An investigation on optimal external cooling condition for an ultra-thin loop thermosyphon-based thermal management system

Highlights: • Conduct thermometric and infrared experiments on a coupled thermal management system. • Investigate the cooling conditions on the start-up characteristics of UTLT-based AATM. • Clarify the effect of vapor-liquid interface with the infrared thermal image. • Reveal the cooling conditions on the operating performance of UTLT-based AATM. • The optimal cooling condition is suggested for the air-cooling thermal management system. - Abstract: Thermal management system plays a critical role in dissipating heat and guaranteeing the safety of facilities. Among the various thermal management technologies, thermosyphon receives increased attentions owing to the fast developing demands in high-efficient cooling technology. In this paper, the heat transfer performance of an air-cooling assisted thermal management system (AATM) with ultra-thin loop thermosyphon (UTLT) is investigated with experimental method and theoretical analysis. Specifically, the effects of the assisted cooling conditions including the placement of the condenser and the consumed fan power on the start-up characteristics, operating temperature and thermal resistance of the ULLT-based system are respectively discussed. During the experiments, conventional point measurement and IR thermography are both adopted to detect the temperature variation and capture the vapor-liquid interface formed in the loop pipeline of the UTLT. By revealing the movement of vapor-liquid interface under various cooling conditions, it is verified that there always exists an optimal cooling condition for the UTLT-based AATM to start up most quickly and operates with the highest efficiency. Simply raising the cooling capacity leads to the liquid stagnation in the pipeline and triggers adverse temperature excursion. A proper regulation on the coupled cooling condition could significantly improve the operational safety and reliability of the UTLT-based AATM. In the present work, the operating temperature of the UTLT under the optimal cooling condition can be decreased by 5.2 K and the thermal resistance can be reduced by 24.2% to only 0.169 K/W. In addition, an effective model to predict the thermal performance of the UTLT-based AATM has been established with 93.6% of the experimental data in the ± 15% error band.