2015 Volume 55 Issue 2 Pages 473-482
Magnesium oxide/water/magnesium hydroxide (MgO/H2O/Mg(OH)2) heat storage system using a composite material mixed with Mg(OH)2 and expanded graphite (EG), named as EM, was discussed experimentally and numerically. Thermal performance of EM tablet of 10 mm diameter and 7 mm thickness was evaluated by packed bed reactor experiments. Thermal performance of a packed bed of pure Mg(OH)2 pellets (diameter of pellet of 2 mm and 5–10 mm length) was compared with one of EM in the same experimental reactor. It was observed that the higher effective thermal conductivity of the bed of EM tablets contributed on enhancing the heat storage performance of the packed bed reactor. The effect of thermal conductivity enhancement of thermochemical heat storage materials was discussed numerically. The numerical model was utilized for a preliminary investigation on the behavior of a larger system, made of bundles of chemical heat storage units (CHSU), designed as pipes (length of 2 m) containing a packed bed of CHS material. It was shown that CHSU charged with EM tablets was capable to be utilized for recovery waste heat from the cooling down process of continuous casting of steel slabs.