The overall objective of the Met4H2 research project is to provide new and improved standards for safe hydrogen applications, flow measurement, hydrogen quality assessment and custody transfer. A significant part of the project is focused on flow measurement. The objective is to collect and analyse data on flow measurements of hydrogen and hydrogen-containing gas mixtures along the entire hydrogen supply chain, and to design a traceability strategy for large-scale hydrogen flow metering to facilitate compliance with, e.g., OIML R137, OIML R140, and the Measurement Instruments Directive.
This technical report presents the findings of an effort in the Met4H2 project to produce a traceability chain for hydrogen flow metering. Relevant flow metering points and requirements for fiscal metering points were identified through surveys of stakeholders involved in large-scale hydrogen applications.
A route for traceability is suggested. It involves the operation of newly developed primary standards to calibrate Critical Flow Venturi Nozzles (CFVN). The primary standards that are suggested are of the pVTt type, for which a concept study and a cost estimate is provided. The CFVNs are then combined in an array to bootstrap to larger flow rate ranges, detailed in an experimental protocol. The array allows for calibration of master meters.
Calibrations of CFVN with hydrogen gas were performed. Early results show that the discharge coefficient curve for hydrogen closely follows that of air, and both are within the uncertainty of the laboratory.
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