Question

In a cyclone separator, if you decrease the cut-point diameter, does the pressure drop across the device increase or decrease?

Accepted Answer

In a cyclone separator, decreasing the cut-point diameter increases the pressure drop across the device. The cut-point diameter, also known as the critical diameter, is the size of the particle that the cyclone is 50 percent efficient at removing. To capture smaller particles, a cyclone must increase the intensity of the centrifugal force acting on the gas stream, which is achieved by increasing the inlet gas velocity or using a smaller, more restrictive cyclone geometry. Increasing the inlet velocity requires more energy to push the gas through the device, which manifests as a higher pressure drop, defined as the difference in static pressure between the inlet and the outlet of the cyclone. Similarly, a smaller cyclone diameter increases the spin speed of the vortex and increases frictional losses, both of which require higher pressure to maintain the flow. Therefore, because improving the separation efficiency for smaller particles necessitates higher kinetic energy and faster vortex motion, the mechanical resistance to flow rises, leading directly to a higher pressure drop.

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In a cyclone separator, if you decrease the cut-point diameter, does the pressure drop across the device increase or decrease?