Preparation and thermal properties of NaOAc·3H2O-CO(NH2)2 non-eutectic binary mixture PCM for radiant floor heating system

Abstract

To make full use of phase change material (PCM) in heat exchanger for radiant floor heating system, the NaOAc·3H2O-CO(NH2)2 non-eutectic binary mixture PCM, using NaOAc·3H2O as phase change principal component, CO(NH2)2 as temperature regulator and Na2HPO4·12H2O as nucleator as well as sucrose (C12H22O11) as auxiliary nucleator, was developed. The possible thermoregulation mechanism of CO(NH2)2 on NaOAc·3H2O was preliminarily discussed. Meanwhile, the supercooling degrees of the non-eutectic PCMs with different Na2HPO4·12H2O and C12H22O11 contents were also investigated. The results showed that the NaOAc·3H2O-CO(NH2)2 non-eutectic binary mixture PCM containing 8% CO(NH2)2, 1.5% Na2HPO4·12H2O and 2% C12H22O11 possessed a proper phase change temperature (48.45 °C), high latent heat (245.4 J/g), the low supercooling degree (2.60 °C), the enhanced crystallization behavior and an excellent thermal reliability. The hydrogen-bond interactions of -NH2 in CO(NH2)2 on three crystal H2O molecules and CH3COO− in NaOAc·3H2O weakened the intermolecular forces of NaOAc·3H2O and the coordination of NaOAc on H2O, thus resulting in a decrease in the phase change temperature of the non-eutectic mixture.