Search Results (125)

Under high-Mach-number flight conditions, the combustion chambers of hypersonic vehicles encounter extreme thermal environments marked by unilateral heating, high-heat-flux density, and supercritical pressure. Traditional hydrocarbon fuel cooling often suffers from insufficient heat sinks, high-temperature cracking and coking blockages, making it difficult to meet long-endurance thermal protection requirements. Liquid metal, due to its extremely high thermal conductivity, wide liquid phase temperature range, low Prandtl number and electromagnetic pump driving capability, has become a key technology for breaking through the bottleneck of high-heat-flux thermal protection. Apart from the magnitude of heat flux, the heat-transfer time scale (such as the characteristic thermal response time of the wall and the fluid) is also crucial. During hypersonic flight, transient thermal loads can change within milliseconds, requiring rapid thermal response. Liquid metals, due to their high thermal diffusivity, have a shorter thermal diffusion time compared to hydrocarbon fuels. This review employs a systematic literature review of approaches using gallium-indium-tin alloy, GaInSn, focusing on three core directions: the flow and heat-transfer characteristics of liquid metals, the optimization of cooling micro-channels, and the application of thermal protection systems. It summarizes the research progress at home and abroad, compares and analyzes the performance differences and applicable scenarios of typical liquid-metal working fluids, and summarizes the advantages and disadvantages of existing models, structural designs, and system schemes. The research shows that liquid metals can significantly alleviate thermal stratification and eliminate coking, and deep, narrow, tree-shaped, and biomimetic micro-channels can effectively enhance heat transfer. The liquid-metal-fuel dual-channel waste heat recovery and thermoelectric power generation system has demonstrated engineering application potential. Currently, the field still faces key challenges, such as unclear heat-transfer mechanisms under extreme conditions, the lack of general heat-transfer correlation formulas, insufficient compatibility with high-temperature materials, poor miniaturization and vibration resistance of electromagnetic pumps, and low system integration. In the future, efforts should be focused on developing multi-field coupled heat-transfer models under extreme thermal environments using engineered micro-channel structures, corrosion-resistant materials, and lightweight electromagnetic pumps, promoting the research and development of integrated thermal protection, heating and power generation systems, and providing support for the development of advanced thermal management systems for hypersonic aircraft and aviation engines. Full article

This study numerically investigates the effects of manifold outlet width and lower-layer microchannel configuration on the thermohydraulic performance of a wedge-shaped manifold microchannel heat sink for high-heat-flux electronic cooling. A three-dimensional steady conjugate heat-transfer model was established in Ansys Fluent and assessed through grid-independence analysis and comparison with experimental pressure-drop and coolant-temperature-rise data. Simulations were conducted at inlet velocities of 1.0, 1.15, and 1.3 m/s to evaluate the average and maximum heat-source temperatures, temperature uniformity, pressure drop, thermal resistance, and performance evaluation criterion (PEC). Within the investigated manifold outlet-width range of 0.62–0.71 mm, increasing the outlet width produced concurrent reductions in the average and maximum heat-source temperatures and pressure drop, while improving the temperature uniformity of the heated surface. Among the outlet-width cases examined, 0.71 mm provided the most favorable thermohydraulic performance within the tested range. The influence of channel configuration depended on the evaluation objective. The wavy channel (WC) yielded the lowest heat-source temperatures and thermal resistance and therefore exhibited the best thermal performance among the investigated configurations. By contrast, the trapezoidal channel (TrC) maintained the highest PEC over the investigated inlet-velocity range and reached a maximum value of 1.140 at 1.3 m/s, indicating the most favorable balance between heat-transfer enhancement and hydraulic penalty. These results demonstrate that manifold outlet width and channel configuration should be selected jointly according to the required balance between temperature control and hydraulic performance. Full article

For high-performance chips with escalating power densities and localized hot spots, liquid-cooled microchannel heat sinks face a critical trade-off between thermal performance and flow resistance. This paper presents a multi-objective topology optimization framework that minimizes average temperature and fluid dissipation while incorporating a high-temperature penalty to suppress extreme local overheating. The model is evaluated under uniform heating and a realistic non-uniform source (AMD EPYC 9965 MCM Chiplet CPU). Results show that the penalty term effectively drives channel evolution toward hot spots, reducing peak temperatures with modest pressure-drop increases. Under uniform heating, optimized channels achieve cooling comparable to serpentine designs but with flow resistance near that of parallel or pin-fin arrays. Under non-uniform heating, the topology adaptively narrows inlet-side channels to redirect coolant to distal CCDs, attaining a peak temperature of 139 °C and a pressure drop of 519 Pa—while conventional parallel and array channels exceed 200 °C due to distal cooling deficiency. This study confirms that topology optimization with localized hot-spot penalties effectively mitigates extreme temperatures, offering a viable path for engineering liquid cold plates in next-generation heterogeneous processors. Full article

Compared with straight microchannels, wavy microchannels have been shown to significantly improve the heat transfer capability of microchannel heat sinks. The present study introduces a bidirectional curved wavy microchannel design aimed at enhancing performance. The thermo-hydraulic performance of bidirectional curved and ordinary wavy microchannels within the Reynolds number range of 300–800 is analyzed numerically under a constant heat flux. The results indicate that the bidirectional curved microchannel achieves optimal performance at an inlet velocity of 0.6 m/s. Compared with the ordinary wavy microchannel, the comprehensive performance factor of the bidirectional curved wavy microchannel with A₂ = 2 mm and λ₂ = 8 mm increases by 48% under the same inlet Reynolds number. For the preferred bidirectional curved wavy microchannel with A₂ = 2 mm and λ₂ = 12 mm, the average secondary flow intensity is enhanced by 153%, the comprehensive performance factor reaches 1.35, and the minimum entropy generation rate decreases by 6.87%. The enhanced heat transfer is attributed to the increased main flow velocity and the secondary flow intensity due to the bidirectional curve, which promotes coolant mixing. Full article

This paper proposes an experimental, intelligent optimization approach to improve the thermal cooling performance of an overclocked graphics processing unit (GPU). A closed-loop liquid-cooling system was built and tested utilizing deionized water and a silver (Ag) nanofluid coolant (0.015% vol.) across a variety of microchannel heat sink topologies with varying fin spacing. Key thermal performance indicators, including GPU temperature, coolant outlet temperature, and thermal resistance, were measured at different coolant flow rates. Experiments revealed that raising the flow velocity and decreasing the fin gap considerably enhanced cooling performance, while the Ag nanofluid consistently lowered GPU temperature by 1–3 °C compared to water. An Artificial Neural Network (ANN) surrogate model was constructed and trained using experimental data to support predictive analysis and system optimization, achieving excellent predictive accuracy with low RMSE. The trained ANN model was combined with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to perform multi-objective optimization, aiming to minimize GPU temperature and thermal resistance while improving heat removal. The Pareto-optimal solutions revealed that nanofluid-based cooling offered the best trade-off circumstances, with optimal designs occurring at moderate flow rates and small fin spacing. The ANN-NSGA-II multi-objective optimization results indicated that the best thermal performance of the GPU cooling system was achieved when using Ag nanofluid (0.015 vol.%) as the coolant, with an optimal coolant flow rate in the range of 1.30–1.84 LPM and an optimal fin/channel spacing of 0.57–0.71 mm, producing GPU temperatures of 29.18–29.66 °C, coolant outlet temperatures of 29.06–29.41 °C, and a minimized thermal resistance of 0.0106–0.0152 °C/W; thus, overall, the suggested ANN-NSGA-II framework works well as a practical design tool for improving GPU cooling systems and may be used to other high-heat-flux electronic thermal management applications. Full article

This study systematically investigated flow boiling characteristics within a novel three-layer microchannel heat sink with 3/4 open-ring pin fin arrays, designed for high-heat-flux thermal management of low-carbon metallurgical reactors. Two-phase flow regimes, pressure drop, and wall temperature responses were analyzed. To evaluate the impact of functional surface material properties on thermo-hydraulic behavior, a hydrophilic nano-coating modification was applied to the inner copper channel walls for comparison. Increasing the flow rate triggered a transition from a vapor-dominated confined slug flow to a liquid-dominated dispersed bubble flow, which effectively improved the thermo-hydraulic stability. Hydrophilic surface modification resulted in an average pressure drop reduction of 33% and significantly diminished the sensitivity of flow resistance to velocity variations. Through hydrophilic treatment, the localized vapor film effect at high velocities was suppressed, and temperature field homogenization was promoted, yielding a maximum convective heat transfer coefficient of 7760 W/(m²·°C), i.e., 72.9% enhancement over the baseline heat sink. The underlying mechanism is attributed to the formation of a stable near-wall thin liquid film and the promotion of high-frequency nucleate boiling. These results will be of high relevance for developing efficient cooling solutions for power electronics, thereby supporting the advancement of low-carbon metallurgical reactors. Full article

Technological development and thermal management are closely related, as chip-based units demand efficient cooling. Microchannel cooling is a key solution. This study, for the first time, experimentally and numerically investigates fin distributions with decreasing numbers, with/without staggered configurations, and the effect of dimples on single-phase flow in micro-pin-finned heat sinks. The database covers mass fluxes from 500 to 750 kg m⁻² s⁻¹ (in 50 increments) and four heat sinks (coded as MH-0, MH-1, MH-2, MH-3), with Reynolds numbers ranging from 234 to 327. Complementary numerical simulations were also employed to visualize flow structures and local Nusselt distributions to elucidate the experimental observations. It was concluded that low-velocity eddies occur in the dimples and between the successive pin-fins. The best thermal performance was obtained for MH-3, while the lowest pressure drop was measured for MH-1. Therefore, if heat transfer is the primary aim, MH-3 is preferred. MH-3 increases average Nusselt Number (Nu_avg) by between 11.45% and 14.38% compared to MH-0. However, the pumping power results underline the importance of MH-1. Compared to MH-0, the pumping power decreases by up to 18.4% for MH-1, 16.6% for MH-2, and 13.8% for MH-3. Full article

Microchannel liquid cooling technology, characterized by high heat-transfer efficiency, represents an effective solution for thermal management in high heat-flux density electronic devices. Existing research has mainly focused on optimizing the structural design of microchannel heat sinks, while neglecting the specific effects of inlet manifold configurations on their heat transfer and flow performance. To obtain more systematic data on microchannel heat transfer performance and internal velocity distribution, this study designed microchannels with single-inlet and triple-inlet configurations. A microchannel cooling performance testing platform was established, and visualization experiments of the internal flow field in straight microchannels were conducted using a particle image velocimetry (PIV) system. The velocity distribution uniformity and heat transfer performance were compared between single-inlet and triple-inlet microchannels with varying channel spacings. The results show that under the same flow conditions, the triple-inlet splitter structure yields a more uniform flow distribution, a lower peak temperature for the heat source chip, and improved heat transfer performance, with its pressure drop reduced to 11.1–26.6% of that of the single-inlet configuration. Furthermore, smaller channel spacings yield improved heat-transfer efficiency in microchannels. Full article

In response to the increasingly severe heat dissipation challenges in electronic devices, three types of manifold microchannel heat sinks (MMC) incorporating rhombic pin-fins were proposed. Under the constraint that the maximum temperature of the heat source surface remains below 343.15 K, numerical comparisons with a conventional straight rectangular microchannel heat sinks (MCHS) reveal that the design featuring a trapezoidal manifold exhibits superior comprehensive thermal performance and improved temperature uniformity. Furthermore, the influence of rhombic pin-fin geometry on thermal performance was investigated for both MCHS with and without the trapezoidal manifold under varying mass flow rates. Results show that for the MCHS without a manifold, performance evaluation criterion (PEC) reaches its maximum when the inlet angle of the rhombic pin-fin is 120°, the side length is 0.17 mm, and the pin-fin height is 0.18 mm. In contrast, for the MCHS with the trapezoidal manifold, optimal PEC is achieved at an inlet angle of 110°, a side length of 0.18 mm, and a pin-fin height of 2.2 mm. Additionally, a multi-objective optimization was conducted using the Latin hypercube sampling method. Three objective functions—maximum temperature (${\mathrm{T}}_{\max }$), thermal performance (PEC), and temperature uniformity (${\mathsf{\sigma }}_{\mathrm{T}}$)—were considered. A total of 150 sample points were used to train Kriging surrogate models for the rhombic pin-fin MCHS with trapezoidal manifold. The optimization results demonstrate a 34.05% enhancement in thermal performance and an 18.6% improvement in temperature uniformity. Full article

Conventional cooling schemes that rely on rigid heat-sink-to-die coupling in vertical stacks fail to track the dynamic, non-uniform heat map of high-performance artificial-intelligence (AI) chips employing chiplet-based heterogeneous integration, giving rise to local hot spots. To eliminate this mismatch, we present a leaf-vein-inspired fractal microchannel tailored for such AI processors. Its hierarchical bifurcation–confluence topology adaptively reshapes the flow field, delivering ultra-low thermal resistance, high heat-transfer coefficients, and uniform dissipation. Coupled with reconfigurable chiplet placement, the design is evaluated through FEM-based orthogonal experiments that rank the influence of coolant, channel diameter/depth, inlet/outlet position, substrate thickness, and flow rate via range analysis and Analysis of Variance (ANOVA). A machine-learned surrogate model of junction temperature is then fed to Particle Swarm Optimization (PSO) for multi-parameter optimization. When re-simulated with the optimal parameter set, the symmetric fractal network lowered the AI chip junction temperature from 127.80 °C to 30.97 °C, a 76% improvement, offering a theoretical basis for hotspot mitigation in advanced heterogeneous AI packages. Full article

This experimental study comparatively investigates flow boiling performance and mechanisms in open and closed rectangular microchannels (ORMs/CRMs) with a high aspect ratio of 4. Fabricated on a copper substrate and sealed with a transparent window for visualization, the systems were tested using refrigerant R245fa. Experiments spanned mass fluxes from 89 to 545 kg/m²·s and heat fluxes from 6.3 to 218.5 W/cm² at an inlet temperature of 14 °C. Flow visualization reveals that the ORM configuration accelerates the transition from bubbly to slug and churn flow regimes and facilitates a unique stratified flow pattern absent in the CRM. Quantitatively, the ORM enhances the heat transfer coefficient by 4.2–14.1% while reducing the system pressure drop by 11.5–58.6% within the low mass flux range (89–269 kg/m²·s). Conversely, at a high mass flux of 545 kg/m²·s, the ORM’s pressure drop increases substantially by 29.9–246.8%, attributed to significant two-phase losses in the top-gap region. As heat flux increases, inertial forces dominate over gravitational effects, shifting the primary heat transfer contribution from nucleate to flow boiling. The figure of merit (FOM) confirms the overall performance superiority of the ORM at low mass fluxes. This work provides valuable insights and design guidelines for high-performance, high-aspect-ratio microchannel heat sinks in advanced thermal management systems. Full article

To address the thermal management challenges of high-heat-flux electronic devices, this study investigates heat transfer enhancement in microchannels with composite cavity-rib triangular prism structures through numerical simulations. Three cavity configurations (arc-shaped, rectangular, and trapezoidal) with depths ranging from 0.2 to 0.35 mm were analyzed. The results reveal that increasing the cavity depth elevated the friction resistance, with the trapezoidal cavities exhibiting the highest increase in friction resistance at Re > 550. The heat transfer performance exhibited a nonlinear improvement with depth: arc-shaped cavities (D = 0.35 mm) achieved maximum Nusselt numbers at low Reynolds numbers, whereas trapezoidal cavities excelled at high Reynolds numbers. The thermal-hydraulic performance evaluation criterion (PEC) identified the arc-shaped cavity (D = 0.35 mm) as optimal, achieving a maximum PEC value of 1.7495, which surpassed the rectangular and trapezoidal configurations by 4.3% and 0.7%, respectively. This study demonstrates that composite cavity-rib structures enhance secondary flow disturbances, providing critical insights for cross-scale parameter optimization in microchannel design. Full article

The escalating heat flux density and temperature in highly integrated microelectronic devices adversely affect their reliability and service life, making efficient thermal management crucial for stable operation. This study utilizes Galinstan liquid metal as the coolant to investigate the flow and heat transfer performance in microchannel heat sinks incorporating various turbulator configurations. It is revealed that for microchannels featuring expanded regions, turbulators that create highly symmetric flow fields are preferable due to improved flow distribution. The long teardrop-shaped turbulator provides the best heat transfer performance among all the investigated heat transfer enhancement structures. And this turbulator yields a 13.8–25.9% higher enhancement effectiveness compared to other configurations, at the expense of a 28–41% increase in pressure loss. However, the sudden cross-sectional expansion in the expanded region causes a significant reduction in fluid velocity. Consequently, microchannels with expanded regions and turbulators exhibit a higher bottom surface temperature than the original, straight microchannels, leading to an overall deterioration in heat transfer performance. Full article

Acoustofluidic devices use Surface Acoustic Waves (SAWs) to handle small fluid volumes and manipulate nanoparticles and biological cells with high precision. However, SAWs can cause significant heat generation and temperature rises in acoustofluidic systems, posing a critical challenge for biological and other applications. In this work, we studied temperature distribution in a Standing Surface Acoustic Wave (SSAW)-based PDMS microfluidic device both experimentally and numerically. We investigated the relative contribution of Joule and acoustic dissipation heat sources. We investigated the acoustofluidic device in two heat dissipation configurations—with and without the heat sink—and demonstrated that, without the heat sink the temperatures inside the microchannel increased by 43 °C at 15 V. Adding the metallic heat sink significantly reduced the temperature rise to only 3 °C or less at lower voltages. This approach enabled the effective manipulation and alignment of nanoparticles at applied voltages up to 15 V while maintaining low temperatures, which is crucial for temperature-sensitive biological applications. Our findings provide new insights for understanding the heat generation mechanisms and temperature distribution in acoustofluidic devices and offer a straightforward strategy for the thermal management of devices. Full article

Integrated circuits have become indispensable in modern society owing to their formidable computational power and high integration, finding extensive applications in critical fields such as artificial intelligence and new energy vehicles. However, continued increases in integration density and reductions in physical size lead to a significantly higher heat flux density, thereby posing major challenges for thermal management and overall chip reliability. To address these thermal challenges, this study introduces an optimized manifold microchannel design. A three-dimensional conjugate heat transfer model was developed, and computational fluid dynamics simulations were performed to analyze the thermal–hydraulic performance. To mitigate temperature non-uniformity, several strategies were implemented: adjusting channel widths, employing uneven inlet gaps, and incorporating micro-fins. Results demonstrate that the optimized configuration achieves a maximum temperature reduction of 7.7 K, with peak thermal stress decreasing from 55.29 MPa to 47 MPa, effectively improving temperature uniformity. This study confirms that the proposed optimized design significantly enhances overall thermal performance, thereby offering a reliable and effective strategy for advanced chip thermal management. Full article