Design considerations for dynamic fluid flow in porous media experiments using X-ray computed micro tomography – A review

Within the past decade, X-ray micro computed tomography (µCT) has become an advanced non-destructive tool to analyse the internal structure of opaque materials. In addition to high spatial resolution, new generations of laboratory-based µCT machines and synchrotron imaging facilities can achieve high temporal resolution. This makes µCT the method of choice to study dynamics processes such as multi-phase fluid flow within porous media at the micro-meter scale. To perform such experiments a system compatible with X-ray imaging is needed. This essentially includes an X-ray transparent flow cell which should both be compatible with the requirements of the experimental study and the constraints of the µCT facilities. So far, most µCT flow cells are custom built and optimised for specific experiments/purposes. This paper reviews the previously published X-ray transparent cell designs, their advantages, and limitations. We present the state-of-the-art in design of X-ray transparent flow systems and discuss the technical challenges around performing µCT-based fluid flow experiments. We also present a review of the main applications which have benefited from µCT imaging studies and discuss the flow cell designs according to applications.