•An ultra-thin vapor chamber is developed with a thickness of only 0.5 mm.•Three kinds of capillary wick structures were prepared and compared.•The composite wick has excellent anti-gravity ...performance.•The maximum critical power of novel UTVC can be up to 60 W.•The UTVC has great potential for heat dissipation in portable electronic devices.
With the development of integrated and ultra-thin portable electronics, the ultimate heat dissipation power in extremely narrow spaces (<1 mm) is increasing year by year. However, the current critical power of ultra-thin vapor chamber (UTVC) is still at a low level, which hinders the development of high-power portable electronic products. In this study, novel UTVCs with a thickness of only 0.5 mm are prepared by utilizing the composite capillary wick. Different from the traditional multi-layer 2D copper mesh wick, the composite (CA/CB) wick is composed of multi-layer 2D copper mesh and 3D spiral woven mesh. UTVCs prepared from three different wicks, referred as to 2D-UTVC, CA-UTVC, CB-UTVC, were compared. Under different working conditions, the CA/CB-UTVC has better heat transfer performance than 2D-UTVC. In the horizontal state, the maximum effective thermal conductivity (Keff) of CA-UTVC and CB-UTVC is significantly improved by 86.8% and 60.2% compared to that of reference 2D-UTVC. The CA design is recommended for low heating power within 40 W, while the CB design is the optimal choice for high heating power above 40 W. The maximum critical power of CB-UTVC is up to 60 W with gravity support. Even at 50 W under anti-gravity condition, the thermal conductivity of CB-UTVC is still up to 11817.1 W/(m K), which is 29.5 times that of copper. The improved heat dissipation is due to the enhanced capillary force of the composite wick. This positive effect is facilitated by the combination of multiple 3D spiral woven meshes in the CB design. The optimized UTVC effectively reduces the maximum temperature by 14.3 °C compared to copper sheet under natural convection at 10 W heating power. The novel UTVC could provide a guarantee for the heat dissipation of high-power integrated portable electronic devices in the future.
Directly integrating ceramic vapor chambers into the insulating substrate of semiconductor power devices is an effective approach to solve the problem of heat dissipation. Microgrooves that could be ...machined directly on the shell plate without contact thermal resistance and mechanical dislocation offer exciting opportunities to achieve high-performance ceramic vapor chambers. In this study, a bioinspired hierarchical microgroove wick (BHMW) containing low ribs via one-step nanosecond pulsed laser processing was developed, as inspired by the Sarracenia trichome. The superwicking behavior of microgrooves with different structural parameters was investigated using capillary rise tests and droplet-spreading experiments. The BHMW exhibited excellent capillary performance and anisotropic hemiwicking performance. At a laser scanning spacing of 30 μm, the BHMW achieved a capillary wicking height of 114 mm within 20 s. The optimized BHMW demonstrated a capillary parameter (ΔP c·K) and an anisotropic hemiwicking ratio of 4.46 × 10–7 N and 11.93, respectively, which were 1182 and 946% higher than references, as achieved through nanosecond pulsed laser texturing under identical parameters. This work not only develops a high-performance hierarchical alumina microgroove wick structure but also outlines design guidelines for high-performance ceramic vapor chambers for thermal management in semiconductor power devices.
With the rapid development of high-power electronic devices, phase change heat transfer has attracted much attention for efficient and lightweight thermal management. However, the mesh structure ...design for aluminum-based pool boiling enhancement still lacks experimental investigation and theoretical analysis. Herein, an aluminum gradient mesh wick is developed for efficient heat transfer performance. The optimized gradient mesh wick is comprised of a large-hole rhombus flat punching structure on the top and a small-hole 2D screen woven mesh on the bottom, providing sufficient active nucleation density sites, timely liquid supply, and rapid bubble departure. The gradient mesh design for pool boiling enables to achieve a high critical heat flux (CHF) of 1095.46 kW/m2 and a high heat transfer coefficient (HTC) of 46.20 kW/m2·K at a wall superheat of 23.70 °C, which is 167.06% and 240% that of Al plate, respectively. The visualization of bubble behaviors and theoretical analysis reveals that the CHF of the gradient mesh wick mainly depends on the bubble departure and liquid supply, and the bubble departure accounts for a greater proportion. Such aluminum gradient mesh wick provides a strategy for efficient thermal management of lightweight and high-power electronic devices.
•An aluminum gradient mesh wick for pool boiling enhancement is proposed.•A high CHF and HTC of 1095.46 kW/m2 and 46.20 kW/m2·K at a wall superheat of 23.70 °C are achieved.•The visualization of bubble behavior and theoretical analysis are proposed for the mechanistic explanation of pool boiling.
•Prediction model of surface roughness for Compacted Graphite Cast Iron is developed by Gaussian process regression (GPR).•The effect of training set size on prediction performance of GPR model has ...been evaluated.•Prediction performances of GPR model with and without k-fold cross-validation are evaluated.•The effect of machining parameters on surface roughness is analyzed from the covariance function of GPR.
This study employs Gaussian process regression (GPR) with square exponential covariance function to predict surface roughness of Compacted Graphite Cast Iron (CGI). In addition, a comparative study is conducted on prediction performances for GPR with and without cross-validation, back propagation neural network (BPNN) and support vector machine (SVM) for milling experiment of CGI. Experimental results indicate that prediction performances of GPR without cross-validation and GPR with cross-validation (GPRCV) are similar, and both superior to BPNN and SVM. The effect of machining parameters on surface roughness characterized via length-scale hyperparameters of covariance function is excavated according to prediction principle of GPR. The result shows that cutting speed and feed speed significantly affect surface roughness, depth of cut produces little impact on surface roughness within the given parameter intervals. The analysis of distance between test and training sets and 3D merged surface of surface roughness have verified that the effect is reasonable.
Ultra-thin vapor chambers (UTVCs) are playing an important role in the cooling of microelectronic devices. However, the small area and low ultimate power of current UTVCs limit the performance ...evolution of integrated microelectronics. In this study, a large-area ultra-thin vapor chamber (204 × 143 mm) with an ultra-thin thickness of only 0.5 mm, referred to as LUTVC, is developed. The welding is carried out using low-cost brazing technology. The composite capillary wick for the LUTVC is a combination of the superhydrophilic multi-layer copper mesh and multiple spiral woven braids after the oxidation chemical treatment. The effects of filling ratio (FR) and different working conditions on LUTVC performance were investigated in detail. It is found that the 20 % FR LUTVC has the best thermal performance at low power (≤50 W) with thermal resistance down to 0.12 °C/W, while the 30 % and 40 % FR LUTVCs have more advantages in heat dissipation at high power. The 30 % FR LUTVC combines the advantages of thermal conductivity and thermal power, with a high thermal conductivity of 13,237.2 W/(m·K) at 85 W and a maximum thermal power of 90 W. Thanks to its large heat dissipation area and ultra-high thermal conductivity, the novel LUTVC is an optimal element for power battery cooling. The LUTVC cooling solution reduces the average temperature, maximum temperature and temperature difference of the battery. The maximum temperature decreases by 2.1 °C and 6.7 °C compared to copper sheet at 1 C charging and 1.3 C charging, respectively, which improves the heat dissipation of new energy vehicle batteries.
•A large-area ultra-thin vapor chamber (204 × 143 × 0.5 mm) is developed.•Low-cost brazing is applied for LUTVC's fabrication.•The maximum effective thermal conductivity of LUTVC is 15,754.9 W/(m·K).•The critical thermal power of the LUTVC is up to 90 W.•The novel LUTVC is an optimal element for power battery cooling.
The existing gantry ship welding robot mechanism is mostly in series, which has the problems of large motion inertia at the end and joint error accumulation.A kind of ship welding robot with hybrid ...structure is designed. The platform control mechanism and rotary mechanism adopt the form of planar parallel mechanism, which can effectively increase the rigidity and error compensation ability of the actuator.And the adjusting mechanism of welding torch adopts series structure and keeps the flexible output ability.The kinematics model of the welding actuator is established by combining the closed-loop vector method, complex vector method and D-H four-parameter method.The positive solution of the mechanism is given, and the velocity and acceleration are analyzed based on it.Through simulation analysis, we get the workspace and kinematic characteristics curve of some components under given trajectories to verified the feasibility of the proposed mechanism.
In view of the problems existed of sugarcane harvester in China, the paper analyzes the types and characteristics of the existing sugarcane collection mechanism. A new type of three degree of freedom ...sugarcane harvester hybrid drive collection mechanism was designed in three dimensions. The geometric model of the new configuration related components and the overall assembly was established. And imported into the ADAMS simulation software. After the simulation, the working point and the force curve of the component node were output and analyzed. In order to obtain the motion law of the new three-degree-of-freedom stacking mechanism, verify the correctness of the theoretical model, and provide reference for the in-depth research and prototype trial production of the stacking mechanism in the future.
As highly integrated and miniaturized power components rapidly develop, the extreme heat accumulation of electronic devices easily occurs, leading to an urgent demand for better thermal performance ...of heat dissipation devices. Besides, an efficient heat dissipation method was still essential for the development of flexible power components. Herein, a novel ultra-thin vapor chamber (UTVC) based on graphite copperclad film with a thickness of only 0.68 mm was fabricated by a simple hot pressing process, and the composite wick structure was used as a capillarity-enhanced structure and a supporting structure for vapor flowing. The different filling liquid mass and test orientations of UTVC were both discussed. The surface temperature, temperature difference, thermal resistance, and thermal conductivity of UTVC were experimentally investigated, respectively. The UTVC could achieve a uniform surface temperature distribution (below 7.5 W), a low temperature difference (less than 2℃ at 6.5 W), a low thermal resistance (0.33℃/W at 6.5 W), and a high thermal conductivity (beyond 10000 W/(m·K)) under different orientations. Moreover, UTVC also showed wonderful flexibility, providing a potential application in the field of flexible folding. Further research will be carried out based on its flexibility.
The development of microelectronic devices is severely limited by the bottleneck of heat dissipation. To address this issue, nowadays, the ultra-thin vapor chamber (UTVC) shows great potential as a ...new type of element for efficient heat dissipation. However, the rapid backflow of working fluid has been a difficult problem in the ultra-thin capillary wick of UTVC. Herein, an ultra-thin vapor chamber (UTVC) as thin as 0.45 mm is proposed. The novel oriented spiral woven wick (SWW) is designed for this UTVC, which proves a near linear transport of working liquid to accelerate the liquid return for two-phase circulation. The SWW demonstrates excellent superhydrophilic property and has superior capillary performance. The thermal transfer characteristics of UTVC were investigated under three typical operating conditions, namely, horizon, gravity, and anti-gravity state. Based on the design of SWW, SWW-UTVC shows excellent anti-gravity performance. The lowest thermal resistance of SWW-UTVC is 0.77°C/W at 7 W under gravity state. The maximum equivalent thermal conductivity of SWW-UTVC is as high as 13553.3 W/(m*K) under gravity state, which is 33.9 times that of copper (about 400 W/(m*K)). This UTVC with the oriented spiral woven wick is an ideal element for the heat dissipation of microelectronic, especially in the extreme limited space less than 1 mm.
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