Modeling and simulation of self-heating effect with temperature difference air flow sensor

Abstract

The paper presents an analysis of self-heating effect on micro-machined temperature difference air flow sensor, and demonstrates through modeling and simulation that self-heating effect can influence the output of the air flow sensor. The mathematical model of the sensor based on an existing microsensor chip is set up, and some details of the chip structure are considered in the model. The sensor's temperature distribution with respect to the flow rate is computed by coupling heat transfer interaction between the fluid and sensor's structure using ANSYS Fluent. The self-heating effects of the two temperature measuring thermistors are studied respectively in order to analyze their influences on the temperature difference compared with results obtained by ignoring the self-heating effect over the flow rate range between 0 and 15m/s. The change of temperature difference between the two thermistors by applying the same or different self-heating power are also studied. According to the simulation results, the conclusion that lower self-heating power and lower the self-heating power difference between the two thermistors helps to reduce the impact of selfheating effects on the sensor's output is made.

New Approach for Airflow Measurement Using Thermal Resistance Simulation

“…B59010), enclosed in the stainless steel housing and suitable particularly well for airflow monitoring. In self heating mode, the sensor is heated and responds to a change in external cooling conditions due to airflow by changing its power consumption [3,4]. The electrical power input is equal to the power lost to convective heat transfer,…”

A low-power thermal-based sensor system for low air flow detection

“…The several types of sensors being utilized for low air flow measurements can be broadly categorized as thermistors thermopiles [1], pyroelectric elements [2], pn junctions [3], intensity modulated fiber optic [4], ultrasound based [5], micro-electro-mechanical systems based [6], capacitive based [7]–[8], electromagnet based [9]–[10], resonating microbridges [11] and prandtl tubes [12] among others. One category of air flow sensor uses an indirect measurement such as the air temperature [13], volume or pressure [14] to determine the air flow. In recent years, several groups have been working on indirect thermal-based air flow sensors to meet the requirements of better accuracy, power efficiency, and smaller form factor.…”