Impingement plane

Relative velocity between particles and the opposite gas flow is greatly increased. The relative velocity round the impinging plane, may be calculated roughly by... 

In addition, according to the feature and number of impingement planes, devices can also be classified as stationary, moving, and multi impingement zone, etc. Readers may refer to Ref. [5]. 

Figures 1.6(c) and (d) show the pressure profile in the impinging streams. The profile is characterized by the considerable pressure gradients in the direction of the chamber axis, as shown in Fig. 1.6(c), and also in the perpendicular plane, as shown in Fig. 1.6(d). Obviously, in the region a little distance away from the impingement plane, the pressure profile is independent of the impinging distance. A decrease in the impinging distance leads to a more rapid increase in pressure only in the impingement zone.

Figure 1.9 Maxi mum static pressure vs impinging distance at the center of impingement plane.

Figure 2.9 shows part of the results Elperin et al. obtained for the axial relative concentrations profile of silica gel particles. The major feature of this distribution is that the concentration sharply increases towards the impingement plane and the value near the impingement plane can be as high as 20-28 times the concentration in the feeding stream. This is mainly accounted for by the penetration of particles to and fro... 

Consider the impingement between two opposed particles-gas suspension streams from accelerating tubes of the same diameter. The assumptions made in the establishment of the model are (1) The streams are symmetrical with respect to both the jet axis and the impingement plane (2) The gas flow velocity and all the physical properties of gas and solid are kept constant and (3) The particles beyond collision penetrate into the opposing stream up to. rlllas, while any particle will be drawn out of the system immediately once it collides with another particle. 

Let Z0 denote the initial number of particles crossing the impingement plane and penetrating into the opposing stream at r = 0. Due to collision, the number of particles is reduced by dZ within the time interval dr. The reduction of particle number is assumed to obey the first-order kinetics, that is... 

If it is assumed that the particles have performed one complete oscillation, the particle crossing the impingement plane may collide with the following particles ... 

Figure 5.1 Impinging stream device for the measurement of droplet size distribution. 1 critical nozzle 2, 3 rotameter 4 frame 5 guider 6 apron A-A impingement plane.

As mentioned earlier, in gas-continuous impinging streams heat and mass transfer between phases are enhanced efficiently mainly by the following factors (1) Very high relative velocity between phases round the impingement plane, even higher than in common devices by several tens of times (2) Oscillation movement of particles or... 

It can be seen in Fig. 10.2 that the flow in the SCISR is in mirror symmetry with respect to the impingement plane, and also approximately in axial symmetry so it is enough to take a half volume of the SCISR, either on the right or the left side, into account in the analysis. 

In order to understand the profile of the pressure fluctuation over the volumetric space inside the reactor, multipoint measurement is carried out in each run with five probes. The measuring points are arranged according to the coordinate system shown in Fig. 11.3, where the x-z plane is the impingement plane, x-y is the horizontal plane, and y-z the vertical plane the values of the coordinates are in mm. The flow inside the SCISR is considered to have an approximately axial symmetry. For convenience, part of the data are interrelated in a pillar coordinate system, and the radial coordinate, r, is determined by... 

However, the experimental results are completely unexpected. The profiles of PSn on the horizontal and the vertical planes measured at an impinging velocity of n0 = 0.1 m s"1 are shown in Figs. 11.4 and 11.5 and those on the impingement plane and its parallel planes in Fig. 11.6. 

As can be expected, the intensive fluctuation region is symmetrical with respect to the impingement plane, provided the two streams leaving the drawing tubes are at the same velocity. This is simply because the two sides of the reactor have the same structure. In addition, the figures also show that the region is essentially symmetrical about the flow axis, suggesting that the above assumption is reasonable. 

The intensive fluctuation region is concentrated between the outlets of the drawing tubes and around the flow axis, and takes the form of a couple of truncated cones with an empty core and with coinciding bottoms. The region is symmetrical with respect to both the impingement plane and the axis of the streams and is essentially independent of nn. The space surrounded by the external surface of the cones is defined as the impingement zone. 

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