Three-dimensional simulation of heat transfer in a microscale flow vector sensor (Numerical study toward improving the sensitivity of the sensor in a high-speed airflow)

Abstract

A micro-machined thermal flow sensor called “Flow Vector Sensor (FVS)” can measure an airflow speed and its direction simultaneously. The FVS is extremely small, and hence it does not disturb flowfields around the sensor. In addition, since a response time of the FVS is very short, the FVS can measure unsteady flows. Therefore, the FVS is expected to be applied to flowfields over various objects such as automobiles. However, when the airflow speed is high, the sensitivity of the prototype of the FVS tends to be lower. In this study, we numerically examine heat transfer from the FVS to the airflow, in order to improve the sensitivity of the FVS in a high-speed airflow. First, we investigate the heat balance between the FVS and surroundings, in order to identify the cause of the lower sensitivity of the FVS. The heat transfer between the FVS and airflows is found to affect the sensitivity of the FVS, especially in the high-speed airflow. Second, we examine the effect of the size of the FVS, in order to discuss the design philosophy of the FVS. The heat transfer from the FVS to airflows is found to decrease with decreasing the size. Consequently, the small size of the FVS can improve the sensitivity of the FVS. These results should provide new insights into the design philosophy of a high performance FVS.