Examining Liquid Hydrogen Wettability Using Neutron Imaging

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Vinaykumar Konduru ◽  
Kishan Bellur ◽  
Ezequiel F. Médici ◽  
Jeffrey S. Allen ◽  
Chang Kyoung Choi ◽  
...  
Keyword(s):  
Contact Angle ◽  
Cone Angle ◽  
Neutron Cross Section ◽  
Liquid Hydrogen ◽  
Contact Angles ◽  
Neutron Imaging ◽  
Test Cell ◽  
Clear Understanding ◽  
Vapor Interface ◽  
Liquid Vapor

The control of propellant boil-off is essential in long-term space missions. However, a clear understanding of propellant cryogenic condensation/evaporation in microgravity is lacking. One of the key factors in designing such systems is the location of liquid surfaces and the relation to wettability. The BT-2 Neutron Imaging Facility located at the National Institute of Standards and Technology (NIST), Gaithersburg, MD, is used to image evaporation and condensation of hydrogenated propellants inside of an aluminum 6061 container. Liquid hydrogen has larger neutron cross-section area than the aluminum, allowing the visualization of the liquid-vapor interface. The test cell has a conical section that enables determination of a contact angle with enhanced accuracy. If the contact angle is equal to the angle of the cone, a flat liquid-vapor interface is expected. The test cell has the cone angle of 10o and a flat interface was not observed. Using the Laplace-Young equation to fit the interface, the contact angle for hydrogen and aluminum was between 0° and 4°. The theoretical Laplace curves with contact angles of 2o and 10o are plotted on the liquid-vapor interface. The of 2o curve is a closer fit as compared to the 10o curve. The uncertainty arises from resolution limits of the neutron imaging setup and edge detection. More details on the neutron imaging mechanism and relevant physics can be found from the authors' other publication of Cryogenics, 74, pp131-137, 2016: doi:10.1016/j.cryogenics.2015.10.016.

scholarly journals The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity

Research ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Yong-Ming Liu ◽  
Zi-Qing Wu ◽  
Sheng Bao ◽  
Wei-Hong Guo ◽  
Da-Wei Li ◽  
...  
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Region ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Angle Measurement ◽  
Measured Parameter ◽  
Material Surface ◽  
Vapor Interface ◽  
Liquid Vapor

The contact angle, as a vital measured parameter of wettability of material surface, has long been in dispute whether it is affected by gravity. Herein, we measured the advancing and receding contact angles on extremely low contact angle hysteresis surfaces under different gravities (1-8G) and found that both of them decrease with the increase of the gravity. The underlying mechanism is revealed to be the contact angle hysteresis and the deformation of the liquid-vapor interface away from the solid surface caused by gradient distribution of the hydrostatic pressure. The real contact angle is not affected by gravity and cannot measured by an optical method. The measured apparent contact angles are angles of inclination of the liquid-vapor interface away from the solid surface. Furthermore, a new equation is proposed based on the balance of forces acting on the three-phase contact region, which quantitatively reveals the relation of the apparent contact angle with the interfacial tensions and gravity. This finding can provide new horizons for solving the debate on whether gravity affects the contact angle and may be useful for the accurate measurement of the contact angle and the development of a new contact angle measurement system.

Neutron Radiography of Condensation and Evaporation of Hydrogen in a Cryogenic Condition

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Kishan Bellur ◽  
Ezequiel Medici ◽  
Jeffrey Allen ◽  
Jimes Hermanson ◽  
Arun Tamilarasan ◽  
...  
Keyword(s):  
Cross Section ◽  
Neutron Radiography ◽  
High Sensitivity ◽  
Liquid Hydrogen ◽  
Neutron Imaging ◽  
Test Cell ◽  
Inner Diameter ◽  
Temperature And Pressure ◽  
Cryogenic Propellants ◽  
Cryogenic Conditions

The condensation and evaporation of hydrogen under cryogenic conditions is visualized by using neutron imaging at the BT-2 Beam Facility at the National Institute of Standards and Technology (NIST). The condensation and evaporation are controlled by adjusting temperature (20 K ~ 23 K) and pressure (1.3 ~ 1.95 bar absolute). The hydrogen contained in the aluminum test cell inside the cryostat has a large attenuation coefficient due to its large scattering cross section. The high sensitivity of neutron radiography to hydrogen allows the visualization of a meniscus and a contact line of evaporating hydrogenated cryogenic propellants. The graphic represents the temperature, pressure and corresponding images of liquid hydrogen in the test cell. The test cell is made of Aluminum 6061 with an inner diameter of 12 mm. The captured images are then median filtered and post-processed in order to find the volume of liquid hydrogen in the test cell as a function of time. The condensation/evaporation rates obtained from neutron imaging along with corresponding temperature and pressure are used to validate the evaporation model being developed by the authors.

Contact Angle Measurement of Liquid Hydrogen (LH2) in Stainless Steel and Aluminum Cells

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Kishan Bellur ◽  
Vinaykumar Konduru ◽  
Manan Kulshrestha ◽  
Daanish Tyrewala ◽  
Ezequiel Medici ◽  
...  
Keyword(s):  
Contact Angle ◽  
Phase Change ◽  
Saturation Temperature ◽  
Neutron Cross Section ◽  
Angle Measurement ◽  
Neutron Imaging ◽  
Space Environment ◽  
Change Models ◽  
Accommodation Coefficients

One of the key limitations to long-term space missions is to avoid propellant boil-off in a microgravity space environment. Even with the use of active and passive controls of propellants, boil off is inevitable. Long-term CFD simulations on propellant behaviors depend on evaporation/condensation coefficients (known as accommodation coefficients) which are in turn dependent upon the wetting characteristics. Phase change experiments were conducted in the BT-2 neutron imaging facility at the National Institute of Standards and Technology (NIST) by introducing vapor H2 in 10 mm Al6061 and SS316L test cells placed inside the 70mm ‘orange’ cryostat. Condensation is achieved by lowering the cryostat temperature below the saturation point and vice versa for evaporation. The high neutron cross-section of liquid H2 in comparison to both the vapor and the test cell materials allows for visualization of a distinct liquid-vapor interface. Multiple images are stacked to increase the signal-to-noise ratio and the meniscus edge is obtained by detecting the pixels with largest gradients in intensities at the liquid meniscus. The contact angle is obtained by curve fitting of the Young-Laplace equation to the detected meniscus. The contact angle for Al6061 and SS316 is found to be between 0° and 4°. The uncertainty arises from edge detection, magnification, and resolution limits of the neutron imaging setup. The test was conducted at a saturation temperature of 21K (1.215 bar). The results from the neutron experiments will be then used in conjunction with FEA thermal models and kinetic phase change models to extract accommodation coefficients.

A Numerical Description of a Liquid-Vapor Interface Based on the Second Gradient Theory

1995 ◽  
Vol 22 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Didier Jamet ◽  
Olivier Lebaigue ◽  
Jean-Marc Delhaye ◽  
N. Coutris
Keyword(s):  
Gradient Theory ◽  
Vapor Interface ◽  
Second Gradient ◽  
Liquid Vapor

scholarly journals Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

2021 ◽  
Author(s):  
Rami Benkreif ◽  
Fatima Zohra Brahmia ◽  
Csilla Csiha
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Moisture Content ◽  
Solid Wood ◽  
Contact Angles ◽  
Surface Moisture ◽  
Wood Coatings ◽  
The Relationship ◽  
Wood Surfaces

AbstractSurface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

scholarly journals Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces: Study of the Links between Morphology and Wettability

Biomimetics ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 38
Author(s):  
Quentin Legrand ◽  
Stephane Benayoun ◽  
Stephane Valette
Keyword(s):  
Contact Angle ◽  
Ginkgo Biloba ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Textured Surfaces ◽  
Replication Process ◽  
Wetting Behavior ◽  
Static Contact ◽  
Biomimetic Approach ◽  
Highly Hydrophobic

This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135∘, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20∘. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40∘ for flat PDMS to less than 10∘ for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

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