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Fin Shape Design for Stable Film-Wise Vapor Condensation in Microgravity

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Abstract

Under microgravity conditions, the dynamics of a thin condensate film on a curved surface is determined by the capillary pressure gradient proportional to the mean surface curvature gradient. A one-parameter family of axisymmetric surfaces is found for which the gradient of mean curvature is constant. The dimensionless equation for rotation angle of the generatrix curve is found. There is a single generatrix curve for an axisymmetric surface for which the rotation angle at the inflexion point assumes a predetermined value. Due to the constant gradient of capillary pressure on such a surface, a stable condensate flow is ensured under microgravity conditions. A similar curve for the planar case, known as the clothoid or "Cornu spiral", is used to find the best transition curve to get the smoothest traffic on the roads. A numerical model for film-wise vapor condensation on such surface has been built. The film thickness distribution and mass flow rate of the HFE-7100 along the cooled curvilinear fin have been calculated. Calculations were done both for terrestrial gravity and microgravity. This work proposes a particular surface shape, found numerically, for conducting experiments on the pure vapor condensation under microgravity conditions in Parabolic Flight Campaigns and onboard the International Space Station.

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Data Availability

The data generated during and analyzed during the current study are available from the corresponding author on reasonable request.

Code Availability

Not applicable.

Abbreviations

P :

capillary pressure, N/m2

\(\frac{\partial P}{\partial S}\) :

capillary pressure gradient along the generatrix curve, N/m3

σ :

surface tension coefficient, N/m

κ(s) :

curvature of the generatrix curve, \({m}^{-1}\)

κ 0 :

curvature on the fin top, \({m}^{-1}\)

\({\kappa }_{1}{,\kappa }_{2}\) :

main curvatures, \({m}^{-1}\)

\({\kappa }_{fin}=\kappa +sin\left(\theta \right)/r\) :

double mean curvature of fin surface, \({m}^{-1}\)

s :

variable along the curved surface S

\({S}_{fin}\) :

end of the fin's curve

\(r\left(s\right)=\underset{0}{\overset{s}{\int }}cos\left(\theta \left(\xi \right)\right)d\xi\) :

radius of the fin along s

\(y\left(s\right)=\underset{0}{\overset{s}{\int }}cos\left(\theta \left(\xi \right)\right)d\xi\) :

coordinate, directed downward

\(\theta \left(s\right)=\underset{0}{\overset{s}{\int }}\kappa \left(\xi \right)d\xi\) :

rotation angle of the curve at s

\(b=a/{\kappa }_{0}^{2}\) :

curve's parameter

\({V}_{\Omega }=\underset{\Omega }{\overset{}{\int }}hds\) :

liquid volume

Ω :

is an element of the surface S

\(J=-\lambda\Delta T/{\rho r}_{lv}h\) :

is volumetric flux of the condensate through the interface

h t :

is velocity of the condensate film, m/s

λ :

is thermal conductivity of liquid, W/m/K

r lv :

is latent heat of vaporization, J/kg

ρ :

is density, kg/m3

\(\overrightarrow q=\frac{h^3}{3\mu}\overrightarrow f+\frac{h^2}{2\mu}{\overrightarrow\tau}_{sur}\)  :

is the liquid flow vector along the surface, m2/s

\(\overrightarrow{f}\) :

gradient of the modified pressure, Pa/m

μ :

is dynamic viscosity, kg/m/s

h :

liquid film thickness, m

h 0 :

initial liquid film thickness, m

t :

time, s

ΔT = Tsat-Tw :

temperature drop, K

Tw :

temperature of the fin's surface, oC

Tsat :

saturation temperature, oC

Bo :

the Bond number

ESA :

European Space Agence

ISS :

International Space Station

PFC :

Parabolic Flight Campaign

IP :

inflexion point

HFE-7100 :

trademark of methoxy-nanouorobutane (C4F9OCH3)

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Acknowledgements

This work was carried out under state contract with IT SB RAS (121031200084-2)

Funding

This work was carried out under state contract with IT SB RAS (121031200084–2).

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Correspondence to Ella Barakhovskaia.

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Barakhovskaia, E., Marchuk, I. Fin Shape Design for Stable Film-Wise Vapor Condensation in Microgravity. Microgravity Sci. Technol. 34, 8 (2022). https://doi.org/10.1007/s12217-021-09918-z

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