Study on flow sensors

Abstract

In the present work, two kinds of flow sensors are developed. One is a micro-thermal flow sensor using thin-film thermocouples. The other is a flow sensor using surface dielectric barrier discharge at atmospheric pressure. First of all, a micro-thermal flow sensor is developed using thin-film thermocouples as temperature sensors. A micro-thermal flow sensor consists of a heater and thin-film thermocouples which are deposited on a quartz wafer using stainless steel masks. Thin-film thermocouples are made of standard K-type thermocouple materials. The mass flow rate is measured by detecting the temperature difference of the thin-film thermocouples located in the upstream and downstream sections relative to a heater. The performance of the micro-thermal flow sensor is experimentally evaluated. The effects of mass flow rate, input power, and position of temperature sensors on the performance of the micro-thermal flow sensor are experimentally investigated. At low values, the mass flow rate varies linearly with temperature difference. The linearity of the micro-thermal flow sensor is shown to be independent of the input power. The position of the temperature sensors is experimentally shown to affect both the sensitivity and the linearity of the micro-thermal flow sensor. Also, the sensitivity of the micro-thermal flow sensor is deeply investigated. A simple numerical model for analyzing heat transfer phenomena in the micro-thermal flow sensor is presented. The proposed model is validated by experimental results. Based on the results from the validated model, a correlation that predicts the sensitivity of the micro-thermal flow sensor is presented. From the correlation, the manner in which the heat loss, the positions of the temperature sensors, the input power, and the heater length affect the sensitivity of the micro-thermal flow sensor is investigated. Secondly, a novel flow sensor is developed using surface dielectric barrier discharge. The surface dielectric...