High resolution air flow velocity monitoring using air flow resistance-type sensor film (AFRSF)

Real time in situ monitoring of air flow rate is critical for diverse engineering units including blowers, air supply pipelines, wind tunnels and anaerobic digestors. Existing air flow sensors are either costly and bulky or require frequent calibration and maintenance. This study explored a distinct solution by developing flat flexible thin air flow resistance-type sensor films (AFRSF) using thermal press technology to precisely print interdigitated sensors onto polyimide films. The continuous flow tests in a wind tunnel indicated that AFRSF sensors accurately measured airflow velocity (7.5 m/s-13.5 m/s) in a real-time in situ mode. The electrical resistance and vibration amplitude of AFRSF exhibited good correlation with airflow velocity with R-2 values of 0.99 and 0.96, respectively. The recovery test showed the variation of the electrical resistance of AFRSF was lower than 1% after 50 times repeated flow rate experiments, meaning that AFRSF possessed high repeatability without the need of recalibration. Furthermore, temperature compensation was conducted to effectively eliminate the temperature impact on the resistance readings of AFRSF and improve the accuracy of AFRSF under different air temperatures. This study clearly demonstrated the great potential for AFRSF to real-time in situ monitor air flow velocity at high accuracy with ultra-low cost and easy fabrication, which contributed to the real-time system monitoring and feedback control to save energy consumption (26.5%) in a designed wastewater treatment process. (C) 2019 Elsevier B.V. All rights reserved.