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• A 3D-OHP with ammonia and liquid metal was first developed for high-power and high-heat-flux dissipation. • Liquid metal can promote the unidirectional flow in the OHP. • Liquid metal improves the heat absorption and release rate of the working fluid. • The 3D-OHP can effectively handle heat dissipation of 1000 W with local heat flux of 111 W/cm2. With the rapid development of microelectronics technology, the power of some advanced electronic devices has reached 1000 W with heat flux of 100 W/cm2. The problem of high-power and high-heat-flux thermal management has become the bottleneck of the development of advanced electronic devices. In this paper, a three-dimensional oscillating heat pipe (3D-OHP) with 18 channels was developed for this problem. A new hybrid fluid of ammonia and liquid metal was used as a working fluid. The wall temperature and heat transfer performance of the 3D-OHP charged with the hybrid fluid were investigated experimentally. The results indicate that the 3D-OHP can effectively solve the problem of heat dissipation with the heating power of 1000 W and the heat flux of 111.1 W/cm2. Liquid metal can ensure the efficient operation of ammonia OHP under supercritical pipe diameter, and promote the working fluid to form a unidirectional flow. Liquid metal has a great ability to absorb and release heat which significantly enhances the heat transfer performance of the 3D-OHP. When the heat flux reached 111 W/cm2, the 3D-OHP with 2.11% liquid metal had the best heat transfer performance, and the thermal resistance was 0.0351 °C/W. Compared with pure ammonia 3D-OHP, it could reduce the temperature difference of the 3D-OHP by 9.1 °C and enhance the heat transfer performance by 20.57%. The capacity of the ammonia-liquid metal 3D-OHP to deal with high-power and high-heat-flux is higher than the existing studies. [ABSTRACT FROM AUTHOR]

• Gallium-based liquid metal-copper foam TIM is prepared by galvanic corrosion. • The thermal conductivity of the TIM is 51.58±0.01 W/(m·K). • Under the pressure of 0.35 MPa, the TIM does not overflow. • With the increase in wettability, the thermal contact resistance decreased by 58.28%. As a promising thermal interface material (TIM), gallium-based liquid metal (GBLM) could significantly reduce the thermal contact resistance (TCR) at the solid-solid interfaces, while the leakage of GBLM and the wettability between liquid metal and solid surface restrict further application. In this study, the GBLM was wrapped with a copper foam (CF) skeleton, which prevents leakage and improves the thermal conductivity of the GBLM. Gallium-based liquid metal-copper foam (GBLM-CF) TIM was prepared by the self-wetting of the CF surface through the galvanic corrosion of GBLM. As the concentration of HCl increases from 0 to 5 M, the interfacial tension (IFT) in the HCl solution decreases from 536.80±1.00 mN/m to 481.52±0.49 mN/m, demonstrating that the IFT of the GBLM is inversely proportional to the concentration of HCl. Meanwhile, the decrease of contact angle (CA) by 8° indicates that the presence of CuGa 2 on the surface promotes the wettability of GBLM. With the increase of external pressure and the improvement of wettability, the TCR between the GBLM and the copper sheet decreased by 58.28%. The TCR of the sample using GBLM-CF as TIM is 83% lower than that of thermal grease. Moreover, the thermal conductivity of GBLM-CF TIM (51.58±0.01 W/(m·K)) is 212.6% higher than that of GBLM (16.50±0.02 W/(mK)). The GBLM-CF TIM presented in this study can be used for the efficient thermal management of electronic equipment. [ABSTRACT FROM AUTHOR]

• A guideline to optimize the structure of 3DCOHP was proposed, which can enhance the heat transfer performance significantly. • Reducing the top bend curvature radius of 3DCOHP with asymmetric heating mode can promote the formation of unidirectional flow without check valve. • The existence of unequal flow pressure drop between the push-up and push-down causes the formation of unidirectional flow in 3DCOHP. The effects of the bend curvature radius and tube diameter on the heat transfer performance of the three-dimensional coil oscillating heat pipe (3DCOHP) were experimentally studied in asymmetric heating mode. Three types of copper 3DCOHPs using water as the working fluid were studied in vertical orientation. And the filling ratio of each 3DCOHP was set to 50%. It was found that reducing the top bend curvature radius and increasing the tube diameter can both strengthen the formation of unidirectional flow and significantly improve the heat transfer performance of the 3DCOHP. The heat transfer performance of the OHP with a tube diameter of 1.90 mm increased by up to 34.6% when the heating power was set to 40 W. At the same time, the reason of the unidirectional flow in asymmetric heating mode was theoretically analyzed. It was shown that the calculated pressure drops in liquid slug flowing from the evaporation section to both sides powered by vapor expansion are different, which develops the unidirectional flow. These findings provide a guideline to optimize the structure of OHP to enhance its heat transfer capacity. [ABSTRACT FROM AUTHOR]

• A liquid metal high temperature OHP (LMHOHP) was first developed. • The LMHOHP that can function at a temperature of over 500 °C. • The LMHOHP can transport heat of 3169 W and achieve a thermal resistance of 0.08 °C/W. This paper introduces the development of a liquid metal high-temperature oscillating heat pipe (LMHOHP) that can function under high-temperature conditions (over 500 °C). The LMHOHP has six turns with a total height of 310 mm. The sodium-potassium alloy (potassium 78%) was used as the working fluid, and the 310S stainless steel tube with an inner diameter of 6 mm as the shell tube. The LMHOHP heat transfer performance was investigated experimentally with a filling ratio of 45% at different input powers. Experimental results show that the LMHOHP can effectively generate steady-state oscillating motions at a working temperature of over 500 °C. When the steady-state oscillating motions exist, the temperature difference and thermal resistance between the evaporator and condenser were reduced significantly. At a heat input of 3169 W, the LMHOHP presents a minimum thermal resistance of 0.08 °C/W. This LMHOHP provides a new approach to next-generation high-temperature cooling devices. [ABSTRACT FROM AUTHOR]