Physics based models for metal hydride particle morphology, distribution, and effective thermal conductivity

2009 ◽  
Vol 1172 ◽  
Author(s):  
Kyle Christopher Smith ◽  
Timothy Fisher
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Effective Thermal Conductivity ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Particle Morphology ◽  
Particle Packing ◽  
Interparticle Contact ◽  
Storage Media ◽  
Particle Size And Shape

AbstractThis paper describes a modeling approach to target aspects of heat conduction in metal hydride powders that are essential to metal hydrides as viable H2storage media, including particle morphology distribution, size distribution, particle packing properties at specified solid fraction, and effective thermal conductivity. An isotropic fracture model is presented that replicates features of particle size and shape distributions observed experimentally. The discrete element method is used to simulate evolution of metal hydride particle contact networks during quasi-static consolidation of decrepitated metal hydride powders. Finally, the effective thermal conductivity of such a powder is modeled assuming that contact conductance is the same for each interparticle contact.

Advanced Transient Plane Source Method for the Measurement of Thermal Properties of High Pressure Metal Hydrides

2009 ◽  
Author(s):  
Scott Flueckiger ◽  
Tyler Voskuilen ◽  
Yuan Zheng ◽  
Timothe´e Pourpoint
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Effective Thermal Conductivity ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Test Method ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Metal hydrides are a promising material type for hydrogen storage in automotive applications, but thermal property data is needed to optimize the necessary heat exchangers. In the present work, the transient plane source method is integrated with a pressure vessel to measure these properties for metal hydride powder as a function of pressure during the hydrogenation process. The properties under investigation include effective thermal conductivity, thermal diffusivity, specific heat, and thermal contact resistance. The results of this work with oxidized Ti1.1CrMn powder provide effective thermal conductivity values similar to data reported in literature for other metal hydride materials. The experimental measurements are also well modeled by the Zehner-Bauer-Schlu˝nder interpretive model for packed beds as a function of gas pressure. Extending the test method and ZBS model to estimate the contact resistance provides values that were two orders of magnitude less than measurements previously reported for other hydride materials.

scholarly journals Particle Morphology Analysis of Biomass Material Based on Improved Image Processing Method

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Zhaolin Lu ◽  
Xiaojuan Hu ◽  
Yao Lu
Keyword(s):  
Image Processing ◽  
Particle Size ◽  
Particle Morphology ◽  
Processing Method ◽  
Image Resolution ◽  
Ultrasonic Dispersion ◽  
Image Processing Method ◽  
Size And Shape ◽  
Nominal Size ◽  
Particle Size And Shape

Particle morphology, including size and shape, is an important factor that significantly influences the physical and chemical properties of biomass material. Based on image processing technology, a method was developed to process sample images, measure particle dimensions, and analyse the particle size and shape distributions of knife-milled wheat straw, which had been preclassified into five nominal size groups using mechanical sieving approach. Considering the great variation of particle size from micrometer to millimeter, the powders greater than 250 μm were photographed by a flatbed scanner without zoom function, and the others were photographed using a scanning electron microscopy (SEM) with high-image resolution. Actual imaging tests confirmed the excellent effect of backscattered electron (BSE) imaging mode of SEM. Particle aggregation is an important factor that affects the recognition accuracy of the image processing method. In sample preparation, the singulated arrangement and ultrasonic dispersion methods were used to separate powders into particles that were larger and smaller than the nominal size of 250 μm. In addition, an image segmentation algorithm based on particle geometrical information was proposed to recognise the finer clustered powders. Experimental results demonstrated that the improved image processing method was suitable to analyse the particle size and shape distributions of ground biomass materials and solve the size inconsistencies in sieving analysis.

Numerical Simulation of Heat and Mass Transfer in Metal Hydride Hydrogen Accumulators of Different Complex Designs

2010 ◽  
Author(s):  
Dmitriy Lazarev ◽  
Valeriy Artemov ◽  
Georgiy Yankov ◽  
Konstantin Minko
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Metal Hydride ◽  
Solid Phase ◽  
Three Dimensional ◽  
Calculated Data ◽  
Sorption Rate ◽  
Gas Admixtures

A three-dimensional mathematical model of unsteady heat and mass transfer in porous hydrogen-absorbing media, accounting for presence of “passive” gas admixtures, is developed. New technique for evaluation of effective thermal conductivity of porous medium, which consists of microparticles, is suggested. Effect of “passive” gas admixtures on heat and mass transfer and sorption rate in metal hydride reactor is analyzed. It is shown that decrease of effective thermal conductivity and partial hydrogen pressure under decrease of hydrogen concentration effect on the hydrogen sorption rate considerably. It is disclosed that an intensive 3D natural convection takes place in a gas volume of reactor under certain conditions. Numerical analysis of heat and mass transfer in metal-hydride reactor of hydrogen accumulation systems was done. Sorption of hydrogen in cylindrical reactors with external cooling and central supply of hydrogen are analyzed including reactors with finned active volume and tube-shell reactor with external and internal cooling cartridge matrix. Unsteady three dimensional temperature and concentration fields in solid phase are presented. Integral curves representing the dynamic of sorption and desorption are calculated. Data on efficiency of considered reactors are presented and compared.

Simulation of Effective Thermal Conductivity of Metal Hydride Packed Beds

2015 ◽  
Vol 37 (7-8) ◽  
pp. 616-624 ◽  
Author(s):  
Yogesh Madaria ◽  
Emadabathuni Anil Kumar ◽  
Prakash Maiya ◽  
Srikantiah Srinivasa Murthy
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Metal Hydride ◽  
Packed Beds

Thermal Conductivity of Metal-Oxide Nanofluids: Particle Size Dependence and Effect of Laser Irradiation

2006 ◽  
Vol 129 (3) ◽  
pp. 298-307 ◽  
Author(s):  
Sang Hyun Kim ◽  
Sun Rock Choi ◽  
Dongsik Kim
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Effective Thermal Conductivity ◽  
Laser Irradiation ◽  
Volume Fraction ◽  
Suspended Particle ◽  
Titanium Dioxide Nanoparticles ◽  
Size Change ◽  
Conductivity Enhancement ◽  
Wide Range

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina, zinc-oxide, and titanium-dioxide nanoparticles is measured using the transient hot-wire method. Measurements are performed by varying the particle size and volume fraction, providing a set of consistent experimental data over a wide range of colloidal conditions. Emphasis is placed on the effect of the suspended particle size on the effective thermal conductivity. Also, the effect of laser-pulse irradiation, i.e., the particle size change by laser ablation, is examined for ZnO nanofluids. The results show that the thermal-conductivity enhancement ratio relative to the base fluid increases linearly with decreasing the particle size but no existing empirical or theoretical correlation can explain the behavior. It is also demonstrated that high-power laser irradiation can lead to substantial enhancement in the effective thermal conductivity although only a small fraction of the particles are fragmented.

scholarly journals Simulated Microstructural Evolution and Design of Porous Sintered Wicks

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Karthik K. Bodla ◽  
Suresh V. Garimella
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Transport Properties ◽  
Effective Thermal Conductivity ◽  
Surface Area ◽  
Microstructural Evolution ◽  
Ad Hoc ◽  
Three Dimensions ◽  
Two Phase ◽  
Sintering Kinetics

Porous structures formed by sintering of powders, which involves material-bonding under the application of heat, are commonly employed as capillary wicks in two-phase heat transport devices such as heat pipes. These sintered wicks are often fabricated in an ad hoc manner, and their microstructure is not optimized for fluid and thermal performance. Understanding the role of sintering kinetics—and the resulting microstructural evolution—on wick transport properties is important for fabrication of structures with optimal performance. A cellular automaton model is developed in this work for predicting microstructural evolution during sintering. The model, which determines mass transport during sintering based on curvature gradients in digital images, is first verified against benchmark cases, such as the evolution of a square shape into an area-preserving circle. The model is then employed to predict the sintering dynamics of a side-by-side, two-particle configuration conventionally used for the study of sintering. Results from previously published studies on sintering of cylindrical wires are used for validation. Randomly packed multiparticle configurations are then considered in two and three dimensions. Sintering kinetics are described by the relative change in overall surface area of the compact compared to the initial random packing. The effect of sintering parameters, particle size, and porosity on fundamental transport properties, viz., effective thermal conductivity and permeability, is analyzed. The effective thermal conductivity increases monotonically as either the sintering time or temperature is increased. Permeability is observed to increase with particle size and porosity. As sintering progresses, the slight increase observed in the permeability of the microstructure is attributed to a reduction in the surface area.

scholarly journals Improved Heat Transfer in Guar Gel Composites Reinforced with Randomly Distributed Glass Microspheres

2021 ◽  
Author(s):  
Ruifeng CAO ◽  
Taotao WANG ◽  
Yuxuan ZHANG ◽  
Hui WANG
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Composite Materials ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Glass Microspheres ◽  
Particle Volume ◽  
Number Of Particles

Improved heat transfer in composites consisting of guar gel matrix and randomly distributed glass microspheres is extensively studied to predict the effective thermal conductivity of composites using the finite element method. In the study, the proper and probabilistic three-dimensional random distribution of microspheres in the continuous matrix is automatically generated by a simple and efficient random sequential adsorption algorithm which is developed by considering the correlation of three factors including particle size, number of particles, and particle volume fraction controlling the geometric configuration of random packing. Then the dependences of the effective thermal conductivity of composite materials on some important factors are investigated numerically, including the particle volume fraction, the particle spatial distribution, the number of particles, the nonuniformity of particle size, the particle dispersion morphology and the thermal conductivity contrast between particle and matrix. The related numerical results are compared with theoretical predictions and available experimental results to assess the validity of the numerical model. These results can provide good guidance for the design of advanced microsphere reinforced composite materials.

scholarly journals Effective thermal conductivity of loose residual coal in goaf: Comparative analysis of experiment and model

2022 ◽  
pp. 014459872110695
Author(s):  
Chunhua Zhang ◽  
Jiahui Shen ◽  
Mei Wan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Ambient Temperature ◽  
Effective Thermal Conductivity ◽  
Void Fraction ◽  
Coal Particle ◽  
Spontaneous Combustion ◽  
Relative Errors ◽  
Residual Coal

The effective thermal conductivity (ETC) model of loose residual coal in goaf is a method to study the heat transfer law of spontaneous combustion in goaf. In order to study the effect of coal particle size and ambient temperature on heat transfer, coal samples of different sizes were taken from the FuSheng (FS) mine, and the void fraction, the thermal conductivity (TC) of the residual coal under different ambient temperature were tested. Additionally, four types of ETC models of loose residual coal in goaf were obtained and the average relative errors of the TC were analyzed. The results showed that the void fraction, the coal particle size and ambient temperature have different effects on the spontaneous combustion of the residual coal. The effect of coal sample size on the heat transfer is 100 times that of the ambient temperature. The changes in the ETC and average relative error of the different models were consistent. The heat transfer in the spontaneous combustion of residual coal has a direct relationship with the spatial distribution and heat transfer modes of the loose residual coal in the goaf.

Heat Conduction in Metal Hydride Nano-Particles

2007 ◽  
Author(s):  
Kyle C. Smith ◽  
Peter D. Gilbert ◽  
Christopher S. Polster ◽  
Timothy Fisher
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Metal Hydride ◽  
Energy Content ◽  
Hydrogen Uptake ◽  
Pure Metal ◽  
Hydrogen Gas ◽  
Nano Particles ◽  
Controlling System ◽  
Uptake Process

Metal hydrides hold significant potential for use in solid-state hydrogen storage through reversible chemical reactions of metal constituents and hydrogen. Managing heat loads in the system is critical to controlling system performance because a substantial amount of the energy content in hydrogen gas is released during the exothermic hydrogen uptake process, and this process must occur in only a few minutes for vehicle applications. These materials often are used in a powder form in which the initial particle size is 50–100 micrometers. However, as the material is cycled by hydriding (M+H2→MH) and dehydriding (M+H2←MH), particle size can decrease by several orders of magnitude. For the solid metal hydride phase, relative contributions of the electronic and phononic thermal conductivities are quantified with varying composition and particle size. Particle size effects are approximated by a boundary scattering term in the phononic thermal conductivity formulation. Also, the electronic contribution to thermal conductivity is estimated as a function of hydrogen content. The results reveal that overall thermal conductivity is highly material-specific. Materials with large electronic contributions in the pure metal state are relatively unaffected by particle size, while those with lower electronic contributions exhibit a substantial decrease in thermal conductivity with particle size.

Sign in / Sign up

Export Citation Format

Share Document