Search

While there are some hydrogen refueling stations (HRS) functioning in different parts of the world, their use is not widespread enough, primarily due to their expensive cost. Hydrogen compression is a main contributor to the capital and operation costs of the HRS. By improving H 2 compression technology, it is possible to optimize the infrastructure for refueling with hydrogen in terms of cost and performance. The use of metal hydride hydrogen compressors (MHHCs), which have the potential to be inexpensive and have the ability to use waste heat and renewable energy sources for the H 2 compression, is a promising solution to overcome this issue. The duration of the H 2 compression cycle is nevertheless a serious challenge due to the metal hydride (MH) bed's low heat conductivity. As a heating technique to improve the performance of MHHCs, electromagnetic induction (EMI) is examined numerically for the first time in this work. The dynamic behavior of a two-stage MHHC with each MH reactor having an external heat exchanger and being ringed by a copper coil traversed by an alternating current is described by a two-dimensional mathematical model, which was established and successfully verified by the reference data. Numerical simulations were performed with the help of this model, and the findings showed that the EMI heating method is faster than the heat transfer fluid (HTF) heating technique. For instance, at a delivery temperature of 373 K and a supply pressure of 20 bar, it is possible to produce 106 NL H 2 per kilogram of HPMH at a pressure of 97 bar with a 74 % shorter compression time than with the HTF heating technique. [ABSTRACT FROM AUTHOR]

Summary: This article presents a numerical investigation of two discharging procedures of a metal hydride‐hydrogen storage tank (MH‐HST). The former is categorized as "simultaneous procedure" as the heating of the MH‐HST and the discharging of hydrogen from the same start simultaneously. The latter is categorized as "separated procedure" as the heating of the MH‐HST was carried out initially and the discharging of hydrogen from the same began only when the desired desorption temperature is attained. To the best of authors' knowledge, the separated procedure is simulated and compared for the first time with the simultaneous case. For the two procedures, the discharging process was carried out in two ways, that is, at constant and variable applied pressure. A computational model governing heat and mass transfer within the MH‐HST was developed and successfully validated with experimental data. The simulation results ascertain that the simultaneous procedure is faster than the separated procedure. For example, with a desorption pressure of 0.1 bar and a heating fluid temperature of 353 K, the "simultaneous procedure" provides a reduction of the discharging time by 57% in comparison with the "separated procedure." [ABSTRACT FROM AUTHOR]

Summary: This study presents the numerical investigation of the performance improvement of Metal Hydride (MH) bed equipped with nano‐enhanced phase change material (NePCM) jacket for heat reaction recovery via U‐tube heat exchanger using Nanofluid. In this study, Mg2NiH6 is used as an MH bed, sodium nitrate (NaNO₃) as heat storage medium (PCM), and sodium‐potassium nitrate (60% NaNO₃‐40% KNO₃) as a heat transfer fluid (HTF). A computational model for this system is developed and validated. Furthermore, the hydriding of the MH bed, the melting of NePCM, and the overall heat transfer characteristics are simulated. With this model, the effect of a few types of nanoparticle additives on the hydriding process is investigated. The nanoparticles of iron oxide (Fe2O3) and copper oxide (CuO) are dispersed at various concentrations (to a range of 0‐1.5 wt.%) in the HTF. Further, CuO and graphene nanoparticles are added to the PCM to a range of 0 to 5 wt.%. The simulation shows that a reduction of hydriding process time by 33.5% is possible by using this MH‐Nanofluid‐NePCM system in comparison with a conventional MH bed system. The use of nanoparticles in the HTF, at an optimum flow rate, did not show a significant effect on the enhancement of the hydriding process. Also, the results show that CuO‐PCM composite has a greater impact in decreasing the time of complete hydriding relative to graphene‐PCM composite. [ABSTRACT FROM AUTHOR]

In this paper, coupled heat and mass transfer during the desorption process of a metal-hydrogen reactor (LaNi5-H2) is numerically investigated. To predict the dynamic behavior of this reactor, a new algorithm based on the lattice Boltzmann method (LBM) is proposed as a potential solver. Based on this algorithm, a computer code is developed using fortran 90. This algorithm is validated successfully by comparison with experimental data reported in the literature and results obtained by finite volume method (FVM). Using the developed code, the time-space evolutions of the temperature and the hydride density within the reactor are presented. In addition, the effect of some parameters (applied pressure, heating temperature, and overall heat transfer coefficient) on the dynamic behavior of the reactor is evaluated. Compared to the FVM, the proposed algorithm presents simple implementation on a computer and with reduced CPU time. [ABSTRACT FROM AUTHOR]

The integration of a phase change material (PCM) with a metal hydride (MH) reactor has received considerable attention recently. In such a system, the exothermic and endothermic processes of the MH reactor can be utilized effectively by enhancing the thermal exchange between the MH reactor and the PCM bed. In this study, a novel design that integrates the MH reactor with cascaded PCM beds is proposed. Magnesium nickel (Mg 2 Ni) alloy is used as the hydride reactor. Two different types of PCMs with different melting temperatures and enthalpies are arranged in series. A parametric study is carried out to identify the optimum distribution of the different PCMs. The results indicate that the proposed cascaded MH-PCM sandwich design improves the heat transfer rate which consequently shortens the time duration of the hydrogenation and dehydrogenation processes by 26% and 51%, respectively, compared to an MH-PCM sandwich design that includes only a single PCM. Image 1 • A new design of a metal hydride reactor equipped with cascaded PCMs was proposed. • Cyclic behaviors of the new design were investigated. • The effect of the PCMs' storage capacity distribution in the new design was studied. • The hydrogenation/dehydrogenation times were reduced by 26% and 51%, respectively. [ABSTRACT FROM AUTHOR]

Phase change material (PCM) is integrated with a metal hydride (MH) storage reactor to enhance its performance. The main function of the PCM is to store the heat released by the MH reactor during the hydrogenation process and reuse it later during the dehydrogenation process. In such a system, the exothermic/endothermic reactions are highly dependent on the heat transfer rate between the MH reactor and the PCM bed. To increase the heat transfer rate, a new configuration of the MH-PCM storage system is proposed. The new configuration consists of an MH reactor encircled by a cylindrical sandwich bed packed with PCM. The results indicate that the proposed configuration of the MH-PCM system improved the heat transfer rate which accordingly reduced the time duration of the hydrogenation and dehydrogenation processes by 81.5% and 73%, respectively, compared to a conventional MH-PCM system that includes only a single PCM bed. Image 1 • A new configuration of a metal hydride reactor equipped with PCM was proposed. • The new configuration consists of an MH reactor encircled by PCM sandwich bed. • The effect of the PCM volume distribution in the new configuration was investigated. • The hydrogenation/dehydrogenation times were reduced by 81.5% and 73%, respectively. [ABSTRACT FROM AUTHOR]

The objective of this work is to study experimentally the behavior of a metal–hydrogen reactor (MHR) during hydrogen desorption by the LaNi 5 hydride. The reactor is surrounded by a small coil traversed by an alternative sinusoidal current. The effect of the voltage applied to the coil is studied. Two kinds of tests are done. In the first one, the reactor is heated to the desired temperature and then it was put in contact with a tank at weak pressure (desorption), and in the second one, desorption and heating start simultaneously. Desorbed mass and temperature evolution within the hydride bed and in the reactor wall, as a function of time, are plotted. A comparison of results obtained by the electromagnetic induction heater and by heat exchanger provisioned by a hot fluid shows an improvement of the efficiency of the reactor when compared to the traditional hot system (fluid system). [ABSTRACT FROM AUTHOR]