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Conformational Changes in Cryogenic Matrices
Published in Leonid Khriachtchev, Physics and Chemistry at Low Temperatures, 2019
Rui Fausto, Leonid Khriachtchev, Peter Hamm
All previous conformational changes described in this section were obtained by resonant vibrational excitation of the molecule itself. In contrast, the trans to cis FA conversion in solid hydrogen was also achieved by exciting rovibrational transition of the solid hydrogen host, suggesting that the lattice vibrational energy is efficiently transferred to the trans to cis reaction coordinate.68 The trans to cis reaction rate precisely follows the absorption profile of the hydrogen matrix as seen in Fig. 13. The conformational process is promoted with similar efficiencies at the FA-induced band at 4139 cm−1 and at “pure” hydrogen absorptions. This observation shows that the host exciton diffusion length is at least not smaller than the mean distance between the FA molecules, which is ~10 nm for the FA/H2 = 1/30000 matrix. The quantum yield of the cis to trans FA conversion at hydrogen absorptions is even higher than that at the OH stretching mode by a factor of 3−10. This difference can originate from the lower energy of the OH stretching vibration because the OH stretching vibration energy is slightly below the computational reaction barrier and tunneling is presumably involved into the process. The quantum yield of conformational change upon the OH stretching excitation is quite low compared to argon, which indicates the participation of host in vibrational energy redistribution.
Two-Phase Heat Transfer and Pressure Drop
Published in Randall F. Barron, Gregory F. Nellis, Cryogenic Heat Transfer, 2017
Randall F. Barron, Gregory F. Nellis
Slush hydrogen has been produced by two techniques: (a) the freeze-thaw method and (b) the auger method. In the freeze-thaw method (Mann et al. 1966), the pressure of a batch of liquid hydrogen is reduced to the triple-point pressure, and a solid crust forms on the liquid surface. The crust is broken and mixed with the remaining liquid to form the slush. In the auger method (Daney et al. 1990), a refrigerated surface is placed in the liquid hydrogen, and the resulting solid hydrogen is scraped from the refrigerated surface by an auger to form the slush.
Chemical Rocket Propellants
Published in D.P. Mishra, Fundamentals of Rocket Propulsion, 2017
Note that hydrogen remains liquid at temperatures of −253°C (20 K). At this cryogenic temperature, liquid hydrogen remains in two isomeric forms: orthohydrogen and parahydrogen. In case of orthohydrogen, two proton spins are aligned in parallel, while in parahydrogen two proton spins are aligned in antiparallel manner. Furthermore, liquid hydrogen has a very low density (0.071 kg/L) and, hence, calls for a storage volume many times greater than other fuels. Besides, liquid hydrogen is difficult to store over long periods of time due to the low temperatures of cryogenic propellants. In spite of these disadvantages, LH2 along with liquid oxygen (LO2) is preferred in modern rocket engines as it delivers a specific impulse (Isp = 430 s at sea level) about 30%–40% higher than most other rocket fuels. In order to overcome the problem of higher storage volume, hydrogen density can be enhanced by using a mixture of frozen (solid) hydrogen and liquid hydrogen. More research is required to overcome the problems of maintaining uniform mixture of (solid) hydrogen and liquid hydrogen.
Thermal-Hydraulic Aspects of an Extruder for Tracer-Encapsulated Cryogenic Pellet: A Research and Historical Perspective
Published in Fusion Science and Technology, 2023
Khlopenkov and Sudo[1] discussed the properties of tracer materials as shown in Fig. 1. They used polystyrene for the production of shells having different wall thicknesses and diameters. Sudo et al.[2] experimentally produced a solid hydrogen pellet with impurity (carbon) cores inside. They used a technique for automatic loading of carbon into the light-gas gun barrel. Sudoa and Tamura[3] developed a multitracer pellet injection system. They used spectroscopic methods to detect the motion of tracer particles. Tamura et al.[4] used a pneumatic pipe-gun technique for injecting the impurity-contained pellet. For the case of a thin shell, they experimentally got 4-cm shallower deposition as compared to a thick shell type of pellet. Tamura et al.[5] recently developed an atomic number Z-based multitracer pellet. They studied the nature of low-Z to high-Z impurities in high-temperature plasma.
Design and Economic Evaluation of Low Voltage DC Microgrid based on Hydrogen Storage
Published in International Journal of Green Energy, 2021
Mohd Alam, Kuldeep Kumar, Viresh Dutta
As stated above, most of the previous studies were focused on the techno-economics analysis of renewable sources based microgrid which have battery storage. Some studies were also focused on the techno-economic analysis of the hydrogen storage in microgrid especially high-pressure storage. However, there are various hydrogen storage technologies such as solid and high-pressure storages (Kumar et al. 2019). Therefore, it would be interesting to analysis the effect of solid hydrogen storage on the techno-economic assessment of solid-hydrogen storage application in microgrid and its comparison with other battery storage technologies. Therefore, contribution of present study aims the designing and techno-economic analysis of DC microgrid using energy storage mediums such as electrochemical energy storage (lead-acid and li-ion batteries) and hydrogen storage systems (MH and high-pressure cylinder).
A Review of Pellet Injector Technology: Brief History and Recent Key Developments
Published in Fusion Science and Technology, 2020
Shashi Kant Verma, Samiran Shanti Mukherjee, Ranjana Gangradey, R. Srinivasan, Vishal Gupta, Paresh Panchal, Pratik Nayak
In 1954, the first high-speed injection of solid fuel (or liquid) was suggested by Spitzer et al.1 A pellet is a frozen deuterium or hydrogen isotope. It is cylindrical in shape and a few millimeters in size. The pellet injection system is used for refueling the fusion power reactor. The International Thermonuclear Experimental Reactor (ITER) is a tokamak holding plasma inside a doughnut-shaped vessel (nuclear fusion reactor). Solid hydrogen in the form of pellets will be injected into the plasma according to the necessity of fueling. Injection of a deuterium-tritium ice pellet is one of the best techniques for fusion plasma fueling. It is also a promising method for edge-localized-mode (ELM) mitigation. The technique has been used on various tokamak devices worldwide, mainly the Axially Symmetric Diverter Experiment (ASDEX), Doublet III (DIII-D), C-MOD, Joint European Torus (JET), etc., in a number of experiments to provide plasma fueling and density profile control.2