Bed Pressure Drop Method

If the first set of measurements is given subscript 1 and the second subscript 2, and if s stands for the gradient of pressure drop with gas velocity, pb is bulk density and pp is the particle effective density, it can be shown (using the well-known Carman-Kozeny equation) that the basic relationship is as follows  

In this equation, pp is the only unknown and can be readily found, by trial and error. 

Note The above equation assumes that the constant in the Carman-Kozeny equation is the same for both maximum and minimum voidages. This is not quite true since the tortuosity factor is slightly different however, the error induced is small (less than 10%). 

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