Multiphase transport

Grahman, T, Philosophical Transactions of the Royal Society of London A 140, 1, 1850. Gray, WG, A Derivation of the Equations for Multiphase Transport, Chemical Engineering Science 30, 229, 1975. 

Finally, there is multiphase transport, which is the transport of more than one phase, usually partially mixed in some fashion. The settling of particles in water or air, the fall of drops, and the rise of bubbles in water are all examples of multiphase transport. Figure 1.3 illustrates three flow helds that represent multiphase transport. 

Figure t.3. Illustration of multiphase transport. In these cases, air bubbles create a water flow and rain drops create an air flow. The oil drops do not have a significant rise or fall velocity in water and are simply transported. 

From this example it can be concluded that any kind of analysis of multiphase transport phenomena in porous media should also include a stability check. 

Current multimedia models are inadequate in many respects. Description of intermedia transport across the soil-air and unsaturated soil-saturated soil zones suffers from the absence of a suitable theory for multiphase transport through the multiphase soil matrix. These phenomena are crucial in describing pollutant migration associated with hazardous chemical waste sites. Existing unsaturated-zone soil transport models fail to include mass transfer limitations associated with adsorption and desorption and with absorption and volatilization processes. Rather, most models assume equilibrium among the soil-air, soil-solid, solid-water, and soil-contaminant phases. 

The shape of the capillary portion of the liquid-vapor interfacial area for sand (Fig. 1-1 lb) resembles simulation results of Reeves and Celia (1996) of interfacial areas in pore networks due to capillarity only. The discussion illustrates potential limitations in using cylindrical pore network models (Reeves Celia, 1996) especially for studies of volatile liquids and surfactants, and other multiphase transport processes where interfacial areas play a crucial role (Kim et al., 1997 Karkare Si. Fort, 1996). Furthermore, the overwhelming role of adsorbed liquid films casts doubts on several proposed constitutive relationships between capillary pressure (saturation) and interfacia] area (Skopp, 1985 Hassanizadeh Gray, 1993) most of which were based on assumed cylindrical capillary geometry in the absence of adsorption. 

D. Pavone, Explicit Solution for Free-Fall Gravity Drainage Including Capillary Pressure, in Multiphase Transport in Porous Media—1989, ASME FED, vol. 92 (or HTD, vol. 127), 55-62,1989. 

R. A. Owen and D. J. Pulling, Wetting Delay Film Boiling of Water Jets Impinging on Hot Flat Metal Surfaces, in T. N. Veziroglu (ed.), Multiphase Transport, 2, pp. 639-669, Hemisphere, Washington, DC, 1979. 

Colver, G. M., and G. S. Bosshart, Heat and Charge Transfer in an AC Electrofluidized Bed, in Multiphase Transport Fundamentals, Reactor Safety, Applications, 1-5, Hemisphere, Wash. DC, 1980, pp. 2215-2243. 

Here we remark that the boundary condition is joined with the governing differential equation, and that means that the heterogeneous reaction rate in equation 1.15 is now beginning to look like a homogeneous reaction rate in equation 1.24. This process, in which a boundary condition is joined to a governing differential equation, is inherent in all studies of multiphase transport processes. The failure to identify explicitly this... 

Choicharoen, K. Devahastin, S. Soponronnarit, S. Numerical simulation of multiphase transport phenomena during impinging stream drying of a particulate material. Drying Technology 2012, 30, 1227-1237. 

Drying of solids is one of the oldest and most common unit operations found in diverse processes such as those used in the agricultural, ceramic, chemical, food, pharmaceutical, pulp and paper, mineral, polymer, and textile industries. It is also one of the most complex and least understood operations because of the difficulties and deficiencies in mathanati-cal descriptions of the phenomena of simultaneous— and often coupled and multiphase—transport of heat, mass, and momentum in solid media. Drying is therefore an amalgam of science, technology, and art (or know-how based on extensive experimental observations and operating experience) and is likely to remain so, at least for the foreseeable fnture. 

The background research in the field of multiphase transport started more than 40 years ago with the study of two-phase flow (27—31), mostly gas and liquid, that exhibits different regimes from stratified (or separated) to annular flow, passing through bubbly and slug flow. 

K. Promislow, J. Stockie, B. Wetton, A sharp interface reduction for multiphase transport in a porous fuel cell electrode, 462, 789-816, 2006. 

S. M. Senn and D. Poulikakos. Multiphase transport phenomena in the diffusion zone of a PEM fuel cell. J. Heat Transfer, 127 1245-1259, 2005. 

In addition to the equivalent circuit method, the impedance results can also be analyzed using mathematical models based on physicochemical theories. Guo and White developed a steady-state impedance model for the ORR at the PEM fuel cell cathode [15]. They assumed that the electrode consists of flooded ionomer-coated spherical agglomerates surrounded by gas pores. Stefan-Maxwell equations were used to describe the multiphase transport occurring in both the GDL and the catalyst layer. The model predicted a high-frequency loop due to the charge transfer process and a low-frequency loop due to the combined effect of the gas-phase transport resistance and the charge transfer resistance when the cathode is at high current densities. 

Adenekan, A.E., Patzek, T.W., Pruess, K. Modeling of Multiphase Transport of Multicomponent Organic Contaminants and Heat in the Subsurface. Numerical Model Formulation, Water Resources Research 29(11), 3727-3740 (1993)... 

Due to recent rapid developments in a variety of nanoscale and microscale devices [1,2], information on the basic characteristics of multiphase transport phenomena in nanochannels and microchannels has become increasingly important. A characteristic feature of such systems is that a surface force or an interfacial force predominates over the body force. The wettability of solid walls of channels and surface tension of liquid, therefore, play an essential role in analyzing the transport phenomena. 

Multiphase flow in gas channels is characterized by different regimes. In PEFC flow channels, slug, annular, and mist flow can occur depending on the flow velocity. In porous media, the description of multiphase transport is more complex. The momentum equation reduces to Darcy s law ... 

---