Flow distortion

Inlet Piping Configurations. An incorrect piping configuration can create undesirable flow distortions that, especiaUy for double-suction pumps, means turbulence. Air pockets trapped in the pipe can cause uneven flow, vibrations, and pump damage. 

Flow distortion Nonuniform airstream velocity profile due to asymmetric... 

Figure 7.2.5 provides a visualization of a localized extinction event in a turbulent jet flame, using a temporal sequence of OH planar LIF measurements. The OH-LIF measurements, combined with particle image velocimetry (PIV) reveal that a distinct vortex within the turbulent flow distorts and consequently breaks the OH front. These localized extinction events occur intermittently as the strength of the coupling between the turbulent flow and the flame chemistry fluctuates. The characteristics of the turbulent flame can be significantly altered as the frequency of these events increases. 

Fig. 7. Schematic representation of laminar flow distortion due to the presence of isolated particles (left) and the corresponding effect at higher concentration when the perturbed flow flelds start to overlap (right). The latter effect causes the hydrodynamic interaction...

A fast chemical sensor that operates at a reduced pressure of 50 torr (6700 Pa) and with a flow of 1 standard liter per minute must be maintained in an instrument shelter. Considerations of flow distortion require that 10 m separate the sensor from its intake on the tower near the sonic anemometer. Three ducting arrangements can be considered. The first would involve drawing air along 10 m of 1/4-inch tubing (0.2 cm internal radius) and controlling the flow and pressure at the sensor itself. The second option would place the pressure-flow controller at the inlet and allow the inlet intake to flow at the reduced pressure. The third course would be to use a... 

Gay (G2), 1958 Experimental study of interfacial drag between liquid surface (nearly horizontal) and air stream flowing over it (co- or counter-flow). Distortion of gas stream profiles by rough liquid surface determination of effective surface roughness. 

Two or more of these conditions can occur at the same time, resulting in asymmetric axial, radial and tangential velocity vectors. Some flowmeters are more sensitive than others to particular types of flow distortion, e.g. orifice meters are affected by pure swirl more than venturi meters are magnetic flowmeters are unaffected by changes in the radial velocity component whereas ultrasonic time-of-flight meters are highly susceptible thereto swirl and asymmetry have the least effect on positive displacement meters and the greatest effect on variable area meters. 

The mass-transfer rate is slow in CIEC. By increasing temperature this parameter is sizably enhanced and the rate of ion exchange becomes more rapid. The increase in temperature, however, may cause the evolution of gas bubbles from the solution and result in their entry into column systems. The gases are formed in chemical reactions and are due to the air dissolved in the solutions employed. They can influence the stability of fluid flow, distort the bandshape, and even promote the formation of cavities in the exchange bed, thereby disturbing the separation process. Because the bubbles rise while the fluid flow is down in a column, it is difficult to remove these bubbles in CIEC. 

Accurate predictions of the shell-side heat transfer coefficient and pressure drop are difficult because of the complex geometry and resulting flow patterns. A number of correlations are available, none of which is as accurate as those above for the tube side. All are based on crossflow past an ideal tube bank, either staggered (triangular pitch pattern) or inline (square pitch pattern). Corrections are made for flow distortion due to baffles, leakage, and bypassing. From 1950 to 1963, values of h , the shell-side, convective heat transfer coefficient, were most usually predicted by the correlations of Donohue (1949) and Kern (1950), which are suitable for hand calculations. Both of these correlations are of the general Nusselt number form... 

MSRs are particularly sensitive to flow distortion as a result of tracer injection. 

Flow distortions pose a limitation on the production rate. 

Formulation UL94 V Rating (3.2 mm) Heat Melt Flow Distortion Index (MFI) Temperature (5 kgl230°C) (°C) (g/10 min) Notched Izod Impact (ASTM D256) (JItn)... 

Physically, Fd and Fp represent the effect of flow distortion caused by the flight edges. 

The presence of electrical charges on the surface of particles leads to extra energy dissipation due to flow distorting of the surroimding charge cloud. Von Smouluchowski accoimted for the effect mathematically as... 

In this section we discuss electrohydrodynamic (EHD) instabilities, that is electric-field-induced phenomena that are caused by the flow of a liquid crystal (see also [8,219]. The reason for the flow is electrical conductivity, which has been disregarded in previous sections. The flow may arise either independently of the anisotropic properties of substance, as in isotropic liquids (isotropic modes of the electrohydrodynamic instability), or may be driven by the conductivity anisotropy, as in liquid crystals (anisotropic modes). The threshold for EHD instabilities depends on many parameters, such as the electrical and viscoelastic properties of substance, the temperature, and the applied field frequency. Due to flow distortion of the director alignment, the instability is usually accompanied by a characteristic optical... 

It would be of interest to find out the role (if any) of backmixing in nondispersive porous membrane based solvent extraction devices. Here, only the shell-side liquid phase can encounter backmixing, or, more correctly, bypassing and channeling. Simple countercurrent devices often display such flow behavior. However, the baffled construction with radial flow illustrated in Figure 8.1.35(f) is thought to be generally free of such flow distortions. 

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