Heat Dissipation Research Articles

Turning of monel 400 using nanoparticles and cryogenic conditions

ABSTRACT Super alloys are the type of material that has good mechanical with thermal properties. Monel 400 has poor heat dissipation ability which enable them to machine difficult material. The important factor in improving machining efficiency is choosing the right lubricant. This study aims to examine the cooling methods on monel 400 with minimum quantity lubrication (MQL) with oil + MQL (OMQL), nanofluid + MQL (NMQL), and LN2 + MQL (LN2MQL). The test was run with a 1 mm depth of cut, spindle velocities (Vc), and feed rate (f). Surface roughness (R a ), cutting temperature (T), and flank wear (F w ) were the responses to evaluate the turning performance. The results demonstrated that compared to alternative cooling regimes, LN2 offered superior lubrication, with decline of 76%, 66% for Ra, 82%, 71.8% for T and 75%, 61% for F w respectively.

Light Weight Organic Composites with High Thermal Management Capability.

With the advancement of science and technology, effectively addressing the issue of heat dissipation in electronic equipment has become a key research topic. Polymers have attracted attention due to their low price, excellent flexibility, and lightweight characteristics, but thermal conductivity has a limitation. In this work, aiming for all-polymer composites with lightweight and high thermal conductivity, poly(p-phenylene benzobisaoxazole) (PBO) fibers were used to construct a long-range ordered heat transfer path in the organosilicon matrix, and an all-organic composite material with a low density of 1.24 g cm-3 and thermal conductivity of 18.44 W/ (m K) was produced. At the same time, the composite material was applied to the cooling performance test of LED lamps, which was 4.8 °C lower than advanced commercial thermal conductive materials, demonstrating its potential in the field of thermal management materials.

Preparation and thermal conduction mechanism of highly thermally conductive PA6/Al2O3/GNP composites via dynamic reactive blending

AbstractHighly thermally conductive polyamide 6 (PA6)/aluminum oxide (Al2O3)/graphene nanoplatelet (GNP) composites were fabricated through dynamic reactive blending. By utilizing the synergistic effect of low viscosity monomer and dynamic shear, uniform dispersion of Al2O3 and GNP in the PA6 matrix was achieved, forming efficient thermal conductive networks. Structural and morphological analyses confirmed the homogeneous dispersion of fillers and good interfacial bonding characteristics. The results showed that when Al2O3 and GNP contents were 43 and 7 wt%, respectively, the thermal conductivity reached 2.71 W/m·K, representing a 984% enhancement over neat PA6 and a 45.7% improvement compared to melt‐blended composites. The P‐S theoretical model was employed to understand the underlying mechanism, showing good agreement between theoretical calculations and experimental results. LED heat dissipation tests demonstrated excellent thermal response characteristics and temperature stability of the composites in practical thermal management applications, indicating their promising potential in electronic cooling applications.Highlights Dynamic reactive blending was used to prepare thermal conductive composites. Low viscosity of monomer and dynamic shear promoted uniform dispersion of fillers. The composites showed thermal conductivity of 2.71 W/m·K, 984% higher than neat PA6. P‐S model showed enhanced parallel effect reduced interfacial thermal resistance. Composites demonstrated effective heat dissipation in LED thermal management tests.

Preparation of copper/binder composites and fused filament fabrication process

Purpose The purpose of this study is to assess the effects of fused filament fabrication (FFF) printing parameters on the surface quality and dimensional accuracy of FFF-fabricated copper green parts using the appropriate filaments. The orthogonal experiments were implemented and the errors in length, width and height were measured and analyzed. The results of range analysis and variance analysis indicated the orders of effect factors. Dissolvent debinding combined with thermal debinding was adopted to remove the binders inside the green part by calculating debinding rate. The influence mechanism of sintering temperatures on the microstructure and shrinkage was elaborated. Design/methodology/approach The extrusion-based FFF in manufacturing copper parts can overcome shortcomings for high reflectivity and heat dissipation in laser powder bed fusion process at cost-saving and materials saving. This study makes an attempt to prepare copper/binder composite filaments through mixing, extrusion and flowability evaluation. Findings The results showed that the suitable composite filaments applied for FFF should balance rigidity and plasticity. The combination of printing speed and heating temperature impacts on the surface quality significantly, and the major factor in determining the dimensional accuracy is layer thickness. Two-stage debinding procedure was beneficial for binder removal and sintering process. The higher sintering temperature results in less voids, sizes shrinkage and densified microstructure, which is attributed to the occurrence of sintering neck among the fused copper powders. Originality/value The self-prepared copper/binder composite filaments were successfully manufactured using the FFF process. This study provides unique approach and print guidance for fabricating complex structures of pure copper components.

Accurate operando measurement of AlGaN/GaN HEMTs channel temperature and optimization of thermal design

The accurate estimation of the temperature distribution of the GaN based power devices and optimization of the device structure is of great significance to possibly solve the self-heating problem, which hinders the further enhancement of the device performances. We present here the operando temperature measurement with high spatial resolution using Raman spectroscopy of AlGaN/GaN high electron mobility transistors (HEMTs) with different device structures and explore the optimization of the device thermal design accordingly. The lateral and depth temperature distributions of the single-finger HEMT were characterized. The channel temperature and self-heating effect of the device under different bias voltages were investigated. By incorporating the two-dimensional electrothermal simulation, the hotspot position can be clearly observed under the gate edge near the drain side. The channel temperature of the multi-finger HEMT was further measured and the experiment results were in agreement with the three-dimensional finite element analysis simulation results. The device structure of the multi-finger device, including the gate width, gate pitch, structure layout, substrate materials, and thickness, were then theoretically optimized to improve the heat dissipation. The peak channel temperature of the device can be reduced by 70 °C when the substrate is substituted from silicon carbide to a single crystalline diamond. These results are of great interest for the thermal management of GaN HEMT power devices and further device performance improvement.

A comprehensive assessment on recent advancements in spent fuel reprocessing and waste management: pioneering technologies for a sustainable nuclear future

Abstract This work analyzes advancements in nuclear energy, focusing on spent fuel reprocessing and waste disposal. Key technologies such as pyroprocessing, aqueous reprocessing, and the DUPIC (Direct Use of Spent PWR Fuel in CANDU) process are examined for their effectiveness in reducing environmental and safety risks. Pyroprocessing is highlighted for its ability to enhance actinide recovery and reduce waste volume, while the PUREX process demonstrates high recovery efficiencies for uranium and plutonium. The integration of Computational Fluid Dynamics (CFD) and chemical kinetics modeling optimizes process parameters, improving reprocessing outcomes. The DUPIC method shows potential in improving reactor performance and minimizing waste. Long-term waste management strategies, such as dry cask storage and geological disposal, are also explored, with advancements in safety and heat dissipation technologies. Innovations like autonomous passive cooling and antineutrino monitoring are promising for spent fuel management security. Additionally, the study highlights Generation IV reactors and Small Modular Reactors (SMRs) as critical to minimizing nuclear energy’s environmental impact. The work emphasizes continued progress in reprocessing and waste management to address technical, economic, and environmental challenges, ensuring the viability of nuclear energy.

Nanoparticle-Assisted Phonon Transport Modulation in Si/Ge Heterostructures Using Neuroevolution Potential Machine Learning Models

Abstract Reducing thermal boundary resistance (TBR) is critical for enhancing thermal management efficiency and optimizing the performance of electronic and thermoelectric devices. In this study, we employed non-equilibrium molecular dynamics (NEMD) simulations using Neuroevolution Potential (NEP) machine learning models to investigate how embedding nanoparticles in Si/Ge heterostructures impacts TBR. Our results show a significant reduction in TBR, attributed to enhanced phonon density of states matching via resonance, promoting more efficient elastic phonon transport across the interface. However, this approach also leads to a substantial increase in bulk thermal resistance, highlighting a trade-off where overall heat dissipation is compromised. To address this, we propose an alternative strategy of positioning a nanoparticle directly at the interface to modulate interfacial modes, improving phonon transport efficiency without adversely affecting bulk thermal properties. NEMD simulations validate this approach, showing comparable TBR reduction while mitigating the bulk thermal resistance increase observed with the resonance-based embedding method. This study offers valuable insights into resolving interfacial heat dissipation challenges, providing a balanced strategy for optimizing thermal transport efficiency in nanoscale material systems.

Current Control in Field-Excited Flux Switching Machines: No-Load Induced Voltage Impact Based on the Winding Connection

Micro and mild hybrid electric vehicles can make a significant contribution to reducing emissions and mitigating the environmental impact. Electric machine designs with fewer or no rare-earth permanent magnets will play an important role in the adoption of hybrid solutions. Doubly salient reluctance machines exhibit a simple structure, robust mechanical strength, excellent fault tolerance, and a wide range of speed regulation, which makes them suitable for in-wheel applications. Particular emphasis should be placed on flux-switching machines with wound-field excitation, which offer great operating flexibility, efficient heat dissipation, and power density of up to 4.8 kW/kg. This paper introduces a wound-field flux-switching machine designed for in-wheel applications, featuring individual field current control. The machine has individual access to each of the field coils. The primary objective of this research is to enhance the machine's operational versatility by enabling multiple configurations of the machine, adjusting the way the field-coils are connected. Firstly, a comparison of the armature no-load induced voltage is made for field coils connected in both series and parallel. Additionally, an assessment of the impact of open-circuit failures in one and two adjacent field coils is conducted. Finally, a current control strategy is proposed to effectively manage each individual field coil.

NanoCoating Preparation to Improve Heat Dissipation of a Heat Sink Inside an Enclosure for Power Electronic Devices

ABSTRACTHeat sinks dissipate heat from electronic components, and the increase in heat generation owing to technological advancements has prompted researchers to improve heat sink efficiency. The present study aims to improve heat sinks by high‐emissivity nanocoating where the coating is prepared using nanoparticles CuO and MWCNT at a rate of 6% in half a liter of Acrylic resin and solvents Xylene and Butyl acetate at a rate of 30%. After coating the heat sink, the emissivity was examined and it was (0.963) while it was before coating (0.202). The heat sink is examined inside a cubic cavity with a right surface containing heaters that give temperature at the same value as the thyristors (58.5°C, 90°C, and 112.5°C) and a cold left surface (30°C). The temperatures at the tip of each fin are measured before and after coating when they change with time and at a steady state. The results showed that the nanocoating significantly reduced the temperature compared to the uncoated condition with the improvement percentage at a heater temperature of 58.5°C ranging from 10% to 15% at 90°C ranging from 24% to 34% and at 112.5°C ranging from 23% to 35%. It is concluded that the nanocoating showed great effectiveness in improving the performance of the heat sink at all temperatures, but the maximum effectiveness was at high thermal loads.

Effect of nozzle arrangement on heat dissipation performance and mechanical efficiency loss of bionic texture gear

Abstract Friction and wear are key issues in gear meshing. Lubrication, therefore, is used to reduce heat. The position and direction of the flow of the lubrication determined by the way the nozzles are injecting the fluid and by the texture on the flanks of the teeth, both have an influence on the heat transfer. Furthermore, the geometric characteristics of the tooth texture influences the friction behaviour directly. This article presents investigations on the impact of the tooth texture on wear. A proposal to prepare the tooth flanks with arc shaped grooves is made presenting the manufacturing process. Different measurements to determine the tooth flank texture and the friction are performed. Measurements showed that the arc groove gear had lower friction coefficients, wear depth, surface roughness Ra, and maximum tooth profile peak height Rq compared to conventional gears. The dynamic process of gear meshing is simulated by FEM analysis to understand the physics of heat flow and friction in detail, which revealed that the arc groove gear had reduced sliding distance, contact pressure, and wear depth, along with a higher convective heat transfer coefficient. Based on the measurement results of orthogonal test, two different nozzle arrangements are predicted: one is linear regression prediction (nozzle arrangement (A), and the other is nonlinear particle swarm optimization neural network prediction (nozzle arrangement (B). By measuring the torque loss value under the two nozzle arrangement conditions, it is found that the nozzle arrangement B is the best arrangement. The specific parameters are: injection distance is 56.0674 mm, injection angle is 8.4527°, nozzle diameter is 3.3955 mm, and pinion speed is 3000 r min−1. Under this condition, the mechanical efficiency loss is reduced by 94.48%.

Flexible and Recyclable Epoxy Vitrimer With Improved Thermal Conductivity for Thermal Management

ABSTRACTThe accelerated evolution of electronic devices has resulted in an increased demand for thermal management materials. In this study, methoxy polyethylene glycol (MPEG) was introduced into a covalent adaptable epoxy network. It is demonstrated that the epoxy material becomes softer as the amount of MPEG content is increased, specifically exhibiting excellent flexibility with an impressive elongation at break of 444.68%. The thermal conductivity of the epoxy resin was enhanced by the incorporation of boron nitride (BN) filler, and the findings demonstrated that the thermal conductivity of the composites was markedly elevated to 3.34 Wm−1 K−1 when the proportion of BN filler reached 50%. The potential use of such composites as thermal management materials is demonstrated in their application for heat dissipation in LED chips. In addition, the covalent adaptive network enables the decomposition of the composites prepared in this study under chemical conditions, with the fillers subsequently being separated by physical filtration. This approach offers a potential pathway toward the sustainable development of thermal management materials.

High-Stretchable and Thermally Conductive Elastomeric Composites for Heat Dissipation in Flexible Electronics

High-Stretchable and Thermally Conductive Elastomeric Composites for Heat Dissipation in Flexible Electronics

Unsteady Magneto-radiative Flow of Copper-water Nanofluid Over an Exponentially Stretching Surface

Understanding the complex behavior of fluid flows under various physical influences is crucial for advancing engineering and industrial applications. This paper presents the investigation of the unsteady, incompressible, single-phase magneto-radiative flow of a copper-water nanofluid over an exponentially stretching surface, considering the effects of viscous dissipation and temperature-dependent heat sources. This model, proposed in the present analysis, is based on fundamentals of the continuity and Navier–Stokesequations with mass conservation. Further, use of a similarity transformation will reduce the equations to dimensionless form and provide a numerical solution using the Runge–Kutta–Fehlberg method. In physics, engineering, and industrial applications, the most interesting parameters are the velocity, temperature, skin friction, and the Nusselt number (Nu). The results of this study are compared with previous works, showing significant agreement with findings under similar conditions. The analysis reveals that both temperature and velocity boundary layer increase when all very specific effects of radiation (R), heat source (Q), copper nanoparticle volume fraction, and magnetic field strength parameter are present. On the other hand, it is found that skin friction increases when considering both copper nanoparticle volume fraction and magnetic field strength parameter, but the Nu decreases if R, Q, copper nanoparticle volume fraction, and magnetic field strength parameter are the factors responsible for that. These outcomes will be further delineated through graphics and be elaborated in engineering and industrial context.

Promoting Heat Dissipation via a Recyclable and Self-Hygroscopic Hydrogel Membrane

Promoting Heat Dissipation via a Recyclable and Self-Hygroscopic Hydrogel Membrane

Synergistic lubrication effect of texture and copper on cutting performance for broaching tool

Abstract The broaching process is a heavy-duty and highly efficient metal cutting technique. The heavy load encounters significant thermal and mechanical stresses on the tool during broaching, resulting in considerable friction within the tool-chip contact area. The friction adversely affects both workpiece quality and tool life. To address this issue, laser technology is utilized in this study to create three distinct textures on the rake face of the broach. Subsequently, an innovative rotary covering device is developed to cover a solid lubricant (copper) onto both surfaces and grooves of cutting tool. Broaching test is conducted to evaluate the impact of different textures and copper on chip morphology, including chip deformation and burr width. The findings demonstrate that employing a stripe-textured broach reduces the chip deformation coefficient by 16.1% compared to its non-textured counterpart. Furthermore, covering copper through rotational friction leads to an additional reduction of 7.7% in the chip deformation coefficient. Copper not only repairs surface defects but also forms a lubricating film during cutting operations, thereby serving as an effective solid lubricant. The synergistic interaction between texture and copper enhances heat dissipation during cutting processes, consequently reducing temperatures within the tool-chip contact area. The temperature reduction alleviates plastic deformation in localized regions of the workpiece, resulting in narrower burrs. Therefore, the use of rotary friction for covering copper onto the rake face of a broaching tool represents a straightforward yet cost-effective strategy for optimizing frictional conditions and enhancing the cutting performance.

High-power (500 mW) narrow-linewidth (21 kHz) low-RIN (−168 dB/Hz) distributed feedback laser

A high-power, narrow-linewidth, low-relative-intensity-noise (RIN) distributed feedback (DFB) laser is demonstrated. The laser employs four strained AlGaInAs quantum wells and three diluted waveguides to reduce internal loss, and enhance heat dissipation performance to reach a high power and low noise operation. At a test temperature of 15 °C, the DFB laser with a cavity length of 1.5 mm exhibited single mode output power of 517 mW in pulsed mode and 424 mW in continuous-wave (CW) mode. with far-field full width at half maximum (FWHM) divergence angles of 10°×20°. In addition, the DFB laser achieved an intrinsic linewidth of 21 kHz, and an ultra-low RIN of less than −168 dB/Hz.

A Conceptual Study of Rapidly Reconfigurable and Scalable Bidirectional Optical Neural Networks Leveraging a Smart Pixel Light Modulator

We explore the integration of smart pixel light modulators (SPLMs) into bidirectional optical neural networks (BONNs), highlighting their advantages over traditional spatial light modulators (SLMs). SPLMs enhance BONN performance by enabling faster light modulation in both directions, significantly increasing the refresh rate of neural network weights to hundreds of megahertz, thus facilitating the practical implementation of the backpropagation algorithm and two-mirror-like BONN structures. The architecture of an SPLM-based BONN (SPBONN) features bidirectional modulation, simplifying hardware with electrical fan-in and fan-out. An SPBONN with an array size of 96 × 96 can achieve high throughput, up to 4.3 × 1016 MAC/s with 10 layers. Energy assessments showed that the SPLM array, despite its higher power consumption compared to the SLM array, is manageable via effective heat dissipation. Smart pixels with programmable memory in the SPBONN provide a cost-effective solution for expanding network node size and overcoming scalability limitations without the need for additional hardware.

A Method for Sensing the Internal Current Distribution State of Press-Pack IGBT Devices Based on Hall Sensors

Flexible DC transmission technology is an important support for constructing new power systems. The press-pack IGBT device has the advantages of double-sided heat dissipation and high power density in series and is the core device in the flexible HVDC project. However, the compact parallel arrangement of multiple chips in the press-pack IGBT (PPI) device easily causes uneven current distribution in the device, which affects its reliability. In this paper, a noninvasive sensing method for the internal current distribution of the PPI device is proposed based on the measurement of the external magnetic field and the numerical analysis of the magnetic field. According to the correlation between the device current distribution and the external magnetic field, a noninvasive current distribution sensing method based on the measurement and numerical analysis of the external magnetic field is proposed, and the placement strategy of the magnetic field measurement points is given. The error of the perception method under ideal conditions is analyzed, the error size and rule are summarized, and the correction methods are given, respectively. Finally, a magnetic field measuring device is designed and verified by experiments. The results can accurately indicate the direction of pressure deviation.

Study on the thermal control performance of lightweight minimal surface lattice structures for aerospace applications

Study on the thermal control performance of lightweight minimal surface lattice structures for aerospace applications

Joule heating and viscous dissipation impact on MHD-hybrid nanofluid flow over non-isothermal stretching/shrinking surface: Dual solution and stability analysis

Joule heating and viscous dissipation impact on MHD-hybrid nanofluid flow over non-isothermal stretching/shrinking surface: Dual solution and stability analysis