Numerical study on cooling performance and structural optimization of a phase change cold storage assisted air conditioning system for data centers

The introduction of phase change cold storage technology offers a novel approach to enhancing the energy efficiency of air conditioning systems for data centers. However, the phase change cold storage assisted air conditioning system needs further energy savings, the structural and parametric optimization of phase change plates (PCP) remains inadequate. This study numerically compared the cooling performance and ventilation resistance of porous PCP, rectangular PCP (RPCP), and trapezoidal PCP. The best-performing RPCP was then selected for a sensitivity analysis, considering the number of segments, number ratio, thickness ratio, wind speed, phase change latent heat, and phase change temperature. Furthermore, the daily energy savings of the traditional (TRS) and optimized (ORS) RPCP systems were compared. Finally, based on the ORS scheme, the influence of the second-segment PCP (PCP2) quantity on the comprehensive performance was further studied to optimize the space utilization of air conditioning units. The results indicate that: (i) With equal PCP volume, the RPCP system achieves the optimal comprehensive performance. (ii) The system achieves optimal cooling and energy-saving performance under three conditions: 4 segments, a number ratio of 14:6, and a thickness ratio of 0.045:0.015, yielding 4-h energy savings of 28 × 10³ kJ, 31.8 × 10³ kJ, and 28.9 × 10³ kJ, respectively. (iii) Compared to the TRS, the ORS improves transient cooling capacity by 36% and achieves an energy saving rate of 22%. (iv) When the number of PCP2 is 12, the system's space utilization and the comprehensive performance are the best.