PREDICTION OF METAL HYDRIDE HEAT TRANSFORMER PERFORMANCE-BASED ON HEAT-TRANSFER AND REACTION-KINETICS

The performance of a metal hydride heat transformer is predicted based on heat transfer and reaction kinetics of the paired hydride beds. Results are computed for a heat transformer working with a ZrCrFe1.4/LaNi5 pair. The results show that due to the low effective thermal conductivity of the hydride beds, the performance of the system is controlled initially by heat transfer. However, when the effective thermal conductivity and overall heat transfer coefficient exceed a certain value, the reaction kinetics assume importance. The performance of the system improves significantly with input temperature as heat is supplied in both the half cycles. The performance also improves as the output and heat rejection temperatures decrease. For the ZrCrFe1.4/LaNi5 system the coefficient of performance lies between 0.27 and 0.30 and the second-law efficiency lies between 0.37 and 0.44.