Performance investigation of a single-stage metal hydride heat transformer

This article presents the performance analysis of a single-stage metal hydride-based heat transformer (SS-MHHT) working with three different alloy pairs, namely LaNi_4.6Al_0.4/MmNi_4.15Fe_0.85, LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8-Mn_0.2, and Zr_0.9Ti_0.1Cr_0.9Fe_1.1/Zr_0.9Ti_0.1Cr_0.6-Fe_1.4. The performances of the SS-MHHT are predicted by solving the conjugate heat and mass (hydrogen) transfer equations in cylindrical coordinates. The effects of various parameters such as heat output (T_H), heat input (T_M), and heat sink (T_L) temperatures on the coefficient of performance (COP_HT), specific heating power (SHP) and second law efficiency (η_E) are presented. The effects of overall heat transfer coefficient and mass ratio on the coefficient of performance (COP_HT) and specific heating power (SHP) are also presented. Numerical results are compared with the experimental data reported in the literature, and a good agreement is found between them. The maximum COP_HT of 0.436 and SHP of 54 W/kg are obtained for LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8-Mn_0.2 pair. For a given operating temperatures of T_M = 358 K and T_L = 298 K, the maximum temperature lift of about 50 K is predicted for Zr_0.9Ti_0.1Cr_0.9Fe_1.1 /Zr_0.9Ti_0.1Cr_0.6Fe_1.4 pair.