Calculating the flow rate in pipes using novel equations based on the heater method

抄録

The heater method is a clamp-on type flow measurement method that can be applied to metal pipes in high-temperature environments and is useful for determining the adequate flow rate in existing pipes for the stable operation of thermal power plants. Specifically, a ring-shaped heater is attached to the outer of an existing pipe, and the outer surface temperature of the pipe near the heater is measured to calculate the fluid flow rate in the pipe. In this study, as the heat transfer coefficient upstream of the heater was found to be constant in the flow direction by computational fluid dynamics (CFD) simulation results, the heat conduction equation was solved to express the correlation between the outer surface temperature and the heat transfer coefficient inside the pipe, upstream of the heater. A correlation equation was then developed for the heat transfer coefficient in the pipe upstream of the heater using CFD simulation results. In addition, to improve the accuracy of the flow rate calculation, a condition equation was incorporated to determine whether the heat transfer rate calculated using the heat transfer coefficient based on the outer surface temperature is consistent with the heating power of the heater. Experimental data confirm that the equations can be used to calculate the fluid flow rate accurately and indirectly in the pipe from the outer surface temperature of the pipe upstream of the heater.