Constriction coefficient

We begin by computing the entrance constriction coefficient a for a conventional slot-type inlet from the empirical formula ... 

As was the case for gas-solids cyclones, we begin by computing the entrance constriction coefficient, a, from Eq. (6.1.1). If, as is often the case for vapor-liquid cyclones, the entrance duct is a circular pipe, the width variable, b,... 

In conventional tangential inlet cyclones the swirl velocity near the wall is determined by the entrance duct velocity Cj , and an entrance constriction coefficient. In swirl tubes, it is mostly determined by the velocity exiting the... 

Flow Nozzles. A flow nozzle is a constriction having an eUiptical or nearly eUiptical inlet section that blends into a cylindrical throat section as shown in Figure 8. Nozzle pressure differential is normally measured between taps located 1 pipe diameter upstream and 0.5 pipe diameters downstream of the nozzle inlet face. A nozzle has the approximate discharge coefficient of an equivalent venturi and the pressure drop of an equivalent orifice plate although venturi nozzles, which add a diffuser cone to proprietary nozzle shapes, are available to provide better pressure recovery. 

Sparrow, E. M., and Kalejs, J. P. (1977). Local convective transfer coefficients in a channel downstream of a partially constricted inlet. Int. ]. Heat Mass Transfer 20, 1241-1249. 

Trinh et al. [399] derived a number of similar expressions for mobility and diffusion coefficients in a similar unit cell. The cases considered by Trinh et al. were (1) electrophoretic transport with the same uniform electric field in the large pore and in the constriction, (2) hindered electrophoretic transport in the pore with uniform electric fields, (3) hydrodynamic flow in the pore, where the velocity in the second pore was related to the velocity in the first pore by the overall mass continuity equation, and (4) hindered hydrodynamic flow. All of these four cases were investigated with two different boundary condi-... 

Antidiuretic hormone promotes the reabsorption of water from the tubules of the kidney, or antidiuresis. Specifically, it acts on the collecting ducts and increases the number of water channels, which increases the diffusion coefficient for water. This results in the body s conservation of water and the production of a low volume of concentrated urine. The reabsorbed water affects plasma osmolarity and blood volume. This effect of ADH on the kidney occurs at relatively low concentrations. At higher concentrations, ADH causes constriction of arterioles, which serves to increase blood pressure. Antidiuretic hormone secretion is regulated by several factors ... 

Faraday s constant (96,487 C/mol) overpotential total current current density exchange current density ratio of ohmic constriction to inter-facial resistance surface exchange coefficient volume-specific interfacial resistance in a composite thickness utilization length characteristic length of a porous microstructure... 

For nebulizers and MDIs, the external resistance (Re) is quite low. Different approaches have been made to describe the external airflow resistance of DPIs. Olsson and Asking [99] derived an empirical relationship between flow rate () and pressure drop (AR), AR = for a number of inhalers (such as Rotahaler , Spinhaler and Turbuhaler ) in which they define the proportionality coefficient (C) as the airflow resistance. This relationship differs only slightly from the general (theoretical) equation for orifice types of flow constrictions ... 

These calculations were done using the typical thickness of a washcoated SCT substrate ( 7 micron) and the effective diffusivity based on the diffusion coefficient (4.148 x 10 m s ) calculated for a real gas matrix and taking representative values of the tortuosity (3.0), porosity (0.4) and constriction (0.8) factors. 

Coefficients of discharge for square-edged orifices with centered circular openings and for rotameters. (Subscript 0 indicates at orifice or at constriction and subscript 1 indicates at upstream... 

When this result is substituted into equation 7, one obtains the extended evolution equation of Radke and Gauglitz (7) for a straight channel of radius r, the constriction neck radius. If surfactant is present the flow coefficient is... 

The flow coefficient of the square constriction cannot be solved analytically. It was determined numerically by the solution of equation 3 for the geometry shown in Figure 4. The geometry in figure 4 is mapped into a rectangle and the problem is solved with a Galerkin spectral technique. The relation between the flow coefficient and interface position is shown in Figure 5 for the surfactant free system. 

From the linear stability analysis one can de ce the effect of the aspect ratio on the snap-off frequency. Let Cq be a locally scaled through radius. Here the characteristic length is the hydraulic radius of the channel at the point snap off occurs. If one assumes that this radius is nearly the constriction neck radius than the flow coefficient may be expressed in terms of the locally scaled thread radius as... 

This derivation neglects the correction of kinetic energy loss due to nonuniformity of flow in both cross sections and the frictional degradation of energy during passage through the constriction. This is corrected by the introduction of a numerical coefficient, Cd ... 

Since diffusion of the electrons and ions tends to spread the discharge radially, one expects that constriction effects will set in at higher pressures for gases which have larger ambipolar diffusion coefficients as is observed (39, 40) for helium relative to the other rare gases. 

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