Capillary Radius Research Articles

Quantitative study of the proportion of the pore volume of human fluorotic enamel filled by resin infiltrant

AimCapillarity theory predicts that the pore volume infiltrated by a liquid in a body with tubular capillaries is directly proportional to the capillary radius. The expected volume available for infiltration is the loosely bound water volume, which can be related to the capillary radii. We tested the hypothesis that the proportion of the pore volume infiltrated by resin infiltrant (Vratioresin) is correlated and agrees with the proportion of the pore volume with loosely bound water (Vratioa2). DesignSeven human fluorotic third molars (4 unerupted and 3 erupted; TF scores 4 to 7; fluoride content of inner coronal dentin ranged from 143 to 934μg Fluoride/g) were prepared and resin infiltration was performed during 10min in fluorotic enamel ground sections. Penetration depths were measured (polarizing microscopy and CLSM) and mineral volume and non-mineral volumes were measured at histological points (n=92) along transversal lines traced from the enamel surface to the enamel-dentin junction. ResultsNo well-mineralized surface layer was found. Infiltration depths ranged from 250μm to 900μm. Vratioresin ranged from 1.8 to 17.7% (mean of 10.13%±4.1%), was lower than Vratioa2 (p<0.00001 Hedge’s g=1.51, 95% CI: 1.18/1.83), and correlated positively with Vratioa2 (R=0.684; 95% CI: 0.557/0.780) and negatively with the air volume remained after infiltration (R=−0.79; 95% CI: −0.698/−0.780). Vratioa2 exceeded Vratioresin in 5% (1/4 of Vratioa2) on average. ConclusionVratioa2 and Vratioresin correlated well, but lacked good agreement. Organic matter, firmly bound water and air remained in enamel pores after resin infiltration.

The influence of spatial patterns of capillary networks on transverse relaxation

Tissue-inherent relaxation parameters offer valuable information about the arrangement of capillaries: in an external field, capillaries act as magnetic perturbers to generate local inhomogeneous fields due to the susceptibility difference of deoxygenated blood and the surrounding tissue. These field inhomogeneities influence the free induction decay in a characteristic way, and, conversely, the above tissue parameters can be recovered by multi-parametric fits of adequate theoretical models to experimentally sampled free induction decays. In this work we study the influence of different spatial patterns of capillary positions on the free induction decay. Starting from the standard single capillary approximation (Krogh cylinder) for a symmetric array of capillaries, the free induction decay is analyzed for increasingly random capillary positions, using a previously described Gibbs point field model. The effects of diffusion are implemented with a flexible and fast random walk simulation. We find that the asymmetric form of the obtained frequency distribution is more robust against variations of capillary radii than against shifts of capillary positions, and further that, for an inclusion of diffusion effects, the single capillary approximation models the uniform alignment of capillaries in the hexagonal lattice to great accuracy. An increase in randomization of capillary positions then leads to a significant change in relaxation times. This effect, however, is found less pronounced than that of changes in the off-resonance field strengths which are controlled by the oxygen extraction fraction, thus indicating that observed changes in BOLD imaging are more likely to be attributed to changes in oxygenation than to capillary alignment.

Reactive infiltration: identifying the role of chemical reactions, capillarity, viscosity and gravity

A wealth of experimental data indicate that while capillarity controlled infiltration gives an infiltration length that varies with the square root of time, reactive infiltration is characterised by a linear relationship between the two magnitudes. In addition the infiltration rate in the latter is at least two orders of magnitude greater than in the former. This work is addressed to investigate imbibition of a non-wetting, albeit reactive, liquid into a capillary, within the framework of a simple model that includes capillarity effects, viscosity and gravity. The capillary radius is allowed to vary, due to reaction, with both position and time, according to either an interface or a diffusion law. The model allows for capillary closure when reaction kinetics dominates imbibition. At short times, and depending on whether infiltration is capillarity or gravity controlled, the infiltrated length varies either as the square root or linearly with time. This suggest the following track for reactive infiltration: i) In most cases, the contact angle is initially larger than $90^\circ$, ii) after some time, reaction gradually replaces the interface liquid/preform by the liquid/reaction product interface and, concomitantly, the contact angle gets closer to $90^\circ$, iii) beyond that time, gravity triggers infiltration (actually the contact angle does not need to be smaller than $90^\circ$ for the initiation of infiltration due to the metallostatic pressure exerted by the liquid metal on top of the porous preform), iv) thereafter infiltration is controlled by viscosity and gravity, provided that, due to reaction, the contact angle remains close to that at which infiltration was initiated.

1D and 2D diffusion pore imaging on a preclinical MR system using adaptive rephasing: Feasibility and pulse sequence comparison

Diffusion pore imaging (DPI) has recently been proposed as a means to acquire images of the average pore shape in an image voxel or region of interest. The highly asymmetric gradient scheme of its sequence makes it substantially demanding in terms of the hardware of the NMR system. The aim of this work is to show the feasibility of DPI on a preclinical 9.4T animal scanner. Using water-filled capillaries with an inner radius of 10μm, four different variants of the DPI sequence were compared in 1D and 2D measurements. The pulse sequences applied cover the basic implementation using one long and one temporally narrow gradient pulse, a CPMG-like variant with multiple refocusing RF pulses as well as two variants splitting up the long gradient and distributing it on either side of the refocusing pulse. Substantial differences between the methods were found in terms of signal-to-noise ratio, contrast, blurring, deviations from the expected results and sensitivity to gradient imperfections. Each of the tested sequences was found to produce characteristic gradient mismatches dependent on the absolute value, direction and sign of the applied q-value. Read gradients were applied to compensate these mismatches translating them into time shifts, which enabled 1D DPI yielding capillary radius estimations within the tolerances specified by the manufacturer. For a successful DPI application in 2D, a novel gradient amplitude adaption scheme was implemented to correct for the occurring time shifts. Using this adaption, higher conformity to the expected pore shape, reduced blurring and enhanced contrast were achieved. Images of the phantom’s pore shape could be acquired with a nominal resolution of 2.2μm.

Role of local geometry on droplet formation in axisymmetric microfluidics

An unsteady model of droplet formation in co-flow and flow-focusing microfluidics is developed and numerically analyzed to investigate the dynamic behaviors of droplet formation in axisymmetric microfluidics with a focus on the role of local geometry. The effects of capillary number and local geometry on the droplet formation regimes, droplet sizes and monodispersity as well as droplet generation frequency are examined and analyzed. Once identified, a drop formation regime diagram is provided to quantitatively describe the respective regime of dripping, dripping-jetting transition, and jetting in axisymmetric microfluidics, depending on the Capillary number and orifice radius. The results indicate that, the existence of focusing orifice induces a strong hydrodynamic focusing effect, causing the droplet formation behaviors in flow-focusing microfluidics depart from the co-flow one. The dripping-jetting transition regime occurs at a smaller Capillary number in flow-focusing microfluidics, and the droplets produced by flow-focusing microfluidics are smaller than those in co-flow system with wider size distribution and higher frequency. Interestingly, the droplet formation in flow-focusing microfluidics is significantly affected by the orifice radius while it is insensitive to the orifice length. In addition, when the orifice radius is sufficiently small or the Capillary number is larger than 0.3, only the jetting regime is observed. As the orifice radius increases, the regions of Capillary number for both the dripping-jetting transition regime and dripping regime turn to be larger.

A new method for the transport mechanism coupling of shale gas slippage and diffusion

In view of the current status that different literature applies different coupling methods to the calculation of shale gas flow, and in order to clarify the relation between slippage and several diffusions, in this paper the slippage effect and various diffusions are analyzed first by theoretical analysis and mathematical models according to the definitions and the mechanisms of microscopic motions. Afterwards, allowing for the spatial effect of the adsorbed molecules on gas flow, the concept “wall-associated diffusion” is proposed for the first time to represent the gross effects of Knudsen diffusion and surface diffusion, and it is pointed out that wall-associated diffusion is equivalent to slippage effect. Therefore a new coupling way where wall-associated diffusion and slippage effect are replaceable and no superposition of them is needed in flow calculation, is proposed. The case study shows that when the capillary radius ranges from 5 nm to 2000 nm, the relative error between wall-associated diffusion and slippage effect mass flux is fairly small, namely less than 10% in the vast majority of the range. The difference between mean values of wall-associated diffusion and slippage effect mass flux in the whole aperture range is 1.4×10- 6 kg·m-2·s-1. That is, the relative error between the mean values is only 5.8%. Therefore, the new method satisfies the requirements for engineering calculations. Taking parameter selection, unfinished improvements in mathematical models of relevant mechanisms and other factors into account, there is some room for further promoting the verification of the proposed method. The development of wall-associated diffusion has practical significance and multiple research significance. And the new coupling way reveals the relation between slippage and diffusions, which prevents reduplicated superposition of shale gas flow mechanisms in nano-scale pores and can well change the status where the current coupling methods for shale gas flow are not consistent, thus specifying a new direction in the quantitative calculations for shale gas development.

Rapid determination of hydrodynamic radii beyond the limits of Taylor dispersion

Taylor dispersion analysis (TDA) is an absolute method for determining the diffusion coefficients, and hence the hydrodynamic radii, of particles by measuring the dispersion in a carrier medium flowing within a capillary. It is applicable under conditions which allow the particles to radially diffuse appreciably across the cross-section of the flow before the measurement and therefore implies long measurement times are required for large particles with small diffusion coefficients. In this paper, a method has been developed by which the diffusion coefficients of large particles can be rapidly estimated from the shapes of the concentration profiles obtained at much earlier measurement times. The method relies on the fact that the shapes of the early-time concentration profiles are dependent on the diffusion coefficient, flow rate and the capillary radius through the dimensionless residence time which, theoretically, is a measure of the amount of radial diffusion undergone by the particles. The amount of radial diffusion for nanospheres of varying sizes was estimated by quantifying the relative change in the shapes of concentration profiles obtained at two points in the flow and a correlation was obtained with the variation of the dimensionless residence time to confirm the theory. This correlation was then tested by applying it to another set of measurements of solutes and solute mixtures of different sizes including a protein. The estimated diffusion coefficients were found to be in good agreement with the expected values. This demonstrates the potential for the method to extend dispersion analysis to regimes well outside the TDA limits to enable the rapid characterization of large particles.

Nephron morphometry in mice and rats using tomographic microscopy

The aim was to quantify the glomerular capillary surface area, the segmental tubular radius, length, and area of single nephrons in mouse and rat kidneys. Multiple 2.5-µm-thick serial Epon sections were obtained from three mouse and three rat kidneys for three-dimensional reconstruction of the nephron tubules. Micrographs were aligned for each kidney, and 359 nephrons were traced and their segments localized. Thirty mouse and thirty rat nephrons were selected for further investigation. The luminal radius of each segment was determined by two methods. The luminal surface area was estimated from the radius and length of each segment. High-resolution micrographs were recorded for five rat glomeruli, and the capillary surface area determined. The capillary volume and surface area were corrected for glomerular shrinkage. A positive correlation was found between glomerular capillary area and proximal tubule area. The thickest part of the nephron, i.e., the proximal tubule, was followed by the thinnest part of the nephron, i.e., the descending thin limb, and the diameters of the seven identified nephron segments share the same rank in the two species. The radius and length measurements from mouse and rat nephrons generally share the same pattern; rat tubular radius-to-mouse tubular radius ratio ≈ 1.47, and rat tubular length-to-mouse tubular length ratio ≈ 2.29, suggesting relatively longer tubules in the rat. The detailed tables of mouse and rat glomerular capillary area and segmental radius, length, and area values may be used to enhance understanding of the associated physiology, including existing steady-state models of the urine-concentrating mechanism.

The Phase Envelope of Multicomponent Mixtures in the Presence of a Capillary Pressure Difference

Confined fluids such as oil and gas mixtures inside tight reservoirs are systems that can experience high capillary pressure difference between the liquid and gas phases. This capillary pressure difference has an effect on the phase equilibrium and in some cases is considerably high. We presented an algorithm which can reliably compute the whole phase envelope for multicomponent mixtures when there is a capillary pressure difference. It uses an equation of state for the phase equilibrium and the Young–Laplace equation for the capillary pressure model. The algorithm proves to be robust and efficient for test mixtures with wide ranges of compositions at different capillary radii and vapor fractions. The calculation results show that the phase envelope changes everywhere except at the critical point. The bubble point and the lower branch of the dew point show a decrease in the saturation pressure, whereas the upper branch of the dew point shows an increase. The cricondentherm is shifted to a higher temperatu...

Hysteresis of the Contact Angle of a Meniscus Inside a Capillary with Smooth, Homogeneous Solid Walls

A theory of contact angle hysteresis of a meniscus inside thin capillaries with smooth, homogeneous solid walls is developed in terms of surface forces (disjoining/conjoining pressure isotherm) using a quasi-equilibrium approach. The disjoining/conjoining pressure isotherm includes electrostatic, intermolecular, and structural components. The values of the static receding θr, advancing θa, and equilibrium θe contact angles in thin capillaries were calculated on the basis of the shape of the disjoining/conjoining pressure isotherm. It was shown that both advancing and receding contact angles depend on the capillary radius. The suggested mechanism of the contact angle hysteresis has a direct experimental confirmation: the process of receding is accompanied by the formation of thick β-films on the capillary walls. The effect of the transition from partial to complete wetting in thin capillaries is predicted and analyzed. This effect takes place in very thin capillaries, when the receding contact angle decreases to zero.

Confined tube flow of low viscosity emulsions: Effect of matrix elasticity

This study is addressed to the effect of the elasticity of the continuous phase on confined flow of low viscosity emulsions, a topic of interest in several applications. A Newtonian silicone oil was used as the dispersed phase, while three different water-based fluids, a Newtonian and two Boger fluids, were used as the continuous phase. All the fluids have the same viscosity (ca. 0.05 Pa s). Emulsions were prepared by feeding the two phases to a T-junction followed by a membrane. When the continuous phase was a Boger fluid, the average drop size of the so obtained emulsions was higher (as compared to the Newtonian continuous phase) and a bimodal distribution was observed. Such lower mixing efficiency for a Boger continuous phase is in line with the result for an isolated droplet that breakup is hindered by matrix elasticity. High-speed microscopy visualization of the emulsions flowing through a microcapillary allowed one to determine the velocity profiles and the droplet spatial distribution as a function of the shear rate. In all the experiments, the formation of a droplet-rich core and of a droplet-devoid wall region Δ was observed, with a significant enhancement when the continuous phase was a Boger fluid (where values of Δ as high as 37% of capillary radius were found). So, confinement here refers to the fact that, although the droplets are much smaller than capillary radius, the droplet-free layer takes up a significant fraction of the capillary radius. The observed nonhomogeneous droplet spatial distribution was not due to a transient entry effect, as shown by imaging the emulsions flow at different sections from the capillary inlet, but can be explained by a balance between collision-induced drop diffusion and wall lift force. The former acts to homogenize droplet spatial distribution, while the latter tends to push droplets away from the wall and is enhanced by matrix elasticity. These effects lead to the accumulation of larger droplets around the center of the channel, while smaller droplets are pushed toward the periphery. The velocity profiles for the Boger continuous phase were flat in the droplet-rich core, thus suggesting that the confined emulsions behave as a Bingham fluid. The corresponding yield stress was determined by data fitting of the velocity profiles and rather large values were so obtained. This result is consistent with the high values, close to the maximum packing for spherical particles in binary dispersions, of the droplet volume fraction in the core, which were estimated by measuring the thickness of the droplet-devoid annular region as a function of the applied flow rate and making a volume balance. Overall, the results of this work bear strong analogies with the confined flow of other concentrated suspensions of deformable particles, such as red blood cells in microcirculation, where the formation of a cell-free layer at the wall, which is referred to as margination, has important pathophysiological implications. These findings suggest that low viscosity emulsions with an elastic matrix under confined flow can be used as a tunable model system of biomedical relevance.

CPMG relaxation rate dispersion in dipole fields around capillaries

Transverse relaxation rates for Carr-Purcell-Meiboom-Gill (CPMG) sequences increase with inter-echo time in presence of microscopic magnetic field inhomogeneities due to nuclear spin diffusion. For a weak field approximation that includes diffusion effects, the CPMG relaxation rate shift for proton diffusion around capillaries in muscle tissue can be expressed in terms of a frequency correlation function and the inter-echo time. The present work provides an analytical expression for the local relaxation rate shift that is dependent on local blood volume fraction, diffusion coefficient, capillary radius, susceptibility difference and inter-echo time. Asymptotic regions of the model are in agreement with previous modeling results of Brooks et al., Luz et al. and Ziener et al. In comparison with simulation data, the model shows an equal or better accuracy than established approximations. Also, model behavior coincides with experimental data for rat heart and skeletal muscle. The present work provides analytical tools to extract sub-voxel information about uniform capillary networks that can be used to study capillary organization or micro-circulatory remodeling.

The Effect of Ion Motion on Laser-Driven Plasma Wake in Capillary**supported by National Natural Science Foundation of China (No. 11247016), the Natural Science Foundation of Jiangxi Province, China (Nos. 2014ZBAB202001 and 20151BAB212010), and the Science Foundation for Youths of the Jiangxi Education Committee of China (No. GJJ14224)

The effect of ion motion in capillary-guided laser-driven plasma wake is investigated through rebuilding a two-dimensional analytical model. It is shown that laser pulse with the same power can excite more intense wakefield in the capillary of a smaller radius. When laser intensity exceeds a critical value, the effect of ion motion reducing the wakefield rises, which becomes significant with a decrease of capillary radius. This phenomenon can be attributed to plasma ions in smaller capillary obtaining more energy from the plasma wake. The dependence of the difference value between maximal scalar potential of wake for two cases of ion rest and ion motion on the radius of the capillary is discussed.

Measurement of Capillary Radius and Contact Angle within Porous Media.

The pore radius (i.e., capillary radius) and contact angle determine the capillary pressure generated in a porous medium. The most common method to determine these two parameters is through measurement of the capillary pressure generated by a reference liquid (i.e., a liquid with near-zero contact angle) and a test liquid. The rate of rise technique, commonly used to determine the capillary pressure, results in significant uncertainties. In this study, we utilize a recently developed technique for independently measuring the capillary pressure and permeability to determine the equivalent minimum capillary radii and contact angle of water within micropillar wick structures. In this method, the experimentally measured dryout threshold of a wick structure at different wicking lengths is fit to Darcy's law to extract the maximum capillary pressure generated by the test liquid. The equivalent minimum capillary radii of different wick geometries are determined by measuring the maximum capillary pressures generated using n-hexane as the working fluid. It is found that the equivalent minimum capillary radius is dependent on the diameter of pillars and the spacing between pillars. The equivalent capillary radii of micropillar wicks determined using the new method are found to be up to 7 times greater than the current geometry-based first-order estimates. The contact angle subtended by water at the walls of the micropillars is determined by measuring the capillary pressure generated by water within the arrays and the measured capillary radii for the different geometries. This mean contact angle of water is determined to be 54.7°.

Effects of graphene oxide nanofluids on heat pipe performance and capillary limits

In the present study, thermal performances of water-filled and 0.01 and 0.03 vol% graphene oxide (GO)/water nanofluids-filled heat pipes with a screen mesh wick were studied in order to investigate the effects of nanofluids on the heat pipe operation. The wall temperatures of the GO/water nanofluids-filled heat pipes were found to be lower than those of the water heat pipe. Also, the heat pipes charged with GO/water nanofluids showed lower evaporator thermal resistances by about 25% compared with the water-filled heat pipe, although the condenser thermal resistances were similar in both cases. The 0.01 vol% GO/water nanofluid-filled heat pipe showed better boiling heat transfer than 0.03 vol% GO/water nanofluid because of the different structures of the deposited nanoparticle layers on the wicks. The capillary limit of the heat pipes containing GO/water nanofluids was higher than for the water heat pipe, because the nanoparticles-coated layer modified the effective capillary radius and meniscus, resulting in an increase of the maximum liquid flow rate through the wick structure. The SEM images and wetting properties for wicks of the heat pipes with nanoparticles-coated layers support the thermal performance characteristics of the heat pipes obtained in the study.

A COMPREHENSIVE MODEL FOR CAPILLARY PRESSURE DIFFERENCE ACROSS A DROP/BUBBLE FLOWING THROUGH A CONSTRICTED CAPILLARY

The capillary pressure is one of the crucial parameters in many science and engineering applications such as composite materials, interface science, chemical engineering, oil exploration, etc. The drop/bubble formation and its mechanisms that affect the permeability of porous media have steadily attracted much attention in the past. When a drop/bubble moves from a larger capillary to a smaller one, it is often obstructed by an additional pressure difference caused by the capillary force. In this paper, a comprehensive model is derived for the capillary pressure difference when a drop/bubble flows through a constricted capillary, i.e. a geometrically constricted passage with an abrupt change in radius. The proposed model is expressed as a function of the smaller capillary radius, pore-throat ratio, contact angle, surface tension and length of the drop/bubble in the smaller capillary. The model predictions are compared with the available experimental data, and good agreement is found between them.

Impact of Microalgae on CO2 Bubble Growth and Detachment in Bubble Column Bioreactor

The biological capture of carbon dioxide (CO2) using microalgae is a promising technology and has gained a huge momentum due to its environment-friendly, low cost and high CO2 fixation efficiency. In the applications CO2 gas usually was pumped into photobioreactors in bubble form. The bubbles behavior significantly affects the mass transfer and distribution of the microalgae. Also the adhesion of microalgae and absorption of CO2 at the gas-liquid interface will certainly have an important effect on the dynamics of CO2 bubbles in bubble column bioreactor. In this work, visual experiments were conducted for studying the impacts of microalgae on CO2 bubble growth and detachment in bubble column bioreactor. It was found that many microalgae cells adsorbed on the surface of the bubble resulting in easier detachment of bubble in microalgae suspension against with pure water. Besides, it was also found that smaller capillary radius and larger CO2 concentration gave rise to decreasing bubble growth rate and detachment diameter which was conducive to CO2 transportation. Moreover, a critical gas flow velocity of 1.7 m/s in capillary was achieved, which divided the bubble growth status into steady and unsteady state, and different bubble growth and detachment behaviors were observed. These findings will be beneficial for the design of aeration system of photobioreactors for microalgae cultivation to enhance the mass transport at the interface.

Electrochemical Separation, Pumping, and Storage of Hydrogen or Oxygen into Nanocapillaries Via High Pressure MEA Seals

High-density storage of gases remains a major technological hurdle for many fields. The U.S. Department of Energy (DOE), for example, reduced their hydrogen storage targets for automotive applications due to the inability of technologies to reach the system-level targets.1 Without significant improvements in hydrogen storage density, hydrogen as a transportation fuel remains unfeasible. In other fields, the low volumetric and gravimetric storage densities of oxygen gas cylinders can be cumbersome or prohibitively expensive for applications like terrestrial and marine breathing apparatus’ or manned space exploration. Emerging technologies such as sorbents and chemical complexes show potential for gas storage. However, the ability to achieve application-specific gas delivery rates and high storage densities, while operating reversibly at ambient temperature, remains elusive.2, 3 In contrast, it may be possible to achieve high gas storage densities and potentially high gas delivery rates using nanocapillaries when used in conjunction with a membrane electrode assembly (MEA). Hoop stress calculations show that the pressure tolerances of cylinders are inversely proportional to the radius. Indeed, glass microcapillaries have already theoretically4 and experimentally5 demonstrated the capacity to achieve DOE hydrogen storage targets at a materials-level. This technology can be further improved by reducing the capillary radius to the nanoscale; however, the capping and pressurization of the gas in micro- or nanocapillaries remains problematic. Presented here is the fabrication of nanocapillary arrays capped by an MEA for highly reversible storage of gases with the potential for high rate pumping and high-density storage. Very high aspect ratio and densely packed nanocapillary arrays are produced through aluminum anodization. The nanocapillary arrays are capped with either a PEM or an alkaline (anion) exchange membrane (AEM) complete with catalyst nanoparticles on either side of the membrane to form an MEA. This MEA is used to provide controllable electrochemical pumping of hydrogen or oxygen gas into and out of the nanocapillaries. The MEA also serves as a high pressure seal. A theoretical discussion of the potential volumetric and gravimetric storage densities of hydrogen and oxygen in nanocapillary arrays will be presented together with experimental results of electrochemical gas compression into lab-scale devices. The evaluation of both commercial catalyst materials and fabricated nanoparticle catalysts (<10 nm) for hydrogen and oxygen pumping will be discussed. In addition, the performance of both PEM and AEM for electrochemical pumping of oxygen will be compared. A discussion of the electrochemistry within nanocapillaries compared to planar MEAs will be given including the charge transport/transfer processes. The potential failure mechanisms and the technical obstacles to the implementation of our electrochemical membrane approach, together with the current state of the technology and overall storage capacities, will be presented. 1. Hydrogen, Fuel Cells and Infrastructure Technologies Program: Multi-Year Research, Development and Demonstration Plan. US Department of Energy, Energy Efficiency and Renewable Energy 2012. 2. Zhou, L., Progress and problems in hydrogen storage methods. Renewable and Sustainable Energy Reviews 2005, 9 (4), 395-408. 3. Pukazhselvan, D.; Kumar, V.; Singh, S., High capacity hydrogen storage: basic aspects, new developments and milestones. Nano Energy 2012, 1 (4), 566-589. 4. Zhevago, N.; Glebov, V., Hydrogen storage in capillary arrays. Energy Conversion and Management 2007, 48 (5), 1554-1559. 5. Zhevago, N.; Denisov, E.; Glebov, V., Experimental investigation of hydrogen storage in capillary arrays. International Journal of Hydrogen Energy 2010, 35 (1), 169-175.

Effect of Changing Source Capillary Radius on Bulk Flow Parameter Scaling Laws for Hypersonically Expanding Arc-Ablated Polycarbonate Plasma for Fusion and Space Applications

Capillary pulsed electrothermal plasma source coupled to a linear converging–diverging nozzle was previously found to be adequate as a simulator for the supersonic bulk flow patterns of the aerosol particulates generated following a hard disruption event that damages the plasma facing components in a fusion reactor. A similar system can assume an important role in the computational studies related to space electric propulsion and electrostatic ion thrusters. Scaling laws for the prediction of bulk temperature, density, pressure, plasma bulk velocity and Mach number as a function of the axial length traversed measured from the source exit had been proposed previously for an arc-ablated polycarbonate plasma jet evolving into a vacuum chamber via the transition nozzle. In the present work, the source capillary radius has been varied and with the sectional lengths remaining fixed, the converging and diverging angles have also been varied with it, as the diverging exit Mach number was kept constant at a high-hypersonic value ~18. The effect of changing source capillary radius as well as the transition region geometry on the aforesaid bulk flow parameters has been studied computationally and new scaling laws have been proposed.

Burst behavior at a capillary tip: Effect of low and high surface tension

Liquid retention in micron and millimeter scale devices is important for maintaining stable interfaces in various processes including bimolecular separation, phase change heat transfer, and water desalination. There have been several studies of re-entrant geometries, and very few studies on retaining low surface tension liquids such as fluorocarbon-based dielectric liquids. Here, we study retention of a liquid with very low contact angles using borosilicate glass capillary tips. We analyzed capillary tips with outer diameters ranging from 250 to 840μm and measured Laplace pressures up to 2.9kPa. Experimental results agree well with a numerical model that predicts burst pressure (the maximum Laplace pressure for liquid retention), which is a function of the outer diameter (D) and capillary exit edge radius of curvature (r).