A review on applications of optical visualization technologies for water management in proton exchange membrane fuel cells

Effective water management is crucial for performing proton exchange membrane fuel cells. The liquid water can be directly observed using an Optically visualized proton exchange membrane fuel cell system that employs optical visualization technologies, which brings great convenience for water management. It is challenging to comprehensively understand and summarize the applications of these technologies. Through insightful analyses of relevant research results, this study provides the first comprehensive and categorized review of optical visualization technologies and their applications in water management. First, the study reviews optical visualization systems, focusing on their composition and differences between in-situ and ex-situ systems, the effects of transparent materials, imaging device selection, and image processing methods. These are key points for optical visualization systems. This can save a lot of time and economic costs in the design process. The review then categorizes the applications of optical visualization technologies in water management research, covering two-phase flow in porous regions and flow fields. This categorization helps to clearly understand the current state of research in different fields and the characteristics of the optical visualization systems used. Finally, a critical assessment of the problems and potential applications of optical visualization systems is presented. The purpose of this review is to provide relevant studies, practitioners and policy makers with a foundation and reference on optical visualization systems and the application of optical visualization techniques in water management research.