Performance enhancement of ice storage capsules by biomimetic fins

Ice storage enhanced by biomimetic fins in spherical capsules is studied numerically based on enthalpy-porosity method. The evolution of water/ice interface, the temperature variation, and the cooling energy storage capacities are examined quantitatively to gain further insight into the solidification process in capsules. Especially, the geometrical configurations of fins, including the maximum bifurcate level and fractal dimension of length, are investigated. In addition, four evaluation criteria are employed to determine the optimum design for the biomimetic fins. The results show that the biomimetic fins are significantly effective in enhancing the heat transfer in the stage of cooling energy storage through sensible heat in ice. The performance enhancement is facilitated as the level of fins is increased that average 24% reduction in solidification time is achieved by the finIII series with only 1.24% loss of cooling energy storage capacity averagely. An optimum design for biomimetic fins is the fin-III with a fractal dimension of 3, which results in a 30.01% increase in dimensionless cooling energy storage capacity per unit time and weight compared to the case without a fin. Aluminum is a favorable fin material considering both the enhancing performance and material cost of the capsule. A prediction formula of ice volume under different cooling conditions is generalized.