How does a calorimetric flow switch work?

If the presence of flow in a piping system should be monitored, a calorimetric flow switch ? also called a flow monitor ? is often used. But so how exactly does a calorimetric flow switch really work? The following blog post explains this in greater detail.
Calorimetric flow switches, which are often generally known as thermal flow monitors, use the physical laws of heat transport in flows. A distinction is basically made between two technical solutions: continuous and regulated heating.
Schematic illustration of a measuring probe for a calorimetric flow switch
Continuous heating
A flow switch which is in line with the calorimetric measuring principle includes a measuring probe with two temperature sensors built-into it (see illustration). Among the sensors is heated continuously using a built-in heating element (wire-wound) with a constant heating power and measures the temperature at the heating element. The second sensor determines the temperature of the medium in the pipe. Consequently, a temperature difference occurs between your two sensors, which is registered by the electronics. The higher the flow velocity of the medium in the pipeline, small this temperature difference is. The basis for this is the cooling effect of flowing media. The molecules in the medium, which are flowing at night probe tip, collect ?packages of heat? and transport them away. The more molecules flow past, the higher the cooling effect. The number of molecules passing by increases continuously with increasing flow velocity.
Regulated heating
The measuring probe is basically identical in design: You can find two temperature sensors in the medium, one of and this can be heated. In Beaming , the heating power is regulated so that the temperature difference between the two temperature sensors is kept constant throughout. Consequently, as the flow velocity increases, the heating power should be increased in order to keep how big is the temperature difference constant. The applied heating power is thus a direct measure of the flow velocity in the medium.
Note
Do you have further questions on the measuring principle behind the calorimetric flow switch or do you need help with the selection of such a product? In its portfolio, WIKA includes a calorimetric flow switch for monitoring the flow of liquid media (model FSD-3). Your contact person will undoubtedly be happy to help you.

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