## Rotor Eff ciency

The time required for a particle to traverse a rotor is known as the pelleting efficiency or k-factor. The k- or clearing factor, which is calculated at the maximum rated rotor speed, is a function of rotor design and is a constant for a given rotor. k-Factors provide a convenient means of determining the minimum residence time required to pellet a particle in a given rotor and are useful for comparing sedimentation times for different rotors. The fe-factor is derived from the equation:

fe = ln (rmaX — rmin) x 1013/(3600tt>2) = 2.53 x 1011 x ln (w — rmm)/rpm2 [18]

where rmax and rmin are the maximum and minimum distances from the centrifugal axis, respectively.

Eqn [18] shows that the lower the fe-factor, the shorter the time required for pelleting. If the sedimentation coefficient of a particle is known, then the rotor fe-factor can also be calculated from the relation:

kadj = k(rprnmax/rprnact)2

term, 6. In Stokes' equation, the term 6m^r describes the frictional coefficient, f0, for a spherical particle. The correction term, 6, is calculated as the ratio of the frictional resistance, f, encountered by a particle of nonspherical geometry to that encountered by a sphere of the same volume, or:

The equation describing the terminal velocity for nonspherical particles in a centrifugal field may be rewritten as:

where T is the time in hours required for pelleting and S is the sedimentation coefficient in Svedberg units.

When k is known (normally provided by the manufacturer), then eqn [19] may be rearranged to calculate the minimum run time required for particle pelleting.

For runs conducted at less than the maximum rated rotor speed, the k-factor may be adjusted according where rpmmax and rpmact are the maximum rated rotor speed and actual run speed, respectively.

fe-Factors are also useful when switching from a rotor with a known pelleting time, t1, to a second rotor of differing geometry by solving for t2 in the relation:

where t1, t2, fe1 and fe2 are the pelleting times and fe-factors for rotors 1 and 2, respectively.

## Solar Panel Basics

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