Sensor Modelling for Gas Flow Measurements using Thermal Time-of-Flight Method

Inhalt:
The authors report a measurement principle for determining the flow velocity of gases in a range of 0.1 m/s and 0.7 m/s. Present works in this area are accomplished with a sensor model consisting of a filament as heating element and several sensible thermocouples serving as detection units in a through-flowed pipe construction. The velocity measurement is based on the pulsed Thermal Time of Flight (TTOF) technique. Since heat transfer occurs in a wide spectrum of fluids, it is applicable as a marker in a flowing fluid. Observing the heat transfer in the flowing fluid field over time, the knowledge of the distance between the thermocouples yields the velocity of the fluid. Time dependent generation and detection of the propagating heat in a downstream direction is the fundamental method. The filament is positioned at a certain place into the pipe, where the mean velocity of the fluid flows according to the laminar velocity profile.