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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Thermal flow instruments behave best using a laminar flow, at least if we look at the thermal mass flow meters and controllers with a bypass sensor. To conduct a precise measurement with this flow instrument, laminar flow is preferred.
However, in practice you will encounter a turbulent flow quite often. A turbulent flow can be caused by 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’. A turbulent flow can affect the accuracy of your measurement, something you would like to prevent.
How can you prevent this turbulence effect? Let’s start with explaining what turbulent flow is.
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 visualized 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.
How do we achieve the goal of increase and decrease? In theory the flow pattern depends on four variables:
Instruments with a bypass sensor work based on a main flow going through a restriction and a small part of the flow going through the actual sensor. The ratio between these two flows is determined by the pressure drop over the sensor and the restriction in laminar flow. The turbulence effect will disturb this ratio. As the instruments with bypass sensor are often used for very precise measurements, the turbulence effect can have a huge effect on the measurement results.
Do you need more information about the working principle of the flow devices?
When using thermal mass flow meters with the bypass sensor, it is advised to do the following:
It depends very much on the application what the consequences are of turbulences. As an example in semicon processes, particularly in coating processes such as layer deposition, turbulent flow is out of the question. A stable process is essential here. However, in other coating processes, such as flame spray techniques, the impact of turbulences will be less due the high pressure in the flow.
If you need any assistance for installation of your flow meter?
Do you know why the choice of piping is important for a mass flow meter? Read our blog about the deviation in measurement of the flow meter or how to prevent frozen pipes.
In many research and production processes the important variable is mass and not volume. Measurements of volumetric flow are not as reliable as mass flow measurement due to the effects that changes in temperature or pressure have on the density of a fixed volume of gas.
Thermal mass flow instruments that make use of a bypass are what most people have in mind when they think of thermal mass flow instruments. What are the differences?