Experimental evidence of thermocapillarity in phase change materials in microgravity: Measuring the effect of Marangoni convection in solid/liquid phase transitions

The Thermocapillary Effects in Phase Change Materials in Microgravity (TEPiM) experiment investigated the potential of Marangoni convection for heat transfer enhancement in Phase Change Materials (PCMs) in weightlessness, where the large melting/solidification timescale compromises their performance as thermal control devices. The TEPiM experiment, which was conducted during the 65th ESA Parabolic Flight campaign, represents the first microgravity research of this nature.

We present here the main scientific outcome of the experimental campaign by measuring the precise contribution of thermal Marangoni convection to the heat transfer rate of the system. The test cells, holding the experimental PCM and air, were heated to drive controlled solid/liquid phase transitions during the microgravity lapses provided in the flight. Careful observation of the melting front confirms the enhancing effect of thermocapillary convection on heat transport, able to increase the phase change rate by a factor of 1.88. This result strongly supports that, as natural convection is exploited on ground, the thermal Marangoni effect can be used in weightless conditions to improve PCMs performance.