Influence of subcooling conditions on pool boiling in microgravity conditions: Single artificial case

A series of boiling experiments on a single artificial nucleation site has been carried out on the International Space Station (ISS) in the framework of the Multiscale Boiling (RUBI) setup installed in space in 2019. The aim of these unique experiments is to understand the bubble nucleation-growth mechanisms involved in heat transfer during boiling under well-controlled operating conditions without being masked/impeded by gravity and natural convection. The bubbles can grow to large sizes that are inaccessible in the presence of gravity. They are observed by a side-view black-and-white camera and by an infrared camera through a transparent heated substrate. In this paper, we present the results of a single-bubble pool-boiling experiment with an emphasis upon the role of the surrounding liquid subcooling, several values of which are investigated. The experimental results are complemented by numerical simulations using a previously developed model. However, the model is slightly modified to account in a simplest way for possible non-condensable residuals, without which we would have a hard time to explain certain observed behaviors.