Dimensionless throughput

A single screw extruder has two Reynolds numbers. One, Re = pD2n/r]o, related to the rotational speed of the screw, and another, ReQ = Qp/rjoD, related to the mass throughput. The ratio of the two gives the dimensionless throughput ReQ /Ren Q / /) n. ... 

For a pitch of 40 mm, the throughput per revolution is now much higher than at the optimum energy level, resulting in an unfavorable operating point. In this case, a pitch of 60 mm would be the better choice. This example clearly shows that no screw element is best in all situations. Rather, the choice of suitable screw element depends significantly on the dimensionless throughput. 

The throughput parameter Q (Eq. 15.3) describes the dimensionless throughput, parameter K (Eq. 15.4) describes pressure build-up, and the PI parameter (Eq. 15.5) describes energy conversion. 

The adsorption equilibrium constant is K, with K = k Jk a-The dimensionless throughput parameter is defined as... 

Fig. 8.10 Selectivity Sr of the undesired byproduct R in carrying out a reaction in a tubular reactor with a jet mixer as a function of the concentration ratios ca/cs and the dimensionless throughput-related propulsion jet power F oc Ap = P/rb for three different throughput ratios < a/< b from [638, 639]...

Dimensionless throughput versus dimensionless pressure gradient from closed-form solution... 

The dashed line in Fig. 7.62 shows at what point along each curve A, becomes zero. When X is zero, the extremum in the velocity profile occurs right at the screw surface. The dimensionless throughput in this case is ... 

Figure 7.64 shows the dimensionless throughput versus pressure gradient for a helix angle of 17.66° (square pitch screw). 

It should be noted that a reduction in the dimensionless throughput does not necessarily mean that the actual throughput reduces as well. Obviously, when the helix angle is zero, the actual throughput will be zero. The dimensionless throughput is determined from ... 

The actual volumetric throughput is related to the dimensionless throughput by ... 

---