If the current presence of flow in a piping system should be monitored, a calorimetric flow switch ? also called a flow monitor ? is frequently used. But how does a calorimetric flow switch actually work? The following post explains this in more 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 actually made between two technical solutions: continuous and regulated heating.
Spunky 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 integrated into it (see illustration). One of many sensors is heated continuously with the aid of a 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, that is registered by the electronics. The higher the flow velocity of the medium in the offing, small this temperature difference is. The basis for this may be the cooling effect of flowing media. Illusive 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, among which may be heated. In this technical solution, the heating power is regulated so that the temperature difference between the two temperature sensors is kept constant throughout. Consequently, because the flow velocity increases, the heating power must be increased to keep how big is the temperature difference constant. The applied heating power is thus a primary measure of the flow velocity in the medium.
Note
Are you experiencing 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 help you.