Critical heat flux enhancement in microgravity conditions coupling microstructured surfaces and electrostatic field

Alekos Ioannis Garivalis,Giacomo Saccone,Paolo Di Marco,Artyom Kossolapov,Giacomo Manfredini,Matteo Bucci

doi:10.1038/s41526-021-00167-3

Alekos Ioannis Garivalis, Giacomo Saccone + Show 4 more

Open Access

https://doi.org/10.1038/s41526-021-00167-3

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Abstract

We run pool boiling experiments with a dielectric fluid (FC-72) on Earth and on board an ESA parabolic flight aircraft able to cancel the effects of gravity, testing both highly wetting microstructured surfaces and plain surfaces and applying an external electric field that creates gravity-mimicking body forces. Our results reveal that microstructured surfaces, known to enhance the critical heat flux on Earth, are also useful in microgravity. An enhancement of the microgravity critical heat flux on a plain surface can also be obtained using the electric field. However, the best boiling performance is achieved when these techniques are used together. The effects created by microstructured surfaces and electric fields are synergistic. They enhance the critical heat flux in microgravity conditions up to 257 kW/m2, which is even higher than the value measured on Earth on a plain surface (i.e., 168 kW/m2). These results demonstrate the potential of this synergistic approach toward very compact and efficient two-phase heat transfer systems for microgravity applications.

Highlights

Pool boiling is an effective means to remove heat: due to the latent heat involved in the evaporation and the fluid motion induced by bubbles, heat transfer coefficients are even two order of magnitude higher than single-phase heat transfer[1]
The boiling process is recorded by a high-speed black and white camera from the side and the temperature of the silicon substrate is acquired via a PT100
The body force generated by the electric field is weak compared to buoyancy and does not affect the overall boiling pattern in normal gravity conditions; this agrees with the analysis reported in the Supplementary results

Summary

Introduction

Pool boiling is an effective means to remove heat: due to the latent heat involved in the evaporation and the fluid motion induced by bubbles, heat transfer coefficients are even two order of magnitude higher than single-phase heat transfer[1]. A stable vapor layer blankets the heated surface. This heat transfer regime is known as film boiling. Space stations and satellites are rather special applications, as they operate in microgravity conditions, which affects the dynamics of nucleate boiling and the CHF limit. In normal gravity conditions (e.g., on Earth), bubbles arise from the heated surface and, for sufficiently high heat fluxes, coalesce into vapor slugs and columns. A large bubble hovers at a short distance from the surface, while many smaller bubbles nucleate and grow underneath. These small bubbles feed the large one, which acts as a vapor sink. Straub proposed that there are two types of heat transfer mechanisms involved in boiling heat transfer[6,7]

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