Vapor Chamber Research Articles

Effect of Energy-driven Molecular Precursor Decomposition on the Crystal Orientation of Antimony Selenide Film and Solar Cell Efficiency.

Antimony selenide (Sb2Se3) consists of 1D (Sb4Se6)n ribbons, along which the carriers exhibit high transport efficiency. By adjusting the deposition parameters of vacuum-deposited methods, such as evaporation temperature, chamber pressure, and vapor concentration, it is possible to grow the (Sb4Se6)n ribbons vertically or highly inclined towards the substrate, resulting in films with [hk1] orientation. However, the specific mechanisms by which these deposition parameters affect the orientation of thin films require a deeper understanding. Herein, a molecular beam epitaxy technique is developed for the preparation of highly [hk1]-oriented Sb2Se3 films, and the effect of evaporation parameters on the film orientation is investigated. It is found that the evaporation temperature can affect the decomposition degree of Sb2Se3, which in turn determines the vapor composition and film orientation. Additionally, the decomposition of Sb2Se3 related to evaporation temperature leads to significant changes in the elemental composition of the film, thereby passivating deep-level defects under Se-rich conditions. Consequently, the Sb2Se3 films with highly [hk1] orientation achieve a power conversion efficiency of 8.42% for the solar cells. This study provides new insights into the control of orientation in antimony-based chalcogenide films and points out new directions for improving the photovoltaic performance of solar cells.

Experimental Research on an Embedded Heat Source Vapor Chamber for Aerospace Electronic Cooling

Abstract In this work, an embedded heat source vapor chamber (EHS-VC) is proposed for efficient and cost-effective heat dissipation in a limited space of aerospace electronics. The effect of the filling liquid mass and the layers of copper mesh under different working conditions on the heat transfer performance is systematically investigated. EHS-VCs are filled by deionized water with different filling liquid mass of 0.5 g, 0.75 g, 1.0 g, 1.25 g, and 1.5 g. The layer numbers of 250 in−1 copper mesh in EHS-VC are 3, 5, and 7. The results indicate that the optimized EHS-VC with a filling liquid mass of 1.0 g and 5 layers of copper mesh shows superior thermal performance among all tested working conditions. The surface temperature distribution of the optimized EHS-VC remains relatively stable and the surface temperature of the optimized EHS-VC increases linearly with heat load. The optimized EHS-VC can achieve a minimum thermal resistance of 0.19 ℃/W and a maximum critical power of 140 W. Compared with diamond/copper composite plate (D/C CP), EHS-VC shows great potential for efficient and cost-effective heat dissipation in a limited space of aerospace electronics, resulting in a 25% reduction in thermal resistance at the same heat load of 140 W.

Thermal resistance optimization of ultra-thin vapor chamber based on data-driven model and metaheuristic algorithm

The ultra-thin vapor chamber(UTVC) is extensively utilized across various fields due to its excellent heat dissipation performance and good temperature uniformity. The data-driven modeling approach is well suited to predict the thermal resistance of the UTVC due to its great flexibility and accuracy. In this paper, a novel approach is proposed to optimize the UTVC thermal resistance, which combines the radial basis function neural network(RBFNN) model with an improved adaptive differential fish swarm evolution algorithm(ADFEA). The mean square error of the RBFNN model was 0.00016 on the training set and 0.00027 on the test sets, which indicates that the model is able to accurately predict the thermal resistance of the UTVC. The data are obtained from experiments on a mesh wick UTVC with dimensions of 124 × 14 × 1 mm. A novel optimization algorithm, ADFEA, has been designed to enhance optimization capability and convergence accuracy. This algorithm combines differential algorithm and artificial fish swarm algorithm, incorporating a parameter adaptation mechanism. The optimal operating parameters of the UTVC are obtained by ADFEA optimization and the accuracy of the optimized results is verified by experiment. The proposed optimization method provides new insights for the design and optimization of UTVC.

Influence of vapor core design on thermal and hydraulic performance of mesh-type ultra-thin vapor chamber

The mesh-type ultra-thin vapor chamber(UTVC), with an internal mesh porous structure, is a cost-effective and efficient heat transfer element for compact spaces. The design of the vapor core plays an important part in enhancing the heat transfer performance of the mesh-type UTVC within the confined space requirements. The present study proposes to design cavities in the supporting coarse mesh inside the vapor core to form a multi-scale combination of vapor channels with the mesh channels. Utilizing a numerical model that considers microporous evaporation as well as the Marangoni effect, the effects of different flow channel designs and designed channel widths on the performance of the UTVC were analyzed. The study determined the flow and heat transfer characteristics of the working medium within the mesh-type UTVC, and found that the most significant performance enhancement was achieved when the designed flow channel passed through part of the UTVC evaporation and condensation sections, reducing the thermal resistance by 17.45%. Whereas the design flow channel width has less influence on the performance of mesh-type UTVC, it satisfies the changing trend of vapor flow pressure drop and thermal resistance decreasing firstly and subsequently increasing with the expansion of the designed channel width.

Experimental study on ultra-thin silicon-based VC for chip-level heat dissipation

The trend towards miniaturization and integration of integrated circuits has led to the emergence of local hotspots with high heat flux and high temperature frequently. Integrating vapor chamber (VC) directly on the surface of semiconductor electronic devices, can effectively address the problem of overheating on the chip surface, and is therefore considered as a promising thermal management solution. However, the challenge of reducing the size of the VC while improving its heat transfer performance cannot be ignored. To address this, a silicon-based VC with thickness of 0.6 mm is designed and fabricated in this study. Structural optimization is carried out, including the design of three types of wicks using square micropillar arrays and two types of support columns including solid and porous and an experimental system is built to study the influence of these structures on the heat transfer performance of VC. The results indicate that the VC can still function normally under the highest heat flux of 123.6 W/cm2, resulting in lowest thermal resistance of 1.54 °C/W. For wicks, the thermal resistance of VC with characteristic size of 10 μm is reduced compared with that of 20 μm. The introduction of gradient wick, that is, using small-size (10 μm) micropillar arrays in heating area and big-size (20 μm) micropillar arrays in non-heating area, can effectively reduce the thermal resistance of VC. Moreover, the solid support columns are found being advantageous in reducing the thermal resistance of VC, while porous support columns improve the surface temperature uniformity of VC. This work provides a feasible path to optimize silicon-based VC.

Experimental investigation on battery thermal management with ultra-thin vapor chamber

In electric vehicles, the chemical reactions occurring within the battery necessitate an efficient thermal management system to keep the battery within its optimal temperature range. Therefore, the development of a compact and effective thermal management system is essential. In this paper, a novel battery thermal management system based on ultra-thin vapor chambers with a thickness of 1 mm is proposed. To analyze the key parameters that affect the thermal performance of the battery thermal management system, an experimental system was established to investigate coolant flow rate, inlet coolant temperature, filling rate, and gravity conditions. Orthogonal design and fuzzy grey relational analysis were employed as evaluation methods. Orthogonal experiments can obtain a balanced sample of high precision with fewer trial runs, while fuzzy grey relational analysis is based on the measurement of similarity or dissimilarity between data sequences to explore the relationships among key system factors. The results show that the implemented battery management system achieves a reduction in maximum temperature by 23.2 %, 24.4 %, and 25.5 % under discharge rates of 1C, 1.5C, and 2C, respectively, while maintaining a temperature difference of less than 2 ℃. Even under conditions of high inlet coolant temperature of 30 ℃ and a discharge rate of 2C, the temperature difference remained below 2.28 ℃. Subsequently, the optimal filling rate is 120 %, and the maximum temperature of the battery pack is minimized with a temperature difference of less than 3 °C at this filling rate. Furthermore, considering the sensitivity evaluation, the discharge rate exhibited the most significant impact on both the maximum temperature and temperature difference, followed by the inlet coolant temperature and filling rate.

Enhanced Heat Spreading Performance of Printed Circuit Boards by Vapor Chamber Implementation

Enhanced Heat Spreading Performance of Printed Circuit Boards by Vapor Chamber Implementation

Study on the thermal performance of pulmonary vascular-inspired grooved vapor chamber

The increasing miniaturization and integration of electronic devices have led to higher requirements for heat dissipation. To further enhance the heat transfer performance of the vapor chamber, this study proposes a novel vapor chamber with a pulmonary vascular-inspired grooved wick. Through a combined approach of numerical simulation and experimental research, the thermal performance of the proposed vapor chamber is tested and compared with the radially grooved vapor chamber(RGVC) of the same size and copper plate. The results demonstrate that within the heating power range of 0 W-30 W, the pulmonary vascular-inspired grooved vapor chamber(PGVC) exhibits superior temperature uniformity and heat transport capability. Under a heat load of 25 W, its thermal resistance is reduced by 52.73 % and 21.21 % compared to the copper plate and RGVC, respectively, while the heat transfer coefficient is increased by 107.61 % and 25.86 %, respectively. Furthermore, the PGVC achieves optimum performance at a liquid filling ratio of 75 %, with a remarkably low thermal resistance of 0.23℃/W at a heat load of 30 W.

Bio‐inspired Thermal Diode with Anti‐Gravity Unidirectional Heat Transfer and Switchable Functionality for Intelligent Thermal Management

AbstractPhase‐change thermal diodes with asymmetric and adjustable heat transfer capacity exhibit great application prospects in spacecraft heat management and solar energy storage. Current heat modulation strategies mainly depend on the anisotropic assistance from gravity and the rectification ratio can hardly be adjusted due to the immobilized inner structures. Here, a novel bioinspired thermal diode vapor chamber has been carried out with magnetic microgroove cones array sealed between two copper plates, where the evaporating plate with porous copper foam can reserve water and the condensing plate with patterned wettability can coagulate vapor into droplets at designated spot. With microgroove cones rooting from the evaporating plate and their tips contacting the condensing plate, these cones can directionally and rapidly transport condensed liquid from the condensing plate to evaporating plate under the unbalanced strong capillarity while prohibiting water flowing backward. This eventually leads to unidirectional liquid‐vapor circulation and anti‐gravitational directional heat transferring with a rectification ratio as high as 7.4. Such flowing of liquid can also be regulated by magnetically controlling the bending of cones to realize switched ON–OFF of thermal diode and achieve further modulation of heat management. This bioinspired thermal diode vapor chamber provides new ideas for intelligent thermal management systems.

Heat Transfer Performance of Copper Foam-Based Vapor Chamber Composite Liquid Cooling System Under Double-Sided Heating

Heat Transfer Performance of Copper Foam-Based Vapor Chamber Composite Liquid Cooling System Under Double-Sided Heating

Vapor flow resistance characteristics in ultra-thin flat heat pipes

Miniaturization of electronic devices drives the development of ultra-thin flat heat pipes (UTFHPs). As the thickness of the heat pipe decreases, the microchannel effect of the vapor chamber exacerbates the deterioration of the vapor flow. The vapor flow resistance, which is often neglected in the conventional theory due to its extremely small effect compared to the liquid flow resistance, becomes a critical factor limiting the heat transfer performance of UTFHPs. To provide a theoretical basis for the design and performance evaluation of UTFHPs, this paper investigated the effect of the wicking structure and working fluid on the vapor flow resistance of UTFHPs based on theoretical derivations, numerical calculations, and experiments. The results indicate that conventional analytical theory is no longer applicable when the total thickness of the heat pipe is less than 1 mm. The vapor flow resistance obtained using the conventional equation is significantly smaller than the experimental results, which is caused by several factors: raised momentum loss at the wall and gas-liquid interface due to the growth of the velocity gradient in the boundary layer; exacerbated flow instability due to the mixing between the vapor and the working fluid; enhanced fluctuating effects on the flow channel due to the presence of the wicking structure. A dimensionless flow resistance coefficient equation was proposed with the vapor Reynolds number and the channel height ratio. An experiment was conducted to verify the accuracy of the flow resistance correlation. The difference between the experimental results and the calculated values is less than 15 %.

Experimental investigation of post and vented vapor chamber designs for high heat flux dissipation

To enhance the dryout heat flux of vapor chambers over a 1 cm × 1 cm area, this study describes the testing of four different vapor chamber design architectures (each having an overall size of 50 mm × 50 mm × 5.5 mm). The designs leverage a combination of internal liquid feeding posts and evaporator vapor venting features to improve the capillary-fed boiling performance. The study provides systematic insight into increasing the dryout limit of a vapor chamber and lowering the thermal resistance by assessing the effect of each geometric feature independently. A jet impingement air cooling test facility is used to measure the total thermal resistance of the package in a representative application, while a liquid cooling test facility is used to measure the thermal resistance of the vapor chamber itself. The results show that a vapor chamber with a combination of machined posts coated with sintered wick and vapor vent features has superior performance over vapor chambers with independent features. It dissipated the highest heat flux of 589 W/cm2 and provided the lowest total package thermal resistance of 0.28 K/W for a 1 cm2 heat input area. The performance improvements are attributed to an improved liquid supply utilizing the porous-wick-coated machined posts and a reduction vapor egress pressure utilizing the vent features above the heater area.

A dual-height wick to improve capillary performance of vapor chambers

The wick performance is a crucial metric for ensuring the reliable and efficient operation of vapor chambers (VCs) away from dry-out. To enhance the performance of VC, a pitcher plant inspired enhanced wick characteristic dual-height microgrooves (DHMW) was fabricated on 6063 aluminum alloy by one-step picosecond laser texturing without chemical modification. This study describes the two-step capillary behavior of DHMW by high-speed camera and infrared camera. The effects of minor rib number, groove height ratio, length scale, and test liquids (water, acetone, ethanol) on the capillary performance were investigated. When using water as the working fluid, the DHMW achieved a K/Reff of 1.182 µm, which was about 71.3 % larger than that of normal microgroove wicks due to the liquid propagation effect and the flow resistance reduction effect. Furthermore, the maximum K/Reff could reach 1.819 µm of the sample with a minor rib depth of about 70 μm. However, the wetting results showed that the droplets of acetone and ethanol tend to spread laterally after contact with the surface, which is unfavorable for the formation of hierarchical transport in the DHMW. This study demonstrates that laser texturing is an effective and controllable method for the complex shaping of grooved aluminum wicks, with the potential to improve the heat transport capability of VCs.

Thermal performance of ultra-thin vapor chamber with etched micro-structure for electronics cooling

As a two-phase heat transfer element, vapor chambers (VCs) have received widespread attention in recent years due to the advantages of high-effective thermal conductivity, lightweight, and flexibility in design and application. With the development of microelectronic products towards higher levels of integration and compactness, there is also a growing demand for thinner VCs. In this paper, the heat transfer performance of novel ultra-thin vapor chambers (UTVCs) with a thickness of only 0.3 mm was designed and tested. The composite wick is made of an etched micro-structure and 300 in−1 copper mesh. The heat transfer performance of UTVCs such as the temperature distribution, the temperature difference and the thermal resistance was investigated under different heating power by evaluating the effect of etched micro-structures, liquid charging ratio and test direction. The results of the experiment showed that the optimal liquid charging ratio for continuous micro-structure and non-continuous micro-structure is 60 % and 80 %, respectively, and the minimum temperature difference is 1.3 °C and 3.5 °C for the heating power of 5.5 W, respectively. In addition, the continuous micro-structure UTVC with a liquid charging ratio of 60 % has better heat transfer performance and the maximum temperature difference is less than 5 °C in all test directions of horizontal direction, gravity direction and anti-gravity direction.

Ultra-thin vapour chamber based heat dissipation technology for lithium-ion battery

A powerful thermal management scheme is the key to realizing the extremely fast charging of battery electric vehicles. In this scheme, a water-cooled plate is set at the bottom of the battery modules, which has a remarkable heat dissipation ability but increases the temperature difference between the top and bottom of the battery. This temperature difference problem is more obvious during the high-rate charge/discharge process; in particular, in the area of battery tabs, which are usually located far from the cooling plate, heat accumulates, risking thermal runaway. To address this problem, a thermal management method based on an ultrathin vapour chamber (UTVC) is proposed in this paper to improve temperature uniformity and reduce the highest temperature of batteries. According to the number of applied UTVCs, a unilateral UTVC (U-UTVC) and a bilateral UTVC (B-UTVC) cooling approach were presented, the effectiveness of which was verified by a set of thermal performance experiments. The test data show that the temperature differences in the batteries under the U-UTVC and B-UTVC schemes are 39.77% and 73.54% lower than those under the traditional method at a 25 °C ambient temperature and a 1.39C charge rate, respectively. The temperature difference on the battery surface with the B-UTVC scheme is approximately 3 °C at 25 °C and 40 °C ambient temperature.

High performance and reliable ultra-thin vapor chamber via an optimised second vacuuming and sealing process

Ultra-thin vapor chambers (UTVCs) have been widely used for cooling high-power electronics owing to their superior heat transfer properties. However, UTVCs, especially those with thicknesses below 0.4 mm, still face poor performance and unreliability problems. As a key processing technology, the second vacuuming and sealing process can significantly improve the heat transfer performance and reliability of UTVC; however, it has seldom been studied. In this study, a UTVC with a thickness of only 0.32 mm was developed, and an optimised second vacuuming and sealing process was proposed to obtain a high-performance and reliable UTVC. The UTVC, prepared via resistance welding sealing, demonstrates reliable performance, operating effectively at high temperatures (240 ℃) and internal pressures exceeding 3.3 MPa, without leakage. Optimising second vacuuming parameters effectively removes most non-condensable gas, thereby enhancing the heat transfer performance of UTVCs. UTVC proposed with the vacuuming time of 35 s, vacuuming temperature of 90 ℃, and gas collecting section length of 20 mm exhibits a thermal resistance of 1.701 W/℃ at a heat load of 3 W. This study benefits the design of a second vacuuming and sealing process for UTVC with thickness less than 0.4 mm, further promoting its industrial applications.

EXPERIMENTAL INVESTIGATION OF ENERGY PERFORMANCE AND EXERGY DESTRUCTION OF SIMPLE AND ROUGH-SUPERHYDROPHOBIC VAPOR CHAMBERS FOR PCB TEMPERATURE CONTROL

In this research, two vapor chambers with the same dimensions were manufactured to control the temperature of the high-power printed circuit board (PCB). In one case, the evaporator and condenser were rough and superhydrophobic, respectively. Another vapor chamber was nonrough and nonsuperhydrophobic (simple). In this study, as new experimental work, the exergy destruction analysis was performed in simple and rough-superhydrophobic vapor chambers and the effect of different parameters on exergy destruction in both vapor chambers was investigated and compared. Also, the effect of different parameters on the thermal resistance of the vapor chamber, taking into account the roughness and superhydrophobicity of the vapor chamber, was investigated and compared with the thermal resistance of the simple vapor chamber. The results showed that roughened evaporator and superhydrophobic condenser affected the amount of influence of other parameters on the thermal resistance and exergy destruction, improved the efficiency of the vapor chamber in most test cases, and reduced exergy destruction. According to the tested cases, the minimum thermal resistance and the exergy destruction were obtained as 0.18 °C/W and 13.32 W, respectively. Also, exergy destruction analysis showed that the amount of exergy destruction depended on the studied parameters in this study.

A PARAMETRIC STUDY ON THE THERMAL HOMOGENEITY OF VAPOR CHAMBER IN A BATTERY COOLING SYSTEM

For the battery cooling system, the large temperature difference of the coolant between the inlet and outlet leads to a decrease in the thermal homogeneity of batteries. To improve the thermal homogeneity, a designed composite liquid cooling system was analyzed combined with a grooved vapor chamber and a cooling plate. The parametric study on the thermal homogeneity was conducted including the height, width, length of grooved wick, filling ratio, flow rate of coolant, heat flux, and inclination angle. The results show that a preferable thermal homogeneity can be obtained at 20% filling ratio as the height and width of the channel increase, especially under the positive inclination angle of 20°. The heat source surface can be kept uniform within the temperature difference of 5°C in spite of the temperature rise of coolant up to 11.5°C under the flowing rate of 8.32 × 10<sup>-4</sup> kg/s. An empirical correlation of the "suppression ratio," containing the structural and operating parameters, is summarized to evaluate the suppressing function of the vapor chamber on the temperature difference of coolant. This research is aimed to provide a scientific basis for predicting the thermal homogeneity of the vapor chamber in a battery liquid cooling system.

Transient Characteristics and Performance of a Dual Compensation Chamber Loop Heat Pipe under Various Heat Loads

The dual compensation chamber loop heat pipe (DCCLHP) technology shows great promise for efficient thermal management in a variety of applications. This study focuses on refining the startup performance of the DCCLHP, particularly for low heat load conditions in terrestrial settings, by utilizing dual bayonet tubes. Empirical investigations examined the DCCLHP’s operational characteristics and improved thermal transfer capabilities across different orientations of the evaporator and compensation chamber (CC), including vertical, 45‐degree tilt angle, and horizontal configurations. Key results demonstrate the DCCLHP’s ability to manage low heat loads across diverse orientations, achieving over 400 W of heat transfer across a distance of 2.0 m while maintaining stable operation. Notably, the DCCLHP operation did not exhibit any significant instability issues. This work enhances the startup performance of the DCCLHP in various orientations and provides valuable insights into the confined natural circulation phenomenon, crucial for improving the overall thermal management capabilities of the system. In summary, the study highlights advancements in DCCLHP design and its potential to address thermal management challenges in diverse applications, particularly in the aerospace industry, through improved startup performance and enhanced heat transfer capabilities.

Influence of transient heat pulse on heat transfer performance of vapor chamber with different filling ratios

Influence of transient heat pulse on heat transfer performance of vapor chamber with different filling ratios