Intensification of heat transfer using active bubble liquid

Although at present, passive liquids are the primary choice for coolants, active liquids can also be used to enhance heat transfer. Here, we demonstrate for the first time a method for intensifying heat transfer on a heat-releasing surface by using an active bubble liquid as a coolant. To obtain an active bubble liquid, TiO2 nanoparticles, which agglomerate into microscopic clusters, are dispersed in an aqueous solution of H2O2. When exposed to ultraviolet light, photocatalytic reactions occur on the surface of the clusters, which are accompanied by the formation of bubbles. Clusters with bubbles adsorbed on their surface move chaotically in the liquid under the action of diffusiophoresis. By mixing different layers of liquid, heat exchange on the heat-releasing surface can be intensified. The results of the study show that with increase in the concentration of H2O2 in an aqueous solution, the intensity of heat transfer increases. The liquid temperature has an ambiguous effect on the temperature of the heat-releasing wall. The study's results show that there is an optimal liquid temperature corresponding to the highest heat transfer rate. If the liquid temperature is below this optimal temperature, the heat transfer rate is limited by the velocity of the active bubbles. However, at high liquid temperatures, mobile bubbles mix relatively hot layers in the liquid, which limits heat exchange at the surface. The results obtained here can serve as a basis for developing a new class of coolants based on active liquids.