Compressor Driven Metal Hydride Cooling Systems: Simulation and System Dynamics

A comprehensive mathematical model to study the performance parameters of compressor driven metal hydride systems is presented. The dynamics of the compressor and the conditioned space has been taken into account. The model also accommodates the transient nature of the external fins. The effect of size and geometry of the heat exchanger has been given due importance while calculating the external heat transfer coefficient of the metal hydride reactors. A 1 TR system is designed using MmNi_4.5Al_0.5 as the metal hydride and its operating characteristics are studied. The average COP and SP power obtained are around 3.1 and 125 W/kg respectively. It is seen that compressor remains idle for 30% of the time during stable cycling. The problem of large initial compressor loads during cut-in as is encountered in vapour compression systems are not faced in such systems. Moreover the compressor is not overloaded during sudden load changes.