Abstract

A two grade phase change material (PCM) based on CaCl 2 -water system has been investigated in a PCM—water heat ex-changer. The crysta llization of diff erent hydrates of CaCl2 ex-tended the temperature range of heat storage and the storage stability was achieved by the application of wood chips as thick-ening agent. A short section of the heat exchanger tube (a few cm) can be characterized by a maximum curve of heat transfer coefficient in function of cooling time. Longer sections (a few
meter) showed nearly constant heat transfer coeffi cient in the range of 1 15 +/- 25 W/ m2 K. The heat storage system is to be ap-plied to store solar energy and the stored heat is used to preheat the water input of domestic hot water supply system.

Keywords heat storage · phase change material · solar energy · heat transfer coefficient

Acknowledgement The authors are indebted to the Hungarian Research Fund (OTKA T-037496) for financial support.