Hydrogen Measurements Techniques

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Bixente Garra

In order to measure hydrogen consumption, various methods can be used depending on the specific application and the level of accuracy required.

Flow meter

A flow meter can be used to measure the hydrogen consumption based on the rate flow, typically in standard cubic meters per unit of time.

:one: Turbine flow meter can be used to measure the flow rate. A rotor with blades is placed in the flow path and as the hydrogen gas flows through the meter it causes the rotor to rotate. The rotation speed is then used to calculate the flow rate. Turbine flow meters are highly accurate and precise, with a typical ±0.5% accuracy and able to reach ±0.25%. They’re also economical to purchase and easy to set up and operate with a compact structure and lightweight.

:two: Coriolis mass flow meter utilizes the principle of Coriolis force to measure the mass of hydrogen. They work by causing the fluid to oscillate within a vibrating tube, and the Coriolis force induced by the fluid’s motion is measured. The magnitude of the Coriolis force is directly proportional to the mass flow rate. Coriolis meters are versatile and can accurately measure the mass flow rate of various fluids, including hydrogen. It provides accurate readings regardless of temperature, viscosity and pressure variations. This kind of meter also measures temperature and density and has a high accuracy. However there is only a limited choice of materials and they need to be properly installed in order not to be vibration sensitive.

:three: Another flow meter is the thermal mass flow meter that works based on the principles of heat transfer. H2 has a very high heat transfer rate and to measure it with high accuracy and repeatability, a thermal flow meter should be calibrated in actual H2. This kind of meter applies only to gases and has a high measuring accuracy and has a rugged construction.

:four: Ultrasonic meters use ultrasonic waves to measure the flow rate of a fluid. These meters typically have transducers that emit ultrasonic signals through the fluid and receive them on the opposite side. The time it takes for the ultrasonic waves to travel between the transducers is measured, and the flow rate is calculated based on the difference in travel time. Ultrasonic meters can be used for both liquid and gas flows, including hydrogen. They are able to operate in both flow directions (forward and reverse) and need low maintenance. Depending on the type of the meter it can be affected by temperature, density and concentration.

:five: Differential pressure flow meters are using pressure sensors and can be employed to measure the pressure drop in a hydrogen storage tank or pipeline during consumption. By monitoring the pressure change over time, the amount of hydrogen consumed can be estimated using the ideal gas law. They’re suitable for extreme conditions of temperatures, pressures and viscosity and are affected by changes of pressure and density. They’re requiring high maintenance and experience in both maintenance and installation. Finally, they have very long inlet and outlet sections.

Electrochemical sensors

Electrochemical sensors, such as hydrogen fuel cell sensors, are frequently used for hydrogen gas measurement. These sensors operate by measuring the electric current generated when hydrogen reacts with an electrode, providing an indication of the gas concentration. By monitoring the decrease in hydrogen concentration using electrochemical sensors at specific intervals, it may be possible to estimate the consumption rate or usage of hydrogen in a system. They have low power requirements, excellent repeatability and accuracy and are economical solutions. However they have a low shelf life (6 months to one year). They’re sensitive if other gases are present within hydrogen and it could lead to potential false readings.

Gas chromatography

Gas chromatography can be used to analyze the composition of a gas sample, including the concentration of hydrogen. By continuously sampling the gas and measuring the change in hydrogen concentration over time, the amount of hydrogen consumed can be determined.