Modeling and Simulation on a Three-Stage Metal Hydride Modeling and Simulation on a Three-Stage Metal Hydride Hydrogen CompressorHydrogen Compressor

Evangelos I. Gkanas1,2†, Sofoklis S. Makridis1,2*, Athanasios K. Stubos2

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 LaNi5, MmNi4.6Al0.4 and Ti0.99Zr0.01V0.43Fe 0.99 Cr0.05Mn1.5. This three – stage compression system yields a pressure ratio of 25:1 for supply conditions 200C and 5 bar. The delivery pressure achieved is 120bar for 1000C desorption temperature

ReferencesReferences

[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.

ConclusionsConclusions

Mathematical ModelMathematical Model

Three-stage MHHCThree-stage MHHC

Material PropertiesMaterial Properties

Boundary ConditionsBoundary Conditions

Simulation ResultsSimulation Results

Temperature-Pressure-Concentration ResultsTemperature-Pressure-Concentration Results

Materials for Energy Applications GroupMaterials for Energy Applications Group* smakridis@uowm.gr, * smakridis@uowm.gr, † egkanas@uowm.gregkanas@uowm.gr

Energy Conservation EquationEnergy 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 FluxHeat Flux

ContinuityContinuity

Thermal InsulationThermal 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 SimulationCompressor Simulation

Validated ModelValidated Model

Pressure Ratio 25:1Pressure Ratio 25:1

Delivery Pressure 120 bar for Delivery Pressure 120 bar for 10010000C TemperatureC Temperature

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