The formation process of self-coordinated microchannels with heat transfer enhancement advantage during phase change cold energy storage

Foam freezing is an ice storage method that increases the contact area between the heat transfer fluid and the phase change material by forming many cold bubbles to increase the charging rate. Microchannels exist in the ice to disperse the cold airflow and form these bubbles. This paper established a solid–liquid phase change numerical model based on the coupling relationship between bubbles and microchannels at the three-phase moving heat transfer boundary. The evolution process from volcano-like ice beards to frozen bodies under the action of microchannels was simulated, and the growth mechanism of microchannels was investigated. The error rate of the model was experimentally verified to be 10.4 %. The results showed that the potential maximum height of isolated ice beards was 3.4–3.5 mm when the inlet temperature of airflow was −20 °C. The growth height of ice beards increased by decreasing the temperature to −30 °C, but it also stagnated at 5.2 mm. Only when the ice beards merged at the bottom did their internal microchannels continue to grow. This maximum height of isolated ice beards caused the microchannels to show self-coordination. It explains the evolutionary mechanism from the isolated ice beards to the frozen body. This limitation on the axial growth of microchannels comes from the critical growth temperature under the coupling of bubble buoyancy and ice adhesion. This study provides a reference for optimizing the charging rate of foam freezing by controlling the temperature, microchannel diameter, and airflow rate.