A SANS Contrast Variation Study of Microemulsion Droplet Growth

When water vapor in moist air reaches supersaturation in a transonic flow system, non-equilibrium condensation forms a large number of droplets which may adversely affect the operation of some thermal-hydraulic equipment. For a better understanding of this non-equilibrium condensing phenomenon, a numerical model is applied to analyze moist air condensation in a transonic flow system by using the theory of nucleation and droplet growth. The Benson model is adopted to correct the liquid-plane surface tension equation for realistic results. The results show that the distributions of pressure, temperature and Mach number in moist air are significantly different from those in dry air. The dry air model exaggerates the Mach number by 19% and reduces both the pressure and the temperature by 34% at the nozzle exit as compared with the moist air model. At a Laval nozzle, for example, the nucleation rate, droplet number and condensation rate increase significantly with increasing relative humidity. The results also reveal the fact that the number of condensate droplets increases rapidly when moist air reaches 60% relative humidity. These findings provide a fundamental approach to account for the effect of condensate droplet formation on moist gas in a transonic flow system.

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Neutron diffraction, inelastic scattering and the structure of amphiphiles and macromolecules in solution

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1975.0129 ◽

1975 ◽

Vol 345 (1640) ◽

pp. 119-144 ◽

Cited By ~ 5

Keyword(s):

Neutron Diffraction ◽

Inelastic Scattering ◽

Cross Sections ◽

Biological Molecules ◽

Variation Method ◽

Contrast Variation ◽

Structure And Dynamics ◽

Spin Resonance ◽

Scattering Lengths ◽

Scattering Cross Sections

The methods by which neutron diffraction and inelastic scattering may be used to study the structure and dynamics of solutions are reviewed, with particular reference to solutions of amphiphile and biological molecules in water. Neutron methods have particular power because the scattering lengths for protons and deuterons are of opposite sign, and hence there exists the possibility of obtaining variable contrast between the scattering of the aqueous medium and the molecules in it. In addition, the contrast variation method is also applicable to inelastic scattering studies whereby the dynamics of one component of the solution can be preferentially studied due to large and variable differences in the scattering cross sections. Both applications of contrast variation are illustrated with examples of amphiphile-water lamellar mesophases, diffraction from collagen, viruses, and polymer solutions. Inelastic scattering observations and the dynamics of water between the lamellar sheets allow microscopic measurements of the water diffusion along and perpendicular to the layers. The information obtained is complementary to that from nuclear magnetic resonance and electron spin resonance studies of diffusion.

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Ultra-Small-Angle Neutron Scattering Study of Colloidal Alloys. 1. Contrast Variation Experiments for Mixtures of Hydrogenated and Deuterated Polystyrene Latices in H2O/D2O

Langmuir ◽

10.1021/la9803171 ◽

1999 ◽

Vol 15 (2) ◽

pp. 293-296 ◽

Cited By ~ 13

Author(s):

Hideki Matsuoka ◽

Takashi Ikeda ◽

Hitoshi Yamaoka ◽

Mitsuhiro Hashimoto ◽

Toshio Takahashi ◽

...

Keyword(s):

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Contrast Variation ◽

Scattering Study ◽

Neutron Scattering Study

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A Heat Transfer Model of Dropwise Condensation Underneath a Horizontal Substrate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.199-200.1604 ◽

2011 ◽

Vol 199-200 ◽

pp. 1604-1608

Author(s):

Yun Fu Chen

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Contact Angle ◽

Fractal Model ◽

Condensation Heat Transfer ◽

Droplet Growth ◽

Transfer Model ◽

Dropwise Condensation ◽

Small Contact Angle ◽

Horizontal Substrate

For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.

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