Single-phase immersion cooling is generally employed as a thermal management technique in which IT equipment is directly submerged in electrically insulating dielectric fluid to dissipate heat. In this study, by positioning the evaporator section of a heat pipe heat exchanger within a single-phase immersion bath, the thermal energy extracted from the immersion-cooled system is passively transferred to the condenser section of the heat pipe. As a result, unlike conventional single-phase immersion cooling systems, the proposed configuration eliminates the need for external chillers and circulation pumps, thereby significantly reducing the operational energy consumption associated with single-phase immersion cooling. In this manner, the requirement for coolant circulation is removed, and chiller-free operation becomes feasible, allowing the system to establish itself as a highly efficient thermal management solution. Our laboratory is continuously conducting research to compare the thermal performance of conventional single-phase immersion cooling systems with that of single-phase immersion cooling integrated with heat pipe heat exchangers, with the ultimate goal of reducing the Power Usage Effectiveness (PUE) of data centers.

For research on two-phase immersion cooling, a non-conductive experimental chamber has been constructed to evaluate boiling heat transfer performance in dielectric fluids. Studies are being conducted on enhancing the convective heat transfer coefficient and the critical heat flux by applying microporous surfaces. In addition, the mutual thermal interactions among individual heat sources in two-phase immersion cooling systems are analyzed to develop more practical and applicable cooling strategies for real-world data center environments.

As the performance of AI and high-performance computing (HPC) hardware continues to increase, energy consumption in data centers is rising rapidly, accompanied by a significant increase in heat generation from server processing units. To address these challenges simultaneously, direct-to-chip (DTC) cooling approaches are being investigated, as they offer high cooling performance capable of substantially mitigating both energy consumption and thermal issues. The in-house developed two-phase flow testbed is equipped with precise flow-rate control and advanced instrumentation, enabling accurate evaluation of cooling performance under conditions closely representative of real operating environments. The Hybrid Boiling Cold Plate (HBCP) under development employs a two-phase cooling strategy that integrates pool boiling and flow boiling, making it well suited for cooling high-heat-flux chipsets while consuming exceptionally low pumping power. Ongoing research focuses on optimizing the design parameters of the HBCP to delay dryout onset and further enhance the thermal performance of the cold plate.