Liquid continuous regime

Here, is the height of the coalescing interface [the interface between the two different liquid continuous regimes corresponding to heater thickness... 

FIG. 22-37 Regimes of separation in a liqiiid-solid-liqiiid system. Phase 1 particle phase 2 = hqiiid (dispersed) phase 3 = liquid (continuous). 

Latent heat associated with phase change in two-phase transport has a large impact on the temperature distribution and hence must be included in a nonisothermal model in the two-phase regime. The temperature nonuniformity will in turn affect the saturation pressure, condensation/evaporation rate, and hence the liquid water distribution. Under the local interfacial equilibrium between the two phases, which is an excellent approximation in a PEFG, the mass rate of phase change, ihfg, is readily calculated from the liquid continuity equation, namely... 

Spray regime (or drop regime, Fig. 14-20c). At high gas velocities and low liquid loads, the liquid pool on the tray floor is shallow and easily atomized by the high-velocity gas. The dispersion becomes a turbulent cloud of liquid droplets of various sizes that reside at high elevations above the tray and follow free trajectories. Some droplets are entrained to the tray above, while others fall back into the liquid pools and become reatomized. In contrast to the liquid-continuous froth and emulsion regimes, the phases are reversed in the spray regime here the gas is the continuous phase, while the liquid is the dispersed phase. 

It is shown, that the performance of a pulsing packed column can be split up into its two component parts, the pulses and the zones in between pulses. The pulses can be described as parts of the bed already in the dispersed bubble flow regime the zones-in between the pulses as parts of the bed still in the gas-continuous regime. The pulse frequency is linearly dependent upon the real liquid velocity. The properties of the pulse, like holdup, velocity and height are quite independent upon all the parameters except gas flow rate. 

For cncnrrfnr ga<-1igiikLHnwnflnuj over a packed bed, various flow regimes such as trickle-flow (gas continuous), pulsed flow, spray flow, and bubble flow (liquid continuous) can be obtained, depending upon the gas and liquid flow rates, the nature and size- of packing, and the nature and properties of the liquid. The flow-regime transition is usually defined as the condition at which a slight increase in gas or liquid flow rate causes a sharp increase in the root-mean-square wall-pressure fluctuations. 

The term froth in Fig. 14-22 suggests aeration in which the liquid phase is continuous. Under certain conditions there can be an inversion to a gas-continuous regime, or spray. The spray has its phase boundaries equivalent to the boundaries for froth shown in Fig. 14-22. 

As pointed out by Bennett and Novak,at low liquid rates the liquid-continuous foamy layer may practically disappear and mass transfer takes place in a vapor-continuous spray regime. Operation in the spray regime is less effective for mass transfer and should be avoided when possible. 

Trickle flow occurs at low liquid and gas flow rates. In trickle flow, the liquid flows down the reactor on the surface of the packing in the form of rivulets and films while the gas phase travels in the remaining void space. This regime is also termed gas continuous regime or... 

In the third diagram, the local concentration increases and the SMNs actually create well-ordered layers between the dispersed phase regimes while the liquid continues to drain. The SMNs cannot get out of the way fast enough, which is more commonly known as depletion flocculation. ... 

A schematic diagram of a perforated tray is shown in Figure 12.28. The zone marked froth (liquid-continuous) can sometimes invert to a spray (vapor-continuous), but quantitative procedures dealing with the spray regime have not yet been developed. Such a regime prevails at very... 

Kappe et al. reported a direct aerobic oxidation of 2-benzylpyridines in a gas-liquid continuous-flow regime [34]. A standard two-feed approach was used. Pressurized air was mixed with the substrate liquid phase in a simple T-shaped mixing device (Figure 23.4). The liquid phase was pumped by the use of an HPLC pump. Pressurized air was monitored by a mass flow controller. The two-phase reaction mixture was pumped through a stainless steel coil (0.8 mm inner diameter, 120 m length) and heated with a standard GC oven. Due to... 

With a liquid continuously feeding the disk at a rate Q, the criteria for the transition between the different regimes is defined in terms of critical flow rate. As reported earlier, three modes... 

An approach that is conceptually simpler and does not require the prescription of transport to hydraulic or diffusion mechanisms was proposed by Janssen [47], and Thampan et al. [22] (hereafter TMT) based on the use of chemical potential gradients in the membrane. More recently, Weber and Newman [27] developed a novel model where the driving force for vapour-equilibrated membranes is the chemical potential gradient, and for liquid-equilibrated membranes it is the hydraulic pressure gradient. A continuous transition is assumed between vapour- and liquid-equilibrated regimes with corresponding transition from 1 to 2.5 for the electro-osmotic drag coefficient. 

Because of the low gas and liquid mass velocities in pilot plant reactors, pressure drop is low and generally difficult to measure. In commercial reactors, however, it is usually important and computations of pressure drop are usually needed to set pump and compressor designs. Several pressure drop correlations are available in the literature. One poDular one is that by Larkins, White and Jeffrey [39] modified by Reiss [58] which applies to both the trickle gas continuous regime and the pulse flow regime. The correlation is represented below. 

As it has appeared in recent years that many hmdamental aspects of elementary chemical reactions in solution can be understood on the basis of the dependence of reaction rate coefficients on solvent density [2, 3, 4 and 5], increasing attention is paid to reaction kinetics in the gas-to-liquid transition range and supercritical fluids under varying pressure. In this way, the essential differences between the regime of binary collisions in the low-pressure gas phase and tliat of a dense enviromnent with typical many-body interactions become apparent. An extremely useful approach in this respect is the investigation of rate coefficients, reaction yields and concentration-time profiles of some typical model reactions over as wide a pressure range as possible, which pemiits the continuous and well controlled variation of the physical properties of the solvent. Among these the most important are density, polarity and viscosity in a contimiiim description or collision frequency. 

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