Performance tests on a double-stage metal hydride based heat transformer

In this manuscript, the performance tests on a double-stage metal hydride based heat transformer (DS-MHHT) are presented. A prototype of DS-MHHT has been built and tested for upgrading the waste heat available from 393 to 413 K to about 463 K using La0.35Ce0.45Ca0.2Ni4.95Al0.05/LaNi5/LaNi4.35Al0.65 alloy combination. The hydrogen transfer between the paired metal hydride reactors of DS-MHHT has been studied experimentally. The effects of operating temperatures such as heat source temperature and heat reject temperature on the performance of DS-MHHT in terms of coefficient of performance (COPHT), specific heating power (SHP) and second-law efficiency (ηE) were investigated. For the given operating temperatures of 463/403/303 K, the experimentally determined COPHT, SHP and ηE were 0.2, 17.1 W/kg of total alloy mass and 0.29, respectively. The maximum engineering temperature lift achieved was about 80.5 K at the operating conditions of heat output temperature 463 K, heat input temperature 393 K and heat sink temperature 298 K.