Thermal performance of a dynamic insulation-phase change material system and its application in multilayer hollow walls

The Building integrated with phase change material (PCM) creates a large thermal barrier between indoor thermal environment and ambient, usually resulting in overheating problem in summer. Dynamic insulation system (DIS) based on air flow is introduced into PCM to form a composite structure featured with switchable thermal resistance to address this issue. Theoretical model is built according to phase transition of PCM and heat transfer between PCM and flowing air. Result indicates that thermal resistance can be modified by natural convection and forced turbulence of air. Forced turbulence case obtains the lowest thermal resistance, orderly followed by natural convection and closed cases. Temperature and phase change contour indicate that turbulent air enables to promote uniformity of temperature and phase transition distribution. Larger H/L ratio and height of PCM cavity inducing more intensive air flow are favorable to heat transfer between air and PCM. A DIS-PCM module with low flowing rate or large inputted heat flux produces rapid heat transfer rate and early PCM melting. The Built DIS-PCM module is then coupled with the multilayer hollow wall component to investigate potential application in relieving building overheating issue. Lower average temperature of the interior wall and higher heat dissipation rate from indoor thermal environment verify that the DIS-PCM module enables to resolve building overheating under constant or variable ambient temperature, even at slight temperature difference between indoor and ambient temperatures. Indoor thermal comfortable temperature can be accurately adjusted according to the air flowing rate. In conclusion, the novel DIS-PCM system eliminates building overheating issue through its thermal resistance switch in response to various working scenarios, with substantial benefits to development of latent heat thermal energy storage available to building energy conservation.