Research and development of liquid hydrogen (LH2) temperature monitoring system for marine applications

Monitoring the temperature in liquid hydrogen (LH₂) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.     

An experimental investigation on hydroxy (HHO) enriched ammonia as alternative fuel in gas turbine

Today, the important challenges with the utilization of hydrogen in power-producing applications (internal combustion engines and fuel cells) are its delivery and storage and these create a big hesitation regarding the application safety. Ammonia, which can be regarded as the most promising alternative fuel to hydrogen, provides the possibility of storage in liquid form at low pressures and high temperatures. This study was carried out to investigate how to compensate the drawbacks of using ammonia as the main fuel in a gas turbine by hydrogen and hydroxy-gas enrichment. During the experiments, propane that is standard working fuel of the gas turbine, neat ammonia, as well as a 10 L/min ammonia fuel enriched with 3 L/min, 5 L/min, and 7 L/min hydroxy gas, were utilized. The results show that hydroxy enrichments cause improvements in the performance data as well as emission values due to the absence of any carbon emissions. When the performance outputs are examined, it has been shown that the power values of NH₃ + 3 HHO and NH₃ + 5 HHO fuels are 10.98% and 3.65% lower than propane, whereas NH₃ + 7 HHO fuel produces 4.12% more power, and the desired performance values are reached. It has been also fund that NO_x emissions should be kept under control in addition to the increase in the performance and elimination of the carbon emissions.     

Hydrogen sensing by RGB investigation of gasochromic coloration of MoO3/Pd-coated polyester fabrics

Recently, colorimetric sensors capable of detecting explosive and toxic molecules have attracted much attention for applications in health and environmental monitoring. Here, we demonstrate the detection of hydrogen gas using gasochromic fabrics and evaluate their performance with a commercial RGB color sensor module. For this purpose, first a thin Pd film was sputter deposited onto the polyester fabric and then amorphous MoO₃ films (several microns) were deposited by RF reactive magnetrons in various O₂/Ar ratios (from 2.5 to 12.5 O₂). Field emission scanning electron microscope (FESEM) identified the morphological changes of the surface at each coating step and showed that the fibrous structure of the fabrics was preserved after coating of the films, which is suitable for better gas adsorption. Exposure to hydrogen caused the obtained MoO₃/Pd/polyester samples to turn blue-gray at room temperature and the UV–Vis spectra showed an increase in optical absorption. Their sensitivity was evaluated in the presence of different H₂ concentrations from 250 to 10,000 ppm by recording the time variation of color difference (RGB Euclidean distance). A significant correlation was found between absorption spectrum and RGB analysis with respect to oxygen content. The color variation showed a linear behavior with respect to hydrogen concentration for all samples. Response and recovery times, reversibility and reproducibility in the presence of hydrogen gas were also evaluated using the RGB readout data. Overall, the RGB module optimally depicts the sensing characteristics of the gasochromic fabrics in terms of reversibility, sensitivity and reproducibility, which may contribute to their commercial development.     

Compression properties of gas diffusion layers and its constitutive model under cyclic loading

The compressive deformation of gas diffusion layer (GDL), which is highly nonlinear and related to the loading history, affects the performance of PEM fuel cell stacks. However, linear elastic models are widely used. In this study, a new nonlinear constitutive model is proposed to describe the compression properties. Macroscopic studies reveal that GDL has different mechanical properties during the first and repeated compression stages. Besides, the tangent modulus has a significant linear relationship with stress. The constitutive model can be rebuilt using the micro-mechanical theory of fiber assemblies by considering the bending of carbon fibers. Furthermore, a prediction method is proposed to describe cyclic compression behavior. The prediction results fit well with the test results with an average and maximum relative error of less than 5.30% and 18.13%, respectively. These conclusions are beneficial to the design of GDL with specific mechanical properties and the real-time analysis of PEM fuel cell.     

Rate equation theory for the hydrogenation kinetics of Mg-based materials

A uniform solid product layer normally assumed in the shrinking-core model cannot predict the kinetic transition behavior of the H₂ adsorption reactions. In this study, the concept of a uniform solid product layer has been replaced by that of the inward growth of solid products on the solid surface. A rate equation is established to calculate the inward growth of the solid product and was implemented into the shrinking-core model to calculate the H₂ adsorption kinetics for various shapes of Mg-based materials. The prediction accuracy of the developed model is verified from the detailed experimental data. To account for the external gas diffusion around the particle and the intraparticle gas diffusion, an analytical equation is derived using the Thiele modulus method. This model can be used to analyze various kinetic aspects and to analyze the effect of change in the particle microstructure on intraparticle diffusion.     

Influence of soil density on gas permeability and water retention in soils amended with in-house produced biochar

Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties(e.g.suction and water retention) of soil.However,variations in densities alter the properties of the soil-biochar mix.Such density variations are observed in agriculture(loosely compacted) and engineering(densely compacted) applications.The influence of biochar amendment on gas permeability of soil has been barely investigated,especially for soil with diffe rent densities.The maj or obj ective of this study is to investigate the water retention capacity,and gas permeability of biochar-amended soil(BAS) with different biochar contents under varying degree of compaction(DOC) conditions.In-house produced novel biochar was mixed with the soil at different amendment rates(i.e.biochar contents of 0%,5% and 10%).All BAS samples were compacted at three DOCs(65%,80% and 95%) in polyvinyl chloride(PVC)tubes.Each soil column was subjected to drying-wetting cycles,during which soil suction,water content,and gas permeability were measured.A simplified theoretical framework for estimating the void ratio of BAS was proposed.The experimental results reveal that the addition of biochar significantly decreased gas permeability k_g as compared with that of bare soil(BS).However,the addition of 5%biochar is found to be optimum in decreasing kg with an increase of DOC(i.e.k_(g,65%) k_(g,80%) k_(g,95%)) at a relatively low suction range(200 kPa) because both biochar and compaction treatment reduce the connected pores.     

Mild hydrogen production from the hydrolysis of Al–Bi–Zn composite powder

The development of mild hydrogen-generating materials is of great significance to improve the working life of hydrogen–oxygen fuel cells. In this study, Al–Bi–Zn composite powders were designed by phase diagram calculation and then prepared via the gas atomization method. The results indicated that the conversion yield of Al–12Bi–7Zn (wt.%) powder reached 98% with stable hydrogen production within 280 min at 50 °C. When composite powder reacted with NaCl solution to produce hydrogen, the dormant period of the reaction process was significantly shortened, but the conversion rate was slightly reduced. Additionally, the evolution of powder morphology during the reaction was investigated. The results showed that the continuous cracking of the powder led to the continuous exposure of fresh Al to react.     

Recent progress of the gas diffusion layer in proton exchange membrane fuel cells: Material and structure designs of microporous layer

Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities.     

Effect of water distribution in gas diffusion layer on proton exchange membrane fuel cell performance

Water management of proton exchange membrane fuel cells remains a prominent issue in research concerning fuel cells. In this study, the gas diffusion layer (GDL) of a fuel cell is partially treated with a hydrophobic agent, and the effect of GDL hydrophobicity on the water distribution in the fuel cell is examined. First, the effect of the position of the cathode GDL hydrophobic area relative to the channel on the fuel cell performance is investigated. Then, the water distribution in the fuel cell cathode GDL is observed using X-ray imaging. The experimental results indicate that when the hybrid GDL's hydrophobic area lies on the channel, water tends to accumulate under the rib, and the water content in the channel is low; this improves the fuel cell performance. When the hydrophobic area is under the rib, the water distribution is more uniform, but the performance deteriorates.     

Effect of fiber orientation on Liquid–Gas flow in the gas diffusion layer of a polymer electrolyte membrane fuel cell

In this study, the lattice Boltzmann method was used to simulate the three-dimensional intrusion process of liquid water in the gas diffusion layer (GDL) of a polymer electrolyte membrane fuel cell (PEMFC). The GDL was reconstructed by the stochastic method and used to investigate fiber orientation's influence on liquid water transport in the GDL of a PEMFC. The fiber orientation can be described by the angle between a single fiber and the in-plane direction; three different samples were simulated for three different fiber orientation ranges. The simulated permeability correlated well with the anisotropic characteristics of reconstructed carbon papers. It was concluded that the fiber orientation had a significant effect on the liquid invasion pattern in the GDL by changing the pore shape and distribution of the GDL. The results indicated that the stochastically reconstructed GDL, taking into account the fiber orientation, better demonstrates the mass transport properties of the GDL.