Horvath et al. [48], who measured the hydrolysis of N-benzoylarginine ethyl ester in a 1.2 m long tube coated with the immobilized enzyme trypsin. The intrinsic rate of this reaction was high enough that mass transfer from the liquid was limiting. The experimental data are reported as Sh versus Is/dh with the Reynolds number Re as a parameter and Sh versus Re with the aspect ratio Is/dh as a parameter. 

Multiphase catalytic reactors are employed in nearly 80% of industrial processes with annual global sales of about 1.5 trillion, contributing around 35% of the world s GDP [17]. Microreactors for multiphase reactions are classified based on the contact principles of gas and liquid phases continuous-phase contacting and dispersed-phase contacting [18]. In the former type, the two phases are kept in continuous contact with each other by creating an interface. In the latter case, one fluid phase is dispersed into another fluid phase. In addition, micro trickle bed operation is reported following the path of classical chemical engineering. The study of mass and heat transfer in two-phase flow in micro trickle bed reactors still remains as a less... 

The detail experimental study of flow boiling heat transfer in two-phase heat sinks was performed by Qu and Mudawar (2003b). It was shown that the saturated flow boiling heat transfer coefficient in a micro-channel heat sink is a strong function of mass velocity and depends only weakly on the heat flux. This result, as well as the results by Lee and Lee (2001b), indicates that the dominant mechanism for water micro-channel heat sinks is forced convective boiling but not nucleate boiling. 

Prodanovic V, Fraser D, Salcudean M (2002) On transition from partial to fuUy developed subcooled flow boiling. Int J Heat Mass Transfer 45 4727-4738 Qu W, Mudawar I (2003a) Measurement and prediction of pressure drop in two-phase micro-channel heat sinks. Int J Heat Mass Transfer 46 2737-2753 Qu W, Mudawar I (2003b) Flow boiling heat transfer in two-phase micro-channel heat sink. 1 Experimental investigation and assessment of correlation methods. Int J Heat Mass Transfer 46 2755-2771... 

Chyu, M. C., 1989, Formation and Heat Transfer Mechanism of Vapor Mass during Nucleate Boiling, in Thermal, Non-equilibrium in Two-Phase Flow, pp. 157-181, ENEA, Rome. (2)... 

Lahey, R. T., Jr., and F. A. Schraub, 1969, Mixing, Flow Regimes and Void Fraction for Two-Phase Flow in Rod Bundles, in Two-Phase Flow and Heat Transfer in Rod Bundles, ASME, New York. (5) Lahey, R. T., Jr., B. S. Shiralkar, and D. W. Radeliffe, 1971, Mass Flux and Enthalpy Distribution in a Rod-Bundle for Single and Two-Phase Flow Conditions, Trans. ASME, J. Heat Transfer, 93 197-209. (5)... 

In conventional continuous-flow configurations [2,3], (bio)chemical reactions, separations based on mass transfer between two phases, and continuous detection occur at different places and hence sequentially. 

In two-phase flow, most investigations are carried out in one dimension in the steady state with constant flow rates. The system may or may not be isothermal, and heat and mass may be transferred either from liquid to gas, or vice versa. The assumption is commonly made that the pressure is constant at a given cross section of the pipe. Momentum and energy balances can then be written separately for each phase, and with the constraint that the static pressure drop, dP, is identical for both phases over the same increment of flow length dz, these balances can be added to give over-all expressions. However, it will be seen that the resulting over-all balances do not have the simple relationships to each other that exist for single-phase flow. 

For mass transfer in two-component cocurrent two-phase flow, very little work seems to have been carried on in systems analogous to those for which pressure-drops have been measured, that is, in tubes, pipes, or rectangular channels. Only two publications dealing with vertical flow (V2, V3), and two concerned with horizontal flow (A5, S6), have appeared. 

Many parameters affect the mass transfer between two phases. As we discussed above, the concentration gradient between the two phases is the driving force for the transfer and this, together with the over-all mass transfer coefficient, determines the mass transfer rate. The influence of process parameters (e. g. flow rates, energy input) and physical parameters (e. g. density, viscosity, surface tension) as well as reactor geometry are summed up in the mass transfer coefficient. The important parameters for Kta in stirred tank reactors are ... 

Zhang, G. J., and Ishii, M., "Isokinetic Sampling Probe and Image Processing System for Droplet Size Measurement in Two-phase Flow", Int. J. of Heat and Mass Transfer, 38, 2019 (1995). 

This study of the turbulent motion in two-phase flows, within a diffuser-confusor reactor, is based on the numerical solution of Reynolds-averaged equations describing the turbulent flow of a continuous medium. A numerical solution has been found for averaged equations of substance (mass, pulse, heat) transfer [63, 65] ... 

The mechanisms by which freely rising bubbles interact with each other in relatively low-viscosity liquids and, specifically, how they approach, contact, and coalesce or break up are important aspects of multi-phase flow. Coalescence and breakup can control the interfacial area and mass transfer rate in bubble columns and gas-sparged chemical and biological reactors. Bubble interaction is fundamental in two-phase flow instability that plagues boilers and oil and gas wells. But bubble interaction remains a relatively mysterious area. 

Analysis of particle size is important in a wide range of industries. When the particles are powders, the information is required for research and development as well as for process quality control. Allen states that two thirds of the 3000 products of Dupont s products were sold as powders and that another fifteen percent contained powders. Whilst figures for other companies may be lower, this illustrates the importance of powders for the chemical process industry. If drops are being considered, the interest usually arises from research and development into sprays from nozzles or from confined two-phase flows. The former can have applications from combustion to crop protection. In two-phase flows, the size of drops can affect momentum, heat and mass transfer. In addition, drop sizes are essential for the design of compact gas/liquid separators. 

If the mass flow rate in Eq. (7.99) is not attained, a condition known as zero delivery results. In order to avert zero delivery, several techniques have been employed. Typically, vents are installed at intermediate points along the transfer line to release some of the trapped vapor, thereby increasing the mass flow rate into the line. Of course, a disadvantage of this method is that some of the cooling capacity is lost in the vented gas. Another technique that has been exploited is to install gas-liquid separators along the transfer line and allow most of the vapor formed in the line to escape continuously at these sites during transfer. Though two-phase flow cannot be avoided, this second technique will reduce the time for liquid delivery at the exit of the transfer line. 

Expressions similar to equations 6 and 7 may be derived in terms of an overall Hquid-phase driving force. Equation 7 represents an addition of the resistances to mass transfer in the gas and Hquid films. The analogy of this process to the flow of electrical current through two resistances in series has been analyzed (25). 

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