Durability to repetitive reaction of magnesium oxide/water reaction system for a heat pump

The feasibility of using a magnesium oxide/water system in a heat pump was examined experimentally From the viewpoint of enhancing the durability of the repetitive reaction cycle and increasing the heat output performance. Three kinds of magnesium oxide materials tested in this study were formed using the following precursors: ultra fine magnesium oxide powder, common magnesium hydroxide and magnesium ethoxide. The reaction cycles for both hydration and dehydration of the magnesium oxide materials were examined in each experiment. A new magnesium oxide material using ultra fine magnesium oxide powder as the precursor was the most appropriate material for the heat pump, because it exhibited high durability and high heat output performance compared to the other oxides. Although reactivity of the new material decreased during the initial five reaction cycles, the reactivity remained relatively constant over the next 19 cycles. Based on the experimental results, the thermal performance of a heat pump using the new material was simulated numerically. The new material produces an outputting of 180 W/kg after 24 repetitions over a 15-min period. It was concluded that the high durability of the new material was due to the high purity of the starting materials. (C) 1997 Elsevier Science Ltd.