Agitation defined

The diffusion layer widtli is very much dependent on tire degree of agitation of tire electrolyte. Thus, via tire parameter 5, tire hydrodynamics of tire solution can be considered. Experimentally, defined hydrodynamic conditions are achieved by a rotating cylinder, disc or ring-disc electrodes, for which analytical solutions for tire diffusion equation are available [37, 4T, 42 and 43]. 

Phosphorus(III) Oxide. Phosphoms(III) oxide [12440-00-5] the anhydride of phosphonic acid, is formed along with by-products such as phosphoms pentoxide and red phosphoms when phosphoms is burned with less than stoichiometric amounts of oxygen (62). Phosphoms(III) oxide is a poisonous, white, wax-like, crystalline material, which has a melting point of 23.8°C and a boiling point of 175.3°C. When added to hot water, phosphoms(III) oxide reacts violentiy and forms phosphine, phosphoric acid, and red phosphoms. Even in cold water, disproportionation maybe observed if the oxide is not well agitated, resulting in the formation of phosphoric acid and yellow or orange poorly defined polymeric lower oxides of phosphoms (LOOP). 

A defining characteristic of dyes is the abiUty to dissolve in a given medium. Dissolution leaves no particles to refract or scatter light and thus a dye solution is transparent. A distinct advantage of a soluble-type stain is this transparency and brightness afforded by use of various dye types. SolubiUty is increased by agitation or heat, or a combination of the two. 

The deposition of ions at the cathode creates a depletion layer across which the ions must migrate in order to deposit. This layer can vary in thickness according to surface morphology. The depletion layer is more or less defined as the region where the ion concentration differs from that of the bulk solution by >1%. The layer thickness can be decreased by agitation. 

Description An agitated dryer is defined as one on which the housing enclosing the process is stationaiy while solids movement is accomplished by an internal mechanical agitator. Many forms are in use, including batch and continuous versions. 

An equihbrium, or theoretical, stage in liquid-liquid extraction as defined earlier is routinely utilized in laboratory procedures. A feed solution is contacted with an immiscible solvent to remove one or more of the solutes from the feed. This can be carried out in a separating funnel, or, preferably, in an agitated vessel that can produce droplets of about 1 mm in diameter. After agitation has stopped and the phases separate, the two clear liquid layers are isolated by decantation. 

Phase Dispersed There is an ill-defined upper limit to the volume fraction of dispersed liquid which may be maintained in an agitated dispersion. For dispersions of organic liquids in water [Quinn and Siglon, Can.J. Chem. Eng., 41, 15 (1963)],... 

Once a plant is built, the conditions of agitation, aeration, oxygen transfer, and heat transfer are more or less set, and sterilization cycles are defined. Those environmental conditions achievable in plant-scale equipment should be scaled down to the pilot plant and laboratoiy equipment (shaken flasks) to insure that results can be translated. 

This form is partieularly appropriate when the gas is of low solubility in the liquid and "liquid film resistanee" eontrols the rate of transfer. More eomplex forms whieh use an overall mass transfer eoeffieient whieh ineludes the effeets of gas film resistanee must be used otherwise. Also, if ehemieal reaetions are involved, they are not rate limiting. The approaeh given here, however, illustrates the required ealeulation steps. The nature of the mixing or agitation primarily affeets the interfaeial area per unit volume, a. The liquid phase mass transfer eoeffieient, kL, is primarily a funetion of the physieal properties of the fluid. The interfaeial area is determined by the size of the gas bubbles formed and how long they remain in the mixing vessel. The size of the bubbles is normally expressed in terms of their Sauter mean diameter, dj, whieh is defined below. How long the bubbles remain is expressed in terms of gas hold-up, H, the fraetion of the total fluid volume (gas plus liquid) whieh is oeeupied by gas bubbles. 

A common process task involves heating a slurry by pumping it through a well-stirred tank. It is useful to know the temperature profile of the slurry in the agitated vessel. This information can be used to optimize the heat transfer process by performing simple sensitivity studies with the formulas presented below. Defining the inlet temperature of the slurry as T, and the temperature of the outer surface of the steam coil as U then by a macroscopic mass and energy balance for the system, a simplified calculation method is developed. 

Note that this equation holds for any component in a multi-component mixture. The integral on the right-hand side can only be evaluated if the vapor mole fraction y is known as a function of the mole fraction Xr in the still. Assuming phase equilibrium between liquid and vapor in the still, the vapor mole fraction y x ) is defined by the equilibrium curve. Agitation of the liquid in tire still and low boilup rates tend to improve the validity of this assumption. 

Figure 7-15 shows plots of Pumping number Nq and Power number Np as functions of Reynolds number Np for a pitched-blade turbine and high-efficiency impeller. Hicks et al. [8] further introduced the scale of agitation, S, as a measure for determining agitation intensity in pitched-blade impellers. The scale of agitation is based on a characteristic velocity, v, defined by... 

Mixing of fluids is necessary in many chemical processes. It may include mixing of liquid vith liquid, gas with liquid, or solids with liquid. Agitation of these fluid masses does not necessarily imply any significant amount of actual intimate and homogeneous distribution of the fluids or particles, and for this reason mixing requires a definition of degree and/or purpose to properly define the desired state of the system. 

Because the most common impeller type is the turbine, most scale-up published studies have been devoted to that unit. Almost all scale-up situations require duplication of process results from the initial scale to the second scaled unit. Therefore, this is the objective of the outline to follow, from Reference [32]. The dynamic response is used as a reference for agitation/mixer behavior for a defined set of process results. For turbulent mixing, kinematic similarity occurs with geometric similarity, meaning fixed ratios exist between corresponding velocities. 

Gas hold-up is defined as Ha = Bubble volume/Reactor volume, which is the volume of gas per unit volume of reactor. Assume the system is an agitated vessel. Let us use Richard s data to define gas hold-up 3... 

Power is defined for a well-agitated vessel with a mechanical stirrer then read power number for turbulent flow from Figure 6.6, Chapter 6 ... 

Roy et al. (R3) define the critical solids holdup as the maximum quantity of solids that can be held in suspension in an agitated liquid. They present measurements of this factor for various values of gas velocity, gas distribution, solid-particle size, liquid surface tension, liquid viscosity, and a solid-liquid wettability parameter, and they propose the following two correlations in terms of dimensionless groups containing these parameters ... 

A Reynolds number for the bubble flow which represents the term for agitation may be defined as ... 

The above analysis is restricted to high Reynolds numbers, although the definition of high is different in a stirred tank than in a circular pipe. The Reynolds number for a conventionally agitated vessel is defined as... 

The shear rate between liquid layers moving at the average velocity is an important factor in macroscale processes involving large blobs. The velocity fluctuations are responsible for microscale processes of homogenization at the molecular level. The data for turbine agitators show that the mean velocity fluctuation, defined as... 

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