Radiography of gas-liquid two-phase flows in porous materials

Part of the project OxySep

Contact persons:        Prof. Dr. et Ing. habil. Kerstin Eckert, Dr. Xuegeng Yang,
Dr.-Ing. Karin Schwarzenberger

Project staff:               Dr.-Ing. Tobias Lappan

Motivation

With the growing need of renewable energies and the goal to achieve climate neutrality, H₂ came into focus for future energy systems due to its high efficiency and easy transportability.

The electrolysis of water represents the major source of H₂. While the process itself as well as the nucleation of hydrogen are well understood, there is still lack in knowledge regarding the O₂ bubbles which is a reason why these systems currently cannot achieve maximum efficiency.

Objectives

• visualisation of the formation and transport of O₂ bubbles in the porous anode material, by means of X-ray and neutron radiography
• development and implementation of model experiments in order to characterise the gas evolution and transport through the liquid flow along the anode under defined conditions
• flexibility of the experimental set-up with regard to the porous materials to be investigated and their dimensions as well as the experimental and flow conditions

Methods

• X-ray and neutron radiography for imaging flow measurements in a field of view of approx. 100 mm x 100 mm and at an imaging frame rate of max. 100 fps
• generic flow experiment: gas bubble generation by introducing compressed air through one or more nozzles into the counter- or cross-flowing liquid phase within the porous material
• with regard to the material-specific attenuation of the radiation, X-ray radiography is suitable for flow visualisation within porous polymeric materials, whereas neutron radiography is particularly suitable for porous metallic materials
• neutron radiography also offers the possibility to visualise the flow front of the liquid phase by partially replacing conventional water (H₂O) with heavy water (deuterium oxide, D₂O), which has different neutron attenuation characteristics
• X-ray radiographic measurements in the X-ray laboratory at the HZDR; neutron radiography in cooperation with the "Laboratory for Neutron Scattering and Imaging" at the Swiss spallation neutron source (SINQ), Paul Scherrer Institute (PSI), one or two measurement campaigns lasting several days per year