Improved Heat Dissipation Research Articles

Parametric study for thermal uniformity analysis on vertical fin located in novel designed impacting-jet double-layer nested microchannel heat sinks verified by SLM 3D printing method

The design of impacting-jet double-layer nested microchannel heat sinks (IJDN-MHS) has been proved to be an effective structure on heat dissipation improvement in electronic components. In order to achieve ideal substrate thermal uniformity for IJDN-MHS, the position research on vertical fin connecting inner/outer cooling circuit in IJDN-MHS has been studied numerically. Moreover, 3D printing test samples are made on the purpose of experimental verification using selective laser melting printing technology. As a result of the analysis, there is a strong correlation between the results of the numerical simulation and the experimental results. Through numerical simulation, it has been determined that the center fin position should be optimized for achieving the best thermal uniformity on the substrate. The model of distance between vertical fin connecting inner/outer cooling circuit and central point in IJDM-MHS equaling 0.27 mm (IJDN-MHS_0.27) has shown the optimal thermal symmetry on substrate. Further, with the streaming fins length increasing to 0.7 mm on the both sides of the vertical fin connecting inner/outer cooling circuit, thermal gradient at the bottom can be significantly controlled, and the peak temperature on substrate also drop to its most extreme limit based on the thermal uniformity on substrate.

Measurement of field emission array current distributions by metal-coated CMOS image sensors

A CMOS image sensor is utilized to determine the time- and spatially resolved distribution of the total electron emission current of a silicon field emission array. The sensor measures electron emission without the need for phosphorus screens or scintillators as converters. However, in initial experiments, rather low field emission currents of several hundreds of nanoamperes per emitter already damaged the sensor surface, which altered the systems’ signal response over the measurement time. In consequence, we coated the CMOS sensor surface with a Cu layer for surface protection. In contrast to the original insulating surface, Cu is an excellent current- and heat-conductor, which avoids lens charging by providing a conductive path for incident electrons and has an improved heat dissipation capability. Measurements using a segmented field emission cathode with four individually addressable tips demonstrate a consistent correlation between the emission current and the sensor signal of the metal-coated image sensor. Furthermore, the characterization of a field emission array showed that single tip emission currents of up to 12 μA per tip are measurable without discernible damage effects of the sensor’s surface.

Effect of Surface Functionalization of Si3N4 Fillers on Thermal and Mechanical Properties of TIMs

AbstractThermal interface materials (TIMs), which consist of polymers and thermally conductive fillers, are crucial for improving heat dissipation. This study examines the impact of surface functionalization of Si₃N₄ thermal conductive fillers on the performance of TIMs. Si₃N₄ fillers are modified with silane coupling agents of varying alkyl chain lengths, producing fillers with contact angles ranging from 25° to 151.2°, thereby ensuring enhanced interfacial compatibility with various polymers. The modified fillers are incorporated into three common polymers—silica gel (SG), epoxy resin (EP), and polyurethane (PU)—to fabricate TIMs. When the contact angle of Si₃N₄ fillers is 73.3°, they demonstrate excellent interfacial compatibility with EP, leading to a 54.37% increase in thermal conductivity and a 162.75% enhancement in elongation at break for the TIM. At a contact angle of 132.7°, the TIMs prepared with SG exhibit an 86.36% increase in thermal conductivity and a 23.88% increase in elongation at break. Given that the original Si₃N₄ already possesses adequate interfacial compatibility with PU, no further modification is required. These findings offer valuable insights for future research aimed at optimizing Si₃N₄ fillers and TIMs to achieve enhanced thermal and mechanical properties.

CFD Simulation and Surface Modification of SG Cast Iron for Hot Rolling Applications

The wear resistance and heat dissipation of hot rolling mill rollers are critical factors affecting their durability and operational efficiency, particularly under extreme thermal and mechanical conditions. This study investigates the surface modification of SG iron rollers through tungsten laser cladding, aiming to improve these properties. A comprehensive approach, combining Computational Fluid Dynamics (CFD) simulations and experimental trials, was employed to evaluate the performance of tungsten-cladded rollers relative to untreated ones. The results revealed a 10-18% improvement in heat dissipation for tungsten-cladded rollers, attributed to enhanced heat transfer rates and better cooling efficiency. The analysis of fluid flow patterns, water volume fraction, and cooling angles demonstrated that tungsten cladding allowed for more effective heat management and uniform cooling across the roller surface. In the experimental trials, the mechanical properties of SG iron showed significant enhancement after laser cladding. The microhardness of the cladded surface increased by 59%, from 220 HV to 350 HV, offering improved resistance to surface deformation and wear. Furthermore, the wear resistance improved by 35% reduction in wear loss, as the tungsten and MoS₂/WC composite coatings provided a strong protective barrier against abrasion. Additionally, the Coefficient of Friction (COF) was reduced by 43%, from 0.7 to 0.4, due to the lubricating properties of MoS₂, minimizing frictional heat and energy loss during operation. These findings reveal the effectiveness of tungsten laser cladding as a surface modification technique for SG iron rollers, with practical implications for improving the durability and operational efficiency of hot rolling mill rollers.

A Computational Analysis of Air‐Cooled Heat Sinks Designs for PV Solar Panel Cooling With Different Fin Numbers

ABSTRACTThe efficiency of photovoltaic (PV) solar panels is highly sensitive to operating temperatures, with increased temperatures leading to a significant decline in electrical output and overall performance. Despite extensive research into thermal management solutions for PV panels, there remains a gap in optimizing passive cooling systems, particularly air‐cooled heat sinks, to achieve effective heat dissipation. This study addresses the challenge by conducting a detailed computational analysis of air‐cooled heat sinks with varying fin configurations to enhance the thermal regulation of PV panels. Using computational fluid dynamics simulations, this work evaluates the influence of fin number and spacing on airflow dynamics and heat dissipation efficiency. Key findings from ANSYS Postprocessor simulations indicate that heat sinks with a higher number of fins improve heat dissipation, with the 11‐fin configuration demonstrating the highest temperature drop of 38.44 K. Comparatively, the base model (nine fins, 0.05 m fin spacing) exhibited a maximum temperature of 331.46 K and a mean velocity of 1.58 m/s. A parametric study of finless designs showed a lower mean temperature of 321.28 K, but with significantly reduced airflow velocity. Intermediate designs, such as the six‐fin and seven‐fin heat sinks, also demonstrated improved thermal performance over the finless model but were outperformed by the 11‐fin configuration. This study contributes to the ongoing efforts to optimize passive cooling for PV solar panels by demonstrating the critical impact of fin number on heat sink effectiveness. The findings offer valuable insights into the design of more efficient cooling mechanisms, potentially enhancing both the performance and longevity of PV systems.

Comparative Analysis of Material Efficiency and the Impact of Perforations on Heat Sinks for Monocrystalline Photovoltaic Panel Cooling

In this research, the design and simulation of a heat sink for photovoltaic panels were carried out using aluminum and copper, the most commonly used materials in heat dissipation systems. This heat sink consisted of fins that were tested both perforated and non-perforated to improve heat dissipation efficiency. This research stems from the need to reduce the temperature of photovoltaic panels during operation, as scientific evidence shows that photovoltaic panels experience a decrease in efficiency as the temperature increases, taking as a reference the temperature under standard test conditions. The simulations of photovoltaic panels with aluminum and copper fins, both perforated and non-perforated, followed a rigorous methodology. For validation, the simulation results were compared with field data, yielding a mean absolute percentage error of 1.71%. The findings indicate that copper fins reduced the temperature of the photovoltaic panel by 2.62 K, resulting in a 1.31% increase in efficiency. Similarly, aluminum fins reduced the temperature by 2.10 K, with a 1.05% increase in efficiency. Perforated copper fins achieved a temperature reduction of 3.07 K, increasing efficiency by 1.54%, while perforated aluminum fins reduced the temperature by 2.49 K, contributing to a 1.25% increase in efficiency.

Fabrication of Die Sink Electrochemical Machining Tools Using Low Melting Fusible Alloy and Polymer Based Additive Manufacturing

The present work introduces a novel approach to fabricating die-sink tools for electrochemical machining (ECM) using low-melting fusible alloy and additive manufacturing. Three methods are proposed, each bettering the previous in manufacturing sustainability. The versatility of the process enables the fabrication of die-sink ECM tools that are hitherto considered challenging to fabricate. Finite element analysis was used to simulate the temperature rise of the low-melting (50 °C) tool due to Joule heating, accounting for electrolyte flow under various process parameters. A novel validation method employed a thermostat temperature probe as a cathode. Experiments based on the simulation data revealed that for a 4 mm tool diameter, the tool is unlikely to melt at 3 A current, 200 μm inter-electrode gap, 11.97 S m−1 electrolyte conductivity, and 1.7 m s−1 electrolyte velocity. A pulsed power supply was subsequently used to improve heat dissipation, and ECM was successfully carried out using tools of various shapes, demonstrating the effectiveness of the developed fabrication methods.

Effect of Source-Sink Misalignment and Sink Cavity Aspect Ratio on the Thermal Performance of Gallium Heat Sinks

Herein, we numerically investigated methods to improve heat dissipation from the base of a phase-change material (PCM) heat sink exposed to high heat flux (15 W/cm2). The sink cavity exhibited a rectangular cross-section with two opposite vertical walls of high thermal conductivity. These walls serve as heat-dissipating fins. We used gallium, a metallic PCM with high thermal conductivity and a low melting point to improve heat dissipation by leveraging buoyancy-driven circulations within the molten gallium. We adopted a method to position the sink base on top of the heat source surface in such a way to augment temperature gradients within the liquid to induce imbalances in gallium density and consequent internal circulations. In this technique, one vertical wall is subjected to forced-convective heat exchange with the surroundings, while the other remains adiabatic. Subsequently, for the case which showed optimum performance, we relaxed the adiabatic thermal boundary condition applied at one of the vertical walls and replaced it with convective heat transfer condition, and assessed the sink performance based on that. Further, we analyzed the impact of various aspect ratios of the sink cavity on the induced internal circulations and base cooling. Sink cavities with aspect ratios of 1.33, 0.96, and 0.64 corresponding to sink heights of 20, 17, and 14 mm, respectively, were examined under a consistent heat flux applied across a 15-mm base length. We also investigated the precise positioning of the sink base relative to the heat source surface and explored its influence on temperature gradients and gallium density imbalances crucial for induced internal circulations. Results indicate that a sink cavity aspect ratio of 0.96 yields the optimal heat dissipation from the base. Further, aligning the left bottom edge of the sink base with the left edge of the heat source surface maximizes heat dissipation to the ambient surroundings, thereby prolonging latent-heat dumping into the sink before the gallium completely melts. Any misalignment between the sink base and the surface of the heat source may have a profound impact on the temporal evolution of induced internal circulations within the molten gallium, essentially affecting heat dissipation from the sink base.

Investigation of hydrothermal characteristics and entropy generation in a microchannel heat sink with elliptical fins

Abstract As the integration of microelectronic devices continues to increase, thermal management issues become increasingly prominent. Microchannel heat sinks are effective for heat dissipation in high heat flux microelectronic devices. This study designs five elliptical finned microchannel heat sinks with different aspect ratios (γ) while maintaining a constant elliptical area to enhance heat transfer performance. The values of γ are 0.74, 0.86, 1, 1.17, and 1.35, respectively. Over the Reynolds number (Re) range of 293 to 740, the hydrothermal characteristics and entropy generation of the microchannels with elliptical fins (MC-EFs) are investigated through numerical simulations. The thermal enhancement mechanism of MC-EFs is analyzed via flow, temperature, and pressure fields. The optimal γ value is determined by maximizing the overall performance factor (OPF) and minimizing the augmentation entropy generation number (N s,a). Results indicate that introducing elliptical fins in the straight microchannel (SMC) significantly improves heat dissipation. An increase in γ enhances thermal performance but also raises flow resistance. Specifically, when γ increases from 0.74 to 1.35, the Nusselt number (Nu) improves by 10.71%-25.64%, and the friction coefficient (f) increases by 30.92%-57.27%. Overall, at Re = 740, the OPF of the MC-EF with γ = 1.35 reaches a maximum of 1.285, and at Re = 597, the N s,a for this configuration is minimized to 0.578. These findings provide valuable insights for effective thermal management in microelectronic devices.

Qualitative analysis of the coupling effect of fluid velocity distribution in microchannels on the performance of water-cooling lithium-ion batteries system

ABSTRACT Lithium-ion batteries are the direct power sources of electric vehicles, but their high heat flux density restricts their development. Microchannel heat sinks (MCHS) can assist in heat dissipation to overcome this. The distribution of fluid velocity among microchannels has a considerable effect on the performance of MCHS for a water-cooling lithium-ion batteries system. In this paper, a new microchannel heat sink with high depth to width aspect ratio is proposed and the influence of four different aspect ratios on the distribution of fluid velocity among microchannels and heat transfer performance of MCHS was numerically studied by computational fluid dynamics (CFD). The results showed that at the same inlet flow rate, the larger the aspect ratio of the microchannels, the better the uniformity of the internal fluid velocity. The heat performance of microchannel structures with four different aspect ratios for a water-cooling lithium-ion batteries is further investigated experimentally. Compared with the simulation results of the fluid velocity distribution, the coupling effect between the fluid velocity distribution in the microchannels and the heat dissipation performance of a water-cooling lithium-ion batteries is analyzed. The results fully demonstrated that a larger aspect ratio of the microchannels results in a better heat dissipation performance on the surface of the lithium-ion batteries. Optimizing the aspect ratio of the microchannels to facilitate a relatively uniform velocity distribution to improve heat dissipation performance of the water-cooling system may be a key factor to be considered, which provides a new idea for passive thermal management of batteries.

The Influence of Thermophysical Parameters on Thermal Runaway Characteristics for Pouch-Type Lithium-Ion Batteries

Abstract The thermal variation during the temperature rise process of batteries is closely related to multiple physical parameters. Establishing a direct relationship between these parameters and thermal runaway (TR) features under abusive conditions is challenging using theoretical equations due to complex electrochemical and thermal coupling. In this paper, a high-temperature thermal runaway model of pouch-type lithium-ion battery is established through electrical-thermal coupled approach, demonstrating a good agreement between the simulation and experimental results. The results reveal distinct trends in thermal parameters of the early temperature rise, trigger time for TR and peak temperature during TR process, for varying convective heat transfer coefficient, cell specific heat capacity, cell density and cell thermal conductivity. Across various convective heat transfer coefficients, the rates of temperature increase, moments of TR, and peak temperatures within a battery emerge as the cumulative outcomes of competing processes of the intricate exothermic secondary reactions within the battery, and the heat transfer with the surroundings. Batteries with lower heat capacity exhibit reduced thermal inertia and heightened sensitivity to temperature changes. Alterations in the thermal capacity of a battery wield a profoundly significant impact upon the moment of thermal runaway within the battery. Enhancing the thermal conductivity yields limited improvements in heat dissipation during thermal runaway primarily due to the relatively small geometrical scale of the battery. Results of this paper can provide valuable insights for size optimization design, thermal management system optimization design, thermal runaway safety warning and prevention of Lithium-ion batteries.

3D Printable Polymeric Composite Material with Enhanced Conductivity Achieved by Affinity Matching.

Polymer-based conductive composites are lightweight, low-cost, and easily processable materials with important applications in various fields. However, achieving highly conductive and 3D printable polymer-based conductive composites remains challenging. In this study, we successfully developed a highly conductive composite suitable for direct ink writing 3D printing using unsaturated polyester resin as the polymer matrix and graphene nanosheets as conductive fillers and rheological modifiers. Due to the well-matched affinity between graphene nanosheets and unsaturated polyester, the graphene nanosheets aggregate within the unsaturated polyester, forming a 3D conductive network. Moreover, the shearing force during direct ink writing 3D printing induces the orientation of the 2D graphene nanosheets, significantly enhancing their conductivity along the printing direction. At room temperature, the unsaturated polyester resin/graphene composite shows a high conductivity of 69.9 S m-1 while maintaining excellent 3D printability. Structures printed using this material exhibit improved heat dissipation and electromagnetic shielding performance. The reported unsaturated polyester resin/graphene nanosheet composites demonstrate outstanding electrical and heat conductivity and excellent processability, making them promising candidates for applications in electromagnetic shielding, printed electronics, and other fields.

Investigating Enhanced Convection Heat Transfer in 3D Micro-Ribbed Tubes Using Inverse Problem Techniques

The improved heat dissipation observed in 3D micro-ribbed tubes is primarily influenced by the intricate interplay of multiple structural parameters. Nevertheless, research into the coupling mechanisms of these multi-structural parameters remains constrained by the absence of effective methodology in numerical solutions. In the present work, a new 3D micro-rib structure based on discrete adjoint method is established. Firstly, the research examines the interplay of different parameters (such as arrangement, relative roughness height, angle of attack, and circumferential rows) on the thermo-hydraulic performance. It is noted that the heat transfer efficiency is notably impacted by the relative roughness height. And the arrangement methodology dictates the optimal positioning for heat transfer efficiency. An increase in the number of circumferential rows enhances fluid mixing, while the angle of attack plays a crucial role in the formation of longitudinal vortices. Secondly, the coupling optimization technique is employed to obtain the optimal structure featuring non-uniform relative roughness height by the developed numerical solution. Overall, in comparison to the smooth tube, the optimized ribbed tube exhibits a remarkable 64.9% enhancement in performance evaluation criteria. Finally, a notable enhancement of 10.65–22.78% is observed when comparing with the prevailing micro-rib structures.

Experimental and machine learning study on the influence of nanoparticle size and pulsating flow on heat transfer performance in nanofluid-jet impingement cooling

Maximizing heat transfer efficiency is crucial for enhancing performance and durability in diverse engineering applications, including fuel cells, EV batteries, and solar PV/T systems, thereby advancing sustainable energy innovation. This study investigates thermal dissipation from a simulated heat sink aligned with a PV cell’s back plate via jet impingement cooling. Specifically, it examines the impacts of pulsatile cooling and nanoparticle size in hybrid nanofluids, comprising combinations of Al2O3 and MWCNT in water, with varied nanofluid volume fraction (0.05 vol% ≤ ɸ ≤ 0.3 vol%) and flow Reynolds number (15000 < Re < 40000). Key findings reveal significant influences of nanoparticle size, nanofluid concentration, and pulsating flow on heat transfer performance. Notably, sample D demonstrated the highest heat transfer enhancement, achieving approximately 52.94 % and 79.06 % improvement in continuous and pulsating jet cooling compared to de-ionized water under continuous jet cooling. Machine learning classifiers were employed to identify critical thermal performance parameters, with Reynolds number identified as the most significant factor influencing heat transfer. Random Forest and Gradient Boosting classifiers showed notable accuracy in predicting Nu, emphasizing the role of machine learning techniques in optimizing thermal management strategies for improved heat dissipation from solar PV cell backplates.

Numerical Study on Heat Transfer Efficiency and Inter-Layer Stress of Microchannel Heat Sinks with Different Geometries

As electronics become more powerful and compact, laminated microchannel heat sinks (MCHSs) are essential for handling high heat flux. This study aims to optimize the MCHS design for improved heat dissipation and structural strength. An orthogonal experiment was established with the average surface temperature of the heat source as the evaluation metric, and the optimal structure was determined through simulation. Finally, cooling uniformity, fluidity, and performance evaluation criterion (PEC) analyses were carried out on the optimal structure. It was determined that the optimal combination was the triangular cavity microchannel (MCTC), with a microchannel width of 0.5 mm, a microchannel distribution density of 60%, and the presence of surface undulation on the microchannels. The result shows that the optimal structure’s peak inter-layer stress is just 34.8% of its longitudinal tensile strength. Compared to the traditional parallel straight microchannel (MCPS), this structure boasts an 8.6 K decrease in the average surface temperature and a temperature variation along specific paths that is only 9.9% of that in traditional designs. Moreover, the optimal design cuts the velocity loss at the microchannel entrance from 75% to 59%. Thus, this research successfully develops an effective optimization strategy for MCHSs.

New Tunable LED With Improved Heat Dissipation on Chip-on-Board

New Tunable LED With Improved Heat Dissipation on Chip-on-Board

Exploring Biomimetic Heat Pipes for Space Radiator Enhancement

This study investigates biomimetic heat pipes for space radiator applications, utilizing nature-inspired structures to potentially enhance heat transfer efficiency. The research addresses the imperative for improved heat dissipation mechanisms in nuclear space systems, crucial for effective thermal management. Heat pipes are passive heat transfer devices widely adopted for thermal control. The study aims to evaluate the effectiveness of a biomimetic heat pipe design in comparison to a traditional design while also validating the fabrication process through industry-made heat pipe comparisons. Innovative hot oil bath testing methods are employed to fabricate and test both heat pipe types, utilizing comprehensive thermal analysis, physical experiments, and validation techniques to assess heat transfer capabilities. Tests span varying temperature levels to analyze heat pipe behavior and performance. Findings suggest the potential for enhanced heat dissipation along the length of the biomimetic heat pipe, hinting at the biomimetic structure’s role in improving heat transfer. This study underscores the promise of biomimetic design principles and their potential for advancing heat pipe technology. Recommendations for further exploration include alternative materials, optimized testing procedures, and refined fabrication processes.

Finite Element Analysis of LED Heat Dissipation Performance Based on Graphene Composites

Abstract With the gradual development of integrated circuits to thin, high-performance and versatile of electronic products is becoming more and more powerful, and its integration and assembly density continue to improve, which will lead to the increase of its working power consumption and heat. If not timely treatment of heat dissipation problems, which will lead to heat concentration in the diode PN junction, it will reduce the service life of LED lights, and in severe cases, it will even burn the LED device. Therefore, it is crucial to improve heat dissipation efficiency of LED and reduce the junction temperature of chip. An LED structure with aluminum material and an LED structure with graphene material are analyzed by finite element method to study the heat dissipation efficiency of the graphene material. The results reveal that the heat dissipation effect of high conductivity graphene composites provides a convenient evaluation method for the subsequent use of the new materials. The research in this paper shows that the software simulation method can effectively analyze the thermal conductivity of practical engineering applications.

A 220 GHz GaN‐based monolithic integrated frequency doubler delivering over 0.25 W output power

AbstractA 220 GHz GaN‐based monolithic integrated frequency doubler with high continuous‐wave output power has been developed. The doubler achieves improved heat dissipation by establishing the terahertz (THz) monolithic integrated circuit topology with GaN Schottky barrier diodes integrated on a high thermal conductivity SiC substrate. It features six anodes to enhance the power‐handling capabilities. A refractory Schottky metal stack is adopted for better thermal stability. The doubler realizes satisfactory performance by introducing the suspended microstrip and an all‐in‐one output structure. For verification, a prototype of the proposed frequency doubler was fabricated and tested. Measured results show that the proposed doubler produces a continuous‐wave output power of 255 mW at 220 GHz with an efficiency of 14.6%, exhibiting excellent potential for powerful THz sources.

Influence of cryogenic CO2 on wood-plastic composite (WPC) turning-performance characteristics: a comparison with dry machining

ABSTRACT Wood plastic composite (WPC) is an environmentally friendly wood material widely used to manufacture wood products for indoor and outdoor use. In traditional WPC cutting, a built-up edge is easily generated in the cutting zone, which negatively affects the machined surface quality. Cryogenic cutting technology can effectively suppress the formation of built-up edges in the cutting zone and improve machining quality. Therefore, this study aims to investigate the cryogenic cutting properties of WPC. Cryogenic turning tests and dry turning tests were carried out on WPC, and cutting temperature, cutting force, and surface roughness were compared and analyzed. The results showed that cryogenic CO 2 airflow improved heat dissipation in the cutting zone and effectively reduced the temperature. Under the effect of cryogenic CO 2 , the strength of WPC increased, resulting in a higher cutting force for cryogenic turning than that for dry turning. Cryogenic cutting of WPC resulted in a smoother surface than dry cutting. During the WPC cryogenic turning process, increasing cutting depth and feed rate causes an increase in cutting temperature, cutting force and surface roughness. Increasing cutting speed also cause an increase in cutting temperature, but the reduction in cutting forces and surface roughness is beneficial. In summary, cryogenic cutting of WPC can achieve better surface quality than dry machining, and these results can contribute to practical guidelines for industrial applications.