09. Heat and Mass Transfer

In recent years, daytime power loads during the summer in Japan have been increasing annually due to the rising demand for air conditioning. This has brought attention to cold thermal storage systems, which are effective for leveling power loads. These cold thermal storage systems have been mainly implemented in large-scale air conditioning systems for office buildings and large facilities. While there has been significant progress in the introduction of renewable energy and the spread of energy storage facilities, the high energy density of these systems can lead to major accidents, raising safety concerns. Thermal storage systems, which store energy as heat, are being reconsidered as a safe and effective technology. This study focuses on TBAB (tetra-n-butylammonium bromide) hydrate, a type of thermal storage material. TBAB hydrate has a phase change temperature close to the temperature range used for cooling, and it boasts 2 to 3 times the thermal storage efficiency within the same temperature range as pure water. However, TBAB hydrate has the issue of supercooling during cold storage. Kumano et al. have investigated the effects of voltage application on resolving supercooling in TBAB aqueous solutions, particularly focusing on the influence of electrode-generated products. In this study, we focused on mass transfer using redox reactions in aqueous solutions induced by voltage application and visualized the concentration field of TBAB aqueous solution using the Schlieren method. Schlieren images of the aqueous solution near the platinum electrode showed light and dark areas near the anode. This result suggests the potential for realizing controlled mass transfer by voltage application.