If the current presence of flow in a piping system must be monitored, a calorimetric flow switch ? also called a flow monitor ? is frequently used. But Plummet how exactly does a calorimetric flow switch really work? The following post explains this in greater detail.
Calorimetric flow switches, which are generally also referred to 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 which is in line with 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 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 your two sensors, which is registered by the electronics. The bigger the flow velocity of the medium in the offing, small this temperature difference is. The foundation for this is the cooling aftereffect of flowing media. The molecules in the medium, which are flowing past the probe tip, collect ? Paralyzed of heat? and transport them away. The more molecules flow past, the higher the cooling effect. The amount of molecules passing by increases continuously with increasing flow velocity.
Regulated heating
The measuring probe is actually identical in design: You can find two temperature sensors in the medium, one of which may be 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 Greedy , 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
Are you experiencing further questions on the measuring principle behind the calorimetric flow switch or do you need help with selecting 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.