Profile Effects

One of the common problems associated with underwater pelletizers is the tendency of the die holes to freeze off. This results in nonuniform polymer melt flow, increased pressure drop, and irregular extrudate shape. A detailed engineering analysis of pelletizers is performed which accounts for the complex interaction between the fluid mechanics and heat transfer processes in a single die hole. The pelletizer model is solved numerically to obtain velocity, temperature, and pressure profiles. Effect of operating conditions, and polymer rheology on die performance is evaluated and discussed. 

Detailed modelling of the fixed bed production of phthalic anhydride from o-xylene is discussed by Froment and Bischoff (1990), involving both axial and radial temperature profile effects. 

The velocity profile effect—For a convex flow velocity profile, for instance, in a steady bubbly flow, the centerline velocity is higher than the average velocity. With bubbles usually concentrating at the center, they attain a higher velocity than the liquid. 

Normal reaction Reaction profile Effect of change Gas evolution Bench-scale reactors (e.g., RC1)... 

Temperature control, 93,194 Temperature profile, effect viscous dis-sipatioo,267... 

Dispersion models, as just stated, are useful mainly to represent flow in empty tubes and packed beds, which is much closer to the ideal case of plug flow than to the opposite extreme of backmix flow. In empty tubes, the mixing is caused by molecular diffusion and turbulent diffusion, superposed on the velocity-profile effect. In packed beds, mixing is caused both by splitting of the fluid streams as they flow around the particles and by the variations in velocity across the bed. 

Velocity Profile Effects Many variables can influence the accuracy of specific flow measurement methods. For example, the velocity profile in a closed conduit affects many types of flow-measuring devices. The velocity of a fluid varies from zero at the wall and at other stationary solid objects in the flow channel to a maximum at a distance from the wall. In the entry region of a conduit, the velocity field may approach plug flow and a constant velocity across the conduit, dropping to zero only at the wall. As a newtonian fluid progresses down a... 

Brandt, W. and Paulin, R. (1977). Positron implantation profile effects in solids. Phys. Rev. B 15 2511-2518. 

The orthogonal collocation polynomial approximation using a single parameter trial function was employed to solve equations (l)-(3), In addition to the solution for time concentration and activity profiles, effectiveness factors representing the combined effect of mass transfer resistance and poisoning in terms of pellet surface conditions were computed according to... 

For transporters, relatively low protein expression level and limited transport capacity makes for nonlinear, enzyme-like transport kinetics that is, the transport rate saturates with increasing substrate concentration. This phenomenon is the basis for the competitive interactions generally found for chemicals that are handled by one or more common transporters this is usually manifest as inhibition of the transport of one chemical by a structural analog. The extent to which these competitive interactions are important depends on the concentrations of the chemicals involved, their relative affinities for the common transporter, and their phar-macological/toxicological profiles (effects, effective concentrations, therapeutic index). Competition for transport is discussed below in the context of drug-drug interactions. 

Byun KM, Kim S J, Kim D (2006) Profile effect on the feasibihty of extinction-based localized surface plasmon resonance biosensors with metallic nanowires. Appl Opt 45 3382-3389... 

Deactivation of large-pore slab catalysts where intraparticle convection, diffusion and first order reaction are competing mechanisms was analyzed by uniform and shelLprogressive models. For each situation, analytical solutions for concentration profiles, effectiveness factor and enhancement factor due to convection were developed thus providing a sound basis for steady-state reactor design. 

The Tobata pilot plant has been conducting experiments since 1974, The gas processing system was of the inflammable gas recovery type originally, but later modified to permit operation on the direct combustion principle, also. At present, the system is operated mostly using the latter method. Using this pilot plant, basic, comparative studies have been made on the furnace profile, effects of the properties of wastes and the oxygen concentration in the blast, the need for supplementary fuel, and how to process the product gas. 

The presence of hollows in cooked rice grains was additionally confirmed for four more cultivars Koshihikari with various amylose contents."" The size, shape and total volume of hollows differed between cultivars. The hypothetical model for the formation of hollows has not been proved experimentally. NMR microimaging was used to determine moisture distribution in boiled Japanese noodles (udon) made from different varieties of wheat.The T2 profile of a piece of boiled udon was monitored in time course measurements during and after boiling. Water permeation from the surface to the core was evaluated by the T2 profile. Effect of moisture distribution on texture of boiled Japanese noodles was discussed. 

Method B. Very few molecules exhibit dramatic fluoresence dynamics of the type observed for 3HF. In most cases the observed effects are more subtle, involving a slight time-dependent variation in the fluorescence band profile. Effects of this type can be due to vibrational relaxation, solvent relaxation and torsional relaxation. 

Summary Screen Tabulated Results Conversion Profile Temperature Profile NH3 Concetration Profile N2 Concetration Profile Effectiveness Factor H2 Concentration Profile CHA Con centrotion Profile Ar Concentration Profile Write Output to File New Problem Exit Program... 

Figure 5-21 shows the coal/oil slurry velocity derived from the peak of the correlation function plotted against the velocity measured by flow diversion. The flow diversion gives basically the mass flow rate divided by density to give the volumetric flow rate and then the flow velocity. The data can be fitted by two linear relationships with slopes of 1.16 and 1.55, corresponding to meter factors of 0.86 and 0.64. The meter factor may be directly related to the flow profile effect (Sheen et al., 1985). 

In conclusion, the capacitive mass flowmeter can be a reliable instrument for measuring the flow of dilute suspended solids. For the flow of high concentrations of suspended solids, the velocity measurement becomes inaccurate. The inaccuracy may be caused by the velocity profile effect, but further study is required to confirm the observation. 

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