Thermodynamic simulation of hydrogen based solid sorption heat transformer

Abstract

The hydrogen absorption and desorption pressure-concentration isotherms (PCI) of La0.9Ce0.1Ni5 and LaNi4.6Al0.4 alloys are measured by static and dynamic method. The hydrogen absorption and desorption kinetics of the alloys also measured. The measured properties are used to study the performance of hydrogen based solid sorption heat transformer (MHHT). The thermodynamic simulation of MHHT is conducted using statically and dynamically measured PCI and thermodynamic properties. Due to variation in statically and dynamically measured metal hydride properties, significant variations in coefficient of performance (COP) and heat transformation capacity of MHHT are observed. In case of thermodynamic analysis using dynamically measured properties the heat transformation capacity and COP are decreased by 42.6% and 22.2% respectively, compared to statically measured data. This is due to the decrease in amount of hydrogen transmission and pressure differential between paired metal hydride reactors, and increase in reaction enthalpies. Later, the actual thermodynamic cycle for MHHT is constructed by considering the variation in pressure during hydrogen transfer processes between the metal hydride reactors.