OPERATING CHARACTERISTICS OF METAL HYDRIDE HEAT-PUMP USING ZR-BASED LAVES PHASES

A prototype heat pump was constructed using Zr-based Laves phase alloy pairs in combination with the tubular-type reactor of 19.1 mm outer diameter, and the operating performance of the system was investigated. To enhance the heat transfer along the radial directions in the tubular reactor, 120 mesh brass screens were inserted in the hydride bed at the intervals of 2 mm. Zr0.9Ti0.1Cr0.9Fe1.1 and Zr0.9Ti0.1Cr0.6Fe1.4 were used as high temperature and low temperature side alloys, respectively. The dependence of the cooling power output on operating parameters such as the hydrogen charged amount, cycle time, air flow rate, heat source temperature was investigated. The optimum operating conditions were evaluated as follows: (i) the initial amount of hydrogen charged = 12.8-13.2 mol; (ii) cycle time: hearing time = 4 min and cooling time = 7-8 min; (iii) air flow rate > 3.8 m(3) min(-1); (iv) heat source temperature > 220 degrees C. The maximum power obtained under optimum operating conditions is about 130 kcal (kg-alloy h)(-1).