1. Modeling and Simulation on a Three-Stage Metal Hydride Hydrogen Compressor Evangelos I. Gkanas 1,2 †, Sofoklis S. Makridis 1,2*, Athanasios K. Stubos 2 1. Materials for Energy Applications Group, Department of Mechanical Engineering, University of Western Macedonia, Bacola and Sialvera Street, Kozani, 50100, Greece 2.Environmental Technology Laboratory, Institute of Nuclear Technology and Radiation Protection, NCSR “Demokritos”, Agia Paraskevi, Athens, 15310, Greece A mathematical and simulation study on a three – stage metal hydride hydrogen compressor (MHHC) is presented. The operation of a MHHC depends on the rate at which the hydrogen is absorbed/desorbed to/from the hydride bed. Multistage MHHC uses a combination of different materials as metal hydrides to increase the final compression ratio, while maximizing the absorption of both the supply pressures of each stage. By solving the coupled heat, mass and momentum transfer equations simultaneously we can predict the performance of a MHHC. The materials used for the current study are LaNi 5, MmNi 4.6 Al 0.4 and Ti 0.99 Zr 0.01 V 0.43 Fe 0.99 Cr 0.05 Mn 1.5. This three – stage compression system yields a pressure ratio of 25:1 for supply conditions 20 0 C and 5 bar. The delivery pressure achieved is 120bar for 100 0 C desorption temperature References [1] Muthukumar P, Kishore Singh Patel, Pratik Sachan, Nished Singhal Int. J. Hydrogen Energy, 37, 3797 – 3806, 2012. [2] Xinhua Wang, Haizhen Liu, Hui Li, Int. J. Hydrogen Energy, 36, 9079- 9085, 2011. [3] Talaganis B.A, Meyer G.O, Aguirre P.A, Int. J. Hydrogen Energy, 36, 13621-13631, 2011. Conclusions Mathematical Model Three-stage MHHC Material Properties Boundary Conditions Simulation Results Temperature-Pressure-Concentration Results Materials for Energy Applications Group * smakridis@uowm.gr, egkanas@uowm.gr * smakridis@uowm.gr, † egkanas@uowm.gr Energy Conservation Equation Hydrogen and Hydride Mass Conservation Equations Darcy’s Law Hydrogen Absorption Kinetic Equation Hydrogen Desorption Kinetic Equation Hydrogen Temperature and Pressure in the combined space immediately after the opening of the valve Reactor 1 absorbs the low pressure hydrogen from the supply tank. The desorbed hydrogen from Reactor 1 is the absorbed hydrogen from Reactor 2. The same process is performed between Reactor 2 and Reactor 3, while at the end of the cycle high pressure hydrogen is stored Hydrogen absorption from supply tank at constant pressure (step A-B) Heating of reactor 1 to external source temperature (step B-C) Coupled desorption (reactor 1) – absorption (reactor 2). (Steps C-D and E-F) Heating of reactor 2 to external source temperature (step F-H) Coupled desorption (reactor 2) – absorption (reactor 3). (Steps H-I and J-K ) Heating of reactor 3 to external source temperature (step K-L) Hydrogen Desorption from reactor 3 at high pressure (step L-M) Heat Flux Continuity Thermal Insulation Temperature distribution across the surfaces of the tanks, during the reactor’s 1 absorption process, the coupling between the first and second reactor, the coupling the second and third reactor and finally the desorption of reactor 3 Simulation results of the temperature distribution at different times of the absorption and desorption processes of the metal hydride tanks Temperature – Pressure and Concentration evolution during a complete three-stage compression cycle Three-Stage Metal Hydride Three-Stage Metal Hydride Compressor Simulation Validated Model Validated Model Pressure Ratio 25:1 Pressure Ratio 25:1 Delivery Pressure 120 bar for Delivery Pressure 120 bar for 100 0 C Temperature h2matters.weebly.com