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 LaNi4.6Al0.4/MmNi(4.15)Fe(0.85), LaNi4.61Mn0.26Al0.13/La0.6Y0.4Ni4.8-Mn-0.2, and Zr0.9Ti0.1Cr0.9Fe1.1/Zr0.9Ti0.1Cr0.6-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 (TH), heat input (TM), and heat sink (T-L) temperatures on the coefficient of performance (COPHT), specific heating power (SHP) and second law efficiency (eta(E)) are presented. The effects of overall heat transfer coefficient and mass ratio on the coefficient of performance (COPHT) 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 COPHT of 0.436 and SHP of 54 W/kg are obtained for LaNi4.61Mn0.26Al0.13/La0.6Y0.4Ni4.8-Mn-0.2 pair. For a given operating temperatures of TM = 358 K and TL = 298 K, the maximum temperature lift of about 50 K is predicted for Zr0.9Ti0.1Cr0.9Fe1.1/Zr0.9Ti0.1Cr0.6Fe1.4 pair.