If the current presence of flow in a piping system should be monitored, a calorimetric flow switch ? generally known as a flow monitor ? is frequently used. But how does a calorimetric flow switch actually work? The following post explains this in greater detail.
Calorimetric flow switches, which are generally 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 using the calorimetric measuring principle includes a measuring probe with two temperature sensors built-into it (see illustration). One of many sensors is heated continuously with the aid of an integrated heating element (wire-wound) with a constant 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 your two sensors, that is registered by the electronics. The higher the flow velocity of the medium in the pipeline, small this temperature difference is. The foundation for this is the cooling aftereffect of flowing media. Savvy 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 amount of molecules passing by increases continuously with increasing flow velocity.
Regulated heating
The measuring probe is basically identical in design: There are two temperature sensors in the medium, one of which is often heated. In this technical solution, the heating power is regulated in order 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 to keep the size of 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 want help with selecting 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.