A critical review of the published literature regarding the computational fluid dynamics (CFD) modelling of single-phase turbulent flow in stirred tank reactors is presented. In this part of review, CFD simulations of radial flow impellers (mainly disc turbine (DT)) in a fully baffled vessel operating in a turbulent regime have been presented. Simulated results obtained with different impeller modelling approaches (impeller boundary condition, multiple reference frame, computational snap shot and the sliding mesh approaches) and different turbulence models (standard k − e model, RNG k − e model, the Reynolds stress model (RSM) and large eddy simulation) have been compared with the in-house laser Doppler anemometry (LDA) experimental data. In addition, recently proposed modifications to the standard k − e models were also evaluated. The model predictions (of all the mean velocities, turbulent kinetic energy and its dissipation rate) have been compared with the experimental measurements at various locations in the tank. A discussion is presented to highlight strengths and weaknesses of currently used CFD models. A preliminary analysis of sensitivity of modelling assumptions in the k − e models and RSM has been carried out using LES database. The quantitative comparison of exact and modelled turbulence production, transport and dissipation terms has highlighted the reasons behind the partial success of various modifications of standard k − e model as well as RSM. The volume integral of predicted energy dissipation rate is compared with the energy input rate. Based on these results, suggestions have been made for the future work in this area.

CFD simulation of stirred tanks: Comparison of turbulence models. Part I: Radial flow impellers

Influence of the management strategy and operating conditions on the performance of an adsorption chiller

Water vapor adsorption kinetics on small and full scale zeolite coated adsorbers; A comparison

Adsorption chilling driven by low temperature heat: New adsorbent and cycle optimization

The plant canopy-atmosphere exchanges of heat, water vapor, carbon dioxide, and other trace materials are critical topics in plant biometeorology. Evapotranspiration and the ecosystem-atmospheric carbon balance are two ubiquitous examples of plant canopyatmosphere exchange. Therefore, the development and refinement of practical and inexpensive measurement and estimation techniques of such canopy-atmosphere exchanges is very important.

Surface Renewal Estimates of Scalar Exchange

In many polymer manufacturing processes, mass transfer operations between a high viscosity liquid and gases are applied, but mass transfer rates have been explained only using k L a. We measured k L for molten polystyrene and corn syrups by using a rotating cylinder with surface renewal action in which surface area was known. As a result, is proved that (1) k L between gases and high viscosity liquids are expressed by Hibgie's penetration theory, and (2) diffusivities are obtained from measurements of k L in corn syrup-CO 2 and glycerine-CO 2 systems.

Mass transfer between gases and high viscosity liquids on rotating cylinder with surface renewal action

There exists no universally accepted technique for evaluating the functional status of equipment for high-viscosity mixing based upon generalized basic information such as flow patterns and shearing deformation characteristics. This paper deals with the measurement of flow patterns. After obtaining the overall flow patterns in a mixing vessel, circulation capacity and fluid deformations which cover information about energy dissipation were correlated with the homogenizing time. The physical meanings of C1=nTM and C2=TM √Pυgc/μ are interpreted by using a concept of striation thickness. A measure of an averaged dimensionless shear rate number √Pυgc/μ/n is plotted against the dimensionless nearest distance between moving part and fixed wall in the mixing vessel. This diagram could give an useful comparison as to averaged shear rate characteristics for any device for high-viscosity mixing regardless of geometrical configuration. A novel technique is also proposed for quick evaluation of the shear distribution in a given apparatus.

Evaluation of performance of mixing apparatus for high viscosity fluids

PURPOSE:To enable extraction, filtration and drying of a particulate material to be carried out in the same apparatus by arranging a ribbon-style stirrer in a vertical conical vessel, by setting an outlet for the particulate material and a filter plate with a filter medium at the bottom parts of that vessel and by attaching a heating jacket to the outside periphery of that vessel. CONSTITUTION:In an example series of treatment which consist of extracting low MW substances in a polymer with a solvent, filtering off the solvent and then drying, first of all, the raw pellets and the solvent are charged into a vessel 1 through an inlet 7. Next, those pellets and solvent are agitated and mixed together to extract low MW substances by rotating a stirrer 3. A heating jacket 4 has a already been heated by passing a heat medium through it. When that low MW substances in the raw pellets has been extracted, a stop valve 21 is opened to separate the solid from the liquid with a filter 20 and the solvent dissolving that low MW substances is discharged out of the vessel 1. After the filtration, those pellets are dried at a reduced pressure by sucking out a gas with a vacuum pump while rotating the stirrer 3. After the drying is finished, a discharged value 8 for the product and a stop valve 13 are opened and the solid pellets are recovered.

Apparatus for mixing treatment

PURPOSE: To permit rubberlike substances to be ground into the fine particles of uniform diameter and the time required for the particles to dissolve in a solvent to be considerably reduced by cooling the rubberlike substance to a temperature not in excess of its glass transition temperature using a liquefied gas and thereafter grinding the same while maintaining its temperature at a value not in excess of the glass transition temperature. CONSTITUTION: A rubberlike substance is precooled in a refrigerator to a temperature nor in excess of its glass transition temperature using a liquefied gas such as liquid nitrogen and liquefied carbon dioxide gas. The rubberlike substance thus cooled is fed into a crusher and ground, while the liquefied gas is being supplied to maintain its temperature at a value not in excess of its glass transition temperature. The resulting particles are then sent into a stirring and dissolving tank, where they are mixed with a solvent and the mixture is stirred until the particles dissolve. This method permits a reduction in the size of the dissolving tank and a remarkable improvement of operational efficiency. COPYRIGHT: (C)1990,JPO&Japio

Dissolving of rubberlike substance

PURPOSE:To provide a process for producing a polyethylene terephthalate having high quality and polymerization degree without generating flow failure at a gas-liquid interface in polymerization reaction. CONSTITUTION:The polycondensation reaction after an esterification reaction is divided into a former-stage polycondensation step to get a polyethylene terephthalate having an intrinsic viscosity [eta] of 0.4-0.9dlambda/g and a latter-stage polycondensation step to get a polyethylene terephthalate having an intrinsic viscosity [eta] of 0.8-1.3dlambda/g. The latter-stage polycondensation is carried out by a stirring polymerizer having plural rotary shafts 12, 13 and stirring blades composed of paddles 21-26 and 31-36 perpendicularly attached to the rotary shafts interposing gaps in the direction of the shaft and scrapers 41-46 and 51-56 attached to the tip ends of the paddles and having a length nearly corresponding to the dimension of the gaps. The stirring blade has an L/D ratio of 2-10, preferably 4-8 wherein D is rotary diameter of the blade and L is the length of the blade in longitudinal direction.

Shimada Takafumi

Papers

Mass transfer between gases and high viscosity liquids on rotating cylinder with surface renewal action

Evaluation of performance of mixing apparatus for high viscosity fluids

Apparatus for mixing treatment

Dissolving of rubberlike substance

Production of polyethylene terephthalate having high polymerization degree