Numerical Study of Solid State Hydrogen Storage System with Finned Tube Heat Exchanger
TL;DR: In this paper, a metal hydride (MH)-based hydrogen storage system generates significant amount of heat and this heat must be removed rapidly to improve the performance of the syst...
Abstract: Absorption of hydrogen gas inside the metal hydride (MH)-based hydrogen storage system generates significant amount of heat. This heat must be removed rapidly to improve the performance of the syst...
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TL;DR: In this paper , the authors developed a metal hydrides (MH) based hydrogen storage using a triply periodic minimal surface (TPMS) structure and a mathematical model was developed to analyze and improve its performance in terms of hydrogen absorption and desorption rates.
Abstract: Metal hydrides (MHs) are highly effective for storing hydrogen because of their stability, relatively low temperature and pressure, and high volumetric hydrogen density. However, their gravimetric density is low because of the weights of the MHs, leading to a low potential for mobility applications unless the reactor also acts as a body frame, thereby compensating for the light weight. Triply periodic minimal surface (TPMS) structures show great potential as heat exchangers (HEs) with extended surface properties per volume and reinforced structures designed to bear mechanical loads. Therefore, these structures are considered promising for application as hydrogen carriers, especially in MH-based hydrogen storage. This study aims to develop MH-based hydrogen storage using a TPMS structure. Furthermore, a mathematical model was developed to analyze and improve its performance in terms of the hydrogen absorption and desorption rates. The analysis using the mathematical model was validated with existing experimental data. Different cooling conditions were compared with natural convection. Moreover, finite element analysis was applied to evaluate the capability of the current structure design in withstanding the working pressure and load. This study's important finding is that the propose structure is proven to have higher hydrogen storage performance, including density and hydrogen charging and discharging performances. In addition, it is also found that improving the cooling conditions could increase the absorption rate. Forced convection (with a heat-transfer coefficient of 500 W/m 2 · K) seems to be a preferable cooling solution that requires low energy consumption and provides sufficient cooling. By using this cooling condition with the proposed TPMS reactor design, 90% of hydrogen is absorbed within 2000 s. Natural cooling requires almost double that time. It was also found that a reactor with a TPMS structure with a 1 mm wall thickness design could withstand MH working pressure conditions and a compression load of 5000 N. Based on this finding, the TPMS-based structure can be considered as a promising novel way of storing hydrogen for mobility applications.
11 citations
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TL;DR: In this paper , two bio-inspired leaf-veinvein type fin configurations for the metal hydride reactor were proposed for heat transfer fluid flow, namely (i) central straight tube and (ii) narrow trapezoidal channels with 10 kg of LaNi5 as a sample alloy.
Abstract: Hydrogenation of metals is an exothermic and reversible process. Thus, metal hydride reactors/devices become essentially heat-driven. Excellent heat control in the MH reactor is required to develop metal hydride devices such as H2 storage systems successfully. Few attempts at nature-inspired designs have proven to have good heat transfer capabilities. Based on this idea, the present study investigates novel bio-inspired leaf-vein type fins for the metal hydride reactor. Two reactor designs are proposed for heat transfer fluid flow, namely (i) central straight tube and (ii) narrow trapezoidal channels with 10 kg of LaNi5 as a sample alloy. Compared to longitudinal finned single tube reactors (LFSTR), these designs provided better heat transmission and temperature uniformity. For LFSTR, Case-1, and Case-2, 90% storage capacity was reached in 210, 145, and 80 s. Different fin configurations, such as parallel, inclined fins, and fins of different thicknesses, are investigated further in the design with narrow trapezoidal channels. The inclined fin configuration shows better performance, and it is further optimized by varying the inclination angle from 3 to 9° and the fin number from 2 to 4. The optimized design with a 7° inclination angle and four fins required 57 s to attain 90% storage capacity and reduced absorption time by 73% compared to LFSTR. The influence of operating parameters such as hydrogen supply pressure, inlet temperature, and velocity of the heat transfer fluid on the performance is evaluated for the optimized design.
9 citations
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TL;DR: In this article, the authors comprehensively review thermal management solutions for the metal hydride (MH) hydrogen storage used in fuel cell systems by also focusing on heat transfer enhancement techniques and assessment of heat sources used for this purpose.
Abstract: Thermal management of metal hydride (MH) hydrogen storage systems is critically important to maintain the hydrogen absorption and release rates at desired levels. Implementing thermal management arrangements introduces challenges at system level mostly related to system's overall mass, volume, energy efficiency, complexity and maintenance, long-term durability, and cost. Low effective thermal conductivity (ETC) of the MH bed (~0.1–0.3 W/mK) is a well-known challenge for effective implementation of different thermal management techniques. This paper comprehensively reviews thermal management solutions for the MH hydrogen storage used in fuel cell systems by also focusing on heat transfer enhancement techniques and assessment of heat sources used for this purpose. The literature recommended that the ETC of the MH bed should be greater than 2 W/mK, and heat transfer coefficient with heating/cooling media should be in the range of 1000–1200 W/m2K to achieve desired MH's performance. Furthermore, alternative heat sources such as fuel cell heat recovery or capturing MH heat during charging and releasing it back during discharging have also been thoroughly reviewed here. Finally, this review paper highlights the gaps and suggests directions accordingly for future research on thermal management for MH systems.
5 citations
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TL;DR: In this paper , the metal hydride Reactor (MHR) is the core device used in achieving the desired stable and comprehensive performance of a hydrogen storage system, and the initial outline of the MHR was sketched reasonably by comparing and referring to wide outstanding findings.
Abstract: Hydrogen storage is now the “bottleneck” to realise the application of hydrogen as renewable energy. This is because most metals can reversibly absorb hydrogen. Undoubtedly, a metal hydride reactor (MHR) is the core device used in achieving the desired stable and comprehensive performance of a hydrogen storage system. This study made significant efforts to outline a design methodology and acquired an optimised large-scale MHR (> 50 kg-MHs) for various applications. It mapped and analysed the MHR research progress in the past 20 years with the aid of CiteSpace, and formed a brief scientometric review from the start. Second, the priority in various applications was concluded in a few keywords to provide assistance to priorities adopted. By means of pre-set MH categories, sketch configurations, and the input/output path of the reaction heat and filling mode, the initial outline of the MHR was sketched reasonably by comparing and referring to wide outstanding findings. The following optimisation procedure would give designers/investigators a deep understanding of complex and multidisciplinary MHR wherein absorption and desorption, and the resultant heat and mass transport, pulverisation, self-densification, and stress characteristics were tightly coupled. Subsequently, anticipative results were obtained by designing and simulating the capacity, system gravimetric capacity, system volumetric capacity, and other core dynamic indices. This paper provides a unified design policy based on excellent reported results which could serve as a roadmap for the design of practical large-scale MHRs and is expected to be satisfied with different application scenarios.
5 citations
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TL;DR: In this article , the absorption and desorption performance of a multi-tubular hydride reactor is numerically investigated and optimized for 60 kg mass of LaNi5 alloy.
Abstract: Heat management during the absorption/desorption process is a key aspect in improving the performance of large-scale hydrogen storage systems. In this article, the absorption and desorption performance of a multi-tubular hydride reactor is numerically investigated and optimized for 60 kg mass of LaNi5 alloy. The 90% absorption with 7, 14, and 19 tubes is achieved in 985, 404, and 317 s with an overall reactor weight of 78.46, 88, and 88.2 kg, respectively. The 14-tube reactor performance is investigated by introducing the longitudinal fins inside the tubes. The reactor performance is enhanced by allocating fins into different pairs of half and full fins constrained by overall fin volume. A thermal resistance network model is presented to investigate the effect of fin distribution and coolant velocity on equivalent resistance of the metal hydride reactor. Storage performance obtained from numerical model validates the thermal resistance analysis from heat transfer viewpoint. With six full fins, 90% hydrogen absorption is achieved in 76 s. However, tubes with 6, 8, and 12 pairs of half and full fins require 74, 58, and 54 s, respectively. The 14-tube reactor with 8 pairs of half and full fins is used for quantifying the augmentation in the absorption performance in response to operating conditions (supply pressure and heat transfer fluid temperature). A design methodology is outlined for the development of a large-scale multi-tubular hydride reactor based on a heat transfer optimization strategy.
4 citations
References
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TL;DR: In this paper, a numerical model for transient heat and mass transfer within metal hydride reaction beds is presented, and theoretical predictions based on this model are compared with experimentally determined reaction rates and pressure-temperature distributions within the reaction beds.
Abstract: A numerical model for transient heat and mass transfer within metal hydride reaction beds is presented. Theoretical predictions based on this model are compared with experimentally determined reaction rates and pressure-temperature distributions within the reaction beds. In addition, a mathematical treatment of the behaviour of coupled reaction beds is shown and as an example calculated hydrogen pressures are compared with experimental results.
183 citations
"Numerical Study of Solid State Hydr..." refers background in this paper
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TL;DR: In this paper, a two-dimensional mathematical model to optimized heat and mass transfer in metal hydride storage tanks (hereinafter MHSTs) for fuel cell vehicles, equipped with finned spiral tube heat exchangers is presented.
Abstract: This paper presents a two-dimensional mathematical model to optimized heat and mass transfer in metal hydride storage tanks (hereinafter MHSTs) for fuel cell vehicles, equipped with finned spiral tube heat exchangers. This model which considers complex heat and mass transfer was numerically solved and validated by comparison with experimental data and a good agreement is obtained. A study of the effect of the pitch, length, thickness and the arrangement of fins on the performance of the charging process of the MHST has been carried out to identify their influence. In addition, the established model is used to study the dynamic behaviour inside various designs of MHSTs. Moreover a novel cooling design option is investigated by introducing a heat exchanger consists of two layers of spirally finned tubes.
129 citations
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TL;DR: In this paper, metal hydride-based hydrogen storage devices are tested using AB5 alloys, namely MmNi4.6Fe0.4 and MmAl0.6Al 0.4.
Abstract: Metal hydride-based hydrogen storage devices are tested using AB5 alloys, namely MmNi4.6Fe0.4 and MmNi4.6Al0.4. Performance studies are carried out by varying the supply pressure, absorption temperature and overall heat transfer coefficient. At any given absorption temperature, hydrogen absorption rate and storage capacity are found to increase with supply pressure for both the alloys. At a supply pressure of 35 bar and a cold fluid temperature of 15 ∘ C , MmNi4.6Fe0.4 alloy stored about 1.6 wt%, while MmNi4.6Al0.4 stored 1.3 wt%. Cold fluid temperature is found to have a significant effect on hydrogen storage capacity at lower supply pressures. The overall heat transfer coefficient has a negligible influence on the hydrogen storage capacities of both the alloys. However, higher values of overall heat transfer coefficients yield better rates of absorption and desorption.
129 citations
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TL;DR: In this paper, the representative achievements with regards to the design issues so far were reviewed in detail, and some comments were made accordingly, concluding that an optimized reactor design comes from integrated considerations of numerous factors, particularly requirements for the applications and characteristics of the metal hydride system.
Abstract: The metal hydride reactors are widely used in many industrial applications, for example, hydrogen storage, heat pump, thermal compression, gas separation, etc. The performance of the reactor is greatly affected by its design, which deserves careful study. Given the complicated nature of the hydride formation/decomposition processes, a series of technical issues are involved in the design of metal hydride reactors, such as primary configuration, thermal management, hydrogen transfer and mechanistic strength. These issues should be well addressed to fulfil the requirement of specific application. In this paper, the representative achievements with regards to the design issues so far were reviewed in detail, and some comments were made accordingly. It was concluded that an optimized reactor design comes from integrated considerations of numerous factors, particularly requirements for the applications and characteristics of the metal hydride system. The analytic hierarchy process was recommended for use in the selection of the optimum reactor scheme.
93 citations