We offer the widest product range of low-flow mass flow meters on the market. Numerous styles of both standard and bespoke instruments can be offered for applications in laboratory, machinery, industry and hazardous areas.
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Bronkhorst instruments are used for numerous applications in many different markets. In this section you will find an overview of the main markets for our equipment, illustrated with some typical examples of applications.
Are you looking for technical documentation, are you interested to learn more about the measuring principles of Bronkhorst products, or you do want to get in contact with a Bronkhorst Service Engineer? This section will guide you to the relevant service & support topics.
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Laminar flow and turbulent flow are two important aspects to take into account when measuring flow. When does a turbulence effect occur? What is the effect on your flow meter? And very important:
''Turbulence is a dangerous topic which is often at the origin of serious fights in the scientific meetings devoted to it since it represents extremely different points of view, all of which have in common their complexity, as well as an inability to solve the problem”. Marcel Lesieur, 1987.
In practice you will encounter a turbulent flow quite often. A turbulent flow can be caused by (too many) restrictions in an installation, such as valves or adapters, in combination with a high velocity of the used fluid. This effect is known as ‘turbulence effect’. In every restriction, the flow has been disrupted and the speed of the gas will change. Besides the usage of restrictions, the pipe length is something to take into account as well. As it takes some time for a turbulent flow to get laminar again, it is important to use the right pipe length.
A turbulent flow is something you would like to prevent at the inlet of your flow measurement instrument, as it can affect the accuracy of your measurement. It is preferable to have a laminar flow just before your flow instrument. However, the instrument itself used as flow controller, with a valve behind the meter, can cause a turbulent flow again.
Not all kinds of flow meters experience this as disadvantageous. Mainly thermal flow meters using the bypass principle are sensitive for this effect. Flow meters based on the Coriolis, CTA (Constant Temperature Anemometry) or Ultrasonic principle are independent of turbulence.
In general it can be said that there are two types of flows: a laminar flow and a turbulent flow. You can see in the picture that laminar flow has been visualised by an experiment using ink in a cylindrical tube. The ink has been injected into the middle of a glass tube through which water flows. When the speed of the water is still low, the ink does not appear to mix with water, the stream lines are parallel; this is called laminar flow.
If the speed of the water increases, a sudden change will occur at a certain speed. The flow completely disrupts and the water turns homogeneous through the ink. The stream lines are chaotic, not linear anymore, which is called turbulent flow.
In theory the flow pattern depends on four variables:
If you use thermal mass flow meters based on the ‘bypass’ sensor principle, I advise you to do the following:
It depends very much on the application what the consequences are of turbulent flow. In semicon processes for example, particularly in coating processes such as layer deposition, turbulent flow is a no-go! A stable process is essential here. However, in other coating processes, like flame spray techniques, the impact of turbulences will be less due to the high pressure in the flow. If you need advise on choosing the best flow meter for your application, please let us know.
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Blog series - Part 1/5: What are low liquid flows? A blog series about how to handle low liquid flows including the definitions and tips.