Serret D., Brutin D., Rahli O., Tadrist L., Convective boiling between 2D plates: microgravity influence on bubble growth and detachment, Microgravity Science and Technology, Vol. 22, (3), pp. 377-385, 2010.

Today, convective boiling is still an important subject in the field of phase change due to its wide range of application. It is mainly used to cool systems like computer chips in recent laptops. Many studies have analyzed different regimes between the entrance and the outlet of a channel where convective boiling occurs: subcooled nucleate boiling, bubbly flow, slug flow… We focus in this research activity on the first time of these regimes, i.e. subcooled nucleate boiling flow in a 2D cell. The originality of this work is to investigate this regime in a Hele-Shaw cell. This kind of experimental configuration has already been used for various experimental studies such as the Maragoni effect, Kelvin Helmotz instability, and the mix of two miscible liquids. Furthermore, the geometry of the cell avoids any optical aberration due to a high thermal gradient in the thermal boundary close to the wall.

This geometry avoids any trouble due to three-dimensional effects (the created bubble is maintained in the same plane during the whole of its growing and detachment phases). This configuration also allows us to use an infrared camera on one side of the cell and the other side is fitted with a visible camera, which has never been used to study a single nucleation site in a 2D cell.

The experiments were carried out at cabin pressure (835 mbar). For this purpose we added a surge tank containing a latex membrane in order to follow the changes in cabin pressure. Nevertheless, locally the pressure can increase to a maximum of 100 Pa. This means that the pressure before the cell entrance can reach 835 mbar + 1 mbar = 836 mbar. After the test cell we measured the absolute pressure of the loop in the buffer tank, which must be equal to the cabin pressure in order to have stable and reproducible operating conditions. We degassed by remotely actuating an electromagnetic valve if the pressure exceeded 845 mbar. It was possible to work at constant ambient pressure.
		Visible images of 2D bubble growth and detachment in microgravity
An infrared picture of the test cell which measured 40 x 20 x 1 mm3 with the corresponding field of view recorded with the visible camera is presented on the side. The shear flow is thus induced by a liquid flow coming from the left. The heating plate is clearly visible with the hot spot. The size of the spot is due to the polycarbonate heated by conduction. The main bubble stuck on the nucleation site is visible as is the secondary bubble a few millimetres to the right. Both bubbles induce a modification of the temperature field.
		Infrared and visible images of a single bubble stuck on the heating plate.

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