Experiment and simulation study on transfer phenomena and performance optimization of MgH2 based hydrogen storage reactors

Abstract

This paper investigated the heat transfer phenomenon and enhancement mechanism in MgH2 based hydrogen storage reactors, aiming to optimize the heat and mass transfer resistance and reaction kinetics issues encountered in practical applications of the hydrogen storage materials. The powdered MgH2 hydrogen storage material and its compacted disks were prepared to study the thermophysical properties and hydrogen absorption/desorption characteristics. For the disk prepared by composite 5 wt% EG under a compression pressure of 100 MPa, its axial and radial thermal conductivity can be as high as 2.53 and 2.03 W/(m·K), respectively, and the average hydrogen absorption rate within 1000 s is 17.2% faster than that of the powder material when applied in reactors. To gain a better understanding of the influence of the material properties, and operating conditions on the heat transfer and reaction performance inside the reactor, mathematical models for the heat and mass transfer and reaction processes of the reactor were established. Simulation results revealed the coupling mechanism of heat transfer and reaction within the storage reactor, and showed that the increased thermal conductivity and hydrogen absorption pressure can further accelerate absorption process. When the thermal conductivity increases from 2 to 10 W/(m·K) and the absorption pressure increases from 1 to 1.8 MPa, the average hydrogen absorption rate can increase by 79.4% and 42.2%, respectively.