Patent ID: 7856892

Claim:
A flow-rate measuring method for measuring a flow rate of a fluid inside a tube by using a heating unit that heats the fluid flowing through the tube from the outside thereof so as to generate a heated portion in the fluid inside the tube and a detecting unit disposed downstream of the heating unit and configured to detect the heated portion, generated by the heating unit, of the fluid inside the tube, the flow rate being measured on the basis of a distance between the heating unit and the detecting unit, a time period between a point at which the heated portion of the fluid inside the tube is generated by the heating unit and a point at which the heated portion is detected by the detecting unit, and a cross-sectional area of the tube, wherein the heating unit heats the fluid by a microwave heating technique, and microwaves are applied to the fluid by using a transmission line, the heating unit includes a microstrip line as the transmission line, a ground conductor, and a dielectric member interposed between the microstrip line and the ground conductor, the tube extends through the dielectric member, and the microstrip line is disposed on the surface of the dielectric member so as to extend crosswise to the longitudinal direction of the tube.