Temperature and installation effects on small commercial ultrasonic flow meters

Experimental work has been performed on a selection of small ultrasonic flow meters for water. This work was accomplished in order to investigate the in fluence of temperature and flow profile disturbances on the performance of flow meters in district heating applications. The flow meters tested were all ultrasonic flow meters of sing-around type. The selection of flow meters contains in total seven meters of three different brands. All meters have a flow range from 0.015 m3/h to 1.5 m3/h. These meters are commonly used in heat meters in small district heating subscriber stations. The flow meters are presented without identification. All tests were performed in a flow meter calibration facility and in a flow range including the minimum and maximum flow of each flow meter. In the tests three different water tempera-tures and three different installations were investigated. Water temperatures of 20 °C, 50 °C and 70 °C were used. These temperatures are representative for district heating applications. The installations tested involved flow meters mounted with long straight pipes both up-and down-stream representing ideal conditions, a single elbow and a double elbow out of plane both generating disturbed flow profiles. All set-ups are in accordance with the flow meter specifications. The results demonstrate that both the change in temperature and the disturbed flow profiles introduce errors in the flow measurements. The change from 20 °C to 50 °C and 70 °C can cause a shift in meter performance larger than the specified maximum permissible error. Compared with the ideal installation the installations generating disturbed flow profiles cause errors up to more than 2 %. The errors due to temperature and installation effects have a bias to add when combined. This might lead to even larger errors.Godkänd; 2000; Bibliografisk uppgift: Undertitel på proceedings: International Conference on Flow Measurement Sider: 036-; 20150402 (andbra