Forced convective boiling experiments of HFE-7000 were conducted in earth gravity and under microgravity conditions. The experiment mainly consists in the study of a two-phase flow through a 6 mm diameter sapphire tube uniformly heated by an ITO coating. The parameters of the hydraulic system are set by the conditioning system and measurements of pressure drops, void fraction and wall temperatures are provided. High-speed movies of the flow were also taken. The data were collected in normal gravity and during a series of parabolic trajectories flown onboard an airplane. Flow visualisations, temperature and pressure measurements are analysed to obtain flow pattern, heat transfer and wall friction data.

A novel type of two-phase heat spreader based on a flat confined thermosyphon is proposed for electronics cooling applications. Two wickless flat copper-water heat pipes with an inner thickness of 3 mm were experimentally investigated for both two-phase flow visualizations and characterization of thermal performance. The effects of heat input, filling ratio, inclination and saturation temperature were studied. Experimental results show that the confinement of the fluid inside the heat spreader induces confined boiling phenomenon with a strong coupling between condensation and boiling mechanisms. They also highlight an enhancement of heat transfer and interesting performance such as high heat transfer capability (tested up to 30 W/cm² with a corresponding thermal resistance around 0.07 K/W at an optimum filling ratio), low sensitivity to inclination and higher degree of freedom on heat sources location compared to a classical thermosyphon.

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