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

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.

Condensation heat transfer in microgravity conditions

“…The fin shape also influences the distribution of the condensate film along the fin surface, hence it can be identified as one of the parameters that must be optimized during the design phase 65 . Barakhovskaia and Marchuk 66 identified the most appropriate fin shape for condensation experiments under microgravity, able to guarantee a stable flow of the condensate film under the effect of a constant capillary pressure gradient. The condensate film thickness of HFE-7100 under terrestrial gravity was found to be half of the one obtained in the absence of gravity, leading to a much higher condensation rate.…”

“…Annular flow observed under microgravity. Barakhovskaia and Marchuk 66 Numerical Axisymmetric curvilinear fin with 9.62 mm height and 4 mm radius of the fin’s base HFE-7100 Natural convection T sat = 53 °C T wall = 10–45 °C Numerical study of FWC on a fin surface designed to guarantee a constant gradient of capillary pressure With the selected fin shape the liquid film on the fin is thick enough for the experimental measurements with an optical system. The condensate film thickness along the fin under terrestrial gravity is half of the one obtained in absence of gravity.…”

Study on the instability of FC-72 vapor-liquid interface in a rectangular channel under different gravity conditions

“…Barakhovskaia [29] suggested using a specific surface shape for conducting vapor condensation experiments under microgravity conditions, facilitating smoother traffic on roads through a similar curve known as the clothoid. Yan [30] focused on analyzing the static liquid surface of axis-symmetric containers, characterizing surface shape using polar coordinates and deriving nonlinear governing equations.…”

Numerical simulation-based design of optimized surfaces for condensation heat transfer

“…When considering condensation heat transfer, the shape of the enhanced surface strongly influences the distribution of the condensate film, hence it can be identified as one of the parameters that must be optimized during the design phase. Barakhovskaia and Marchuk [1] identified the most appropriate fin shape for condensation experiments under microgravity, able to guarantee a stable flow of the condensate film under the effect of a constant capillary pressure gradient. Glushchuck et al [2],…”