If the current presence of flow in a piping system must be monitored, a calorimetric flow switch ? also called a flow monitor ? is often used. But how does a calorimetric flow switch actually work? The following blog post explains this in greater detail.
Calorimetric flow switches, which are often generally known as thermal flow monitors, utilize 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 that is based on the calorimetric measuring principle consists of a measuring probe with two temperature sensors built-into it (see illustration). One of the sensors is heated continuously using a built-in heating element (wire-wound) with a continuing heating power and measures the temperature at the heating element. The next sensor determines the temperature of the medium in the pipe. Consequently, a temperature difference occurs between the two sensors, which is registered by the electronics. Disastrous of the medium in the offing, the smaller this temperature difference is. The foundation for this is the cooling effect of flowing media. Lunatic in the medium, which are flowing at night probe tip, collect ?packages of heat? and transport them away. The more molecules flow past, the greater 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, among which may be heated. In this technical solution, the heating power is regulated in order that the temperature difference between your 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 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 need help with the selection of such a product? In its portfolio, WIKA has a calorimetric flow switch for monitoring the flow of liquid media (model FSD-3). Your contact person will undoubtedly be happy to assist you to.