Semicircular impinging streams

Figure 5.5 shows the principle of semicircular impinging streams in which a primary gas stream is split equally into two secondary streams flowing inside two ducts bent to form semicircular channels. In this case, the flow of the drying material (and, to a smaller extent, the flow of the carrying gas) is affected by centrifugal forces, which might reduce the thickness of the boundary layer at the solid surface. 

Figure 5.3 Basic types of impinging-stream flows a) coaxial b) mutually perpendicular X conflguration c) curvilinear countercurrent d) semicircular impinging streams ( chain configuration ) e) counterrotating countercurrent f) co-rotating countercurrent.

Figure 5.5 Particle trajectory for double penetration in a semicircular impinging streams (F = centrifugal force Fg, = centripetal force Fo = drag force F = lift force).

Dengying L, Xiulan H, Zuyi, L, Qun M, Xiaoming C. Experimental investigation on the flow and drying characteristics of two stage semicircular impinging stream dryer. Proc Asian-Australian Drying Conference, Bali, Indonesia, 1999, pp 652-659. 

FIGURE 20.36 Semicircular impinging stream dryer (Vortex spray dryer, 0.8/1.2 type) for thermal processing of grains in superheated steam. 

Semicircular Impinging Stream Dryers for Drying/Puffing of Grains... 

There are another configurations of IS such as a semicircular IS, two and four IS, and a variety of multistage and combined systems [3,47]. One of such systems that combines coaxial IS and curvilinear IS and allows particle segregation and recycling of oversize (wet) particles into impinging streams is shown in Figure 21.31. 

More information on other types of industrial dryers with impinging streams can be found in open literature (Kudra et al., 1995, Tamir, 1994). These are the semicircular configuration developed for thermal processing of grains in superheated steam (e.g., drying, puffing, and carrying out certain... 

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