If the presence of flow in a piping system must be monitored, a calorimetric flow switch ? also known as a flow monitor ? is frequently used. But how does a calorimetric flow switch really work? The following blog post explains this in greater detail.
Calorimetric flow switches, which are generally also referred to 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 that is using the calorimetric measuring principle consists of a measuring probe with two temperature sensors integrated into it (see illustration). One of many sensors is heated continuously with the aid of a built-in 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 the two sensors, that is registered by the electronics. The bigger the flow velocity of the medium in the pipeline, small this temperature difference is. The foundation for this may be the cooling effect of flowing media. The molecules in the medium, which are flowing at night probe tip, collect ? ไดอะแฟรม ซีล of heat? and transport them away. The more molecules flow past, the higher the cooling effect. The number 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 that may be heated. In this technical solution, the heating power is regulated so the temperature difference between the two temperature sensors is kept constant throughout. Consequently, as the flow velocity increases, the heating power should be increased in order 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
Are you experiencing 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.