Heat penetration reduction through PCM walls via bubble injections in buildings

In this study, a novel Phase Change Material (PCM) wall device using bubble injection method is proposed for the application of PCM in building envelopes. When bubbles are injected into the bulk PCM wall, the density difference between PCM and bubbles causes the upward movement of the bubbles and flow in the liquid PCM. The movement of the bubbles destroys temperature stratification in the PCM. Therefore, applied heat can be successfully used for PCM phase change, and heat penetration across the PCM is reduced. To evaluate the effect of the bubble injection method, two experimental cells-a cell with bubbles injected into the walls of bulk PCM and a cell without bubble injection-were operated simultaneously for comparison. As a result, with the application of the bubble injection method, 11% more latent heat energy was stored in the PCM and 28% less heat penetrated across the PCM wall. For further analysis, visualizations were created via shadowgraph and particle image velocimetry to compare the trends of phase change and analyse the internal flow fields. The average flow rate inside the liquid PCM with bubble injection was 19 times higher than the one without. Based on these results, the bubble injection method was confirmed to improve the performance of insulation and energy storage of PCM walls. Therefore, bulk PCM application was validated to improve the building of envelopes.