Systems renewal phase

The main characteristic of the classical manifold architecture for in-line LLE (Fig. 8.11) is that analyte extraction occurs mostly via the thin liquid film established on the inner wall of the tube, which is continuously renewed. Phase separation however is often a limiting factor in determining system performance. Nonetheless, the flow system can be designed to permit segmentation of the sample zone by the confluent organic stream, analyte extraction in the downstream reactor and... 

Zhang, R Ma, Z.W. An overview of fundamental studies and applications of phase change material slurries to secondary loop refrigeration and air conditioning systems. Renew Sust Energ Rev 16 (2012) 5021-5058. 

In addition to design, a major failing of many otherwise effective systems is the lack of a renewal phase or process. To be successful, systems must periodically be reevaluated to determine if they are... 

Salunkhe PB, Shembekar PS. A review of phase change material encapsulation on the thermal performance of a system. Renew Sustain Energy Rev 2012 16 5603-16. 

Koca A, Oztop HE, Koyun T, Varol Y. Energy and exergy analysis of a latent heat storage system with phase change material for a solar collector. Renew Energy 2008 33 558-67. 

In a detersive system containing a dilute surfactant solution and a substrate bearing a soHd polar sod, the first effect is adsorption of surfactant at the sod—bath interface. This adsorption is equivalent to the formation of a thin layer of relatively concentrated surfactant solution at the interface, which is continuously renewable and can penetrate the sod phase. Osmotic flow of water and the extmsion of myelin forms foHows the penetration, with ultimate formation of an equdibrium phase. This equdibrium phase may be microemulsion rather than Hquid crystalline, but in any event it is fluid and flushable... 

There has been renewed interest over the last few years in erosion-corrosion, i.e. essentially velocity-assisted corrosion since it appeared in the feed systems of certain nuclear plant. This prompted extensive experimental investigations . Erosion-corrosion is influenced by many factors-chemistry, flow, temperature, heat flux, and whether one or two phases exist. It also varies with the material, resistance increasing from mild steel, through 1% Cr-Mo to 2% Cr-Mo. 

As we shall have occasion to note in dealing with solutions, the composition of the surface phase is very different from that of the bulk liquid. When a liquid interface is newly formed the system is unstable until the surface phase has acquired its correct excess or deficit of solute by diffusion from or into the bulk of the solution. This process of diffusion is by no means instantaneous and, as has been observed in discussing the drop weight method, several minutes may elapse before equilibrium is established. In the ripple method the surfece is not renewed instantaneously but may be regarded as undergoing a series of expansions and contractions, thus we should anticipate that the value of the surface tension of a solution determined by this method would lie between those determined by the static and an ideal dynamic method respectively. 

In the impinging streams of gas-liquid systems, high relative velocity between phases and collision between droplets favor surface renewing of droplets, resulting in reduced liquid film resistance and thus increased overall mass transfer coefficient. 

Lactic acid can be produced from a petrochemical route or from fermentation (6,7). The petrochemical route can only produce racemic mixtures of lactic acid, whereas fermentation canproduce optically pure isomer. D(-)-Lactic acid is toxic and must be limited in animal feeds (8), and an optically pure lactic acid is required to produce a specific PLA (9). In addition, fermentation utilizes renewable resources thatmake fermentationmore attractive than the petrochemical route. Extractive fermentation, which couples fermentation with on-line product removal, can eliminate end product inhibition and increase product yield, final product concentration, and reactor productivity. A number of extractive fermentation methods have been reported in the literature, including solvent extraction (10-12), precipitation (13), electrodialysis (14,15), adsorptionby ion-exchange resin (16-18), and an aqueous two-phase system (19-20). 

Although they can extend the substrate scope, these modified systems use more expensive bases and oxidants than the original conditions. In 2004, the triphasic system saw renewed interest when Geller and co-workers found that the addition of a phase-transfer catalyst allows much faster reactions without the induction period otherwise needed for catalyst activation, and far lower quantities of base and... 

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