Investigating Simultaneous Effects of Flow Rate and Chamber Structure on the Performance of Metal Oxide Gas Sensors

The effect of flow rate variations on the performance of high-temperature metal oxide gas sensors is investigated in a new proposed chamber and compared to four conventional structures. Velocity, temperature, and gas concentration at the sensor surface were calculated by Computational Fluid Dynamics (CFD) studies. Responses and rise times of a TGS-2602 sensor were experimentally measured. Calculations indicate that increasing the flow rate increases the velocity and decreases the rise time and sensor temperature. The chamber structure also affects these parameters. Particularly, when the sensor is exposed to fluid from more faces, the sensor temperature is more affected by the flow rate. Comparing theoretically and experimentally results revealed that as flow rate variates or while using different structures, the surface temperature is the main factor that changes the sensor sensitivity. It is proved that in chambers with more sensor temperature variations, the highest response variations occur. Flow rate variations can lead to increased, decreased, or even peaked of the sensor response, depending on the sensor operating temperature related to the optimum temperature of the sensor. The sensor rise time depends on the chambers, but the differences were fewer than 8 seconds. It is concluded that in the new structure, slight response variation occurs at flow rate changes by placing the sensor in a cavity inside the chamber. Finally, using the proposed design is more accessible than eliminating the effect of flow rate fluctuations from the sensor response.