Different reactor and heat exchanger configurations for metal hydride hydrogen storage systems – A review (original) (raw)
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Numerical simulation and performance test of metal hydride hydrogen storage system
International Journal of Energy and Environment, 2011
Metal hydride reactors are widely used in many industrial applications, such as hydrogen storage, thermal compression, heat pump, etc. According to the research requirement of metal hydride hydrogen storage, the thermal analyses have been implemented in the paper. The metal hydride reaction beds are considered as coupled cylindrical tube modules which combine the chemical absorption and desorption in metal hydride. The model is then used metal hydride LaNi5 as an example to predict the performance of metal hydride hydrogen storage devices, such as the position of hydration front and the thermal flux. Under the different boundary condition the characteristics of heat transfer and mass transfer in metal hydride have influence on the hydrogen absorption and desorption. The researches revealed that the scroll design can improve the temperature distribution in the reactor and the porous tube for directing hydrogen can increase the penetration depth of hydride reaction to decrease the hyd...
Thermal Management Techniques in Metal Hydrides for Hydrogen Storage Applications: A Review
Energies
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 hig...
Heat and mass transfer of hydrogen storage in metal-hydrogen reactors
cder.dz
Hydrogen energy is the best alternative to fossil fuels due to its high calorific value and being environmentally friendly. Hydrogen also produces more energy per unit weight than any other fuel. However, storage problem of hydrogen prevents its wide usage and commercialization. Hydrogen absorption in two LaNi5-H2 reactors is experimentally and theoretically investigated. In the experimental program, two tanks are filled with LaNi5 alloy and hydrogen is charged with a constant pressure. The temperature changes in the tanks are measured at several locations and recorded in a computer. Hydriding process is identified from measured temperature histories. An experimental set up is designed to study main characteristics of hydriding process and effect of bed geometry and heat transfer on the hydriding process. Hydriding process is characterized by exothermic reaction between LaNi5 and H2 and rapid temperature increase due the heat release. Hydriding time mainly depend on the successful heat removal from the bed. A bed geometry which provides more heat transfer area significantly reduces hydriding time In the theoretical program, a two dimensional mathematical model, which considers complex heat and mass transfer and fluid flow is developed and numerically solved. The governing equations are numerically solved and calculated results are compared with experimental data. It is found that mathematical model adequately captures the main physics of the hydriding process and can be employed for a better hydride bed design to reduce hydriding time. A reasonable agreement between the numerical results and experimental data is obtained.
Enhancement of hydrogen charging in metal hydride-based storage systems using heat pipe
International Journal of Hydrogen Energy, 2018
Heat transfer in metal hydride bed significantly affects the performance of metal hydride reactors (MHRs). Enhancing heat transfer within the reaction bed improves the hydriding rate. This study presents performance analysis in terms of storage capacity and time of three different cylindrical MHR configurations using storage media LaNi 5 : a) reactor cooled with natural convection, b) reactor with a heat pipe on the central axis, c) reactor with finned heat pipe. This study shows the impact of using heat pipes and fins for enhancing heat transfer in MHRs at varying hydrogen supply pressures (2e15 bar). At any absorption temperature, hydrogen absorption rate and hydrogen storage capacity increase with the supply pressure. Results show that using a heat pipe improves hydrogen absorption rate. It was found that finned heat pipe has a significant effect on the hydrogen charge time, which reduced by approximately 75% at 10 bar hydrogen supply pressure.
Thermal optimisation of metal hydride reactors for thermal energy storage applications
Sustainable Energy and Fuels, 2017
Metal hydrides (MHs) are promising candidates as thermal energy storage (TES) materials for concentrated solar thermal applications. A key requirement for this technology is a high temperature heat transfer fluid (HTF) that can deliver heat to the MHs for storage during the day, and remove heat at night time to produce electricity. In this study, supercritical water was used as a HTF to heat a prototype thermochemical heat storage reactor filled with MgH 2 powder during H 2 sorption, rather than electrical heating of the MH reactor. This is beneficial as the HTF flows through a coil of tubing embedded within the MH bed and is hence in better contact with the MgH 2 powder. This internal heating mode produces a more uniform temperature distribution within the reactor by increasing the heat exchange surface area and reducing the characteristic heat exchange distances. Moreover, supercritical water can be implemented as a heat carrier for the entire thermal energy system within a concentrating solar thermal plant, from the receiver, through the heat storage system, and also within a conventional turbine-driven electric power generation system. Thus, the total system energy efficiency can be improved by minimising HTF heat exchangers.
Enhancement of Hydrogen Storage Process Using Heat Pipe
مجلة الجامعة الأسمرية
Heat transfer from/to the metal hydride bed is a critical factor affecting the performance of metal hydride storage tanks (MHSTs for short). This study examined the effect of heat pipe on the metal hydride tank by means of heat management. The experimental study explains the use of heat pipe for enhancement the heat transfer in MHSTs, which built using LaNi4.75Al0.25 as the storage media and under various hydrogen pressure supply in the range of 2 to10 bar. This study also presents comparisons between the two different MHSTs which are designed with and without heat pipe. Two configurations of metal hydride tanks are considered and consisted of tubular cylindrical tanks with same base dimensions. The first one is a closed cylinder that exchanges heat through its lateral and base surfaces by means cool with natural convection. Heat pipe is made of copper–methanol combination and situated along the axis of the second reactor. Results show that the usage of heat pipe can be a good choi...
Analysis of hydrogen storage performance of metal hydride reactor with phase change materials
International Journal of Hydrogen Energy, 2019
h i g h l i g h t s A metal hydride (MH) tank equipped with phase change material (PCM) was investigated. A model was developed and validated for both absorption and desorption processes. The use of PCM shows an improvement in the energy efficiency of the MH system. The effect of some properties of PCM on the performance of MH-PCM system was studied. The latent heat of the PCM affects more on the MH bed than the thermal conductivity.
Optimization of hydrogen storage in metal-hydride tanks
International Journal of Hydrogen Energy, 2009
The storage time of hydrogen in metal-hydride tanks (MHTs for short) is strongly influenced by the rate at which heat can be removed from the reaction bed. In the present work a two-dimensional mathematical model is developed and validated against experimental results. This model is used, first, to evaluate the impact of the tank wall thermal mass on the hydriding process. Walls in steel and in brass are tested and the obtained results show that there is no significant effect on hydrogen storage time. Then, the established model is used to study the dynamic behaviour inside various designs of MHTs: i) a cylindrical tank, ii) a cylindrical tank with external fins, iii) a cylindrical tank with a concentric tube filled with flowing cooling fluid and iv) a cylindrical tank with a concentric tube equipped with fins. Optimization results indicate that almost 80% improvement of the storage time can be achieved over the case where the tank is not optimized.
International Journal of Hydrogen Energy, 2012
In this paper, a performance analysis of a metal hydride based hydrogen storage container with embedded cooling tubes during absorption of hydrogen is presented. A 2-D mathematical model in cylindrical coordinates is developed using the commercial software COMSOL Multiphysics 4.2. Numerical results obtained are found in good agreement with experimental data available in the literature. Different container geometries, depending upon the number and arrangement of cooling tubes inside the hydride bed, are considered to obtain an optimum geometry. For this optimum geometry, the effects of various operating parameters viz. supply pressure, cooling fluid temperature and overall heat transfer coefficient on the hydriding characteristics of MmNi 4.6 Al 0.4 are presented. Industrial-scale hydrogen storage container with the capacity of about 150 kg of alloy mass is also modeled. In summary, this paper demonstrates the modeling and the selection of optimum geometry of a metal hydride based hydrogen storage container (MHHSC) based on minimum absorption time and easy manufacturing aspects.