Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2007.12116

Experimental behaviour of a three-stage metal hydride hydrogen compressor

A. R. Galvis·F. Leardini·J. R. Ares·F. Cuevas·J. F. Fernandez
View original source ↗Read source document ↗Export metadata ↓

Abstract

A three-stage metal hydride hydrogen compressor (MHHC) system based in AB2-type alloys has been set-up. Every stage can be considered as a Sieverts-type apparatus. The MHHC system can work in the pressure and temperature ranges comprised from vacuum to 250 bar and from RT to 200C, respectively. An efficient thermal management system was set up for the operational ranges of temperature designed. It dumps temperature shifts due to hydrogen expansion during stage coupling and hydrogen absorption/desorption in the alloys. Each reactor consists of a single and thin stainless-steel tube to maximize heat transfer. They are filled with similar amount of AB2 alloy. The MHHC system was able to produce a compression ratio (CR) as high as of 84.7 for inlet and outlet hydrogen pressures of 1.44 and 122 bar for a temperature span of 23 to 120C.

Explore related subjects

physics.app-phcond-mat.mtrl-sci

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. R. Galvis, F. Leardini, J. R. Ares, F. Cuevas, J. F. Fernandez. 2020-07-23. Experimental behaviour of a three-stage metal hydride hydrogen compressor. https://doi.org/10.1088/2515-7655%2Fab869e

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

RCS angular control with gradient metasurfaces: design and measurement

This letter proposes the design and measurement of a periodic metasurface that achieves anomalous reflection with reduced RCS in a given parasitic direction. A previous study proposed a semi-analytical model to predict the RCS behavior of such a metasurface. However, this first study did not include any experimental exploration to verify the theoretical results. To complete this study, this work presents an experimental validation of the proposed design, with a focus on manufacturing and measurement issues. The synthesis, design specifications, fabrication method and experimental setup are presented and discussed. Measurement results are also examined in detail, highlighting some limitations in metasurfaces RCS measurements. The proposed metasurface effectively achieves the predicted RCS level reduction in the considered parasitic direction. The agreement between simulation and experimental results demonstrates the accuracy of the modelling and the efficiency of the optimisation procedure.

physics.app-ph↗
arXiv2026

Maximum-Power-Transfer Power Coordinates for Fully Coupled Multiport Thévenin Sources

A power-normalized scattering representation is developed at a fixed frequency for a passive linear time-invariant multiport load driven by a fully coupled multiport Thévenin source. The source is obtained by reducing, at the load reference planes, an independent-source network whose suppressed internal impedance is passive, together with an intervening passive matching network. No diagonal-reference, uncoupled-source-channel, reciprocity, or commutation assumption is required. With $R_s=\mathrm{Herm}\{Z_s\}\succ\mathbf{0}$, completing the square in accepted power identifies the available-power current and motivates the coordinates $\mathbf{a}=\frac12R_s^{-1/2}(\mathbf{V}+Z_s\mathbf{I})$, $\mathbf{b}=\frac12R_s^{-1/2}(\mathbf{V}-Z_s^H\mathbf{I})$. They satisfy $\|\mathbf{a}\|_2^2-\|\mathbf{b}\|_2^2=\Re\{\mathbf{I}^H\mathbf{V}\}$ and yield $\mathbf{S}=R_s^{-1/2}(Z_{load}-Z_s^H)(Z_{load}+Z_s)^{-1}R_s^{1/2}$. An exact operator identity establishes passivity--contractivity equivalence and gives excitation-specific, reachable-subspace, and complete conjugate-matching conditions. On the physically reachable incident subspace, singular values characterize the best- and worst-case source-normalized port-reflection TARC, while a restricted Frobenius norm gives the basis-averaged squared TARC. Equal-magnitude phase-only control is formulated separately as a constant-modulus problem, with generator-side constraints mapped through the coupled source network before power normalization. For antenna loads and excitations with $P_{acc}>0$, $P_{rad}/P_{av}=η_{rad}(1-\mathrm{TARC}^2)$, so terminal scattering data alone do not determine radiation efficiency. When $R_s$ is singular, finite available power exists exactly for $\mathbf{E}\in\mathrm{range}(R_s)$, and the construction applies on the positive-resistance support.

physics.app-ph↗
arXiv2026

Bimorph Lithium Niobate Thickness-Shear Overtone Film Bulk Acoustic Resonator

High quality factor ($Q$) and overtone operation enable narrow-linewidth acoustic devices with multiple discrete frequencies in a single cavity. Maintaining both high $Q$ and sufficient electromechanical coupling at higher mode orders remains challenging. Here, we demonstrate a bimorph periodically poled piezoelectric film (P3F) lithium niobate (LN) platform for high-order thickness-shear (TS) overtone excitation. The device comprises a bonded 80-$μ$m-thick single-crystal X-cut LN bimorph with opposite polarizations, patterned top and floating bottom electrodes, and a suspended air cavity. The P3F configuration mitigates charge cancellation from the alternating stress distribution of higher-order TS modes, enabling measurable coupling across a broad sequence of overtones. The thick LN acoustic cavity and increasingly confined high-order mode profiles support low-loss operation. Measured TS overtones extend to 1.75 GHz. At room temperature, representative overtones at 0.77 and 0.89 GHz exhibit 3-dB $Q$ values of 11,338 and 11,917, corresponding to $fQ$ products of $8.74\times10^{12}$ and $1.06\times10^{13}$ Hz, respectively. Cooling from 297 to 12 K systematically enhances $Q$, yielding a peak 3-dB $Q$ of 20,507 at 779 MHz and a maximum $fQ$ product of $1.98\times10^{13}$ Hz at 1.379 GHz. These results establish bimorph P3F LN as a promising platform for high-$Q$, frequency-scalable micro-acoustic resonators in the sub-GHz and low-GHz regimes.

physics.app-ph↗