Metering method and flow metering device

The present invention provides a measure of the flow inside the piping method and a flow metering device. Measuring temperature of the surface of the pipe when the pipe flow measurement within the heater may not be needed, but do not damage the pipe itself, and can also be measured in the vicinity of the elbow. The metering pipe surface with a predetermined surface temperature of the pipe upstream and downstream sides of the two distances by the surface temperature of the pipe to the fluid in terms of temperature, the temperature is obtained in the pipe flowing fluid. Determination of temperature and measurement results obtained from the measurement point on the upstream side of the determined, the temperature of the fluid at a time with the same time difference from the measurement result of the measurement point on the downstream side. According to the time difference and the predetermined distance is obtained in the pipe flow velocity of the fluid flow rate determined in accordance with the cross-sectional area of ​​the flow rate and pipe.