Vortex Tube Outer Surface

Erosion of the outer surface of the gas outlet tube or vortex finder can occur from several possible causes and we will briefly discuss each of these below. Perhaps the most obvious cause is direct impaction, which can occur if any part of the vortex finder lies in the projected path of the particles entering the cyclone. See Fig. 12.1.3a. As shown in Fig. 12.1.3b, the incoming gas can be expected to constrict, either due to the geometry or due to the effect of the gas already rotating in the cyclone and flow around the gas outlet tube. But this is not always the case for the solids. 

Equipping the cyclone with an inlet scroll or decreasing the width of the inlet duct, as shown in Figs. 12.1.3c and 12.1.3d, are two common ways of preventing the particular problem shown in Fig. 12.1.3a. In the latter case, the height of the inlet may be increased in proportion to the decrease in inlet width if one wishes to maintain the same inlet velocity. In some instances, it may be possible to decrease the diameter of the vortex tube or increase the barrel diameter to avoid the interference. It may even be possible to install two smaller inlets, spaced 180° apart, as per Fig. 12.1.3e. Helical roof designs 

One of the most interesting aspects of the flow shown in Fig. 12.1.3b, and another potiential cause of vortex tube erosion, is the very abrupt change in flow direction at the location where gas that has already entered the cyclone circles around and encounters the incoming gas stream. In the detailed plan view shown in Fig. 12.1.4, this is seen to occur at about the 2 30 clock position. It is here that the gas that is abont to complete its first revolntion within the 

One might also expect that any such abrupt collision and deflection of the solids-bearing gas stream would have a negative impact on separation performance. However, according to Funk and Hughs (2000), just the opposite may be true. They report. 

In the plan view of the cyclone streamlines, air makes one revolution in the barrel of the cyclone, then makes an abrupt change in direction near the entrance (where it collides with incoming air). This forces the dust-laden air to make a tight turn inward and downward. The fact that the air is leaving the dust behind at that point appears to be more important to cyclone efficiency than the fact that the dust 

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There are also vortex coolers. Compressed air passes from a tube or pipe into a chamber that causes the air to spin in a vortex. The temperature of the air along the outer surface of the vortex drops as a result of rotation. Bleeding off the outer air can provide a significant amount of cooling capacity with little cost. 

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