92. A Method to Eliminate the Effect of Sound Path Length Change of Ultrasonic Heat Meter

Ultrasonic heat meter (UHM) plays a key role in the heat consumption sensing in automatic metering and control system of district heat supply pipe network; however, the large temperature changes (below 10℃ to above 90℃) of water in the network generally cause sound path length (SPL) changes due to thermal expansion and contraction, which will greatly reduce the accuracy of UHM in practice. This paper proposes a method to eliminate the effect of SPL change for UHM. In the method, a novel model has been developed to calculate flow rate and then heat consumption from upstream and downstream transmit times and sound velocity, but not containing the SPL parameter commonly existing in traditional models. A sample learning method is proposed in addition to correct the effect of sound velocity changes under different temperatures. The method is validated on actual UHMs by flow rig experiments on simulating serious temperature variations.