Mass flow measurement of hydrogen and low solubility gases in laboratory-scale systems : water displacement method

Abstract

The augmented necessity to produce hydrogen and use it for energy applications has introduced a new requirement for a simple and affordable hydrogen measurement system. The purpose of this thesis was to design and develop a gas measurement system based on the water displacement method, utilizing Archimedes’ principle and buoyancy. The water displacement unit was evaluated using four different flow rates (0.02, 0.03, 0.04, and 0.05 NL/min) and compared with experimentally measured and converted to normal liters flow rates 0.0223, 0.0334, 0.0450, and 0.0545 NL/min, respectively. The determined percent error was 11.5%, 11.4%, 12.6% and 8.9% corresponding to accuracies of 88.5 %, 88.6%, 87.5%, & 91.1% respectively. The study considered the major uncertainties associated with the pressure sensor and the repeatability of the measurements. The results exhibited consistent repeatability, with a relative standard deviation of 0.24%. The linear regression analysis of the results has a value of R² = 0.9994. Also, the expanded uncertainty at 95% confidence level was ± 5.92%, and the combined standard uncertainty was 2.96%.

The mean maximum volume from the measured flow rates was 170.5 ml ± 10.09 ml. Overall, the designed and developed method exhibited the capability to provide a simple and low-cost approach to estimate the mass flow rate of low solubility gases in water for laboratory applications under stable experimental conditions, in particular, when a stable temperature is maintained between the water and the gas.