Interfacial kinetics liquid flow

Qu W, Mudawar I (2002) Experimental and numerical study of pressure drop and heat transfer in a single-phase micro-channel heat sink. Int J Heat Mass Transfer 45 2549-2565 Qu W, Mudawar I (2004) Measurement and correlation of critical heat flux in two-phase micro-channel heat sinks. Int J Heat Mass Transfer 47 2045-2059 Ren L, Qu W, Li D (2001) Interfacial electro kinetic effects on liquid flow in micro-channels. Int J Heat Mass Transfer 44 3125-3134... 

Yeong et al. [100,101] used a microstructured film reactor for the hydrogenation of nitrobenzene to give aniline in ethanol at a temperature of 60 °C, a H2 partial pressure of 0.1-0.4 MPa, and residence times of 9-17 s. Palladium catalysts were deposited as films or particles on a microstructured plate. Confocal microscopy was used to measure the liquid film thickness, which increased from 67 to 92 pm as flow rates were increased from 0.5 to 1.0 cm3 min-1. The value of kha characteristic of this system was estimated to be 3-8 s 1 at an interfacial surface area (per reactor volume) of 9000-15000 m2 m 3. Conversion was found to be affected by both liquid flow rate and H2 partial pressure, and the reactor operated between the kinetic and mass transfer-controlled regimes. 

Workers have also used a number of commercially available FEM packages to allow the simulation of immiscible liquid-liquid interfacial measurements [125-127] and approach curves for scanning electrochemical microscope applications [128]. Compton and coworkers have also used a commercial FEM package to model coupled heat and mass transport at a wire [129], and dissolution kinetics in flow-through devices [130]. 

For this two-phase gas/liquid flow, the gas Weber number is introduced as the ratio between the applied relative kinetic energy (here by the relative velocity of the gas and the liquid (emulsion) phases) and the interfacial energy (restriction for interface deformation) of the sprayed emulsion. For the spraying process, two gas Weber numbers were defined (i) concerning the tertiary spray droplet (Wgg Nozzle)... 

Developed by Freeman and Tavlarides [45,46], and based on the liquid jet technique [47,48], the LJRR provides a method of measuring liquid-liquid reaction kinetics with direct contact, known interfacial area, renewable interface, and reasonably defined hydrodynamics. This method operates by employing an aqueous liquid jet in a concurrent, coaxially flowing organic solution, shown schematically in Fig. 8. 

The influence of gas density on the gas-liquid interfacial area could be related to the flow patterns and to the interpenetration between gas and liquid. It is probable that the gas-liquid interface results from two distinct mechanisms. The first one is based on the extent of the solid surface where liquid films could develop (wetting of particles), virtually controlled by fluid velocities and liquid properties. The second mechanism depends on the kinetic energy content of the gas phase. The more important the gas inertia, the more important is the contribution of fine gas bubbles penetrating liquid films. 

The solvent-extraction process for metal ions depends intrinsically on the mass transfer to or across the interface and the chemical reaction in the interfacial region. Therefore, the study of the role of the interface is very important for analyzing the real extraction mechanism and for controlling the extraction kinetics. In the early 1980s, the high-speed stirring (HSS) method was developed by Watarai and Preiser [4,5]. Thereafter, some new methods were proposed in our laboratory, which included the two-phase stopped-flow method [6], the capillary plate method [7], reflection spectrometry [8], the centrifugal liquid membrane (CLM) method [9], and the two-phase sheath flow method... 

The mathematical description considered in Section 10.3.3 was used as a modeling basis for the specially developed completely rate-based simulator [80]. This tool consists of several blocks including model libraries for physical properties, mass and heat transfer, reaction kinetics and equilibrium as well as specific hybrid solver and thermodynamic package. It also contains different hydrodynamic models (e.g., completely mixed liquid - completely mixed vapor, completely mixed liquid - vapor plug flow, mixed pool model, eddy diffusion model [80]) and a model library of hydrodynamic correlations for the mass-transfer coefficients, interfacial area, pressure drop, holdup, weeping and entrainment that cover a number of different column internals and flow conditions. 

By suitably choosing the solubility, the concentration of the reactant and the rate of reaction, either the mass transfer coefficients, or the interfacial area or both groups of parameters can be deduced from the overall rate of absorption (lA). Generally but not always, a steady flow of each phase through the reactor is assumed. Indeed the competition between the phsyical and chemical kinetics at the level of mass transfer between gas and liquid (the mass transfer reaction regime where the reaction belongs) may allow for the choice of the type of gas-liquid contactor (I). This is clearly shown in Fig. I that represents schematically the concentration profiles for A and B on each side of the interface. 

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