| Zugriffsnummer | 40240 |
| Dokumenttyp | Dissertation |
| Peer Review | unbekannt |
| Sprache | Englisch |
| Titel | Characterization and validation of the high accurate heat meter calibration facility of the Physikalisch-Technische Bundesanstalt PTB |
| Autor(in); Institution |
Cordova Murillo, Moritz Leopoldo; 7.5, Wärme und Vakuum, PTB-Berlin
|
| Quelle/Jahr | (2016), 120 S. |
| Dissertationsvermerk | Dissertation, Technische Universität Berlin, 2016 |
| DOI | |
| Verlag | Berlin: |
| Freie Schlagworte | flow rate measurement ; heat meatering ; uncertainty ; calibration facility ; comparison ; ultrasonic flow rate measurement ; validation |
| Zusammenfassung | Flow rate calibration facilities have the task to establish a flow rate under predefined conditions and to measure this flow rate within a declared uncertainty. To proof the correctness of the declared uncertainty requires in depth understanding of every hardware component. In cases where those components can not be directly isolated and modeled it is necessary to make assumptions and to make experimental validations. After the heat meter calibration rig of the Physikalisch-Technische Bundesanstalt WZP (Wärmezähler Prüfstrecke) was overhauled, establishing an uncertainty budget for the flow rate range up to 1000 m8/h and from 3 °C to 90 °C was necessary. All relevant components were modeled and characterized. Special attention was payed to the time measurement system, resulting in a novel characterization method hat has been successfully applied. The main objective of this research work is to validate the uncertainty declaration of the flow and heat meter calibration facility of the WZP and to establish for this purpose a methodology to improve the actual state-of-the-art on uncertainty validation methods for flow calibration facilities. The developed methods are capable of detecting several types of unknown systematic influences on the measurement results. But in order to guarantee that no relevant systematic errors are still present a comparison to an external absolute reference was also necessary. This reference was the National Institute of Advanced Industrial Science and Technology in Japan (NMIJ). Reciprocally, the NMIJ considered the WZP as its external reference. The challenge of this bilateral comparison trial was to find a transfer standard that was stable and robust enough to make it possible to relate discrepancies in the comparison results directly with the performance of the facilities and not with that of the flow meter itself. The flow rate and temperature ranges allowed only for ultrasonic flow meter to be considered. To define the required measurement conditions for an ultrasonic flow meter to meet the requirements of the interlaboratory comparison is one of the aims of the present work. It was determined that the most relevant influence quantity besides the flow profile within the flow meter body is the influence of the transducer pockets into the flow and consequently into the flow meter signal. By taking advantage of a specially designed window chamber for performing local velocity measurements within the ultrasonic flow meter, it was possible to determine the magnitude of the errors introduced by the transducer pockets and to define, based on the findings, the best procedure to perform the comparison. The comparison results proved directly the consistency of the measurements for 20 °C. That was not the case for higher temperatures, but considering additionally that the applied validation methods confirmed the internal consistency of the WZP across all temperatures, it can be confirmed that if the results for 20 °C are valid, the measurements at higher temperatures are necessarily also valid. Differences found in the measurement results of both laboratories could be attributed to the flow profile sensitivity of the used flow meter. The findings about ultrasonic flow metering can be used for further flow metering developments. |
