Innovative integration of mechanical refrigeration and loop thermosyphon with liquid reservoir control: enhancing energy efficiency and dynamic stability in data center cooling systems.

The rapid expansion of data centers driven by emerging technologies demands cooling solutions that are both energy-efficient and operationally reliable. This study proposes a novel integrated mechanical refrigeration and loop thermosyphon system (IMLS) incorporating a liquid reservoir with coordinated valve control to adaptively manage refrigerant charge differences between thermosyphon and vapor compression modes. By actively balancing refrigerant distribution during mode transitions, the system addresses a key stability challenge in hybrid cooling, ensuring consistent capacity and safe operation. Experiments under representative conditions identified optimal charges of approximately 2.5 kg for thermosyphon mode and 2.0 kg for refrigeration mode, with peak cooling capacities of 8.4 kW and 8.7 kW, respectively. The reservoir-valve control enabled smooth transitions without overcharge or shortage, achieving stable operation within 165–180 s and preventing issues such as liquid slugging. Pressure-enthalpy analysis highlights the distinct thermodynamic and hydraulic characteristics of the two modes, underlining the importance of adaptive refrigerant management. The results demonstrate an effective pathway to improve dynamic stability and energy efficiency in hybrid cooling systems, offering practical guidance for the design of advanced solutions in data center applications.