What is a Volume circulation rate?

Volume circulation rate is the measurement of just how much fluid is flowing past a selected suggest over a size of time. Design designs, specifications and also schematics often list volume flow rates. We measure a volume flow rate in the SI devices of meter cubed per second (m3/s) however you will certainly often find them provided as litres per 2nd (l/s) or litres every hour (l/h). In the united state it will certainly still be detailed in British imperial units the cubic feet per second (ft3/s).

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Volume flow rate is often noted as Vdot or a V v a dot above it e.g.


Other typical flow rate dimensions include

Velocity flow rate (m/s)

In this post we will emphasis only top top volume flow rate,to learn about the others just follow the web links above. If you discover this short article interesting and useful please like and also share, girlfriend can also comment in ~ the bottom that the page.

How is volume flow rate measured?

There space two main ways to measure the volumetric flow rate.

Let the fluid circulation into a measure tank end a length of timeCalculate it from either the velocity or mass circulation rate

The very first method commonly isn’tpracticalbut the is an extremely simple. Simply let the fluid circulation into a measuring tank over a duration of time then division the measure up volume (m3) by the lenght that time (s) to gain m3/s.


The second technique is the most common strategy in industry since the fluid is no disturbed in the process, this permits real-time data analysis for processes and also services. To calculation the volume flow rate, you need to recognize the typical velocity and also the cross-sectional area. The volume flow rate is then calculated by merely multiplying the two together.

You will require some extr equipment to measure up the velocity. There space a variety of instruments and equipment tomeasure the velocitysuch as an Orifice plate, venturi meter, Pitot tube, wind turbine or Ultrasonic meter.

lets watch at an example of a pipe.


You’ve been asked to calculation the volumetric circulation rate within a pipe, you find that the median velocity within the pipeline is 2m/s and the pipes within diameter is 0.5m. First calculate the cross-sectional area (CSA) that the pipeline by: CSA=(π x Diameter2) ÷ 4CSA = (3.142 x 0.5m2)÷ 4 = 0.196m2Then multiply the CSA by the median velocityVdot = 0.196m2x 2m/s = 0.393m3/s or Vdot = 0.393m3/s * 1000 = 392.7 l/s

It can likewise be calculation if you know the mass flow rate and also the fluids density. Let’s look at another example.


You’ve been asked to calculation the volumetric flow rate within a pipe, you find that the mass circulation rate is 389.6 kg/s and that the liquid flowing within the pipeline is 40°c water at a pressure of 101.325kPa.

First you should lookup the density of water at the pressure and also temperature, luckily us have currently tabulated this for you click hereDensity = 992.22kg/m3Mass circulation rate = 389.6kg/sVolume circulation rate = 389.6kg/s÷ 992.22kg/m3 = 0.393m3/sAnswer = 0.393m3/s

What influence volume flow rate?

It is important to remember that volume circulation rate will readjust with temperature and also pressure! the volume flow rate will also adjust if there is a constriction in the pipe/duct, this is since the mass circulation rate is constant,this means that in a constriction the velocity must boost so that the mass flow rate right into the pipe equates to the mass circulation rate out of the pipe, if the velocity boost then the volume circulation rate increases.

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Volume flow rate is measure up in m3/sVolume flow rate transforms with pressure and also temperatureVolume flow rate alters with velocityVolume flow rate have the right to either it is in calculated or measuredVolume flow rate is calculated native the cross sectional area and the velocity or by dividing the mass flow rate through the liquid density.