Abstract
AbstractThe 90 ° - bend represents the most common structural element in piping systems and can have a significant impact on the measuring accuracy of flow meters installed downstream. Within the type-approval procedure of water meters, its impact is emulated by means of a segmental orifice plate with a segment area of 7 % (SOP7). In research and development, coverage rates of 33 % (SOP33) or more are sometimes used as an alternative. The purpose of this study is to evaluate the comparability of the flow conditions and their influence on the measurement deviation of flow meters, which is the basic requirement for using SOPs as a substitute for the 90°- bend. We present laser Doppler measurements downstream of an SOP33 and a 90°- bend and describe the flow development in a distance range from 2 to 30 diameters. Besides a quantitative comparison with performance indicators, the measurements are used to model the response of an ultrasonic and electromagnetic flow meter, including recent investigations of an SOP7. The results demonstrate the consistently poor agreement between the SOP7 and the 90°- bend, whereas the SOP33 provides similar flow conditions starting at a distance of 10 diameters. Further studies are necessary to develop a disturbance generator emulating the near-field range.
Highlights
In flow measurement applications, installation components such as bends, valves and pumps create flow disturbances deviating from the swirl-free and symmetric reference state
The purpose of this study is to evaluate the comparability of the flow conditions and their influence on the measurement deviation of flow meters, which is the basic requirement for using segmental orifice plate (SOP) as a substitute for the 90°- bend
Following a singular symmetric state measured at a distance of 5.1 D, the secondary motion results in a shift of the core flow to the left, similar to the observations made by Eichler [13] and Straka et al [23] for the SOP7 and SOP33 in DN 80 and DN 200, respectively
Summary
Installation components such as bends, valves and pumps create flow disturbances deviating from the swirl-free and symmetric reference state. Non-ideal flow conditions can have a significant impact on the measuring accuracy of flow meters installed downstream. The development of meter designs and standardized type-approval procedures are accompanied by tests including the most relevant flow disturbances. The construction of a reproducible measurement section with bends is not always possible, especially for larger pipe diameters. For this reason, the investigated flow conditions are emulated by means of designated disturbance generators. Tests are limited to a small selection of disturbed flow categories
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
