Nanostructured phase-changeable heat transfer fluids

Cooling is one of the most important technique challenges faced by a range of diverse industries and military needs. There is an urgent need for the innovative heat transfer fluids with improved thermal properties over the currently available. This review paper discusses the concept of using phase-changeable nanoparticles to increase the effective heat capacity and the heat transfer rate of the fluid. A large amount of heat can be absorbed or released when these nanoparticles undergo phase transition from solid to liquid or liquid to gas or vice versa and, thus, enhancing the heat transfer rate. Two types of phase-change fluids are introduced: one contains liquid nanodroplets that will evaporate at elevated temperatures or solidifies at reduced temperatures, called “nanoemulsion fluids”; the other is suspensions of solid-liquid metallic phase-change nanoparticles. The material synthesis and property characterizations of these phase-changeable fluids are two main aspects of this paper. The explosive vaporization of the dispersed nanodroplets would significantly improve the heat transfer in the nanoemulsion fluid. The solid-liquid metallic phase-change nanoparticles will increase the effective heat capacity and thermal conductivity of the base fluids simultaneously. This paper also identifies the several critical issues in the phase-changeable fluids to be solved in the future.