Experimental study of a solar storage packed bed using PCM capsules having different melting points.

A solar storage packed bed using sphere capsules filled with phase change material having different melting points was presented. The thermal performance of its energy charge process was experimentally studied. Two different charge modes of constant inlet temperature mode and solar charge mode were both researched and analyzed. The experimental results indicated different temperature histories of phase change material (PCM) with that of traditional single-type packed bed. PCM at highest segment of the packed bed started and ended melting latest while PCM at other segments started and finished melting at nearly the same time. The duration time for completing whole energy charge process was reduced, so the energy charge efficiency was consequently improved. The effects of inlet water temperature and inlet flow rate were also experimentally analyzed. High inlet temperature or high inlet flow rate reduce the charge duration with shortened melting process. Solar charge mode experiment showed on sunny weather condition, the whole charging time needed is much shorter than that on cloudy weather condition.