Experimental study on phase transition behaviour of shape stable phase change material for application in vacuum insulation panel

Abstract

Abstract Phase Change Materials (PCMs) are a unique ingredient in the Vacuum Insulation Panel (VIP) core to improve its thermal mass. The integrated PCM in VIP core is exposed to a pressure below 1 mbar, so its phase transition behaviour needs to be investigated in the vacuum environment. Phase transition effect of three types of Shape Stable Phase Change Material (SSPCM) during charging-discharging in ambient pressure and 0.4 mbar pressure was analysed in this work. Neopentyl Glycol (NPG), Polyurethane (PU) and Microencapsulated Paraffin (MEP) were used as the SSPCMs in this study. Temperature-time (T-t) plot and the mass loss of the three SSPCM during its charging-discharging period in both pressure conditions were analysed. Structural, morphological, chemical and thermophysical properties differences of SSPCM after charging-discharging cycles in both pressure conditions were analysed separately. From XRD analysis, the structural stability was observed with slight percentage changes in crystallinity. DSC analysis reveals more phase transition reversibility and low subcooling effect for samples from vacuum condition. PU and NPG experienced an increase in thermal diffusivity after vacuum thermal cycle. T-t plot analysis was effective for the analysis of phase transition behaviour of bulk SSPCM during charging-discharging in different pressure. The difference in phase transition behaviour in both pressure conditions was analysed. MEP recorded the least mass loss of 0.78% and 0.82% in both pressure conditions while NPG at vacuum showed the highest mass loss of 8.45%. The results show that MEP was comparatively better SSPCM for integration in VIP.