Effects of various carbon additives on the thermal storage performance of form-stable PCM integrated cementitious composites

Abstract

This study focuses on further development of a novel paraffin/hydrophobic expanded perlite form-stable PCM composite to increase its heat transfer performance when used in cement-based composites. For this purpose, various high conductive carbon-based additives, such as graphite (G), carbon nanotubes (CNT) and graphene nanoplatelets (GNP), were integrated into form-stable PCM composite and their heat transfer enhancement was studied and compared. It was found that all additives have good chemical compatibility, high latent heat and significant enhancement in thermal conductivity of PCM composite. The use of 0.5 wt% of G, CNT and GNP led to the thermal conductivity enhancement of 45%, 30% and 49% respectively. Although G and GNP additives showed high thermal conductivity increment, heat transfer performance tests showed that GNP leads to highest performance enhancement and graphite the least. It was inferred that irrespective of the improvement in thermal conductivity, heat transfer performance of form-stable PCMs largely depends on the formation of the high conductive interconnecting network in the porous granules. The additives with the high specific surface area and smaller particle size than the pore diameter would be an excellent candidate to improve heat transfer performance of form-stable PCMs. TES performance of cementitious composites, as measured from prototype test cell experiments, revealed that the integration of G, CNT, and GNP into form-stable PCM enhanced the heat gain energy of interior walls by 78%, 122%, and 200% respectively.