Effective Thermal Control Research Articles

Analytical simulation of Darcy-Forchheimer nanofluid flow over a curved expanding permeable surface

Abstract This research paper presents an analytical simulation of Darcy-Forchheimer flow over a porous curve stretching surface. In fluid dynamics, the Darcy-Forchheimer model combines Forchheimer adjustment and high-velocity effects with Darcy's formula for porous media flow: two nanofluid particles, molybdenum disulfide, and graphene oxide, form nanofluid with the base fluid blood. The governing partial differential equations for momentum and energy are converted into a nonlinear ordinary differential equations system by applying the appropriate similarity transformations. The homotopy analysis method (HAM) is used to solve the transform equations analytically. The impact of essential factors includes the Forchheimer parameter, porosity parameter, slip parameter, Eckert number, nanoparticle volume friction, magnetic field parameter, and curvature parameter. The results have applications in the design of sophisticated cooling systems, where effective thermal control is essential.

Heat transfer in a non-uniformly heated enclosure filled by NEPCM water nanofluid

Purpose This paper aims to focuses on by investigate the heat transmission and free convective flow of a suspension of nano encapsulated phase change materials (NEPCMs) within an enclosure. Particles of NEPCM have a core-shell structure, with phase change material (PCM) serving as the core. Design/methodology/approach The enclosure consists of a square chamber with an insulated wall on top and bottom and vertical walls that are differently heated. The governing equations are investigated using the finite element technique. A grid inspection and validation test are done to confirm the precision of the results. Findings The effects of fusion temperature (varying from 0.1 to 0.9), Stefan number (changing from 0.2 to 0.7), Rayleigh number (varying from 103 to 106) and volume fraction of NEPCM nanoparticles (changing from 0 to 0.05) on the streamlines, isotherms, heat capacity ratio and average Nusselt number are investigated using graphs and tables. From this investigation, it is found that using a NEPCM nano suspension results in a significant enhancement in heat transfer compared to pure fluid. This augmentation becomes more important for the low Stefan number, which is around 16.57% approximately at 0.2. Secondary recirculation is formed near the upper left corner as a result of non-uniform heating of the left vertical border. This eddy expands notably as the Rayleigh number rises. The study findings indicate that the NEPCM nanosuspension has the potential to act as a smart working fluid, significantly enhancing average Nusselt numbers in enclosed chambers. Research limitations/implications The NEPCM particle consists of a core (n-octadecane, a phase-change material) and a shell (PMMA, an encapsulation material). The host fluid water and the NEPCM particles are considered to form a dilute suspension. Practical implications Using NEPCMs in energy storage thermal systems show potential for improving heat transfer efficiency in several engineering applications. NEPCMs merge the beneficial characteristics of PCMs with the enhanced thermal conductivity of nanoparticles, providing a flexible alternative for effective thermal energy storage and control. Originality/value This paper aims to explore the free convective flow and heat transmission of NEPCM water-type nanofluid in a square chamber with an insulated top boundary, a uniformly heated bottom boundary, a cooled right boundary and a non-uniformly heated left boundary.

Consequence of Cattaneo-Christov heat and mass flux models on bioconvective flow of dusty hybrid nanofluid over a Riga plate in the presence of gyrotactic microorganisms and Stephan blowing impacts

This study investigates the impact of the Stephan blowing and Cattaneo-Christov flux model on bioconvective flow of dusty hybrid nanofluid over a Riga plate in the presence of gyrotactic microorganisms and variable dust particles volume friction. Mass and heat phenomena are explored in the context of Stefan blowing impacts. The hybrid nanofluid consists of nanoparticles of MgO and Ag base fluid water. The Cattaneo-Christov mass and heat flux model has a significant impact on the bioconvective flow. The model predicts a slower temperature distribution and a higher concentration gradient than the traditional Fick's law and Fourier's law, respectively. The occurrence of gyrotactic microorganisms enhance the flow characteristics. This model is important for optimizing mass and heat transfer in a variety of engineering systems, including heating and cooling technologies, where effective thermal control is essential. It can be used by employing the regulated migration of microbes. By maximizing the removal of impurities, it helps with the design of sophisticated water purification systems in environmental engineering. The amalgamation of gyrotactic microorganisms and Stefan blowing effects augments the comprehension of intricate fluid dynamics, maybe resulting in advancements in microfluidic apparatuses and bio-inspired technologies. In order to transform the controlling PDEs into nonlinear ODEs, a new set of non-dimensional variables is used. The MATLAB (RKF-45th) technique is then used to resolve the ODEs numerically. As the Stephan blowing parameter (0.1≤Sb≤1.9) increases, the outcomes show that the flow distributions upsurge for both the dust and fluid phases, but the dust and fluid phase thermal distributions drop.

Effects of sinusoidal wall temperature on thermal dynamics and irreversibility around an inclined plate embedded in a square cavity

Abstract Effective thermal and flow control within complex geometries is essential for engineering applications. In this study, an in-depth examination of flow dynamics, entropy, and thermal regulation is undertaken within a square cavity featuring sinusoidal wall temperature. To introduce complexity, an inclined plate obstacle is strategically positioned within the cavity with an inclination angle of 45o, and the investigation spans three distinct scenarios: adiabatic, cold, and hot conditions. The initial physical model is developed by formulating a system of partial differential equations, which are then transformed into a dimensionless representation using relevant variables. Subsequently, the Galerkin method is employed for approximated analysis of the simplified fluid flow model, and the computational code is verified in tabular format. The embedded physical parameters are constrained to specific numerical values to ensure the convergence of the physical model in each scenario. The physical characteristics of isotherms, streamlines, Nusselt numbers, entropy, and Bejan numbers are investigated. Notably, the results demonstrate that the introduction of a cold inclined plate leads to peak values in generating the entropy and average heat transfer rates. When comparing the cold inclined plate to the heated inclined plate, an increase of approximately 20% in the average heat transfer rate and a 15% rise in the entropy generation rate was found for the cold inclined plate. Furthermore, the Bejan number showed a 10% decrease for the cold inclined plate compared to the heated inclined plate. Additionally, increasing the amplitude and wavenumber led to a rise in average heat transfer and entropy generation rates, with 25% and 30% increases, respectively.

Structural color tunable intelligent mid-infrared thermal control emitter

This work proposes a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. In the beginning, we investigate an intelligent thermal control emitter based on a multilayer membrane formed by the phase change material vanadium dioxide, metal material Ag, and dielectric materials Ge and ZnS. By incorporating the thermochromic material vanadium dioxide, the structure exhibits a high emissivity of εH = 0.85 in the range of 3–13 μm wavelength when in the high temperature metallic state, enabling efficient heat radiation. In the low temperature dielectric state, the structure only has a low emission capacity of εL = 0.07, reducing energy loss. Our results demonstrate that the structure achieves excellent emission regulation ability (Δε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Furthermore, the thermal control emitter exhibits selective emission of peak wavelength due to destructive interference and shows a certain independence on polarization and incidence angle. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials.

The Development of a 2D Numerical Model of a Device Using the Elastocaloric Effect to Cool Electronic Circuits

The scientific community has been working hard lately to develop fresh, environmentally friendly refrigeration technologies. Those based on solid-state refrigerants are among the Not-In-Kind Refrigeration Technologies that show great promises. The one based on the elastoCaloric Effect is among the most interesting of them. This paper presents the development of a 2D numerical model for a device harnessing the elastocaloric effect with the primary objective of cooling electronic circuits. The study focuses on the intricate interplay between mechanical and thermal aspects, capturing the dynamic behavior of the elastocaloric material in response to cyclic mechanical loading. The numerical model incorporates detailed descriptions of the electronic circuits, accounting for heat dissipation and thermal management. Through simulations, the optimal configuration for efficient cooling is explored, considering various operative conditions and mechanical loading conditions (tensile and bending). The findings contribute to the advancement of elastocaloric cooling technology, offering insights into the design and optimization of devices aimed at enhancing electronic circuit performance through effective thermal control. The results that the most promising configuration is based on bending, a design choice resulting appropriate for cooling the electronic circuits.

Boosting thermal regulation of phase change materials in photovoltaic-thermal systems through solid and porous fins

This study explores the integration of porous fins with phase-change materials (PCM) to enhance the thermal regulation of photovoltaic-thermal (PVT) systems. Computational simulations are conducted to evaluate the impacts of different porous fin configurations on PCM melting dynamics, PV cell temperatures, and overall PVT system effectiveness. The results demonstrate that incorporating optimized porous fin arrays into the PCM region can significantly improve heat dissipation away from the PV cells, enabling more effective thermal control. Specifically, the optimized staggered porous fin design reduces the total PCM melting time and decreases peak cell temperatures by about 5°C . This is achieved by creating efficient heat transfer pathways that accelerate the onset of natural convection during the PCM melting process. Further comparisons with traditional solid metallic fins indicate that while solid fins enable 12.2% faster initial melting, they provide inferior long-term temperature regulation capabilities compared to the optimized porous fins. Additionally, inclining the PV module from 0° to 90° orientation can further decrease the total PCM melting time by 13 minutes by harnessing buoyancy-driven convection. Overall, the lightweight porous fin structures create highly efficient heat transfer pathways to passively regulate temperatures in PVT systems, leading to quantifiable improvements in thermal efficiency of 16% and electricity output of 2.9% over PVT systems without fins.

Performance of impingement-jet double-layer nested microchannel heat sinks with vertical central bifurcation–A numerical approach and experimental verification

The present research discusses a new design which makes use of vertical central bifurcation (CB) to improve the thermal performance of the impingement-jet double-layer nested microchannel heat sinks (IDN-MHS) which was produced via 3-Dimension printing methodologies. The CBs are introduced into the IDN-MHS to improve the heat transfer performance in comparison with the traditional inner-outer nested circuit IDN-MHS. Five 3-Dimension printing tests were produced for experimental verification, and it was shown that the results of simulation are in good agreements with results of experiment. The introduction of CBs shows effective thermal control of substrate temperature, and reduction of peak temperature on the substrate of IDN-MHS-CB. Yet, a distance of 0.76 mm between the vertical central bifurcation and the center plane shows the best overall performance. Both experimental studies and numerical simulations indicate that the heat transfer enhancement of IDN-MHS-CB_0.76 is significantly superior. Additionally, the average Nusselt number of IDN-MHS-CB_0.76 is higher than that of IDN-MHS. Although the proposed CB structure generates higher pressure drop penalty, the overall heat transfer characteristics factor of IDN-MHS-CB_0.76 still prevails other designs, which significantly outperforms that of IDN-MHS without bifurcation.

Enhancing four-axis machining center accuracy through interactive fusion of spatiotemporal graph convolutional networks and an error-controlled digital twin system

Mitigating thermal errors constitutes a crucial method for enhancing the machining accuracy of four-axis machining centers. At the heart of effective thermal error control lie the thermal error control platform and a resilient thermal error prediction model. It is imperative to note that thermal errors exhibit intricate dynamic and nonlinear spatiotemporal dependencies. However, prevailing thermal error prediction models tend to primarily focus on temporal features or employ simplistic spatiotemporal characteristics, resulting in diminished accuracy and robustness. Furthermore, the present thermal error compensation system is plagued by a lack of user-friendliness, stemming from its suboptimal execution efficiency. In response to the aforementioned challenges, an innovative approach: the interactive fusion spatiotemporal graph convolutional network is proposed. This novel model is specifically designed to capture the intricate dynamic spatiotemporal dependencies inherent in thermal errors. The interactive fusion spatiotemporal graph convolutional network model consists of three essential components: a bilinear temporal convolutional network, a multi-layer spatiotemporal module, and a linear module. These components work in harmony to comprehensively extract both global and local spatiotemporal features. Subsequently, a mapping relationship between thermal errors and compensation components is established, laying the foundation for theoretical advancements in thermal error compensation within the realm of four-axis machining centers. A digital twin system framework tailored for error control is devised, which leverages cloud-edge computing to enable dynamic control and real-time monitoring of thermal errors. To assess the effectiveness of this digital twin system framework and the interactive fusion spatiotemporal graph convolutional network model, a series of rigorous experiments were conducted. The oriented to error-controlled digital twin system coupled with the interactive fusion spatiotemporal graph convolutional network model yielded exceptional machining accuracy, resulting in minimal geometric disparities of [−3.0 μm, 3.0 μm] for the central hole diameter D and [−3.5 μm, 4.0 μm] for the hole distance H.

A novel fabrication method for polymeric flat plate pulsating heat pipe via additive manufacturing

Advancements in material development and fabrication techniques have led to the production of a new generation of electronic devices that are flexible, compact, small-scale, and lightweight. Effective thermal control management is crucial to ensure their performance, reliability, and durability. This paper proposes the fabrication of a polymeric pulsating heat pipe (PPHP) using a common stereolithography technology. The heat transfer performance of three PPHPs with different channel configurations was compared at heating powers ranging from 5 to 30 W and at a constant filling ratio of 50 %, using FC-72 as the working fluid due to its compatibility with the solid material. All three PPHPs have eight turns and length, width, and thickness of 185 mm, 85 mm, and 2 mm, respectively. All experiments were conducted for four thermal hysteresis cycles. The findings revealed that pressure and temperature distributions displayed similar patterns and fluctuations in response to heating power for all the PPHPs. Despite the simple technique and the use of a standard plastic material, the thermal resistance ranged from 2.5 to 1.7 °C/W, i.e., the effective thermal conductivity was already more than one thousand times higher than the conductivity of a solid plastic sheet for a 30 W heat input. The non-uniform channel configurations in PPHPs offered the potential of better heat transfer performance, fluid distribution, and operational stability. The present overture investigation paves the way for a more extended development of plastic 3D printing technologies for prototyping flexible PHPs and for teaching purposes.

ANSYS Simulation of Enhanced Heat Transfer in Compact Pipes Using Al2O3-Water Nanofluids

Al2O3-Water nanofluids have become popular for their significantly higher heat transfer rates, which are related to their increased thermal conductivity. These fluids are particularly useful in tiny pipelines, especially in situations where effective thermal control is required. Because of this, they are particularly beneficial to sectors like aerospace and automotive, where the need for lightweight and compact heat exchanger designs is crucial. This research investigates several input factors, such as temperature and velocity, using ANSYS Fluent. The investigation's initial temperature was 290 K, and the pipe's entry velocity was 3.78×10-1 m/s. At 2.98×102 K, the exit temperature stabilized. However, a clear inverse link between the temperature at the pipe's output side and the velocity at its entrance side was found. This unique development served as the main focus of our investigation on how to optimize heat flow and thermal conductivity inside the pipe. We used a two-phase approach, incorporating the nanofluid phases phi-0 and phi-4, to increase our comprehension. This methodological decision departs from traditional research, which frequently uses simulations in a single phase. Our new method was inspired by the necessity for a more thorough investigation. The results of this study demonstrate the effectiveness of the two-phase method, showing a significant rise in heat flow and thermal conductivity when compared to traditional one-phase simulations used in earlier research. This emphasizes how our approach was original and significant, bringing fresh perspectives to the field of nanofluid heat transfer research.

Improving a Fuel Cell System’s Thermal Management by Optimizing Thermal Control with the Particle Swarm Optimization Algorithm and an Artificial Neural Network

The thermal management of proton exchange membrane fuel cell systems plays a significant role in a stack’s lifetime, performance, and reliability. However, it is challenging to manage the thermal system precisely due to the multiple coupling relationships between the stack’s components, its operating environment, and its thermal management system. In addition, temperature hysteresis (temporal inconsistency of temperature with electrochemical reactions and fluid mechanics) imposes more difficulties on thermal control. We aim to develop an effective thermal control model for the fuel cell system to improve the temperature regulation accuracy and response speed and thus achieve highly stable temperature control. A dynamic mechanistic model is first developed based on the physical processes of the stack and its thermal management system. The model is then validated through experiments. Based on this dynamic mechanistic model, a control model is proposed for stack thermal management with the particle swarm optimization algorithm and an artificial neural network. It is applied and compared with the traditional PID algorithm. The simulation results indicate that the regulation time of the coolant inlet temperature as the current changes is reduced by more than 74%, and the overshoot is reduced by more than 50%. Therefore, the control model can enhance the dynamic response capability and temperature control precision under complex operating conditions with constantly changing load current and preset stack temperature, ensuring the temperature’s stability and thus improving the fuel cell system’s reliability and durability.

Mesoscopic thermal field reconstruction and parametrical studies of heterogeneous rock-filled concrete at early age

Rock-filled concrete (RFC) is a highly heterogeneous material composed of rock blocks and self-compacting concrete (SCC). There is still limited literature regarding the non-uniform thermal behavior of early-age RFC, making it difficult to predict equivalent homogeneous parameters. In this study, a novel mesoscopic FEM model was developed to simulate the full-scale heterogeneous RFC, both considering the pre-placement of stochastic rocks and layered filling process of SCC into rock voids. Based on on-site experiments of an integrally-poured RFC arch dam, the mesoscopic simulation results were validated and showed good accordance with the monitoring data. The results show that: (1) Spatial heterogeneity in RFC is most pronounced within the first 4 h after SCC pouring, and the RFC temperature typically reaches its peak within about 3 days. (2) The maximum temperature rise observed for SCC is only around 6∼7 °C, whereas the presence of the rockfill skeleton aids in the absorption of hydration heat, leading to a maximum temperature rise of 12.9 °C. (3) With a 5 % increase in the rock-fill ratio, the overall temperature level of the RFC model decreased by approximately 1 °C. (4) Increasing the adiabatic temperature rise of SCC by 10 °C, will lead to an approximate 3 °C rise in the highest temperature observed in RFC. These findings offer valuable insights for effective thermal control strategies in practical engineering applications.

Analysis of the Impact of Parameters of Gravity Heat Pipe Radiator on the Temperature Control of Gangue Hill and Engineering Test

ABSTRACT Deep within coal gangue hills, there is a substantial amount of wasted thermal energy. Prolonged accumulation of these hills leads to significant damage to the atmosphere and soil. Gravity heat pipes, as efficient heat transfer components, can safely, efficiently, and conveniently extract the accumulated heat in gangue hills to achieve effective thermal control. In this study, we first analyzed the optimal height of the heat dissipation fins through a single fin heat dissipation model. Then, we determined the optimum spacing between the heat dissipation fins through analysis with multiple fins. The results showed that when the height of the heat dissipation fins was 80 mm and the spacing between fins was 80 mm, the heat dissipation performance and economic costs were most reasonable. Through an engineering trial conducted for 143 days at the Maotergou coal mine gangue hill, it was found that the average heat dissipation rate of a single gravity heat pipe ranged from 243.52W to 494.32W. The total heat dissipation during the entire experimental process was 54.39 kJ, and the total heat dissipation at the elevation of 890 meters was 1087.71 kJ. This indicates that managing the internal temperature accumulation in coal gangue hills using gravity heat pipes is entirely feasible.

Transparent spacecraft smart thermal control device based on VO2 and hyperbolic metamaterials.

Effective spacecraft thermal control technologies are essential to avoid undesirable effects caused by extreme thermal conditions. In this paper, we demonstrate a transparent smart radiation device (TSRD) based on vanadium dioxide (VO2) and a hyperbolic metamaterial (HMM) structure. Using the topological transition property of HMM, high transmission in the visible band and high reflection in the infrared can be achieved simultaneously. The variable emission essentially originates from the phase change material VO2 film. Due to the high reflection of HMM in the infrared band, it can form Fabry-Pérot (FP) resonance with the VO2 film after adding the dielectric layer SiO2, which further enhances the emission modulation. Under optimized conditions, solar absorption can be reduced to 0.25, while emission modulation can reach 0.44 and visible transmission can be up to 0.7. It can be found that the TSRD can simultaneously achieve infrared variable emission, high visible transparency and low solar absorption. The HMM structure instead of traditional metal reflectors offers the possibility to achieve high transparency. In addition, the formation of FP resonance between the VO2 film and HMM structure is the key to achieving variable emission. We believe that this work can not only provide a new approach for the design of spacecraft smart thermal control devices, but also show great potential for application in spacecraft solar panels.

Preparation and characterization of diphenyl silicone rubber/microfiber glass wool composite thermal control films.

Innovative research on the development of thermal control films for spacecraft surfaces is presented. A hydroxy-terminated random copolymer of dimethylsiloxane-diphenylsiloxane (PPDMS) was prepared from hydroxy silicone oil and diphenylsilylene glycol by a condensation reaction, and then liquid diphenyl silicone rubber base material (denoted as PSR) was obtained by adding hydrophobic silica. Microfiber glass wool (MGW) with a fiber diameter of ∼3 μm was added to the liquid PSR base material, which upon solidifying at room temperature, formed a 100 μm thick PSR/MGW composite film. The infrared radiation properties, solar absorption, thermal conductivity, and thermal dimensional stability of the film were evaluated. Moreover, the dispersion of the MGW in the rubber matrix was confirmed by optical microscopy and field-emission scanning electron microscopy. The PSR/MGW films exhibited a glass transition temperature of -106 °C, thermal decomposition temperature exceeding 410 °C, and low α/ε values. The homogeneous distribution of MGW in the PSR thin film resulted in a notable reduction in its linear expansion coefficient, as well as its thermal diffusion coefficient. Consequently, it exhibited a significant capacity for thermal insulation and retention. For the sample with 5 wt% of MGW, the linear expansion coefficient and thermal diffusion coefficient at 200 °C were reduced to 0.53% and 2.703 mm s-2, respectively. Thus, the PSR/MGW composite film has good heat-resistance stability and low-temperature endurance, along with low α/ε values and excellent dimensional stability. Additionally, it facilitates effective thermal insulation and temperature control, and can be an ideal material for thermal control coatings on spacecraft surfaces.

Stress analysis and thermal performance of ultra-thin heat pipes for compact electronics

The ultra-thin heat pipe (UTHP) has been established as a highly effective thermal control component for cooling electronics with large heat generation rate and limited space for cooling. However, UTHP has been severely limited in application because of buckling or breaking on the shell of UTHP during the flattening process. In this study, a series of high-accuracy UTHPs with a thickness of 0.38–0.47 mm were fabricated by the phase-change flattening process. An internal vapor pressure model of the heat pipe during flattening was constructed and the heat transfer performances of UTHPs under different working conditions were experimentally investigated. According to the internal vapor pressure model, the pipe wall stress after flattening was the first to reach the yield strength of the material, and the upper limit heating temperature of UTHPs decreased with the decrease of flattened thickness. The maximum heat transfer capacity decreased with the decreased flattened thickness. UTHP with a thickness of 0.47 mm has a maximum heat transfer capacity of 4.5 W and a minimum thermal resistance of 0.64 °C/W. Moreover, gravity appeared to impose minimal effects on the heat transfer performance of UTHPs and the heat transfer capabilities of the UTHPs fluctuated within ±0.5 W for different gravity orientations.

Thermal smart materials and their applications in space thermal control system

Effective thermal control technologies are increasingly demanded in various application scenarios like spacecraft systems. Thermal conductivities of materials play a key role in thermal control systems, and one of the basic requirements for the materials is their reversibly tunable thermal properties. In this paper, we briefly review the recent research progress of the thermal smart materials in the respects of fundamental physical mechanisms, thermal switching ratio, and application value. We focus on the following typical thermal smart materials: nanoparticle suspensions, phase change materials, soft materials, layered materials tuned by electrochemistry, and materials tuned by specific external field. After surveying the fundamental mechanisms of thermal smart devices, we present their applications in spacecraft and other fields. Finally, we discuss the difficulties and challenges in studying the thermal smart materials, and also point out an outlook on their future development.

Numerical and experimental investigations on thermal management for data center with cold aisle containment configuration

This study proposes the container data center with the featured cold aisle containment (CAC) as effective thermal control strategy. In design, the overhead downward flow system is implemented with a heat exchanger arranged right above the data center on the air side and an evaporative water chiller on the water side to form the cooling approach. The cold airflows and hot exhausts of racks are separately transported by the contained cold and hot aisles to alleviate the problem of cold and hot air mixing. The measurements of air temperature and velocity of racks are used to validate the prediction accuracy of the computational fluid dynamics (CFD) model. The performance metrics in terms of the rack cooling index (RCI), return temperature index (RTI), supply heat index (SHI) are used to examine the design effectiveness of the proposed test data center. The simulations are then extended to assess the air distribution and thermal management at varied supply air temperatures and velocities for a large-scale data center to be built in the green energy technology demonstration site of the Shalun smart green energy science city. Overall, the calculated average PUE of 1.38 for the large-scale data center is notably less than the average PUE of 1.59 from the results of 2020 data center industry survey, indicating the potential savings of cooling energy and cost. This paper demonstrates a generalized approach as an easily adaptable, cost-effective solution for data centers to be deployed in tropical and subtropical areas.

Vapor chamber with two-layer liquid supply evaporator wick for high-heat-flux devices

Modern electronic devices with high heat flux increasingly exceed the capability of thermal management method. Two-phase thermal dissipation devices such as vapor chambers offer effective method for high heat flux cooling. Various new structural designs of vapor chambers are used as effective thermal control methods for high heat flux devices. However, the optimization criteria for the capillary wick structures are different. The combinations between the structural surface parameters and pore size of the capillary wick are different, while their influence on the heat transfer performance need to be studied. In this work, it is reported that the fabrication and thermal performance of vapor chambers with multi-layer sintered wicks and multi-artery wick design for liquid supply. We numerically and experimentally characterize the two types of sintered multi-artery wick for replenishing liquid and escaping vapor effectively with high heat flux. Three kinds of combinations of different copper particle sizes were applied to the sintered wicks in order to balance the liquid collecting rate and flow resistance. The copper particles of large particle size (60 μm/100 μm/150 μm) in the upper layer wick and copper particles of small particle size (30 μm/50 μm/100 μm) the lower layer wick were applied in the vapor chambers. In the present study, as an evaluation criteria for capillary wick designs, the relationship between surface porosity, surface area and critical heat flux was analyzed to obtain the experimental optimization of structural design and pore size combination as 50/100 μm. It was found that with similar multi-artery structure wicks, higher surface area porosity can effectively increase the critical heat flux of the vapor chambers. Judging from the experiment results, the minimum through-plane direction heat transfer resistance of the vapor chamber is 0.1426 K/W, the minimum in-plane direction heat transfer resistance is 0.016 K/W, while the critical heat flux of the vapor chamber is 262 W/cm2.