Liquid plug

Bubble columns (BCs) Non plug-flow for liquid Plug-flow for gas 0.005-0.01 0.01-0.1... 

Liquid Flow Patterns on Large Trays The most popular theoretical models (below) postulate that liquid crosses the tray in plug flow with superimposed backmixing, and that the vapor is perfectly mixed. Increasing tray diameter promotes liquid plug flow and suppresses backmixing. 

Length of Liquid Flow Path Longer liquid flow paths enhance the liquid-vapor contact time, the significance of liquid plug flow, and therefore raise efficiency. Typically, doubling the flow path length... 

In order to maximize sample handling efficiency, microcoil experiments can be performed on samples of limited volume with a setup similar to that shown in Figure 7.3.1.8. The liquid susceptibility-matching approach [7] described earlier allows observe factors of up to 70 % without broadening the linewidth. One recent example uses perfluorinated liquid plugs to restrict the total sample... 

Flow measurement has been achieved without the use of beads or dyes. A short heating pulse generated by a C02 infrared laser (10.6 pm) was delivered through the IR-transparent Si wafer into the channel. The radiative image of the hot liquid plug was recorded by an IR camera [414]. 

Most popular theoretical models (such as the AlChE and the Chan and Fair models, Sec. 7.2.1) postulate that liquid crosses the tray in plug flow (Fig. 7.7a) with superimposed backmixing, and that vapor is perfectly mixed. Increasing tray diameter promotes liquid plug flow and suppresses backmixing. This should enhance efficiency in large-diameter columns, but such enhancement has not been observed (147,148). Liquid maldistribution is the common explanation to the observation. 

Liquid plug flow produces a horizontal (i.e., flat) flow profile (Fig. 7.7a), Channeling produces a U-shaped flow profile (Fig, 7.8a). The liquid moves fast at the tray center and slow near the walls. Wide stagnant zones, a steep U shape, and liquid recirculation in the stagnant zones (Fig. 7.35) signify a highly channeled flow profile. The... 

Achieving identical flow in each charmel can be difficult at low flow rates. A careful analysis of fhe hydrod)mamic sfabilify teaches that a monolith system is intrinsically unstable in cocurrent upflow. Conversely, cocurrent downflow is sfable when fhe flow velocity exceeds a critical value. A first approximation of fhe crifical flow velocify is fhe velocity that a liquid plug has when it falls under fhe influence of gravity inside the channel when it is open to the atmosphere at both ends. 

Electro-osmosis d.c. electric field liquid plug or capillary liquid displacement electro-osmotic volume flow per unit field strength eo.E jj)4V-ls l... 

Streaming current pressure gradient liquid plug or capillary electric current streaming current per unit of pressure difference C m N S = A m2 N->... 

Streaming potential pressure gradient liquid plug or capillary potential difference streaming potential (difference) per unit of pressure difference s(r Vm N- ... 

At the inlet the gas and liquid which are introduced form liquid plugs and Taylor bubbles. A short liquid plug is known to be unstable, and it falls back and merges with the liquid slug coming from below, causing it to approximately double its length. 

Usually, an adiabatic operation of MR is assumed in modeling. This seems to be a reasonable assumption, especially for ceramic monoliths of low thermal conductivity and in the absence of significant radial temperature gradients. In practice, there is no convective radial heat transfer because of barriers between the adjacent channels. The radial heat transfer occurs only by conduction through the walls and, to some extent, by convection in liquid plugs. 

GL gas-liquid GS gas-solid / liquid liquid plug L liquid LS liquid-solid m mean orif orifice p particle R reactor... 

Figure 2 presents three typical flow patterns were observed at narrow annulus, which are the flow with small bubbles whose size is less than a channel width (see Fig. 2a), the flow with large Taylor bubbles (see Fig. 2b) and the flow with the cell structure of liquid plugs, (see Fig. 2c). The flow pattern map is presented on Fig. 3. The first type of the flow is observed at the superficial liquid velocities greater than 2 m/s when the flow becomes turbulent (point 1 and line A in Fig. 3). At such velocities the flow is turbulent and small bubbles...

Data have been presented allowing identification of different flow patterns in a narrow annular channel with a gap less than capillary constant. For large superficial velocities the flow with Taylor bubbles and cell flow regime with liquid plugs are typical. 

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