Scaling Cyclones in Practice

The formal rules for scaling of cyclones have thus provided us with some fairly simple scaling rules. In practice, even further simplification is possible, and we shall discuss this below. 

1 Approximately Constant Stkso over a Wide Range of Re 

Equations (8.1.7) and (8.1.11) suggest that if we arrange experiments in a geometrically similar model to have the same Re as the prototjrpe, then Stkso and Eu will be the same as well. From Stkso a nd Eu we can then calculate the cut size and the pressure drop in the prototjrpe. Thus, although the pressure drop or the cut size for the prototjrpe and the model are different in general, one can use the pressme drop and cut size obtained from model tests to predict these same quantities for the prototjrpe. 

there is a practical problem. Due mainly to their difference in the characteristic size D), it is not always easy to obtain Rejmolds number similarity in a laboratory model with an industrial-scale cyclone without operating the model at very high velocities or constructing a very large model . The first example presented in Appendix 8.B is included to help illustrate this point. 

To avoid the problem of having to deal with extremely high velocities in the model experiments, it is possible to perform such studies with water as the carrier fluid, rather than a gas. 

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The model developed and tested at Bradford recently is an example of a chemical engineering approach to the design and scale-up of single or multiple cyclone installations. It is based on fundamental theory combined with dimensional analysis to produce the necessary correlations, and, in keeping with the usual practice in chemical engineering, the required constants are derived from tests rather than from theory. 

To separate particles from gaseous streams, cyclones are frequently used in large-scale practices. In fact, cyclone based dust collectors are one of the most widely used devices for removing larger-sized particles. Virtually all cyclones used industrially are reverse-flow cyclones. There are two other types of cyclones rotary-flow (CiUberti and Lancaster, 1976a, b) and uniflow (Ter Linden, 1949). Only the reverse-flow cyclone will be considered here. 

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