시험소간 성능 검증을 위한 벽면 속도 보상 10회선 초음파 유량계 개발

Development of near-wall flow velocity factor Wet-type Ten-Path Ultrasonic Flowmeters to Validate Their Performance at multiple laboratories.

Most wet- type multi-path ultrasonic flowmeters have their measurement accuracy rate to be deteriorated as the flow rate is decreased. Curve-fitting on the characteristics of ultrasonic flowmeters is essential to improve their measurement accuracy rate. This hinders their use as transfer standards in inter-laboratory comparisons for water flow metrology. A breakthrough to enhance the measurement accuracy rate of ultrasonic flowmeters is needed. This study suggests that the concept of near-wall flow velocity should enhance the characteristics of ultrasonic flowmeters. As a result, the repeatability can be improved as low as 土0. 02% which should be suitable to be used as transfer standards. Two main points of using the near-wall flow velocity for ultrasonic flowmeters are emphasized. One is a formula to describe the near-wall flow velocity as a function of both Reynolds number and surface roughness. The other one is the results of comparison calibrations between two national metrology institutes, which can support measurement equivalence. In particular, the number of equivalence is less than one (¦E_n¦ ≤ 1), and the inconclusiveness parameter is less than two (u_comp/u_base≤ 2) if the near- wall flow velocity is applied for ultrasonic flowmeters. This implies that the ultrasonic flowmeters could be used as transfer standards for the forthcoming inter-laboratory comparisons.