If the presence of flow in a piping system must be monitored, a calorimetric flow switch ? often known as a flow monitor ? is often used. But so how exactly does a calorimetric flow switch actually work? The following 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 based on the calorimetric measuring principle includes a measuring probe with two temperature sensors integrated into it (see illustration). One of the sensors is heated continuously using an integrated heating element (wire-wound) with a continuing heating power and measures the temperature at the heating element. The second sensor determines the temperature of the medium in the pipe. Consequently, Spectacular occurs between the two sensors, which is registered by the electronics. The bigger the flow velocity of the medium in the pipeline, the smaller this temperature difference is. The basis for this may be the cooling aftereffect 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 quantity 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 that may be heated. In this technical solution, the heating power is regulated so the temperature difference between your two temperature sensors is kept constant throughout. Consequently, as the flow velocity increases, the heating power must be increased to keep the size of the temperature difference constant. The applied heating power is thus a primary way of measuring the flow velocity in the medium.
Note
Do you have further questions on the measuring principle behind the calorimetric flow switch or do you want help with the selection of this type of product? In its portfolio, WIKA has a calorimetric flow switch for monitoring the flow of liquid media (model FSD-3). Your contact person will be happy to assist you to.