Hydride Reactor Research Articles

The effect of powder and pellet forms of added metal hydride materials on reaction kinetics and storage

In the present research, metal hydride pellets were synthesized to enhance the kinetics of hydrogen charge/discharge processes. By incorporating ENG (expanded natural graphite) and copper additives, we observed improvements in the heat transfer coefficients and storage capacities of the hydrogen storage materials. The reactor is designed to contain 1000 g of storage material in the form of powder or 25 pellets each weighing 40 g. The influence of storage materials with enhanced thermal conductivity on the hydrogen charge/discharge process was experimentally studied in a metal hydride reactor under a pressure of 10 bar. The reactor was heated under vacuum (10−4 mmHg) to approximately 200 °C for 2 h in order to complete the activation process. Following the heating process, the reactor was allowed to cool to ambient temperature, after which the hydrogen was introduced to the reactor at 10 bar pressure for 50 min. The absorption and desorption procedure was reiterated up to 20 cycles, and recordings of data were taken at intervals of 5 cycles to monitor the variations between the cycles. After 10 charge/discharge cycles under pressure of 10 bar, the hydrogen stored in the reactor amounted to approximately 9.93 g in pellet form and 7.20 g in powder form.

Modeling and Validation of Assisted Cold Start for a PEMFC Coupled to a Thermochemical Preheater

Cold start from sub-zero temperatures poses a challenge for automotive application of polymer electrolyte fuel cells (PEMFC), as product water freezes inside the cells hereby endangering operation safety. Therefore, ice formation in the cathode pores has to be avoided by preheating of the fuel cell above sub-zero temperatures. The concepts for such assisted cold start can be divided into internal and external heating strategies [1]. Amongst the latter, especially thermochemical preheating by metal hydrides presents a compelling yet efficient technology, as the heat is provided by exothermal hydrogen absorption without consumption of additional external energy.In this work, assisted PEMFC cold start is simulated with the transient 2D numerical model for a single fuel cell thermally coupled to a thermochemical preheater via a coolant fluid developed by Gießgen and Jahnke [2]. Here, the numerical model is validated against cold start experiments of the coupled system for both cell behavior and thermal balance of the heat transfer fluid. Starting from an initial temperature of -5°C, fuel cell behavior is then studied for 300 s of open circuit voltage (OCV) followed by a current density ramp up to 0.33 A/cm² in 150 s and a subsequent constant current period up to 500 s. Model validation is done with respect to temperature and voltage evolution as well as the energy balance of the coupled system. When the cold start is unassisted, a significant voltage drop down to 0.6 V is observed to occur already at 0.22 A/cm² and thus before reaching the maximum current density by the end of the ramp. Whereas difficult to deduce from experiments, this intermediate voltage drop can be linked to massive ice formation blocking up to 87% of the cathode catalyst pores, eventually causing a significant decrease of the electrochemically active surface (ECSA). For this ECSA reduction, an exponential dependence on the ice saturation is identified, suggesting that initial ice nucleation primarily occurs on the macroporous catalyst surface, thereby blocking the nanoporous surfaces of the primary particles within. When the cold start is assisted, a preheating phase of 41 s is performed prior to the current ramp. As the metal hydride reactor effectively heats up the heat transfer fluid, the fuel cell temperature in turn raises rapidly above the freezing point in less than 20 s. Consequently, ice formation is observed to be effectively reduced to saturations of less than 1%. As a result of this assisted cold start, the voltage drop is significantly attenuated and a minimum voltage of 0.65 V is now reached for a maximum of 0.33 A/cm² only at the end of the current ramp.

Effect of expanded natural graphite addition and copper coating on reaction kinetics and hydrogen storage characteristics of metal hydride reactors

Experimental and numerical studies are carried out to determine the effects of copper coating and/or ENG (expanded natural graphite) addition on the hydrogen storage performance of ground LaNi5. The amounts of copper coating and/or ENG addition are also investigated. The results reveal that the thermal conductivity of ground LaNi5 can be improved by up to ∼6 and ∼12 times with copper coating and ENG addition, respectively. This results in enhanced hydrogen absorption kinetics thereby significantly reduced hydrogen charging times, compared to those determined for LaNi5 without any addition. On the other hand, the amount of hydrogen stored shows a decreasing trend with increasing copper coating and ENG addition since the weight of storage material loaded to the reactor is kept the same. Nevertheless, the optimum copper and ENG contents are determined regarding the amount of stored hydrogen and the corresponding charging time. Similar H/M values are obtained with the optimized powders with additives compared to that of ground LaNi5. Based on these results, various new samples are also prepared by mixing the decided copper coated LaNi5 and ENG added LaNi5 powders and examined to optimize the composition of these blended powders.

Design of a Low-pressure Metal Hydride Reactor Designed for Hydralloy C5

Design of a Low-pressure Metal Hydride Reactor Designed for Hydralloy C5

Design and optimization of metal hydride reactor with phase change material using fin factor for hydrogen storage

The solid-state hydrogen storage in metal hydride (MH) is safer and energy efficient than the gaseous and liquid storage methods. The absorption of hydrogen in MH is highly exothermic. Hence, a good heat management system is required to increase the charging rate. The phase change material (PCM) can be integrated into the reactor to reuse the absorption heat for hydrogen desorption. The present numerical study models the concentric cylindrical reactor with magnesium (Mg) as MH surrounded by sodium nitrate (NaNO3) as PCM using COMSOL Multiphysics v6.1. The effect of buoyancy inside the PCM domain is investigated. An iterative approach is used to determine the required amount of PCM. Copper fins are added inside both MH and PCM. The effect of the number of fins, corresponding fin thickness and pitch on hydrogen absorption are determined to optimize the MH reactor. The outcomes reveal that the hydrogen absorption rate increases with fin numbers. The reactor with 10 and 30 fins takes 86.5 and 97.3 % less time than without fins for 90 % hydrogen absorption, respectively. The novel approach is proposed to estimate the fin efficiency (ηf) using temperature profiles of MH and fin during prevailing unsteady heat and mass transfer. The fin factor (Ff) is presented using the ηf and mass of MH. The performance evaluation criterion (PEC) is discussed based on hydrogen absorption relative to the system's weight. Further, the effect of operating parameters like hydrogen supply pressure and the initial temperature is studied on the reactor performance.

A kind of numerical model combined with genetic algorithm and back propagation neural network for creep-fatigue life prediction and optimization of double-layered annulus metal hydride reactor and verification of ASME-NH code

The safety and stability of metal hydride reactor (MHR) structure are significantly important for normal operations of hydrogen isotope storage and supply system. Moreover, considering that the experiments of studying the fatigue and creep properties of MHR structure are always time, money, difficulty and energy consuming. To further improve the service life of MHR as well as lower the failure risk, this paper proposes a system integration method based on ASME code validation, which combines genetic algorithm (GA) and back propagation neural network (BPNN) for rapid assessment of creep-fatigue life (CFL) and optimal design of structural parameters. First, numerical simulation is applied to perform thermal-mechanical coupled finite element analysis and verified by ASME code. Then, parametric sensitivity analysis and experimental design of parameter-based training set based on Taguchi method were performed, and response values are obtained from physical models combined with numerical simulations. Finally, a parametric optimization procedure combining BPNN and GA is developed based on the training data. In the workflow, parametric data flow is passed through the experimental design, numerical simulation, prediction and optimization processes. The results show that the proposed BPNN proxy model based on ASME code validation has good performance in predicting the life of MHR. Based on this, the life of the MHR is improved by 8% compared to the reference sample.

Optimization of tree-shaped fin structures towards enhanced discharging performance of metal hydride reactor for thermochemical heat storage based on entransy theory

Integrating fin structures into metal hydride (MH) bed can enhance heat discharging performance of the reactor for thermochemical heat storage. In this study, based on the entransy theory, the entransy dissipation rate (Eh,st) or the entransy dissipation (Eh,tr) of a simplified two-dimensional (2D) steady-state or transient heat conduction model for the MH bed was used to be an objective to optimize the tree-shaped fin (TSF) structures. Furthermore, response surface method (RSM) was adopted to explore the relationship between Eh,st or Eh,tr and structural parameters (i.e., branch number N, branch level M, length ratio α, width index β, and angle ratio γ). The results show that RSM can effectively predict influences of structural parameters of TSFs on heat discharging performance. Based on RSM with entransy theory, the obtained optimal combination parameters were N = 8, M = 3, α = 1, β = 0.5, and γ = 1, corresponding to the maximum gravimetric exergy-output rate (GEOR) of 20.98 W/kg. Furthermore, the GEOR with optimized fins was 11.5 % higher than that with unoptimized TSFs. The optimization method based on the entransy theory was effective to optimize the TSF structures by solving 2D model instead of three-dimensional model, and shorten the calculation time for optimization.

Design and optimization of longitudinally finned embedded tube-type hydride reactor based on standardized responses using MO-desirability-based technique

The current research comprehensively investigates a longitudinal finned LaNi5 hydride-based hydrogen storage device. The design factors, namely the heat fin's thickness and height, are selected for optimization. The employed Central Composite design formulated eight cases when design factors varied between 2–5 mm fin heights and 1–2 mm thicknesses. The investigation emphasized the influence of the contact area between the copper fin and LaNi5 hydride on output responses such as 90 % and 100 % saturation time, thermal power, and alloy weight ratio. The optimal design for the longitudinally finned hydride reactor is determined using a quadratic regression model and a multi-response desirability technique. The desirability approach indicated a final design archetype for a capacity of 5 kg LaNi5 (assuming 20 % expansion volume) comprising a fin thickness of 1 mm and a height of 5 mm, yielding a combined desirability of 0.737. The simulation results of the optimum design show response values of 131 s, 612 s, 0.572, and 233.39 W/kg for 90 % saturation, 100 % saturation, weight ratio, and thermal power, respectively, against the regression model predicted values of 129.5 s, 609.33 s, 0.572085, and 233.587 W/kg with an overall deviation less than ±1.5 %. Additionally, a comparative study against the reactor designs reported in the literature revealed the modeled design's betterment, and henceforward, scaling up the present design improved the weight ratio without much hampering the absorption time and thermal power. Subsequently, a sensitivity study is performed to evaluate the means by which different operational conditions impact system performance.

Metal hydride reactor for output temperature control

Precise temperature control of fuel cell stacks is crucial to avoid degradation mechanisms and thus to extend lifetime. The present study demonstrates that metal hydride based modules can assist in controlling this temperature by serving as active thermal energy storage. The reversible reaction of metals with hydrogen is characterized by a temperature pressure correlation. Therefore, the temperature as well as the thermal power at which the thermal energy is released can be defined by the gas pressure. This enables the design of temperature controllers using the pressure as actuating variable on the metal hydride device. In this study, an existing metal hydride reactor based on LaNi4.85Al0.15 is integrated into a hydrogen and cooling fluid testing infrastructure. Based on experiments indicating the step response behaviour, the parameters for a 0D model have been identified. A PI controller was designed based on simulations and implemented on the test rig hardware. First experimental results show that it is possible to stabilize the temperature of the cooling fluid circuit to 70°C ± 1.5 K while a thermal power of +755 W/kgMH and 140 W/kgMH is provided for absorption and desorption, respectively.

Thermal performance of a metal hydride reactor for hydrogen storage with cooling/heating by natural convection

Metal hydride (MH) systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones. Recently, the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling fluid. Natural convection of air may be used to passively remove/add heat as required for proper operation of a MH reactor. Under these conditions, the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of hydrogen. Since operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet, a tubular MH reactor based on this principle is examined in this paper. Two-thirds of the internal volume of ø25.4 × 1 mm tube is occupied by a composition of LaNi5 and aluminium foam (one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2). Annular fins are used to increase heat transfer to air. Detailed and simplified mathematical models of the systems of this class are proposed and validated. It is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining characteristics. Charging from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30 °C takes 15 min. A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30–300 W fuel cells.

A novel design for fin profile in metal hydride reactor towards heat transfer enhancement: Theoretical derivations and analysis

Hydrogen storage using metal hydrides is one of the research hotspots in the field of energy storage. However, metal hydride powders are known to have low thermal conductivity, which causes significant temperature fluctuation and hinders further reaction, hence efficient thermal management is a must for hydrogen storage using metal hydrides. In this paper, based on the principle of entransy dissipation, the optimal profile of fin in a cylindrical reactor under steady-state conditions is deduced. The expression for the temperature distribution of the bed is also obtained, which could clearly account for the influences of multiple involving factors, such as fin thickness, fin spacing, and radius of reactor. Through simulation, the characteristic time of hydrogen absorption for reactor inserting the optimized fin, is shortened by 19.1 % compared with the conventional uniform thickness fin. The influence of the geometric parameters of storage reactor was further discussed. When the ratio of the inner and outer radius of the reactor is confined (rr/rt≤2), linear thinning fin can be seen as a reasonable simplification of the optimized fin with comparable heat transfer enhancement effect. This study proves that the thermal management of metal hydride reactors, particularly those inserting high thermal conductivity materials like graphite, can be optimized quantitatively by entransy theory.

Experimental investigation, development of machine learning model and optimization studies of a metal hydride reactor with embedded helical cooling tube

Metal hydride hydrogen storage systems are gaining popularity due to their advantages and suitability for various applications in variety of fields. In this study, a metal hydride reactor using LaNi5 as metal hydride and using water as heat transfer fluid flowing through embedded helical tube was fabricated and experimentally studied. The aim of this study is to experimentally investigate the effect of internal heat transfer arrangement on the absorption and desorption of hydrogen in a metal hydride system. The effect of mass flow rate and temperature of heat transfer fluid, effect of hydrogen supply pressure on the rate of hydrogen absorption and desorption was investigated. It was found that the increase in the hydrogen supply pressure, increase in mass flow rate and decrease in the temperature of heat transfer fluid, results in faster hydrogen absorption rate. Similarly, the increase in mass flow rate and the temperature of heat transfer fluid results in faster hydrogen desorption rate. It was also found out that maximum hydrogen absorbed inside metal hydride reactor was around 34.5 g which corresponds to a gravimetric capacity of 1.34 wt%. Further based on the experimental data various machine learning models were developed and tested and then these models were used for performance prediction. It was found that tree-based regression machine learning models are better compared to other models. Such models can thus be used for prediction of rate of hydrogen absorbed or desorbed and metal hydride bed temperature for different parametric values without doing detailed experimental and numerical trial. Finally, the brute force approach is used to optimize the system for three different applications. The optimization techniques help to fix the value of parameters for particular application and hence save multiple experimental run of absorption and desorption. This is a novel work in the field of using machine learning for modelling and optimizing the metal hydride-based reactor. Use of such tools can save lot of computational time, efforts and experimental resources.

State of the Art in Development of Heat Exchanger Geometry Optimization and Different Storage Bed Designs of a Metal Hydride Reactor.

The efficient operation of a metal hydride reactor depends on the hydrogen sorption and desorption reaction rate. In this regard, special attention is paid to heat management solutions when designing metal hydride hydrogen storage systems. One of the effective solutions for improving the heat and mass transfer effect in metal hydride beds is the use of heat exchangers. The design of modern cylindrical-shaped reactors makes it possible to optimize the number of heat exchange elements, design of fins and cooling tubes, filter arrangement and geometrical distribution of metal hydride bed elements. Thus, the development of a metal hydride reactor design with optimal weight and size characteristics, taking into account the efficiency of heat transfer and metal hydride bed design, is the relevant task. This paper discusses the influence of different configurations of heat exchangers and metal hydride bed for modern solid-state hydrogen storage systems. The main advantages and disadvantages of various configurations are considered in terms of heat transfer as well as weight and size characteristics. A comparative analysis of the heat exchangers, fins and other solutions efficiency has been performed, which makes it possible to summarize and facilitate the choice of the reactor configuration in the future.

Multi-objective optimization of a metal hydride reactor coupled with phase change materials for fast hydrogen sorption time

Recently, the utilization of phase change materials (PCM) for the heat storage/recovery of the metal hydride's reaction heat has received increasing attention. However, the poor heat management process makes hydrogen sorption very slow during heat recycling. In this work, the H2 charging/discharging performance of a metal hydride tank (MHT) filled with LaNi5 and equipped with a paraffin-based (RT35) PCM finned jacket as a passive heat management medium is numerically investigated. Using a two-dimensional mathematical model validated with our in-house experiments, the effects of design parameters such as PCM thermophysical properties and the fin size on hydrogen charging/discharging times of the MHT are investigated systematically. The results showed that the PCM's melting point and apparent heat capacity have a conflicting impact on the hydrogen sorption times, i.e., the low melting point and high specific heat capacity reduce the H2 charging time. In contrast, the hydrogen discharging time follows the opposite trend. As a result, a multi-objective optimization was conducted to simultaneously minimize the H2 charging/discharging times using the thermal properties and size of the PCM. The optimum solutions selected from the Pareto front show that the PCM melting point should be around 42–43 °C for fixed hydrogen ab/desorption pressures of 10/1.5 bar. Moreover, the comparison between the MHT-PCM using the optimized PCM and reference PCM showed that the former reduced the hydrogen charging/discharging times by 48.6 % and 4 %, respectively. At the same time, the hydrogen storage efficiency of the optimal design is 100 % as compared to 96 % for the reference design. Besides, among the practical PCMs, inorganic PCMs (salt hydrates and eutectics) display favorable hydrogen charging time below 3000 s at the expense of hydrogen discharging time (above 7000 s) in our case study.

2D-axisymmetrical modeling and experimental study of hydrogen absorption in copper coated metal hydride

The storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi5.

Numerical study on storage performance of metal hydride reactors with multiple spiral fins

Metal hydride (MH) is an efficient hydrogen storage method with high density and moderate operating conditions. Thermal management is required for hydrogen storage and release to cope with the strong thermal effects generated by the reaction. The MH reactor with spiral fins is proposed to improve the hydrogen storage efficiency by increasing the heat transfer characteristics of the reactor. The hydrogen absorption and desorption performances of the MH reactors with different spiral fin structures have been discussed. The results show that the MH reactor with spiral fins present better reaction performance compared to that of the MH reactor with longitudinal fins. And the larger the fin spiral cycle (SC), the faster the reaction rate. The hydrogenation time and dehydrogenation time could be maximally reduced 29.8% and 29.2% with fin spiral cycle increasing from 1/4 to 1, where the hydrogen storage density kept constant. The hydrogenation time and dehydrogenation time could be reduced 53.1% and 34.7% with fin number (FN) increasing from 4 to 16, while the hydrogen storage density is reduced 24.1%. Keep the volume of fins consistent, the fin number and fin thickness (FT) are optimized, and the results are FN = 8, SC = 1, FT = 1 mm, the corresponding hydrogen storage density is 0.087 g mm−1. The performance of the reactor with the optimal fin parameters under different operation conditions was also analyzed. The recommended operation parameters are concluded as the hydrogen pressure of 1.0 MPa for absorption and 0.1 MPa for desorption, heat transfer wall temperature of 293.15 K for absorption and 353.15 K for desorption.

Single-stage metal hydride-based heat storage system

The effective use of renewable energy sources (RES) becomes increasingly important, and energy storage systems are needed to ensure their stable operation. Metal hydrides (MH) can be used both for hydrogen storage and for thermal energy storage (TES). We present experimental results of heat, mass transfer and dynamic processes in a single-stage MH-based TES system based on a 5 kg La Ni4.8Mn0.3Fe0.1 metal hydride reactor. Stable cyclic operation in the temperature range 20–90 °C is demonstrated with volumetric energy storage density of 208 MJ/m3 and peak thermal power of 1.05 kW. The systems performance is analyzed regarding the energy and exergy efficiencies. The main bottlenecks include the connected thermal mass of the reactor and the necessity to use lightweight and efficient heat exchanger. In addition, a liquid flow rate in the heat exchanger should be kept low enough to decrease the difference between temperatures of the MH bed and coolant. Optimized low-temperature metal hydride TES systems can be used in climatic-oriented applications, such as MH starters for cold weather or “keep warm” systems.

Experimental studies on novel multi tubular reactor with shell having integrated buffer storage

This study concentrates on experimental analysis of a large scale metal hydride based hydrogen storage reactor having 50 kg LaNi5. In order to cater the heat transfer limitations of hydrogen storage in large scale systems, the present design have been developed as multi tubular reactor with shell having integrated buffer storage configuration with 7 tubes supported by means of 4 baffles having total 50 kg LaNi5 distributed equally among them and water as heat transfer fluid flows across the shell for heat transfer. The experimental study was performed for studying the absorption and desorption performance of the present hydrogen reactor wherein in case of absorption the parameters varied were HTF flow rate at 30 °C and supply pressure of hydrogen and in case of desorption which was carried out at atmospheric pressure, HTF flow rate and HTF temperature were varied. The metal hydride reactor reversibly stores 680 g of hydrogen amounting to 1.34 wt% of gravimetric capacity of metal hydride and equivalent energy storage of 10.4 MJ. In case of absorption, when the flow rate selected was 20 LPM the absorption time for 90 % reaction completion was observed to be 1286 s (21.4 min) at 30 bar H2 supply pressure. In case of desorption studies, it was observed that the varying flow rate from 15 to 25 LPM has negligible effect on hydrogen desorption hence 15 LPM was selected as flow rate for further desorption experiments. Further increasing HTF temperature from 60 °C to 80 °C improves the performance significantly.

Thermal Management Techniques in Metal Hydrides for Hydrogen Storage Applications: A Review

Metal hydrides are a class of materials that can absorb and release large amounts of hydrogen. They have a wide range of potential applications, including their use as a hydrogen storage medium for fuel cells or as a hydrogen release agent for chemical processing. While being a technology that can supersede existing energy storage systems in manifold ways, the use of metal hydrides also faces some challenges that currently hinder their widespread applicability. As the effectiveness of heat transfer across metal hydride systems can have a major impact on their overall efficiency, an affluent description of more efficient heat transfer systems is needed. The literature on the subject has proposed various methods that have been used to improve heat transfer in metal hydride systems over the years, such as optimization of the shape of the reactor vessel, the use of heat exchangers, phase change materials (PCM), nano oxide additives, adding cooling tubes and water jackets, and adding high thermal conductivity additives. This review article provides a comprehensive overview of the latest, state-of-the-art techniques in metal hydride reactor design and heat transfer enhancement methodologies and identifies key areas for future researchers to target. A comprehensive analysis of thermal management techniques is documented, including performance comparisons among various approaches and guidance on selecting appropriate thermal management techniques. For the comparisons, the hydrogen adsorption time relative to the reactor size and to the amount of hydrogen absorbed is studied. This review wishes to examine the various methods that have been used to improve heat transfer in metal hydride systems and thus aims to provide researchers and engineers working in the field of hydrogen storage with valuable insights and a roadmap to guide them to further explore the development of effective thermal management techniques for metal hydrides.

Thermal performance enhancement of metal hydride reactor for hydrogen storage with graphene oxide nanofluid: Model prediction with machine learning

Some metals and metal alloys can store gaseous hydrogen, making the storage of hydrogen in metal hydrides (MHs) possible. For the MH reactor to store hydrogen at a higher rate, improved heat transfer is required. The 2-D material graphene oxide (GO) attracted researchers’ attention due to its excellent thermal properties. The present work aims to improve heat transfer and hydrogen storage rate of the LaNi5 MH reactor. A 2-D axis-symmetric numerical model of the reactor is formed and simulated using COMSOL Multiphysics 5.6 software. Water and its based nanofluids (NFs), namely, GO, GO-SiO2 (50:50), GO-TiO2 (50:50), and Al2O3 are employed as heat transfer fluids (HTFs). The effect of inlet temperature and flow velocity of the HTF; and hydrogen supply pressure on the reactor performance is examined. The findings demonstrate that the storage rate is greatly improved by lowering the HTF inlet temperature; and increasing its inlet velocity and hydrogen supply pressure. In comparison to water and all other NFs, the GO NF with 1 vol% demonstrated comparatively better heat transfer. It reduces the duration by 61.7% of that of water to attain 90% hydrogen storage capacity at similar conditions. The data acquired in the numerical investigations were used to build a prediction metamodel using the evolutionary machine learning (ML) technique of gene expression programming (GEP).