Wall effects
In practice, the influence of the confining walls on the fluid flow will be
significant only when the ratio of the particle to container diameters is less than
about 30 [Cohen and Metzner, 1981]. Particles will pack less closely near the
wall, so that the resistance to flow in a bed of smaller diameter may
5.6.4 Effect of particle shape
The voidage of a bed of particles is strongly influenced by the particle shape,
orientation and size distribution. However, voidage correlates quite well with
sphericity, as shown in Figure 5.9; values of sphericity for different shape
particles have been compiled by Brown et al. [1950] and German [1989]
amongst others.
For beds of spheres of mixed sizes, the voidage can be significantly less
if the smaller size spheres can fill the voids between the larger ones. In general,
the voidage of a bed of mixed particles is a function of the volume fractions f
of each particle size and the ratio of the sizes. Hence, for a binary-size particle
system, the mean voidage of the bed will be a function of d1=d2 and f1, f2,
and the curves of " versus .d1=d2/ and f1=f2 will pass through minima. Some
predictive expressions for voidage of beds of binary and ternary spherical and
non-spherical particle systems are available in the literature [Yu et al. 1993;
Yu and Standish; 1993]
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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