Flow rate

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Flow rate is the com­mon­ly used term for vol­ume flow (or flow rate) and comes from flu­id me­chan­ics. It is the mea­sure of the amount of a flow­ing or stream­ing medi­um per pe­ri­od of time that pass­es through a de­fined cross-sec­tion. The unit of mea­sure­ment used is cu­bic me­ters per sec­ond (m³/s).

A wide range of me­dia can be con­sid­ered for the flow rate. In the case of liq­uid me­dia, for example:

• Wa­ter, what is let through a dam
• An­tifreeze, which is passed right in­to the en­gine to pre­vent freezing
• Oil, which is trans­port­ed through pipelines over many kilometers
• Gaso­line or diesel when re­fu­el­ing at the gas station
• Blood, which flows through the veins of hu­man beings
• Waste­water, which moves through our sewage systems

In the case of gaseous me­dia, these are, for example:

• Air in the form of “com­pressed air” which is used for brak­ing sys­tems, spring and damp­ing com­po­nents, and respirators
• Air used for ar­ti­fi­cial res­pi­ra­tion in hospitals
• Wa­ter va­por as an en­er­gy car­ri­er used in man­u­fac­tur­ing processes 
• Nat­ur­al gas, which flows through pipelines
• Chem­i­cals used in var­i­ous industries
• Ex­haust gas emit­ted by a car or truck

Why is the flow rate determined?

Flow rate is the flow vari­able that is most com­mon­ly mea­sured tech­ni­cal­ly. The flow rate or its mea­sure­ment al­ways pro­vides in­for­ma­tion about the ca­pac­i­ty of a flu­id pow­er sys­tem. Prac­ti­cal ex­am­ples would be the fill­ing of dif­fer­ent con­tain­ers, cans and bar­rels, pre­cise dos­ing of sub­stance mix­tures in the chem­i­cal in­dus­try or the non-over­load­ing of kilo­me­ter-long pipelines un­der­ground. Flow mea­sure­ment is car­ried out by spe­cial mea­sur­ing de­vices, so-called flow me­ters, which de­ter­mine the val­ues ac­cord­ing to dif­fer­ent meth­ods. With a da­ta log­ger, the flow can be mea­sured at two dif­fer­ent points and tracked over a longer pe­ri­od of time.

How can I regulate the flow rate?

Lim­iters, con­trol valves, or con­stant flow switch­es are used to de­crease or in­crease the flow rate as need­ed. These are in­clud­ed in the de­sign, but can al­so be retro­fit­ted to old­er sys­tems or in the event of failures.

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