Enhanced thermal performance of Na2HPO4·12H2O composite phase change material supported by sepiolite fiber for floor radiant heating system

Abstract

The application of phase change materials (PCMs) with latent heat storage characteristics in building system can coordinate the imbalance between energy supply and demand by absorbing excess heat, thereby achieving the overall energy consumption reduction. In this study, a novel kind of composite PCM (CPCM) composed of modified Na2HPO4·12H2O and sepiolite fiber (SEP) is developed. It is shown that adding 4 wt% of α-Al2O3 and 1.5 wt% of sodium alginate (SA) can reduce the supercooling degree of Na2HPO4·12H2O from 18.4 °C to 1.0 °C. The obtained PCM mixture is absorbed into SEP to fabricate form-stable composite PCM at a loading of 60 wt%, which has a melting temperature of 35.7 °C and a high latent heat of 127.8 kJ kg−1. The composite processes good thermal reliability and a moderate thermal conductivity of 1.069 W m−1 K−1. Furthermore, thermal performance of the CPCM is evaluated by combining a floor radiant heating system with CPCM layer in a small testing room. It is found that the average central temperature of the testing room with CPCM floor can be increased by 3.1 °C compared to that of the reference room. Besides, the thermal comfort time of indoor air temperature in CPCM room can be up to 252.5 min longer. The better thermal regulation performance of the CPCM floor is attributed to its suitable phase change temperature and high latent heat. The results indicate that the obtained CPCM can be employed into floor system for building energy conservation purpose.