Simulation and Correlation of Flow-Rate Measurement in an Ultrasonic Time-of-Flight Heat Meter

Abstract: The flow-rate measurement that occurs in a heat meter is critical to the accuracy of the energy-measurement requirements of heat providing utilities around the world. With knowledge of the heat-meter spool body dimensions, including the acoustic path length, the flow-rate accuracy can be modeled in a simple spreadsheet format to determine the entitled flow-rate accuracy. Since all heat meters are essentially integrating flow totalizers, this simulated flow-rate entitlement can provide insight into the trade-offs required to develop a cost-effective flow-rate measurement solution. Once the simulations are completed, the meter’s actual flow-rate accuracy can be measured using supporting time-to-digital converter electronics and matching piezoelectric transducers mounted in a spool body with the same dimensions as those used in the simulation model. Because of the effects of flow turbulence and mechanical design limitations in the spool body, the actual flow-rate measurement accuracy is limited and can only approach that of the simulation model with averaging, flow compensation and multipoint calibration.