Spread Parameter Calculation for a Rosin-Rammler Curve — Lesson 2

Why is the spread parameter calculation for a Rosin-Rammler curve fit showing negative values?

This could arise if the "mean diameter" (d_bar) used in the curve fit calculations does not correspond to a cumulative mass fraction (Yd) = 0.368. Note that the mean diameter required in the curve fit calculations may not equal the actual Sauter mean diameter value. Rather, the mean diameter used in the calculations makes the ratio d/d_bar = 1, so that Yd = exp(-1) = 0.368.

Thus, Yd < 0.368 for larger particle diameters where d > d_bar, tending towards 0 for the highest diameter.

On the other hand, Yd > 0.368 for smaller diameters where d < d_bar, tending towards unity for the lowest diameter.