Major scientific creativities can be concluded as follows:
1. Study on low-melting temperature alloy (LMTA), thermal contact resistance and long-term stability during thermal cycle.
We investigated the LMTA for reducing the thermal contact resistance. The thermal behavior of several indium-based LMTA have been studied and compared. We also proposed a novel seal concept, which is able to definitely prevent LMTA leakage issue without performance decay. The aforementioned content has been published in Appl. Therm. Eng. and J. Electron Packaging ASME. Meanwhile, a novel LMTA is proposed to decrease the thermal contact resistance to 0.017 K/W at the power of 250 W/m for optical fibers, showing the lowest thermal contact resistance in existed publications. The reliability is verified under hundred thermal cycles. The result indicates great innovation in practical application.
2. Study on thermal management in data centers, artificial intelligence (AI) control for energy-saving, novel heat sink and junction temperature prediction.
The multi-scale model for thermal management containing CPU, server and data center has been developed. The localized thermal uniformity and corresponding evaluation criteria have been proposed. Meanwhile, studies on simulated data center experiment, real data center test and computational fluid dynamics (CFD) calculation were adopted to solve the heat dissipation of servers under compact and high heat flux environment. The machine learning and AI are applied to achieve a comprehensive control, indicating a pronounced energy-saving for various operating conditions. A total of 6 journal papers has been published in Appl. Energ., J. Electron Packaging ASME and T. Comp. Pack. Man. IEEE. Meanwhile, we proposed a novel two-layer and separated heat sink based on multi-objective optimization. Results showed that the junction temperature can be effectively reduced. The above conclusion has been applied for 2 invention patents. The mathematic model for predicting junction temperature is proposed, and the fundamental analysis has been submitted to Int. J. Heat Mass Trans. which is in under-review process.
3. Study on thermohydraulic performance of SCO2 near pseudo-critical point, performance evaluation criteria for printed circuit heat exchanger (PCHE), optimization of inlet headers.
Based on the dramatic variation of thermal properties of SCO2 near the pseudo-critical point, we proposed the design criteria for PCHE condenser, which aims to reduce the pressure drop of SCO2 for higher priority. The experimental and numerical results consistently showed that the major thermal resistance is on the SCO2 side in a PCHE condenser. Meanwhile, the diffusion bonding technology has been investigated for reliability verification, containing tensile stress test and metallographic examination. Secondly, the empirical correlations of PCHE condensers under different SCO2 operating pressures have been proposed. The buoyancy force caused by the density difference was considered, which can provide a more accurate prediction for the fluid with strong thermal property variation. Thirdly, based on the continuous flow concept, a novel helix inlet header has been proposed, which can efficiently improve flow uniformity for multi-layer heat exchangers. Based on the definition of shape factor, the mathematical model for quantitatively calculating the uniformity and its influence on thermal performance decay has been proposed.
4. Study on two-phase condensation in micro-channel heat sink, novel thermal fin integrating with thermosyphon cycle.
The liquid film may degrade the condensation performance and efficiency of heat sinks. A novel micro-channel heat sink with trapezoid drainage has been proposed, which can definitely remove the film by the capillary effect in typical cases. The effective heat transfer coefficient would be improved and the pressure drop is reduced simultaneously. The comprehensive performance under different mass flowrates, vapor mass fractions and orientation angles has been experimentally investigated. The combined effect of gravity, buoyance force and at the interface is also theoretically analyzed. The above content has been published in the Exp. Therm. Fluid Sci.. Meanwhile, for heat sources with vertical arrangement, the upper heat source suffers at more serious environment. we proposed a thermal fin coupling with a thermosyphon system, which can improve the fin efficiency to almost 1.0. The porous media is also implemented to entrain fluid to upper region, thereby the dry-out issue will be solved. The above content has been summarized into 2 manuscripts and submitted to Int. Commun. Heat Mass and Appl. Therm. Eng..