Thermodynamic analysis and optimization of compressor-driven metal hydride cooling systems

A novel thermodynamic model for performance evaluation of compressor-driven metal hydride cooling systems is presented. This model takes into account the effect of external heat transfer in the reactors and reaction kinetics of metal hydride. An evaluation of available metal hydrides for the above system is conducted and of the four metal hydrides studied, MmNi(4.5)Al(0.5) seems to be the best available option for a given compressor and reactor geometry. Once heat transfer is taken care of, reaction kinetics seems to be the major factor that can hinder the commercial applicability of these systems. Hydrides with a higher slope factor are found to be preferable for compressor-driven systems, provided COP and operating pressures do not create design limitations. There exists an optimum heat of formation for which COP is maximum. The model presented here can be used in association with other theoretical models to predict the ideal alloy combination in metal hydrides for different cooling applications. (c) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.