Experimental and numerical study on flow characteristic and thermal performance of macro-capsules phase change material with biomimetic oval structure

The emergence of bionics provides new ideas for the innovation of engineering technology, which has been widely used in energy storage, heat transfer enhancement, and solar thermochemical reactions. To improve the flow characteristic and thermal performance of phase change material (PCM) capsules, the idea of heat storage unit with biomimetic oval structure is proposed. An experimental system is developed, and PCM capsules with different structures (bionic-oval, sphere, and ellipse) are prepared by 3D printing. The experimental and numerical analyses show that the unconstrained melting time of oval-shaped capsule is 12% shorter than that of sphere capsule, and the average Nusselt number of oval-shaped capsule is 20% higher than that of sphere capsule. The optimization results show that the oval-shaped capsule can provide a lower resistance coefficient when the long-short ratio and long-symmetry ratio are 1.25 and 1.67, respectively. The research results can provide guidance and new ideas for the application of bionics in the field of energy storage.