Heat Dissipation In Devices Research Articles

Efficient heat dissipation in devices by graphene/hexagonal boron nitride in-plane heterostructure

Efficient heat dissipation in devices by graphene/hexagonal boron nitride in-plane heterostructure

Thermal conductivity enhancement of polyethylene glycol/NF composite as stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG) has the advantages of large latent heat of phase transition, a wide range of phase transition, and cheap price, but the application of PEG in the latent thermal energy storage (TES) systems is hindered due to its lower heat transfer rate and leakage. Porous metal foam has excellent thermal conductivity and high strength, which can effectively improve the problems of PEG. In this study, PEG/nickel foam (NF) composite phase change materials (PCM) were prepared by vacuum molten impregnation method using NF as substrate. It was found that PEG had good compatibility with NF, and the highest impregnation rate of PEG6000/NF reached 85.73 %. The thermal conductivity of PEG2000/NF can be increased to 1.58 1.58 W·m−1 K−1, nearly 4 times larger than that of pure PEG. The phase change temperature range of the composite PCM is 51–63 °C, and the phase change enthalpy is 67.8–126.3 J·g−1. Furthermore, the PEG/NF composite demonstrated outstanding photothermal conversion properties and high thermal stability, which can be widely used in the field of building temperature control and device heat dissipation.

Volume-Metallization 3D-Printed Polymer Composites.

3D printing polymer or metal can achieve complicated structures while lacking multifunctional performance. Combined printing of polymer and metal is desirable and challenging due to their insurmountable mismatch in melting-point temperatures. Here, a novel volume-metallization 3D-printed polymer composite (VMPC) with bicontinuous phases for enabling coupled structure and function, which are prepared by infilling low-melting-point metal (LM) to controllable porous configuration is reported. Based on vacuum-assisted low-pressure conditions, LM is guided by atmospheric pressure action and overcomes surface tension to spread along the printed polymer pore channel, enabling the complete filling saturation of porous structures for enhanced tensile strength (up to 35.41MPa), thermal (up to 25.29Wm-1K-1) and electrical (>106Sm-1) conductivities. The designed 3D-printed microstructure-oriented can achieve synergistic anisotropy in mechanics (1.67), thermal (27.2), and electrical (>1012) conductivities. VMPC multifunction is demonstrated, including customized 3D electronics with elevated strength, electromagnetic wave-guided transport and signal amplification, heat dissipation device for chip temperature control, and storage components for thermoelectric generator energy conversion with light-heat-electricity.

Wearable thermoelectric cooler encapsulated with low thermal conductivity filler and honeycomb structure for high cooling effect

Thermoelectric coolers (TEC) based on Peltier effect has been widely used in small scale cold storage because of its zero emission, and high efficiency, while wearable thermoelectric coolers (WTEC) for personal temperature management is garnered tremendous scientific attention. For out-of-plane structured WTEC using inorganic TE materials encapsuled in flexibility substrate, on the one hand, encapsulating materials are required to have low thermal conductivity, high reliability and high flexibility, and on the other hand, heat dissipation of devices is required to be lightweight, portable and efficient. For this reason, we propose a composite material synthesised from SiO2 aerogel, hollow glass beads (HGB) and polydimethylsiloxane (PDMS) as a filler, which takes advantage of the low thermal conductivity of (0.094 W/mK) to increase the temperature difference in the encapsulation layer of the device, and moreover performs the fabrication of honeycomb holes, which further reduces the thermal conductivity of the encapsulation layer and at the same time brings a certain degree of compression resistance to the device. Radiative cooling (RC) films synthesised using hexagonal boron nitride (HBN) and PDMS for lowering the temperature of the hot side in outdoor environments without additional energy consumption, providing heat dissipation at the hot side. Honeycomb wearable thermoelectric cooler (HWTEC) proposed in this work deliver high cooling temperature difference of 9.1 °C and 6.5 °C indoor and outdoor through human wear. Our work represents an important step in the development of flexible TE devices and is believed to have promising future applications in personal thermal management, e-skin and smart textiles.

Heat Dissipation Mechanisms in Hybrid Superconductor-Semiconductor Devices Revealed by Joule Spectroscopy.

Understanding heating and cooling mechanisms in mesoscopic superconductor-semiconductor devices is crucial for their application in quantum technologies. Owing to their poor thermal conductivity, heating effects can drive superconducting-to-normal transitions even at low bias, observed as sharp conductance dips through the loss of Andreev excess currents. Tracking such dips across magnetic field, cryostat temperature, and applied microwave power allows us to uncover cooling bottlenecks in different parts of a device. By applying this "Joule spectroscopy" technique, we analyze heat dissipation in devices based on InAs-Al nanowires and reveal that cooling of superconducting islands is limited by the rather inefficient electron-phonon coupling, as opposed to grounded superconductors that primarily cool by quasiparticle diffusion. We show that powers as low as 50-150 pW are able to suppress superconductivity on the islands. Applied microwaves lead to similar heating effects but are affected by the interplay of the microwave frequency and the effective electron-phonon relaxation time.

Magnetic refrigeration enhanced by magnetically-activated thermal switch: An experimental proof-of-concept

In the era of energy transition and climate change, environmentally safe refrigeration technologies are of utmost importance. Magnetocaloric refrigeration (MCR) is one of the most promising alternatives to the existing vapor-compression systems. Overcoming the primary challenges of the low heat dissipation and elevated device production costs is imperative for MCR development. This work provides the first demonstration of an MCR prototype that combines the magnetocaloric material (MCM) gadolinium with a ferrofluidic thermal switch (TS). The performance was assessed using dispersions of MnFe2O4/Ethylene Glycol:Water and Fe3O4/paraffin oil. For the first time, a strategic asymmetry was introduced into MCR cycles. The inclusion of the TS did not uncover any advantages in the Gd-alone system by using symmetrical cycles. However, by applying/removing the magnetic field asymmetrically, a remarkable temperature span of up to 0.6 °C was achieved within the TS+MCM prototype. This represents a substantial improvement, reaching up to 60% compared to the Gd-alone configuration. The prototype ensures that a single magnetic field, responsible for driving the magnetocaloric effect, also activates the TS, thereby streamlining system operability and improving performance. To validate our findings, we developed a 1D numerical model, which consistently confirmed that system optimization can be achieved through the exclusive use of asymmetric cycles. Consequently, the application of magnetically-activated fluidic TSs and asymmetric cycles emerge as important strategies for enhancing MCR across a diverse range of systems.

Research Status of Heat Dissipation Technology for Electric Vehicle Drive Motors

Background:: The application of electric vehicles in daily life is becoming increasingly widespread. However, the heat dissipation issues of the electric motors directly impact electric vehicles' stability and safety. Thus, research on the heat dissipation of the electric motor is conducive to improving the reliability of the drive motor and ensuring the overall stability and safety of electric vehicles; there is a growing emphasis on the development trends of heat dissipation technologies for electric vehicle drive motors. Objective:: In order to meet the increasing requirements of electric vehicles for stability and safety and to solve the problems of low heat dissipation efficiency of electric vehicle drive motors, the size of heat dissipation devices, and the short life span caused by the high temperature of drive motors, the heat dissipation of drive motors is optimized and the heat dissipation structure is improved. Methods:: Based on the structural characteristics of heat dissipation of electric vehicle drive motors, various representative patents related to the current heat dissipation technology of electric vehicle drive motors are summarized. Results:: By summarizing a large number of patents on electric vehicle drive motor heat dissipation technology, it is concluded that the current research on electric vehicle drive motor heat dissipation mainly focuses on liquid heat dissipation or gas heat dissipation and that the main reason for the heat dissipation problem of electric vehicle drive motors is the low heat dissipation efficiency due to over-reliance on a single heat dissipation method, and the reliability is poor due to failure to reasonably control heat dissipation according to the need for heat dissipation. This paper proposes a new idea of heat dissipation for electric vehicle drive motors, which effectively combines liquid heat dissipation and gas heat dissipation. Moreover, the heat dissipation efficiency will be significantly higher than the existing heat dissipation scheme, and the proposed heat dissipation concept of "ondemand distribution" will effectively improve the utilization rate of the heat dissipation medium and reduce the heat dissipation cost and the reasonable heat dissipation structure will reduce the volume of the heat dissipation device. The reasonable heat dissipation structure will also reduce the volume of the heat dissipation device. In addition, the future development of heat dissipation technology for electric vehicle drive motors is also discussed. Conclusion:: The heat dissipation scheme proposed in this paper will effectively improve the heat dissipation problem of electric vehicle drive motors. Compared with the existing heat dissipation methods, the heat dissipation efficiency of the heat dissipation scheme proposed in this paper will be improved by more than 8.5%, and the service life of the drive motor will be extended by more than 5.1%, while the size of the electric vehicle drive motor will be reduced by 6%. More related patents will be invented in the future.

Direct observation of tunable thermal conductance at solid/porous crystalline solid interfaces induced by water adsorbates

Improving interfacial thermal transport is crucial for heat dissipation in devices with interfaces, such as electronics, buildings, and solar panels. Here, we design a strategy by utilizing the water adsorption-desorption process in porous metal-organic frameworks (MOFs) to tune the interfacial heat transfer, which could benefit their potential in cooling or heat dissipation applications. We observe a changeable thermal conductance across the solid/porous MOF interfaces owing to the dense water channel formed by the adsorbed water molecules in MOFs. Our experimental and/or modeling results show that the interfacial thermal conductance of Au/Cu3(BTC)2, Au/Zr6O4(OH)4(BDC)6 and Au/MOF-505 heterointerfaces is increased up to 7.1, 1.7 and 3.1 folds by this strategy, respectively, where Cu3(BTC)2 is referred to as HKUST-1 and Zr6O4(OH)4(BDC)6 is referred to as UiO-66. Our molecular dynamics simulations further show that the surface tension of Au layer will cause the adsorbed water molecules in MOFs to gather at the interfacial region. The dense water channel formed at the interfacial region can activate the high-frequency lattice vibrations and act as an additional thermal pathway, and then enhance heat transfer across the interfaces significantly. Our findings revealed the underlying mechanisms for tailoring thermal transport at the solid/porous MOF heterointerfaces by water adsorbates, which could motivate and benefit the new cooling system design based on MOFs.

Pool boiling heat transfer performance of micro-embossing molds for the fabrication of polymer wicks

As flexible heat dissipation devices are urgently needed for flexible electronics, polymers with the advantages of good flexibility, insulation, and low density have attracted wide attention. It would be interesting to fabricate thermal functional structures on polymers to overcome their low thermal conductivity. This study aims to design and fabricate a micro-embossing mold to process polymer three-dimensional microgroove wicks (3D-MWs), which are applied in flexible heat pipes and achieve high thermal conductivity. Three kinds of tungsten steel molds were processed by using two wire electrical discharge machining processes (WEDM), two electrical discharge shaping machining processes (EDSM), and a combination of WEDM and EDSM. The 3D-MWs of the tungsten steel mold were reprinted onto the polymer films by a two-step embossing process. To investigate the effects of microstructures on boiling heat transfer performances, tungsten steel molds fabricated by different methods were tested to reflect the heat dissipation potential of the polymer 3D-MWs. The results showed that the 3D-MWs fabricated by the combination of WEDM and EDSM exhibit good boiling heat transfer performance and high processing efficiency, with a critical heat flux of 1040.1 kW/m2 and a maximum heat transfer coefficient of 38.4 kW/m2·°C. These values are 46% and 611% higher than those of the smooth tungsten steel surface, respectively, making it a superior choice for micro-embossing molds.

Ultralow Voltage Resistive Switching in Hafnium–Zirconium Oxide

AbstractUltralow SET and RESET voltage are essential for high‐density, low‐power, and small heat dissipation nonvolatile random‐access memory (NVRAM) elements. A nanoscale polycrystalline Hf0.75Zr0.25O2 (HZO) thin films on Pt/Si substrate are fabricated and investigated for suitability for bipolar resistive switching. The device illustrates monoclinic and tetragonal/orthorhombic phases with weak ferroelectricity and robust resistive switching. Small remanent polarization (≈0.1 μC cm−2) may assist in the height reduction of barrier height and ease the electron for transport. Remarkably, the Al/HZO/Pt/Si device, consisting of thin films with 10 and 5 nm thicknesses, exhibits a switching voltage below −30 mV from a low‐resistance state (LRS) to a high‐resistance state (HRS). It shows a significant ROFF/RON ratio of 106, making it suitable for low power consumption and minimal heat dissipation devices. Moreover, the utilization of an ultrathin film (5 nm) results in an improved reduction (< 0.7 V) of the operating window at the positive voltage. Direct tunneling and the Fowler–Nordheim tunneling model are performed in current–voltage (I–V) data to study the charge transportation behavior over a trapezoidal and triangular potential barrier. These results of the HZO candidate may stimulate the futuristic nonvolatile resistive random‐access memory (ReRAM) in the optoelectronic industry.

Molecular dynamics study of boiling heat transfer in nanochannels under capillary flow

The increasing heat flux of electronic devices poses significant challenges in thermal management. Passive heat dissipation technology based on capillary drive has been widely concerned because it does not require external driving force and stability. However, due to the small size of the internal capillary structure, typically in the micro and nano scales, and the significant scale effect, further research is needed to understand the mechanism of internal boiling heat transfer. This study systematically investigates the boiling process of liquid in nanochannels under capillary flow with varying wettability using molecular dynamics simulations. It is found that increasing the energy coefficient (c) causes a greater accumulation of atoms near the wall, thereby enhancing the efficiency of solid–liquid heat transfer. The bubble has a larger stable volume as c increases and will burst in the case of high c. As c increases, the region of high potential and kinetic energy expands more rapidly, reducing the time it takes for bubble nucleation and rupture. The behavior of bubbles is significantly influenced by capillary flow, which is also influenced by wettability. When c = 0.9, the flow velocity reaches its maximum before bubble nucleation occurs. It leads to a more homogeneous heat transfer, resulting in a higher location of bubble nucleation. Furthermore, the presence of capillary forces increases the average potential energy of surrounding liquid atoms, thereby enhancing the growth rate of the bubble. This study provides a theoretical basis for the optimal design of capillary-driven two-phase heat dissipation devices.

Study on the microstructure and properties of HfCxNy-Cu composites prepared by spark pulse sintering

In this work, novel HfCxNy-Cu composites with varying HfCxNy contents were fabricated via subsequent spark pulse sintering (SPS). The influence of HfCxNy addition on the mechanical properties, wear properties, and electrical conductivity of the HfCxNy-Cu composites was systematically studied. The 5HCu composites exhibit a hardness of 136.8 HV and an electrical conductivity of 50.2 % ICAS. Whereas, the hardness of the 10HCu composites increased to 148.3 HV. Moreover, 5HCu composites rather than 10HCu exhibited better lubrication performance and wear resistance, the average friction coefficient and wear rate were measured to be 0.41 and 0.026 mg/min, respectively. The potential applications of HfCxNy-Cu composites include high-temperature structures and electronic device heat dissipation.

Heat Dissipation Design Based On Topology Optimization And Auxiliary Materials

Abstract In this paper, a variable density topology optimization method is used to design a high thermal conductivity path structure for efficient heat dissipation. The temperature and stiffness in the module volume are taken as the objective function. Simulations are carried out to compare with a high-power electronics device heat dissipation. The heat dissipation performance (HDP) of structures optimized topologically is further enhanced through the use of auxiliary materials, including highly thermally conductive coating material and phase change material (PCM). The efficient heat dissipation of the constructed topology optimization model and the effectiveness of the proposed method are verified.

Recent Developments in CTE-Matched Composite Thermal Materials

A surprisingly large number of engineered materials are available to the module and system packaging engineer that have been designed for a target coefficient of thermal expansion (CTE, stated both at room temperature and across a specified range of temperatures) and possessing bulk thermal conductivity values useful for device heat dissipation. There are continuing research and development programs for new forms and variations of such materials, intended to meet continuing demands for improvement on a spectrum of requirements. These requirements include higher bulk isothermal conductivity values, lower cost, lower CTE values, reduced density and weight, and, for certain types of applications, a target CTE and highly anisotropic property. This discussion seeks to identify both existing and common materials (for comparison purposes) and new developments that are being brought to market and/or are in production today. The purpose is to add to the design engineer’s tool kit for available materials of these types. In addition, high temperature effects on selected materials are illustrated.

Heat dissipation promotion of LED chips by c-BN film

The light-emitting diodes (LEDs) are now the most important lighting devices due to their excellent wall-plug efficiency (WPE). However, their unique structure means that heat dissipation from the chip can only be achieved by conduction. The insulating thermal conductivity layer becomes a bottleneck in the heat transfer of the chip, seriously affecting its lifetime and reliability. Cubic boron nitride (c-BN) has good thermal stability, electrical insulation and high thermal conductivity, making it a potential insulating and heat dissipating material. In this study, we investigate the application of c-BN films to promote heat dissipation in LEDs based on c-BN films grown by physical vapor deposition (PVD) sputtering. In our study, we highlighted the performance variations between c-BN and Si substrates under different driving powers, ranging from 9 W to 12 W. By incorporating the c-BN film onto the Si substrate, we observed a distinct improvement in the temperature distribution of the LED array. Specifically, with a driving power of 9 W, the temperature was reduced by approximately 4.1 °C, and with 12 W, the reduction reached 16.8 °C. This enhanced thermal management not only augments the stability and lifespan of the components but also boosts the optical output power of the LED chip array, with an increase ranging from 21.3% to 27.9%. We find that c-BN films can effectively enhance chip heat dissipation, significantly improve WPE, and suppress light decay, as demonstrated by temperature distribution and luminescence power measurements. The experimental and simulation results demonstrate that c-BN films can reduce the temperature of LED beads by approximately 5–17 °C compared to Si substrates. This c-BN thin film substrate shows promise for use in commercial device heat dissipation structures.

A critical review on single-phase thermo-hydraulic enhancement in geometrically modified microchannel devices

The usage of liquid-cooled microchannel heat dissipation devices is gaining importance in thermal management of electronic components owing to miniaturization. The development of such devices requires a deeper knowledge of the flow characteristics within geometrically modified microchannels. This article critically examines the research on modifications in geometry of channels for thermo-hydraulic performance enhancement. The article aims to determine the best channel configuration with optimal parameters that can maximize the overall performance of the device. For this purpose, collected research have been scrutinized in ascending order of the complexity in channel design. This article explores various designs and their influencing parameters, starting with linear and non-linear microchannel shapes, followed by bifurcated and connected secondary channels and, in the end, configurations with structured roughness such as cavities, ribs and cavity-rib combinations in it. Finally, conclusions of the examined research are presented with an analysis of their implications as well as gaps and potential recommendations for future research.

Thermal enhancement of heat sinks with bio-inspired textured surfaces

The current requirements of the electronics industry for heat sink design are to increase heat dissipation and to reduce the occupied space and weight. Research to improve the thermal efficiency and reduce the size of heat sinks has mainly been conducted by modifying their geometry to increase the heat transfer area. In the field of tribology research, one way to modify a surface is to apply texture, which involves reducing the contact area but increasing the external area, which in turn could improve the performance of heat dissipation devices. In this paper, bio-textured surfaces are fabricated on straight fin heat sinks and numerically evaluated by thermal finite element analysis. The simulation results are validated by experimental measurements on a single-fin heat sink. The potential of surface texturing in heat sinks is demonstrated here through a numerical parametric analysis of a full-scale heat sink. The results show a reduction in operating temperatures of more than 26 %, reduction in thermal resistance around 34 % and increase between 21 % and 40 % of heat sink effectiveness for textured surface heat sinks compared to smooth fin heat sinks, depending on the convection coefficient. These results suggest that the design methodology proposed here is more relevant for heat sinks used in high power dissipation applications such as computer CPUs and GPUs.

Performance analysis of a novel flat lay-type synthetic jet pump with Y-shaped jet chamber.

Recently, synthetic jet pumps have been expected to be used in electronic heat dissipation devices due to the vortex suction phenomenon for transporting fluids. Aiming to improve the delivery ability of the jet pump to output fluid continuously, a novel flat lay-type synthetic jet pump (FLTSJP) with a Y-shaped jet chamber is proposed in this paper. Based on the synthetic jet effect, the pump chamber continuously outputs fluid in one cycle. The output performance of FLTSJP is theoretically analyzed to be affected by the outlet cone angle. The one-cycle flow mechanism of the fluid in the Y-shaped jet chamber is simulated. FLTSJP is manufactured, and a test system is built. Experiments show that the Y-shaped jet chamber effectively improves the output performance. The optimum flow rate and outlet pressure were both reached at 160V and 40Hz, which were 20.63 ml/min and 333.43Pa, respectively. This FLTSJP effectively improves the output performance of synthetic jet pumps and provides a new research concept of water-cooled devices for electronic heat dissipation.

Enhancing heat transfer performance in 3D-printed integrated vapor chamber using composite structures

The demand for lightweight heat dissipation devices in aerospace and various other fields has spurred the development of aluminum-based vapor chambers. However, the surface of the aluminum particles is covered by a dense alumina layer, which poses a challenge in preparing the aluminum-based porous wick structure by sintering aluminum powder. In this study, two aluminum-based vapor chambers (60 mm × 50 mm × 4 mm) with distinct wick structures were integrated with the container utilizing 3D technology. The wicks of the vapor chamber included an aluminum-based grooved wick structure (GVC) and an aluminum-based grooved-porous composite wick structure (GPVC). A comprehensive experiment was conducted to evaluate the heat transfer characteristics of the vapor chamber, including startup performance, temperature uniformity, and thermal resistance, under different filling ratios and wick structure parameters. The working fluid was acetone. The results indicated that the GPVC demonstrated excellent startup performance under both low and high heat loads. The startup time of the GPVC was found to be 230 s, 30.3% less than that of the GVC under a heat load of 80 W. Furthermore, at a 60% filling ratio, the GPVC demonstrated lower thermal resistance and better temperature uniformity compared to the GVC. The GPVC achieved a minimum thermal resistance of 0.033 K/W with a maximum temperature difference of only 4.51 °C. This resulted in a reduction of thermal resistance by 47.5% and an improvement in temperature uniformity by 69%. The findings of this study provide valuable insights to the application of 3D printing technology to the production of aluminum-based composite porous wick structures.

Design of Injection Mould for Lithium Battery Heat Dissipation Device Connector Bottom Cover

The design process of the injection mould for the Lithium battery heat dissipation device connector bottom cover is described in detail. In the design process, the UG software is used to establish the three-dimensional model of the plastic part, and the mould flow analysis is carried out with the help of the moldflow software to determine the optimal gate position of the plastic part. By determining the injection process parameters of Lithium battery heat dissipation device connector bottom cover material, the design of the cavity layout of the plastic part is completed, and the basic size and mould structure of the mould base are determined. Then, the UG injection mould design guide module was used to carry out the parting design, and the structural design of the mould’s gating system, molding parts, lateral parting mechanism, core-pulling mechanism, ejection mechanism, exhaust system and cooling system was completed in turn. The whole design process improved the efficiency of mould design and saved a lot of time and cost.