Characteristics of on-wall in-tube flexible thermal flow sensor under radially asymmetric flow condition

We investigated the ability of an on-wall in-tube flexible thermal flow sensor to measure the flow rate under a radially asymmetric flow condition in a curved tube. The sensor was fabricated on a polyimide film substrate using polymer MEMS technologies. A ring-shaped sensing structure was formed by mounting the sensor on the inner-wall surface of a straight tube that follows a curved tube. The sensor characteristics were experimentally evaluated by varying the distance L from the end of the curved tube, the curvature angle θ, and the curvature radius r of the curved tube. The output signals from the sensor were the same when the distance L was over 5 mm at various curvature angles and curvature radiuses. The sensor is thus well suited for measuring the flow rate in spiral tubes.