Effective Heat Dissipation Research Articles

Characteristics of motor temperature distribution in plateau

The motor temperature distribution characteristics help to understand the working condition of the unit, thus improving efficiency. Currently, the motors are gradually being used at high altitudes. However, the plateau region has low air pressure, thin air and large differences in humidity. There is a lack of research on the effect of its complex and special working environment on motor temperature. Therefore, in this study, the numerical analysis of the motor temperature field is carried out from the novel perspective of plateau characteristics. In this paper, the finite volume method is used to analyse the flow-heat-solid coupling of a 20 MW motor. By comparing and verifying the experimental data with the simulation data, it is found that the error between the two is within 5 %. In order to have a more comprehensive picture of the motor's operation in the plateau environment, the temperature effects of different air pressure, air intake and relative humidity on the motor were investigated. The results of the study show that air pressure changes have a large effect on the temperature of the stator structure. The temperature decreases when the air pressure increases and the temperature difference decreases gradually with the increase of air pressure. The largest temperature difference in the stator structure occurs when the air pressure increases from 10 kPa to 40 kPa. The change in air intake has a positive effect on the stator structure temperature, which decreases when the air intake increases. After simulation calculations, it was found that the best heat dissipation effect was achieved in the range of air intake between 3.5 m/s and 4.5 m/s. Relative humidity has a minimal effect on the stator structure temperature. The conclusions of this paper can provide certain theoretical reference for the temperature change law of the motor under plateau operation, which is of great significance to improve the comprehensive hydraulic performance.

Research on the Influence of Biomimetic Patterns Surface on the Surface Temperature of Drum Brake Lining

Vehicles need to brake frequently on long downhill sections. In this case, the surface of the friction lining is prone to accumulating a large amount of heat, which will reduce the performance of the braking material and lead to braking failure. This article analyzes the heat generation and dissipation mechanism during the braking process of drum brakes based on the law of energy conservation, and establishes a thermal conductivity differential equation. Subsequently, with the honeycomb texture as the biomimetic target, circular, square, and honeycomb patterns with different parameters were designed on the surface of the friction lining, and a finite element model was established using Ansys Workbench. Thermodynamic coupling analysis shows that patterned friction lining can reduce the maximum temperature of the braking surface. Honeycomb patterns have better heat dissipation effects than circular and square patterns. Compared with non patterned brake pads, honeycomb patterns can reduce the maximum surface temperature of brake pads by 14.6%. When the surface area ratio of the honeycomb is 56.8%, its heat dissipation effect is the best.

Thermal behavior and dynamics of flow boiling in a pin-fin microchannel

As the need for effective heat dissipation in specialized systems intensifies, the study of flow boiling in microchannels has gained prominence due to its high efficiency and cost benefits. Utilizing a three-dimensional computational model incorporating the Volume of Fluid (VOF) and Saturated Interfacial Volume (SIV) methodologies, this research scrutinizes the behavior of saturated flow boiling in a microchannel featuring a centrally positioned, heated square cylinder. The analysis focuses on variations in bubble morphology, fluidic behavior, and thermal profiles, revealing that the evaporation of a thin liquid film contributes significantly to heat transfer efficacy. A systematic assessment of temperature gradients, heat transfer coefficients, and liquid film metrics uncovers the critical drivers behind effective heat transfer across different surfaces. Additionally, the study elucidates the role of Reynolds number and initial bubble size, indicating that higher Reynolds numbers thicken the liquid film, reducing heat transfer efficiency, while larger initial bubble diameters thin the liquid film, thereby boosting efficiency. Factors such as thermal boundary layer disruption and superheated fluid absorption further contribute to heat transfer optimization. This investigation enriches the current understanding of phase-change heat transfer dynamics and bubble interactions in microchannel environments equipped with a heated square cylinder.

Study on Parameters Influencing Heat Dissipation Performance of Body-Mounted Fluid Tube Radiators

Body-mounted fluid tube radiators (BMFTR) serve as integral components in manned spacecraft and are crucial for effective heat dissipation. This study presents a comprehensive simulation analysis model for BMFTR, accounting for the errors in simulation accuracy resulting from assumptions of constant parameters. Through simulation analysis, this research investigates the multifaceted influences of parameters—such as spacecraft orbital β angle, solar absorptivity of coating, fluid temperature, and fluid flow rate—on the heat dissipation performance of BMFTR. Quantitative assessments uncover distinct impacts of these parameters on radiator performance. The findings offer insights essential for optimizing the operating conditions of BMFTR, providing guidance for enhanced operational management during missions in orbit. This work contributes to advancing radiator technology and facilitating efficient heat management in space exploration.

Soft and Damping Thermal Interface Materials with Honeycomb-Board-Mimetic Filler Network for Electronic Heat Dissipation.

High-power-density electronic devices under vibrations call for soft and damping thermal interface materials (TIMs) for efficient heat dissipation. However, integrating low hardness, high damping, and superior heat transfer capability into one TIM is highly challenging. Herein, soft, damping, and thermally conductive TIMs are designed and prepared by constructing a honeycomb-board-mimetic boron nitride nanosheet (BNNS) network in a dynamic polyimine via one-step horizontal centrifugal casting. The unique filler network makes the TIMs perform a high through-plane thermal conductivity (> 7.69W m-1 K-1) and a uniform heat transfer process. Meanwhile, the hierarchical dynamic bonding of the polyimine endows the TIMs with low compressive strength (2.16MPa at 20% strain) and excellent damping performance (tan δ > ≈0.3 at 10-2-102Hz). The resulting TIMs also exhibit electrical insulation and remarkable recycling ability. Compared with the commercial ones, the TIMs provide better heat dissipation (4.1°C) for a high-power 5G base station and less temperature fluctuation (1.8°C) for an automotive insulated gate bipolar transistor (IGBT) under vibrations. This rational design offers a viable approach to prepare soft and damping TIMs for effective heat dissipation of high-power-density electronic devices under vibrations.

Substrate dependence of the self-heating in lead zirconate titanate (PZT) MEMS actuators

Lead zirconate titanate (PZT) thin films offer advantages in microelectromechanical systems (MEMSs) including large motion, lower drive voltage, and high energy densities. Depending on the application, different substrates are sometimes required. Self-heating occurs in the PZT MEMS due to the energy loss from domain wall motion, which can degrade the device performance and reliability. In this work, the self-heating of PZT thin films on Si and glass and a film released from a substrate were investigated to understand the effect of substrates on the device temperature rise. Nano-particle assisted Raman thermometry was employed to quantify the operational temperature rise of these PZT actuators. The results were validated using a finite element thermal model, where the volumetric heat generation was experimentally determined from the hysteresis loss. While the volumetric heat generation of the PZT films on different substrates was similar, the PZT films on the Si substrate showed a minimal temperature rise due to the effective heat dissipation through the high thermal conductivity substrate. The temperature rise on the released structure is 6.8× higher than that on the glass substrates due to the absence of vertical heat dissipation. The experimental and modeling results show that the thin layer of residual Si remaining after etching plays a crucial role in mitigating the effect of device self-heating. The outcomes of this study suggest that high thermal conductivity passive elastic layers can be used as an effective thermal management solution for PZT-based MEMS actuators.

Dynamic Response of Phase Change Heat Exchange Unit with Layered Porous Media for Pulsed Electronic Equipment

Effective heat dissipation challenges transient high-power electronic devices in hypersonic vehicle cabins. This study introduces a Phase Change Heat Exchange Unit with Layered Porous Media (PCHEU–LPM) employing pulsed heat flow at the top and forced convection at the bottom. The primary aim was a comparative parametric study analyzing the thermal response of the heating surface under pulsed heat flow conditions. The geometric model was generated using electron microscopy images of manufactured objects and the numerical model was established based on the enthalpy–porosity method. Numerical simulations explored amplitude and frequency effects on pulsed thermal excitation, evaluating temperature and phase fields. A comprehensive time-frequency transformation assessed the temperature response. The results indicated an initial decrease and subsequent increase in interface temperature fluctuation with pulse heat flux amplitude growth. Temperature field uniformity correlated with natural convection strength in two-phase and liquid-phase regions. At mid and low frequencies, the phase change process increasingly suppressed interface temperature fluctuations. Optimal pulse thermal excitation selection was crucial for minimizing temperature fluctuations while maintaining the interface temperature within the expected phase transition range. In conclusion, a novel design concept is posited herein, aiming to enhance surface temperature uniformity and broaden the applicability of electronic devices through the manipulation of porosity rates.

Fabrication and heat dissipation performance of diamond/Cu composite with diamond bars inserted in the normal direction

In this paper, a new type of diamond/Cu composite with diamond bars inserted in the normal direction is designed and prepared by vacuum brazing. In order to reduce the negative effect of the low thermal conductivity of Cu-Sn-Ti solder, diamond particles were added into the solder area. The microstructure, thermal conductivity, and heat dissipation performance of the diamond/Cu composite under water-free and water-cooling conditions were studied and compared. Besides, the heat dissipation mechanism of the composite was explored through finite element analysis. The results show that the diamond bars and diamond particles can be connected well by the CuSnTi solder, and the diamond particles scatter in the solder area. The TC tests show that the sample with 2000 mesh diamond particles has the highest TC (515.25 W/(m·K)). Besides, both the heating experiments on the electronic heating platform and the actual heat dissipation performance under water-cooling conditions affirm the excellent heat dissipation effect of the composite with 2000 mesh diamond particles. In conclusion, the diamond/Cu composite with diamond bars inserted vertically possess an excellent structural design, which is promising in heat dissipation material for electronic devices.

Surface functionalization of naturally occurring silicate minerals infused hydrocarbon polymer matrix for ultra‐low dielectric performance at high frequency domain

AbstractThe expanding realm of high‐frequency electronics necessitates materials with exceptional attributes: notably, a low dielectric constant (Dk) to minimize signal propagation delays, high thermal conductivity for effective heat dissipation, higher breakdown strength, and robust mechanical properties to withstand demanding operational environments. While cycloolefin copolymers (COC) excel in electrical insulation, chemical resistance, and mechanical durability, their intrinsic slightly higher dielectric constant compared to other polymers, along with challenges such as poor dispersibility and low compatibility with nanoparticles, hinder their full potential in this domain. Considering these drawbacks, this study fabricated a series of COC/mica composites by integrating natural mica particles into the COC matrix via a CTAB‐assisted surface modification of mica to enhance dispersibility and mitigating particle aggregation through in‐situ mixing and hot‐press methods. The resultant composites demonstrate an outstanding ultra‐low Dk of 1.44, marking a significant decrease of over 36% compared to pristine COC with a Dk of 2.26, along with exceptionally low dielectric loss (δ) of 0.00013 at the frequency of 10 GHz, high dielectric breakdown strength ~49.40 kV/mm and enhanced thermal conductivity up to 0.88 W/(m K) at 40% mica loading. Additionally, the composites heightened mechanical performances like tensile strength 69 MPa at 6.5% elongation at break, impact strength up to ~17.9 kJ × m−2, and exceptional water resistance with absorption below 0.097%. These exceptional ultra‐low dielectric performance with above mentioned properties can meet the stringent requirements of modern high‐frequency electronics packaging for next generation electronics development.Highlights Surface modification by CTAB enhanced homogeneous dispersibility of composites. Achieved ultra‐low dielectric constant and loss compared to pure COC. Thermal conductivity improved significantly with incorporation of mica. Unlocking high‐frequency applications potential with ultralow Dk performance.

Structural Design and Strategy Optimization of PEMFC in Thermal Management

Due to growing energy and environmental issues, clean energy technology has gained recognition around the world. Because of its great energy transfer efficiency, outstanding power density, low operational temperatures, and environmental protection, PEMFC has been employed extensively in a variety of fields. But the thermal management of PEMFC has been a great challenge limiting its commercialization. Ineffective heat management strategies can shorten the fuel cell battery's lifespan in addition to affecting its performance. Therefore, this study provides an overview of how fuel cell bipolar plate structure and thermal management techniques have improved fuel cell performance. The results show that the tree-shaped fractal fuel cell bipolar plate, novel tapered dual serpentine channel and so on can enhance the heat dissipation effect of the bipolar plate and the temperature uniformity of the MEA, and form a uniform temperature distribution and pressure. Process strategies such as the new thermal management system with a thermal peak regulator can efficiently regulate the peak temperature and the average temperature of the fuel cell system to improve its starting performance. Most importantly, this research can help to alleviate the energy tension and reduce the environmental pressure.

Variable orientation in material extrusion of short carbon fiber reinforced polymer composites with high thermal conductivity

Controllable orientation architecture possesses tunable thermal behavior for effective heat dissipation in unidirectional product fields, meanwhile without interference with adjacent components. Herein, we proposed a variable orientation strategy in material extrusion of short carbon fiber (SCF) reinforced polymer composites framework with spatially tunable thermal properties. It was achieved due to the following reasons: (Ⅰ) Inherent shear flow in the nozzle; (Ⅱ) Increasing tensile flow by changing the ratio between the printing speed of monofilament and the feeding speed of filament (Vp/f); (Ⅲ) Further surface tension due to thinning monofilament by varying Vp/f. The SCF with different orientations and content reinforced polyether-ether-ketone (PEEK) composites were successfully fabricated. The microcosmic orientation of SCF could be programmed from a three-layer hierarchical framework to a single-layer oriented framework at different Vp/f. Benefit from variable orientation, the through-plane thermal conductivity of SCF/PEEK composites achieved a thermal conductivity enhancement of 173.9 %. In addition, the simulated application of SCF/PEEK composites in the CPU of the computer showed excellent heat transfer during heating. Further, the thermal conductivity mechanism of the synergistic influence between Vp/f and SCF content was analyzed by cross-sectional microstructure. The proposed strategy in this work for fabricating variable orientation of SCF reinforced polymer composites showcases great application prospects in electronic devices and unidirectional product fields.

Controlling TPMS lattice deformation for enhanced convective heat transfer: A comparative study of Diamond and Gyroid structures

This study investigates the enhancement of convective heat transfer in Triply Periodic Minimal Surfaces (TPMS), focusing on Gyroid and Diamond lattice structures. An innovative lattice structure control method, employing a Deform-Control parameter (β), is proposed to modulate lattice deformation within their mathematical frameworks. Numerical simulations validated by experimental measurements were conducted to analyze the impact of varying β values from 0 to 0.75 on the thermo-hydraulic performance of both lattice types at flow rates ranging from 0.4 m3/h to 2 m3/h. The results indicate significant improvements in heat transfer efficiency with increasing β. For Gyroid structures, increasing β from 0.1 to 0.75 led to a 3.8% to 32.7% rise in convective heat transfer coefficients and a 3.2% to 23.7% increase in Nusselt numbers. Diamond structures also demonstrated enhancements, with coefficients and Nusselt numbers climbing by 2.9% to 10.4% and 3% to 7%, respectively. Notably, both Gyroid and Diamond structures showed increase in flow resistance at higher β values, highlighting a critical balance between heat transfer efficiency and fluid flow considerations. This research presents a promising control method for optimizing heat transfer in TPMS structures, offering opportunities for more efficient and effective heat dissipation solutions.

Preparation of Highly Thermally Conductive Hexagonal Boron Nitride‐Polyvinyl Alcohol/Polydimethylsiloxane Composite Using Combined Freeze‐Drying and Spatial Confining Forced Network Assembly Method

With the rapid advancement of electronic products, an increasing number of electronic components are being integrated onto chips, leading to a higher power consumption per unit area. Consequently, effective heat dissipation has become increasingly important. To address this heat dissipation challenge, this article introduces and prepares a highly thermally conductive polymer composite based on freeze‐drying, coupled with the spatial confining forced network assembly (SCFNA) method. The freeze‐drying process is used to create a three‐dimensional thermal conductive network. This network provides a well‐defined heat path. The SCFNA method enhances the regularity of the thermal conductive network within the matrix. Ultimately, this results in the significant thermal conductivity enhancement of the polymer composite. After freeze‐drying, when the mass ratio of hexagonal boron nitride to polyvinyl alcohol is 4:1, the sample prepared by SCFNA presents 72.6% higher thermal conductivity than the one obtained through direct infiltration. This achievement holds significant value for the advancement of polymer composites with high‐thermal conductivity and excellent mechanical properties. It can improve the low‐dissipation performance of polymer thermal conductive composite systems, meet the needs of high‐performance and low‐dissipation use of thermal management materials, and reduce the working temperature of electronic chips.

Performance optimization of nanofluid-cooled photovoltaic-thermoelectric systems: A study on geometry configuration, steady-state and annual transient effects

In this study, we explored Photovoltaic-Thermoelectric (PV-TE) systems in-depth, addressing complexities in both steady-state and annual transient performance under realistic conditions. The analysis involved twelve distinct PV-TE configurations featuring diverse thermoelectric designs incorporating various semiconductors, multi-staging, non-uniform cross-sections, and material segmentation. Model 6, the PV-TE system with a multi-stage segmented rectangular design, emerged as the top performer, exhibiting a remarkable 12% increase in electric power output during peak sunlight compared to the base model, despite a marginal decrease in efficiency. Furthermore, this research delved into the potential of advanced nanofluid cooling, investigating options such as distilled water, titanium oxide, aluminum oxide, iron oxide, and graphene. The results underscores graphene nanofluid's superiority, demonstrating a significant enhancement in thermal management at an optimal flow velocity of 2 m/s. This improvement in thermal management refers to the effective heat dissipation and temperature control within the PV-TE system. This study underlines the critical role of strategic system design and component selection in optimizing the performance of PV-TE systems. By providing a comprehensive foundation for future developments in effective and sustainable energy solutions, this research contributes to advancing the understanding and implementation of PV-TE technology.

A novel hybrid liquid-cooled battery thermal management system for electric vehicles in highway fuel-economy condition

A hybrid liquid cooling system that contains both direct and indirect liquid cooling methods is numerically investigated to enhance the thermal efficiency of a 21700-format lithium-ion battery pack during the discharge operation. One of the most significant challenges that liquid-based direct cooling systems face is the filling of the heat capacity of the coolant during the cooling process, hindering the effective dissipation of heat generated from batteries. This paper aims to introduce a battery thermal management system to address this issue. In the present study, the influences of immersion and flow cooling methods using HFE-7100 and water (as working fluids), inflow velocities of cooling channel and tubes, parallel and counter flow, battery cell space, and highway fuel-economy test on the temperature distribution of batteries were studied comprehensively. Results highlight that immersion cooling with water outperforms due to the lower thermal conductivity of HFE-7100. In addition, Flow cooling significantly reduces the battery pack's highest temperature and non-uniformity compared to immersion. According to the numerical results, using cooling tubes as an indirect cooling system integrated with the direct flow cooling method can remarkably improve the thermal efficiency of the battery pack. Moreover, results exhibited that counterflow between cooling tubes/channels can keep the highest temperature and temperature variance of Li-ion battery package below 32.15 °C and 3.04 °C, respectively. Varying battery cell spaces shows that a 14 mm space reduces the battery package's highest temperature by 1.54 °C compared to a 10 mm space. Finally, highway fuel-economy condition is applied to the simulations of this study, illustrating the effect of an innovative hybrid battery thermal management system for a 21700-type Li-ion battery pack.

Artificial neural network-based cooling capacity estimation of various radiator configurations for power transformers operated in ONAN mode

Power transformers submerged in oil are universally acknowledged as very useful elements in electrical power networks. A fraction of the electrical energy involved in the conversion from high to low voltages is lost as thermal energy, which is produced inside the transformer's windings and core. The effective dissipation of heat is of paramount significance and can be accomplished through the strategic installation of radiators on the tank. This study aims to examine the total cooling capacity of a radiator employed for cooling a power transformer operating in oil, natural air, and natural mode. The investigation is conducted by varying the design parameters, specifically the number of fins per radiator and the radiator length. The study also utilizes computational fluid dynamics results to achieve a substantial convergence with experimental findings. In the context of the verification study conducted for a specific study point, it was found that the simulation outcomes at a mass flow rate of 0.15 kg/s corresponded to about 7.4 % of the experimental results. Additionally, the cooling capacity value obtained was 7.2 %. In the context of machine learning, the performance of the numerical approach was assessed by employing the Bayesian regularization method. The evaluation revealed that the margin of deviation, mean squared error, and coefficient of determination (R2) metrics yielded values of −0.001 %, 1.32E-02, and 0.99930, respectively.

A graphene nanoflake-based flexible composite phase change material for enhanced heat dissipation in chip cooling

Efficient heat dissipation is a key requirement for stable performance retention and failure prevention of microelectronic components. In practical applications, the interface thermal resistance between the component and the heat dissipation unit affects the heat dissipation effect. Thermal interface materials (TIM) are used to fill the voids at the solid interface between the device and the heat sink to create a thermally conductive path for heat dissipation. Phase change materials (PCMs) are candidates as TIM for next-generation electronic devices due to their excellent latent heat storage. However, some inherent problems of PCMs, such as low thermal conductivity, high solid-state rigidity, and easy leakage, also limit their application in the thermal management of electronic equipment. This study prepared a biomass cotton cloth substrate with a woven structure attached to graphite nanosheets and further constructed a thermally conductive matrix through drying or high-temperature carbonization. Through the composite of thermally conductive matrix and paraffin wax (PW), a flexible phase change thermal interface composite material was obtained. The phase change enthalpy of composite materials is as high as 157.7 J/g. The thermal conductivity of the composite material is 293.7 % higher than that of pure PW. On its excellent flexibility and structural strength, the composite material can better adapt to the thermal interface, reduce contact thermal resistance, and thus achieve good leakage resistance. The flexible phase-change TIM developed in this study have broad application prospects in the fields of chip heat dissipation and thermal management of wearable electronic devices.

Highly Thermally Conductive Triple-Level Ordered CNT/PVA Nanofibrous Films.

The escalating thermal power density in electronic devices necessitates advanced thermal management technologies. Polymer-based materials, prized for their electrical insulation, flexibility, light weight, and strength, are extensively used in this field. However, the inherent low thermal conductivity of polymers requires enhancement for effective heat dissipation. This work proposes a novel paradigm, emphasizing ordered structures with functional units, to create triple-level, ordered, low-filler loading of multi-walled carbon nanotube (MWCNT)/poly(vinyl alcohol)(PVA) nanofibrous films. By addressing interfacial thermal resistance through -OH groups, the coupling between polymer and MWCNT is strengthened. The triple-level ordered structure comprises aligned PVA chains, aligned MWCNTs, and aligned MWCNT/PVA composite fibers. Focusing on the filler's impact on thermal conductivity and chain orientation, the thermal transport mechanisms have been elucidated level by level. Our MWCNT/PVA composite, with lower filler loadings (10 wt.%), achieves a remarkable TC exceeding 35.4 W/(m·K), surpassing other PVA composites with filler loading below 50 wt.%.

Characterization of a Novel Cost-efficient and Environmentally Friendly Graphene-enhanced Thermal Interface Material

With the continuous development of electronic devices, effective heat dissipation has become a major factor affecting service life. Thermal interface materials (TIM) play a key role in controlling heat dissipation of electronic devices and have thus attracted widespread attention. In this study, we used graphene flakes (GF) derived from graphene film that is wasted during the preparation of commercial large-scale graphene-enhanced TIMs as thermally conductive fillers to formulate a new TIM. The thermal conductivity of the developed TIM is 50% higher with GFs than without. Furthermore, the TIM has a tensile strength of 0.46 MPa with an elongation at break of 1225%, a maximum compression strength of 0.64 MPa at 50% compression, and high mechanical cycle stability. This report provides a cost-efficient and environmentally friendly approach to producing high-performance TIMs for electronic cooling applications.

Enhancement of interfacial thermal conductance by introducing carbon vacancy at the Cu/diamond interface

Effective heat dissipation of semiconductor devices is crucial for their extended lifespan and operational stability, and the interface of semiconductors provides an effective window for thermal design and management. In this work, we have systematically investigated the effect of the carbon vacancy on the thermal conductivity of diamond and the interface thermal conductance (ITC) of Cu/diamond by using both first-principles calculation and molecular dynamics methods. Although the carbon vacancy leads to a decrease in the thermal conductivity of diamond, a marked increase in ITC from 37.98 MWm−2K−1 to about 177 MWm−2K−1 for diamond (1 1 1) plane and from 78.8 MWm−2K−1 to about 241 MWm−2K−1 for diamond (0 0 1) plane is observed between Cu and diamond with carbon vacancy. The increase of the ITC is mainly due to the anharmonic phonon scattering, revealed by the phonon density of states and phonon participation ratio.