Thermo-Hydraulic Performance of Evaporator in a Hybrid Two-Phase Loop

The widespread adoption of emerging technologies such as artificial intelligence (AI), big data, and the Internet of Things (IoT) has imposed significant challenges in managing thermal loads within modern data centers. Advanced cooling strategies, particularly those involving two-phase technologies, are crucial for maintaining the operational efficiency and longevity of data centers, enabling the management of rising heat flux while adhering to strict temperature limits. Achieving minimal thermal resistance and sustained thin-film evaporation is desirable for developing highly efficient and cost-effective cooling systems for data centers. In this regard an experimental investigation was conducted on a hybrid two-phase loop (HTPL), which integrates active mechanical pumping with passive capillary pumping. Deionized water was used as the working fluid in this study. Key parameters, including evaporator heat input, pump flow rate, condenser coolant temperature, the amount of non-condensable gas (NCG) in the system, and fluid charge ratio, were evaluated for their impact on evaporator thermal performance and thermal resistance. The results indicate that thermal resistance decreases with increasing evaporator heat flux at a constant flow rate. A reduced coolant flow rate also lowers thermal resistance due to mild flooding; however, this increases the risk of premature dry-out. Higher condenser coolant temperatures promote nucleate boiling, further reducing thermal resistance. While an increase in NCG and fluid charge ratio has minimal impact on evaporator thermal resistance, it significantly raises the overall system temperature and pressure within the HTPL. The overall finding of this research will contribute to achieving an optimal operational parameter, which can lead to energy efficient and reliable cooling solutions for future high performance computing systems