Numerical simulation and optimization of a high-performance serpentine tube phase change cold storage unit based on high thermal conductivity ice/expanded graphite

Abstract

To build a high-performance cold storage device integrated into refrigeration, air conditioning, and large energy storage systems, this study presents a high-performance phase change cold storage material based on a combination of expanded graphite (EG) and water and designs a corresponding serpentine tube cold storage unit. By incorporating EG into water, the thermal conductivity of the composite material is significantly enhanced, increasing by more than tenfold, while the phase change enthalpy remains almost unaffected. Utilizing this composite material, a serpentine tube cold storage unit was constructed, and the structural parameters were optimized using numerical simulation methods. The cold storage density exceeds 100 kWh/m³, with a maximum power density exceeding 200 kW/m³, and efficient cold energy release was achieved with an inlet and outlet pressure drop of <30 kPa. Numerical simulation results indicate that different structural parameters have a significant impact on the cold energy release performance of the storage unit. By studying the effects of flow rate, composite material ratio, tube diameter, tube spacing, and flow path length on cold energy release performance, a rapid design method for the structural parameters of serpentine tube structures was summarized. This provides important reference and guidance for the design of high-performance cold storage units in various application scenarios.