Hydrodynamics circulation

Passive safety systems based on natural circulation are intended to provide the ultimate heat sink in cases of failure of the normal operation of the reactor cooling system. Because of its critical importance, fundamental understanding of the properties and characteristics of namral-circulation hydrodynamics, thermal responses, and thermodynamics in the complex engineering equipment of nuclear reactor power systems is essential. For the Gen IV systems that are based on natural circulation at normal operating states the properties and characteristics under steady-state conditions must also be well understood. 

Yet anotlier example of SD is provided by tire leukocytes which are constantly circulating in tire bloodstream but do not nonnally interact witli tissue. Venules of inflamed and infected tissue are dilated, however, which changes tire hydrodynamic regimen and allows some leukocytes to come into contact witli tire venule wall (endotlielium)... 

To evaluate the flow pattern efficiency, a knowledge of the actual hydrodynamic behavior of the process gas circulating in the centrifuge is necessary. Primarily because of the lack of such knowledge, the flow pattern efficiency has been evaluated for a number of different assumed isothermal centrifuge velocity profiles. 

It is generally tme to say that, as speed increases, the oil viscosity decreases, that is, if hydrodynamic conditions exist. Relatively low viscosity oil will allow the oil to spread rapidly over the tooth surfaces before meshing and, in the case of forced lubrication, ease circulation. In the case of bath lubrication, it will eliminate the oil drag effect. 

Gas holdup and liquid circulation velocity are the most important parameters to determinate the conversion and selectivity of airlift reactors. Most of the reported works are focused on the global hydrodynamic behavior, while studies on the measurements of local parameters are much more limited [20]. In recent years, studies on the hydrodynamic behavior in ALRs have focused on local behaviors [20-23], such as the gas holdup, bubble size and bubble rise velocity. These studies give us a much better understanding on ALRs. 

Hydrodynamics, Heat and Mass Transfer in Inverse and Circulating Three-Phase Fluidized-Bed Reactors for WasteWater Treatment... 

Recent research development of hydrodynamics and heat and mass transfer in inverse and circulating three-phase fluidized beds for waste water treatment is summarized. The three-phase (gas-liquid-solid) fluidized bed can be utilized for catalytic and photo-catalytic gas-liquid reactions such as chemical, biochemical, biofilm and electrode reactions. For the more effective treatment of wastewater, recently, new processing modes such as the inverse and circulation fluidization have been developed and adopted to circumvent the conventional three-phase fluidized bed reactors [1-6]. 

To provide the pr equisite knowledge for designing the three-phase fluidized-bed reactors with new modes, the hydrodynamics such as phase holdup, mixing and bubble properties and heat and mass transfer characteristics in the reactors have to be determined. Thus, in this study, the hydrodynamics and heat and mass transfer characteristics in the inverse and circulating three-phase fluidized-bed reactors for wastewater treatment in the present and previous studies have been summarized. Correlations for the hydrod3aiamics as well as mass and heat transfer coefficients are proposed. The areas wherein future research should be undertaken to improve... 

Orally administered dosage forms are absorbed into the systemic circulation following dissolution in the GI tract. Because substances must be in solution for the absorption from the GI lumen, the absorption rate of poorly water-soluble drugs is limited by their rate of dissolution. The dissolution rate is affected by the unique physicochemical properties of the drug and by physiological factors the pH, composition, and hydrodynamics of the GI medium. 

Small, properly scaled laboratory models operated at ambient conditions have been shown to accurately simulate the dynamics of large hot bubbling and circulating beds operating at atmospheric and elevated pressures. These models should shed light on the overall operating characteristics and the influence of hydrodynamics factors such as bubble distribution and trajectories. A series of different sized scale models can be used to simulate changes in bed behavior with bed size. 

Arena, U., Cammarota, A., Massimilla, L., and Pirozzi, D., The Hydrodynamic Behavior of Two Circulating Fluidized Bed Units of Different Size, Circulating Fluidized Bed Technol. 11, (P. Basu, and J. F. Large, eds.), Pergamon Press, Oxford (1988)... 

Glicksman, L. R., Hyre, M., Torpey, M., and Wheeldon, J., Verification of Simplified Hydrodynamic Scaling Laws for Pressurized Fluidized Beds Part II Circulating Fluidized Beds, Proc. 13th Int. Conf. for Fluidized Bed Combustion, ip. 991 (1995)... 

Tsukada, M., Nakanishi, D. Takei, Y., Ishii, H., and Horio, M., Hydrodynamic Similarity of Circulating Fluidized Bed under Different Pressure Conditions, Proc. llthlnt. Conf. Fluidized Bed Comb., p. 829(1991)... 

The solids circulation pattern and solids circulation rate are important hydrodynamic characteristics of an operating jetting fluidized bed. They dictate directly the solids mixing and the heat and mass transfer between different regions of the bed. 

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