Jet impingement heat transfer using air-laden nanoparticles with encapsulated phase change materials

Nanoparticles made of polymer encapsulated phase change materials (PCM) are added in air to enhance the heat transfer performance of air jet impingement flows applied to cooling processes. Encapsulation prevents agglomeration of the PCM (paraffin) nanoparticles when they are in the liquid phase. The sizes of the particles are chosen to be small enough so that they maintain near velocity equilibrium with the air stream. Small solid paraffin particles can absorb a significant amount of energy rapidly from a heat source by changing phase from solid to liquid. Nanoparticle volume fraction is found to play an important role in determining the overall pressure drop and heat transfer of the jet impingement process. Specifically, air jets laden with 2.5% particulate volume fraction were shown to improve the average heat transfer coefficient by 58 times in the air flow speed range of 4.6 to 15.2 m/s when compared to that of pure air alone. In addition, the structural integrity of the encapsulating shells was demonstrated to be excellent by the repeated use of the nanoparticles in closed loop testing.