Stockage de l'hydrogène par adsorption sur charbon actif : Etude des effets thermiques lors de la charge dynamique d'un réservoir à lit fixe adsorbant

This work presents an experimental and numerical investigation of the thermal effects occurring during the charge of adsorbent fixed bed tank. The influence of these thermal effects, which result from the exothermal character of the adsorption process and the pressure forces work, on the storage capacity is specially analysed. An experimental setup allowing the dynamic measurements of the temperature and pressure profiles has been used. Then the numerical protocol, with the Fluent software, has been validated by comparison of the simulated pressure, flow rate and temperature fields in the tank with the results obtained from an experimental investigation carried out the dynamic storage. Several predictive simulations have been carried out in order to study the effect of the boundary conditions, as the wall temperature or effective thermal conductivity of the porous bed, on the storage capacity of the reservoir. We searched the optimal geometry of an interbed thermal dissipater for a given industrial tank. To do this we made vary the H/L ratio, which represents the ratio of the height of an elementary stage and the total length of the tank. We could determine an optimal geometry which corresponds to the value 1/3 of the ratio H/L. From this optimum we studied the effect of five additional cooling tubes on the tank storage capacity. The stored mass is 15 % higher than that obtained without these tubes.Le cadre de cette étude est le stockage de l'hydrogène par adsorption sur charbon actif sous pression à température ambiante. Cette thèse porte sur les effets thermiques intervenant lors des remplissages à l'hydrogène de réservoirs à lit fixe adsorbant. La partie expérimentale a été effectuée au LIMHP et l'étude numérique à l'aide du logiciel Fluent a été menée au LEGI à Grenoble. Un dispositif expérimental permettant la mesure dynamique de champs de températures et de pression a été mis en place. Une étude expérimentale des effets thermiques au sein du lit en fonction du débit et de la température du lit fixe a été faite pour le gaz hydrogène. Une étude comparative a été faite avec l'hélium. Ensuite une validation des simulations, à l'aide du logiciel Fluent, de remplissages de réservoirs à lit fixe adsorbant a été effectuée par comparaisons des résultats expérimentaux et numériques. Puis des simulations prédictives des effets thermiques ont été faites pour différentes valeurs de la conductivité thermique effective du lit, de températures de parois et de température initiale du lit. L'étude de dissipateurs thermiques internes a été menée à l'aide du logiciel Fluent sur des réservoirs de volume plus important en géométrie 3D. L'augmentation de la conductivité effective du lit permet d'améliorer significativement la quantité stockée par adsorption lorsque les températures du gaz entrant et des parois sont relativement basses, de l'ordre de 233 K. L'étude de dissipateur thermique, sous forme de d'empilements de disques, a montré qu'il existe un nombre optimal de disques

Stockage de l'hydrogène par adsorption sur charbon actif (étude des effets thermiques lors de la charge dynamique d'un réservoir à lit fixe adsorbant)

Le cadre de cette étude est le stockage de l'hydrogène par adsorption sur charbon actif sous pression à température ambiante. Cette thèse porte sur les effets thermiques intervenant lors des remplissages à l'hydrogène de réservoirs à lit fixe adsorbant. La partie expérimentale a été effectuée au LlMHP et l'étude numérique à l'aide du logiciel Fluent a été menée au LEGl à Grenoble. Un dispositif expérimental permettant la mesure dynamique de champs de températures et de pression a été mis en place. Une étude expérimentale des effets thermiques au sein du lit en fonction du débit et de la température du lit fixe a été faite pour le gaz hydrogène. Une étude comparative a été faite avec l'hélium. Ensuite une validation des simulations, à l'aide du logiciel Fluent, de remplissages de réservoirs à lit fixe adsorbant a été effectuée par comparaisons des résultats expérimentaux et numériques. Puis des simulations prédictives des effets thermiques ont été faites pour différentes valeurs de la conductivité thermique effective du lit, de températures de parois et de température initiale du lit. L'étude de dissipateurs thermiques internes a été menée à l'aide du logiciel Fluent sur des réservoirs de volume plus important en géométrie 3D. L'augmentation de la conductivité effective du lit permet d'améliorer significativement la quantité stockée par adsorption lorsque les températures du gaz entrant et des parois sont relativement basses, de l'ordre de 233 K. L'étude de dissipateur thermique, sous forme de d'empilements de disques, a montré qu'i! existe un nombre optimal de disques.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Hydrogen storage by adsorption on activated carbon: experimental and numerical study

Session The use of hydrogen for fuel cell systems requires an adequate hydrogen storage medium. Solid state storage, as a safe and efficient handling of hydrogen, attains commercial interest if the amount of reversible hydrogen is more than 6.5 wt.. The storage in a solid-state matrix fails for most materials with respect to the total weight of the tank system. Therefore carbon with its low atomic weight could help to overcome these disadvantages. According to the American Department of Energy standard (DOE), the tank must be able to store 63 kg of hydrogen in a 1 m3 tank and to satisfy a ratio of 6.5% between the mass of stored hydrogen and the total mass of the system. Moreover, the viability of this storage method requires very short filling times, typically less than 5 minutes. Due to the exothermic nature of the adsorption process, these low filling times cause an increase in the adsorbing-bed temperature, which in turns limits the tank-gas density to a level lower than which could be expected in the absence of adsorbing-bed heating. The main objective of this work was the investigation of thermal effects during high-pressure charge in the adsorbent packed bed for the storage reservoir. The adsorption column is a laboratory-scale (2L) stainless-steel cylinder. Its geometric shape is similar to that of the commercial gas cylinder. The column is packed with activated IRH3 carbon, which has an average surface area of 2800 m2/g. The IRH3 activated carbon is produced from coconut coal by Institut de Recherche sur l'Hydrogene. Six type J thermocouples were positioned along the column to obtain radial and axial temperature profiles. The pressure was measured by a Heise digital pressure transducer (model ATS 2000, precision: 0.02% of the full scale). The hydrogen flow is measured by a HTDS turbine volumetric flowmeter (model FTO-1NIR3-PHC-5). The precision represents 0.02% of the full-scale the range of which is included between 6.9.10-7 et 9.5.10-6 m3.s-1. This range permits to obtain filling times ranging between 210 s et 2810 s. An upstream micrometer valve allows to regulate the hydrogen flow with a reproducibility of + - 0.3%. The data were acquired by means of the Labview (Labview 7.0) software platform. This interface allows us to follow the inlet flow, the pressure increase and the temperature profiles. Several tank-charging experiment were carried out with and without the adsorbent present in the tank and using either hydrogen or helium. These experiments allowed us to get qualitative information on the interplay between flow dynamic and adsorption processes in the observed heating of the bed. Typical average temperature increase measured during hydrogen charging experiments with IRH3 activated carbon was about 50K at 10 Mpa. The simulation of this charge conditions has been carried out with the commercial code Fluent. The results from simulations agreed reasonably with experiments. An undergoing work is carried out with a higher performances new adsorbent bed. A particular effort will be devoted to increase the heat transfer from the centre of the tank toward the outside walls. This can be done by increasing the thermal conductivity of the adsorbent in the radial direction or by inserting supplementary interbed heat exchangers, such as fins, to the system

Hydrogen storage by adsorption on activated carbon: investigation of the thermal effects during the charging process

International audienceThis paper presents an investigation of the thermal effects during high-pressure charging of a packed bed hydrogen storage tank. The studied column is packed with activated IRH3 carbon, which has an average surface area of 2600m^2/g and is fed with hydrogen or helium from an external high-pressure source. The temperature at six locations in the storage tank and the pressure value at the bottom of the tank are recorded during the charging stage. Several experiments were carried out to investigate the effect of the initial flow rate on the temperature field in the reservoir and on the duration of the charging process. A study of the respective contribution of adsorption and mechanical dissipation effects to the thermal phenomena is done in the case of hydrogen. Experimental results are compared to those obtained with the commercial code Fluent. A fair agreement is found when comparing typical pressure and temperature evolutions during the tank filling

Hydrogen storage in an activated carbon bed: Effect of energy release on storage capacity of the tank

Thermal effects during dynamic charging of a two-liter, adsorbent, packed bed, hydrogen storage tank were studied through numerical modeling. For packed-bed materials having adsorption capacities smaller than 2 wt%, the conversion to heat of the mechanical work required to feed the tank produces more than 60% of the temperature increase that occurs during the charging process. However, for materials having adsorption capacities greater than 3 wt%, 60% of the heating is due to the adsorption process. The temperature increase for a material that would fulfill the DOE recommendation of 6 wt% storage capacity is 130 K. This reduces the storage capacity by 20% relative to what would be obtained from an isothermal charging process. Simulations showed that the limitation in the storage capacity can be reduced to less than 10%, if a packed bed having an effective conductivity of a few W m−1 K−1 can be used

Numerical simulation of hydrogen storage under high pressure in porous packed bed

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Experimental and numerical investigation of the thermal effects during hydrogen charging in packed bed storage tank

This paper reports on an experimental investigation and numerical simulations of the heating dynamics during hydrogen charging in activated carbon packed bed storage tank. Results showed that the experimentally observed heating dynamics is well predicted using a two-dimensional transport model that makes use of classical averaging rules usually adopted to describe flows in porous media and a linear driving force model to describe the adsorption kinetics. The contribution of the different phenomena to the overall temperature increase of the tank during the charging process was analysed both experimentally and using the developed numerical model. Results showed that the adsorption process is responsible for about 24% of the temperature increase even for moderately adsorbing activated carbon