Flow Instability Evaluation at the NMISA Gas Flow Laboratory |
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| D. Jonker, W. M. Dlamini, R. M. Molefe |
- Abstract:
- Interlaboratory comparison and verification measurements performed in the Gas Flow Laboratory indicated stability problems in the flow ranges below 50 mL/min and above 30 L/min. Initially the stability problems in the low flow range below 50 mL/min were attributed to the flow cell used as reference standard. The unstable measurements above 30 L/min were attributed to the lack of sufficient pressure drop in the flow path from the gas cylinder to the measuring point. However, further measurements performed indicated that this might not be the cause of the instabilities experienced. To further investigate the matter, a second reference standard was acquired, and the flow path was lengthened and equipped with more pressure regulators to ensure better pressure control and a larger pressure drop. This paper discusses the methods to determine the causes of the instability, the measurements performed, analysis of the measurement results and measures implemented to eliminate further problems.
This paper includes a discussion of the possible flow instability generated by the insertion of thermistors in the flow path to perform temperature measurements of volume flow devices. The Flow Laboratory regularly receives volumetric flow devices and to calculate standardised flow conditions, it is necessary to measure the gas temperature and pressure at the unit under test (UUT) location. Emphasis is given to the determination of the immersion depth and measurement position of the temperature sensor in the flow path to ensure no, or negligible, disturbances in the gas flow path. - Download:
- IMEKO-TC9-2019-059.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC9
- Event name:
- FLOMEKO 2019
- Title:
18th International Flow Measurement Conference 2019
- Place:
- Lisbon, PORTUGAL
- Time:
- 26 June 2019 - 28 June 2019