Thermal mass flow meters
Thermal mass flow meters measure the mass flow of gases, employing a combination of heated elements and temperature sensors, with thermodynamic principles used to derive actual flow. They need limited correction for changes in temperature, pressure or density and are extremely accurate, especially when measuring low and very low flow rates.
Picture 1: Laminar Flow Element, LFE
Laminar flow element; a critical element
The Laminar Flow Element as seen in Picture 1 is a critical component of the thermal mass flow meter based on the bypass principle. The functionality of the Laminar Flow Element (LFE) is to create a shunt. In the case of a thermal mass flow meter based on a bypass principle the mass flow is measured in a bypass of the main flow channel. Due to the specific dimensions of the LFE the same linear pressure/ flow characteristics as the capillary sensor tube can be created.
Thin stacked plates – etched to precise standards- are used to create the Laminar Flow Element and allow the measurement of very small to medium flow rates (< 1 mln/min up to 20 ln/min). The bypass is a capillary tube with an internal diameter of 0.2mm, and this small size allows for fast response times and low energy requirements, as only a small tube volume needs to be heated.
The importance of a laminar flow and the difference compared to a turbulent flow is described in this blog.
Picture 2: Shunt principle of the laminar flow element (LFE); only a part of the gas flow will flow through the sensor. The rest flow will flow through the LFE.
Creating industry-leading products with Chemical-Etched metal parts
Miniaturization of products – and therefore components – is a necessity for manufacturers in order to create industry-leading products. For the flow discs in LFE we apply the Chemical etching process, a subtractive manufacturing method for micro-precision parts.
Chemical Etching
Chemical Etching (also known as Photo-Chemical Machining (PCM) and Chemical Milling) is as precise as it is quick and economical. Complicated, multi-level, multi-feature, high precision parts can be produced without the need for expensive tooling or machinery. Compared to ‘traditional’ machine processes such as CNC Machining, Stamping, Pressing, Wire Erosion and even more ‘contemporary’ processes such as Laser Cutting and Electro Chemical Machining, Chemical Etching with its flexible tooling and scalability provides you with an extremely competitive alternative right through from prototyping to large scale production. Rapid prototypes can be produced from your drawings in a matter of days.
Key benefits
Key benefits
Stress and burr free parts
Micron sized features
Tight tolerances
Wide range of materials
Thicknesses from 25um to 2mm
Round holes, sharp edges, straight or profiled edges
Rapid prototyping
Cost effective manufacturing
Flexible tooling allowing easy modifications
Gas flow measurement in general
Flow measurement is recognized as one of the ‘need-to-know’ process parameters, alongside temperature, pressure and level measurement. Accurate mass flow measurement of gases is critical in operations and control of many industrial and laboratory processes.
In the food and beverage sector, the chemical industry and semiconductor fabrication, flow meters accuracy is often the determining factor between optimum quality and rejected products. In areas like laboratory research, pilot plants and custody transfer, precise and repeatable measurement is equally critical.
EL-FLOW Prestige mass flow meter
EL-FLOW Prestige thermal gas flow meter is the next generation of Bronkhorst Mass Flow Meters / Controllers for gases. Nearly all core components have been redesigned, and many improvements and innovations have been incorporated. With this new series Bronkhorst introduced the “Differential Temperature Balancing” technology, ensuring a superb sensor stability. You can sign in for the White Paper ‘A holistic view based on data to design components which offer optimal performance of a thermal mass flow meter/controller’, written by Bronkhorst, which describes the innovations integrated in the EL-FLOW Prestige.
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Related blog articles
Laminar flow vs Turbulent flow
Mass flow vs Volume flow
Bypass flow meter