Phase separation and supercooling are common phenomenon of salt hydrates

which is a key problem affecting the thermal stability and thermal performance of phase change material. Sodium acetate trihydrate (SAT)

as a low and medium temperature hydrate salt

is the main study object. Carboxyl methyl cellulose (CMC) and disodium hydrogen phosphate dodecahydrate (DHPD) were firstly used to modify SAT by melt blending method. A high-performance composite phase change material (PCM) was prepared by optimizing the ratio of the additives. The thermophysical properties and stable performance of different samples were tested by using differential scanning calorimetry (DSC) and a melting-freezing setup. The effects of the additives on phase change enthalpy

phase transition temperature

supercooling and phase separation were analyzed. Finally

a high-density heat reservoir was built by using the modified PCM and a latent heat storage water system was set up. The charging and discharging performance of the system under different working conditions were analyzed. The results showed that adding 0.5% CMC as the thickening agent and 2% DHPD as the nuclear agent could avoid phase separation and decrease supercooling degree. The phase change enthalpy and temperature range of modified SAT were 258 kJ·kg-1 and 57℃

respectively. The modified PCM had good cycling stability and its supercooling degree was smaller than 2℃. In addition

the output water temperature of the latent heat storage system under different cooling conditions can be heated up to over 50℃. The efficiency was higher than 90% and the heating power was as high as 10 kW. The heating power

energy storage capacity and thermal storage efficiency increased with the decrease of the inlet water temperature. The system has good charging and discharging performance and its volume heat storage density is 2.6 times as higher as traditional water tank.