Macro level mixing - Physical processing
Pumping. This is not a common concept and can mean different things to different people. This has nothing to do with pumps, but it does have to do with flow generation. Since this is in the macro mixing section, this is a process requirement that can be seen or felt. Well not really, but you get the idea.
Each impeller generates some flow. This flow is called a pumping capacity. In some rare cases, a mixing specification could merely be, "Provide an impeller than can generate a pumping capacity of 1000 GPM or maybe 4000 m3/hr." Then the only mixing requirement is the generation of flow. Sometimes its called pumping.
Examples where pumping is important is when:
- Generic mixing specification: A pumping capacity, or pumping rate, or amount of flow is specified. This is often part of a mechanical spec.
- Waste water treatment plants may often require that impeller provide a certain pumping capacity
- Quench tanks often require a minimum flow rate
- Solvent Extraction plants will require that the pumping impellers provide a certain amont of flow
- Conintuous processes where the impeller is specified to pump more that the through-put flow rate.
The way to determine the direct pumping capacity is quite simple. Q = Nq.N.D3. Nq is the flow number and is impeller specific. It is a dimensionless number. Several flow numbers are shown on the Impeller Page. N is the rotational impeller speed in RPM (min-1) or rps (s-1), and D is the impeller diameter (tip-to-tip, or swept diameter) in millimeters, meters, inches, or feet. Q will be in GPM, cubic feet per minute (CFM) or m3/s or m3/hr or Liters per minute (LPM) depending on application.
The micro mixing counterpart of pumping is Heat Transfer.