Experimental investigations of heat transfer characteristics of MPCM during charging

Experimental investigations of the heat transfer characteristics during charging were performed for a 25 wt% microencapsulated phase change material (MPCM), which was synthesized by polymerization. The shell and core were urea-formaldehyde and hexadecane (C16H34), respectively. The shell-core ratio of the MPCM was 3:7 by weight. A direct mixing stratified water storage tank was installed in the experimental system to decrease the chilled supply water temperature fluctuation. The influences of different stirring rates on the heat transfer performance of the MPCM slurry was also compared. The experimental results indicated that the volumetric thermal energy storage capacity of the MPCM slurry was 1.74 times that of pure water at 200 rpm. The charging rate and heat transfer coefficient increased rapidly in the phase transition region, however, there is no significant improvement compared with pure water during the whole charging process.