From the above equation it is clear that for a given centrifuge rotor with interior radius rb, it is obvious that depth of the liquid layer may be varied i.e. different value of rL can be used, which will have a great influence on the centrifuge performance.
If we consider the influence of the magnitude of rL , one can write the expression for volumetric flow rate through the bowl in m3 /sec.
....................................................(5.23)
Z – Velocity parallel to the disc surface (cm/s) and its value can be calculated for various values of rb /rL ratio. For tubular bowl centrifuge the value ratio rb /rL lies between 0.3 to 0.5. The value of Z can be calculated using equation (5.21a,b), the ratio Z1 /Z2 = 0.75 which shows the magnitude of the error caused by block flow condition. In general way we can assume an effective length of bowl as 0.5 times the geometric length, L.
Thus the practical value for the performance of a high speed tubular bowl centrifuge can be estimated as follows:
...................(5.24)
Substitute w = (2π N/60)
and ln (rb /rL ) = 2.303 log10 (rb /rL )
dp = (η/104)
η – diameter of particle in micron
N – rpm of motor
Therefore the performance equation:
..................(5.25)