High sensitivity calorimetric sensor for flow measurements

Industrial mass flow controllers (MFC) are limited to high-sensitivity measurements. Two methods for mass fluid flow detection and measurement are presented in this work. The flow sensor consists of a temperature sensor and a reference thermistor to accurately detect laminar flows with high sensitivity. The thermistor is self-regulated maintaining a positive temperature coefficient (PTC) due to the utilization of resistive Joule heating. This, in turn, ensures constant power dissipation to the fluid. Measurement of transient fluid flow is achieved through variations in the enthalpy advection to the fluid. The relationship between the enthalpy advection and the fluid flow is found to be in agreement with the first-order model for high sensitivity response to temperatures. Finally, we have shown superior sensitivity of the measured flow in comparison with that of the available commercial MFC devices.