Studies on metal hydride based single-stage heat transformer

• Metal hydride based single-stage heat transformer was built and tested.
• The estimated COPHT and SHP of the system were 0.35 and 44 W/kg.
• Maximum temperature lift achieved was 44 K.
• Numerically predicted results were in good agreement with the experimental data.

In this manuscript, experimental and numerical studies on a single-stage metal hydride based heat transformer (MHHT) are presented. A prototype of a single-stage MHHT is built and tested for upgrading the waste heat available from 393–413 K to about 428–440 K using LaNi5/LaNi4.35Al0.65 pair. The transient behavior of hydrogen exchange associated with heat transfer is presented for a complete cycle. The effects of heat source temperature and heat rejection temperature on the performance of MHHT in terms of coefficient of performance (COPHT), specific heating power (SHP) and second law efficiency (ηE) are investigated. At the given operating conditions of heat output temperature 428 K, heat input temperature 413 K and heat sink temperature 298 K, the experimentally predicted COPHT and SHP are 0.35 and 44 W/kg, respectively. Both COPHT and SHP are found to increase with the heat source temperature. The numerically predicted results are in good agreement with the experimental data.