Lightweight Thermal Management Research Articles

Aluminium-Silicon Lightweight Thermal Management Alloys with Controlled Thermal Expansion

With the ever-growing emphasis on global decarbonization and rapid increases in the power densities of electronics equipment in recent years, new methods and lightweight materials have been developed to manage heat load as well as interfacial stresses associated with coefficient of thermal expansion (CTE) mismatches between components. The Al–Si system provides an attractive combination of CTE performance and high thermal conductivity whilst being a very lightweight option. Such materials are of interest to industries where thermal management is a key design criterion, such as the aerospace, automotive, consumer electronics, defense, EV, and space sectors. This paper will describe the development and manufacture of a family of high-performance hypereutectic Al–Si alloys (AyontEX™) by a powder metallurgy method. These alloys are of particular interest for structural heat sink applications that require high reliability under thermal cycling (CTE of 17 μm/(m·°C)), as well as reflective optics and instrument assemblies that require good thermal and mechanical stability (CTE of 13 μm/(m·°C)). Critical performance relationships are presented, coupled with the microstructural, physical, and mechanical properties of these Al–Si alloys.

Self-driven manifold microchannel heat sink for cooling electronics

The advancement of passive, compact, and lightweight thermal management technology for high-power chips is essential for the stable and efficient operation of the next generation of electronic devices. A novel self-driven heat sink based on embedded manifold microchannel heat dissipation technology is proposed, which uses capillary force as the driving force to replace the pump, and minimize pressure drop and thermal resistance between the heat sink and heat source. This design of the embedded self-driven manifold microchannel heat sink allows for the integration and miniaturization of the heat sink and the chip heat source. Through Micro Electromechanical Systems technology, an experimental sink with microchannels with a high aspect ratio was fabricated. A theoretical model is constructed to analyze the influence of the width and depth of the microchannel on the limit heat flux, and the correctness of the model is verified by experiments. The results indicate that the width has a more significant impact on the limit heat flux compared to the depth. An optimal width of 6.5 μm is identified. As the depth increases, the influence of depth on the limit heat flux diminishes. By conducting theoretical calculations on the embedded self-driven manifold microchannel heat sink, it was determined that the device using HFE7100 as the working fluid demonstrates a wider heat load range than ethanol and acetone, and the limit heat flux can reach 41.5W/cm2.

An efficient aluminum gradient mesh wick for enhancing boiling heat transfer performance

With the rapid development of high-power electronic devices, phase change heat transfer has attracted much attention for efficient and lightweight thermal management. However, the mesh structure design for aluminum-based pool boiling enhancement still lacks experimental investigation and theoretical analysis. Herein, an aluminum gradient mesh wick is developed for efficient heat transfer performance. The optimized gradient mesh wick is comprised of a large-hole rhombus flat punching structure on the top and a small-hole 2D screen woven mesh on the bottom, providing sufficient active nucleation density sites, timely liquid supply, and rapid bubble departure. The gradient mesh design for pool boiling enables to achieve a high critical heat flux (CHF) of 1095.46 kW/m2 and a high heat transfer coefficient (HTC) of 46.20 kW/m2·K at a wall superheat of 23.70 °C, which is 167.06% and 240% that of Al plate, respectively. The visualization of bubble behaviors and theoretical analysis reveals that the CHF of the gradient mesh wick mainly depends on the bubble departure and liquid supply, and the bubble departure accounts for a greater proportion. Such aluminum gradient mesh wick provides a strategy for efficient thermal management of lightweight and high-power electronic devices.

Experimental study and simulations of hydrogen cooling effectiveness for aviation PEM fuel cells

Proton exchange membrane fuel cells (PEMFCs) are seen as one possible future means of driving the change towards a zero-emission society. In a civil aircraft, fuel cell systems can have multiple potential benefits, such as reduced noise, lowered emissions and higher fuel economy compared to jet aircraft. For controlling the fuel cell temperature, thermal management systems are required which can be optimized for aircraft applications regarding their weight and reliability. In this work, a simplified and light-weight thermal management system relying on hydrogen cooling is presented and analysed. To investigate the feasibility, a test rig and a three-dimensional, singular channel model in ANSYS Fluent were designed. Fuel cell temperature could be maintained within the set threshold in the model and the test rig, thus showing that controlling the fuel cell temperature via the hydrogen reactant flow is a viable alternative thermal management system. Results from the model indicate that both the hydrogen mass flow and hydrogen inlet temperature should be used to control the fuel cell temperature. Furthermore, operating the fuel cell at medium to low current densities is favourable for hydrogen cooling. Future studies will explore alternate flow field designs to facilitate thermal management system relying on hydrogen.

Enhanced capillary performance of multiscale ultrathin titanium wicks guided by modified wicking dynamics

Ultrathin titanium vapor chambers with wicks fabricated by ultrafast laser direct writing provide a promising solution for future electronics' lightweight thermal management. However, despite being a powerful tool for wick manufacturing, the application of ultrafast laser is restricted by its low fabrication efficiency and imperfect model for wick design. Herein, a multiscale titanium wick with stable superhydrophilic nano ripples and microgrooves was high-efficiently fabricated by a multi-beam femtosecond laser processing technology. A modified wicking dynamic model was proposed for ultrafast laser manufactured microgroove wick design. It considered the extra capillary force by laser induced nanoripple and viscous resistance of the narrow V-shape grooves, which is ignored in the classic model. The prediction error of wicking performance reduced from 72.9 % to 4.5 %. Compared to the conventional V-shape design the optimized microgrooves wick improved by 56.7 % and exhibited capillary performance parameter (K/Reff) of 1.88 μm at a thickness of 80 μm, which outperformed most of the recently reported data. The modified model, multiscale high-performance wick, and its highly efficient fabrication method propose a universal and handy approach for accurate and quantitative wick design and manufacturing.

Freeform thermal-mechanical Bi-functional Cu-plated diamond/Cu metamaterials manufactured by selective laser melting

The leverage of selective laser melting (SLM) successfully fabricate metal matrix composites (MMCs) metamaterials with freeform intricate triply periodic minimal surface (TPMS) structures that are not possibly fabricated by conventional methods and exhibit exceptional mechanical properties. SLM fabricated high precision MMCs metamaterial TPMS structures are of great potential in energy conversion, heat management and lightweight applications. Due to the self-supporting geometric characteristics of TPMS, the metamaterial structures could effectively overcome the manufacturing constraints of SLM. Besides, their freeform capability offers great opportunities to be bi-functional or multi-functional through the selection of materials as well as the design optimization of structure. Diamond can offer unique advantages in the field of heat management due to its outstanding thermal and mechanical properties. The addition of micro-sized diamond particles into copper can tailor its coefficient of thermal expansion (CTE) while enhancing its thermal conductivity (TC). SLM fabricated diamond reinforced copper MMCs metamaterials with TPMS structure could bring outstanding thermal-mechanical bi-functional properties for prospective lightweight thermal management applications. In our previous work, the interfacial bonding issue between diamond particles and Cu matrix was resolved by a coating of copper on micro-sized diamond particle reinforcement. In this present work, 1 vol% Cu-plated diamond/Cu metamaterials with three various TPMS (Gyroid-G, Schwarz Primitive-P, Diamond-D) structures were successfully fabricated via SLM for the first time. Their bi-functional heat transfer and compression behaviors were evaluated by measurement and numerical simulation for three TPMS (G, P, D) structures and TPMS (D) structures with various lattice thicknesses. From the lightweight perspective of three TPMS structures with 0.2 mm wall thickness, the order of these structure is TPMS P structure, TPMS G structure, TPMS D structure (0.2 mm wall thickness, 0.2 P > 0.2 G > 0.2D). If heat transfer performance is an important consideration, The 0.2D structure can be selected from the three TPMS structures. This research also investigated the continuous design of TPMS D structure with various wall thickness and creatively proposed a flexible TPMS design paradigm toward advanced thermal-mechanical bi-functional Cu-plated Diamond/Cu metamaterials via SLM for prospective lightweight thermal management applications.

Numerical investigation of a compact and lightweight thermal management system with axially mounted cooling tubes for cylindrical lithium-ion battery module

To construct a compact and lightweight cooling system for cylindrical batter module, developing cooling tubes inserted into spaces between batteries is a promising way. Yet, the constant distance kept between adjacent cells in battery array makes the reported weight ratio values not satisfactory enough. Merits and demerits between different battery arrangement modes (staggered and aligned) are also unclear. Therefore, in this work, a novel liquid cooling thermal management system with axially mounted cooling tubes inserted into spaces between tightly assembled batteries is presented to provide a compact and lightweight solution to the cooling of cylindrical battery module. Designs with staggered and aligned battery arrangements are compared. Corresponding results show that design with staggered battery arrangement is superior to the aligned one based on the trade-off of different design requirements including cooling performance, system weight and volume cost. BTMS with staggered design reports a remarkably high performance in terms of the lightweight extent, which only accounts for 5.4 wt% of the battery module, much lower than those in previous studies. Further, extended studies are performed for the optimization of BTMS with staggered battery arrangement and the results could provide useful guidance in the future design of BTMS for cylindrical battery modules.

A Low-Cost and Lightweight Thermal Management System for Lithium-Ion Battery Modules Based on Composite PCM under Normal EV Operating Conditions

In this paper, a novel low-cost and lightweight lithium ion batteries thermal design based on EG-based composite phase change material to store heat under normal EV operating conditions is developed and verified theoretically. The three dimensional thermal simulation model is proposed to compute the transient temperature of the battery at some actual driving conditions during discharge. The capability of battery thermal management system based on composite PCM under four kinds of actual electric vehicles thermal safety evaluation condition is investigated, and some factors influencing the system are discussed in detail. Simulation results show that the temperature of the lithium ion battery can be maintained within a reasonable range by adopting the cooling system. The highest temperature of battery discharging at 1C rate can be kept no more than 45.1 °C in the cost of 0.5mm in thickness and 1.02kg in weight increment of PCM and the temperature consistency evaluation methods based on integral values were proposed. The conclusions got in this paper can be valuable reference for battery thermal management design and analysis of dissipating heat against daily driving discharge condition.

Lightweight and thermally conductive thermoplastic polyurethane/hollow glass bead/boron nitride composites with flame retardancy

Polymeric composites with low density and high thermal conductivity (TC) are greatly demanded in some specific applications such as aeronautics, astronautics, and deep-sea exploration. It is a great challenge to obtain lightweight and thermally conductive polymer composites because the heat fillers have high density (>2 g/cm3) Herein, lightweight and thermally conductive thermoplastic polyurethane/hollow glass bead/boron nitride composites (TPU/HGB/BN) were prepared with the construction of a 3D BN network under the assistance of ultralightweight HGB by a solution-mixing and hot-pressing method. A 3D BN heat network has been constructed in the TPU matrix due to the alignment of the BN platelets along with the HGB microspheres during hot-pressing, which leads to a higher TC (5.34 W/mK) of the TPU/HGB/BN composites with a low density of 1.23 g/cm3, which is close to the density of pure TPU (1.20 g/cm3). In addition, the TPU/HGB/BN composites show good thermal stability with TC losses of 4.24% and 2.22%, respectively, even after treated for 50 hot-cold cycles and heated at 80 °C for 50 h. Moreover, the limiting oxygen index (LOI) of the TPU/HGB/BN composites is 51%, and they can extinguish in 8 s after ignition and exhibit enhanced flame retardancy. This work presents a simple method to design and prepare lightweight, flame retardant and thermally conductive composite materials, which can be used as lightweight thermal management materials.

2D-Topology-Seeded Graphitization for Highly Thermally Conductive Carbon Fibers.

Highly thermally conductive carbon fibers (CFs) have become an important material to meet the increasing demand for efficient heat dissipation. To date, high thermal conductivity has been only achieved in specific pitch-based CFs with high crystallinity. However, obtaining high graphitic crystallinity and high thermal conductivity beyond pitch-CFs remains a grand challenge. Here, a 2D-topology-seeded graphitization method is presented to mediate the topological incompatibility in graphitization by seeding 2D graphene oxide (GO) sheets into the polyacrylonitrile (PAN) precursor. Strong mechanical strength and high thermal conductivity up to 850 W m- 1 K-1 are simultaneously realized, which are one order of magnitude higher in conductivity than commercial PAN-based CFs. The self-oxidation and seeded graphitization effect generate large crystallite size and high orientation to far exceed those of conventional CFs. Topologically seeded graphitization, verified in experiments and simulations, allows conversion of the non-graphitizable into graphitizable materials by incorporating 2D seeds. This method extends the preparation of highly thermally conductive CFs, which has great potential for lightweight thermal-management materials.

Thermal response of the two-directional high-thermal-conductive carbon fiber reinforced aluminum composites with low interface damage by a vacuum hot pressure diffusion method

A two directional high thermal conductive carbon fiber reinforced aluminum matrix composite with low interface damage is prepared by a vacuum hot-pressure diffusion method using the mesophase-pitch-based carbon fiber (CFMP) cloth as fast heat conduction channels. The fiber/matrix interface is composed of an amorphous gradient transition layer between aluminum matrix and CFMP rather than Al4C3 interface phase, thus endowing the continuous heat conduction channels in the composite. The composites deliver the high thermal conductivity of 305.5 W∙m−1∙K−1 in the X (Y) direction and the low volume density of only 2.53 g∙cm−3 when the fiber volume fraction reaches 30 vol%. The high thermal conductivity of the composite is attributed to the highly oriented fast heat transfer effect of the CFMP, the isotropic heat transfer effect of the aluminum matrix and the low-damage CFMP/aluminum interface. This study opens a new avenue to design and select the high thermal conductivity and lightweight thermal management materials for the aerospace field.

Enhancing mechanical properties of glass fabric composite with surfactant treated zirconia nanoparticles

Significantly enhanced specific mechanical properties of Glass Fabric Composite (GFC) by optimal dispersion of yttria stabilized zirconia (YSZ) nanoparticles in matrix-fabric system is reported. Dispersion of as low as 3 wt% of YSZ is found to be optimal for the developed processing condition. The enhancement is due to two-fold effects, one is the nano-cluster segregation by surfactant and the other one is an optimal interfacial stress/fracture modification in the matrix-fabric system via optimal length-scale effects of nano-composite with respect to the fabric interface. A detailed understanding is developed with the help of microscopic characterization and finite element simulation results. Specific modulus and strength increased by ∼18% and ∼17% (compressive), ∼14% and ∼17% (tensile) and ∼34% and ∼64% (flexural), respectively. The developed nanocomposite has potential applications in light-weight thermal management.

Nanomanufacturing of graphene nanosheets through nano-hole opening and closing

Abstract Facile and scalable fabrication of highly dense and high-quality graphene films and articles is extremely attractive for a range of electronic and mechanical applications. Pristine, high-quality graphene with its inherent impermeability poses challenges in fabricating dense films and thick parts with high electrical conductivity due to the difficulty in removing trapped air and/or solvents used in various fabrication methods. To overcome this deficiency, nano-holes were intentionally created in pristine graphene (“holey graphene”) with an average diameter of approximately 15 nm. The holes serve as pathways for the rapid removal of gases or liquids and enable the fabrication of dense holey graphene nanostructures. Subsequently, a high-temperature process is applied to effectively repair the nano-holes and recover the high-quality graphene conjugated network. Through the creation and repair of the nano-holes, dense graphene articles that exhibited an ultrahigh conductivity of 2209 S/cm and superior thermal conductivity of 863 W/mK were created. This unique processing methodology enables the facile and scalable fabrication of high-quality graphene constructs, which can be easily integrated into the next generation of electronic circuits and high-power battery systems for highly efficient and lightweight thermal management.

Extremely high thermal conductivity of nanodiamond-polydopamine/thin-layer graphene composite films

The hybrid composite films containing nanodiamonds (ND) coated with polydopamine (pDA) (ND-pDA) and reduced graphene oxide (rGO) converted from graphene oxide (GO) films are designed for achieving extremely high thermal conductivity. The ND-pDA/rGO films are successfully fabricated using the vacuum-filtration process followed by a heat treatment at 800 °C. The thermal conductivities of the films in the in-plane (K//) and through-plane (K⊥) directions are measured by the laser flash method to better understand how the addition of dopamine, the amount of ND-pDA, and the test temperature affect the thermal properties of the hybrid films.The experimental results show that the addition of dopamine results in dense structure of the ND-pDA/rGO hybrid films, which is favorable for phonon transport, and thus remarkably increase the thermal properties of the film. Additionally, films with higher ND-pDA loading possess lower in-plane but higher through-plane thermal conductivity. K// and K⊥ of 1406 and 0.677 W m−1 K−1, respectively, for 20ND-pDA/20rGO measured at 25 °C are achieved. Both the K// and K⊥ of 20ND-pDA/20rGO increase with test temperature. Maintaining such high thermal conductivities at high temperature, the hybrid films are believed to be suitable for lightweight thermal management materials with high heat transfer properties in a specific direction.

High-Performance and Lightweight Thermal Management Devices by 3D Printing and Assembly of Continuous Carbon Nanotube Sheets.

Free-standing carbon nanotube films or buckypaper can provide a significant platform to develop practical applications of nanocarbon materials. For this research, buckypaper with high thermal conductivity (20 W/m K) and large surface area (350 m2/g) was mass produced in-house to investigate for use in lightweight thermal management devices. Floating catalyst chemical vapor deposition carbon nanotube sheets were also studied in this work. We introduced two manufacturing techniques to use the sheets for heat dissipation: (1) printing conductive composite ink on the sheets to make lightweight thermal devices, such as heat sinks and (2) assembling the sheets directly into 3D structures that were mounted on the back of heat-generating devices. These manufacturing techniques resulted in extremely lightweight, high-performance heat dissipation devices compared with other heat sink materials.

Convective heat transfer in a lightweight multifunctional sandwich panel with X-type metallic lattice core

The thermo-fluidic characteristics of an ultralightweight X-type lattice cored sandwich panel with simultaneous thermal and mechanical load bearing capabilities are studied both experimentally and numerically. Comparisons with competing sandwich panels with periodic cellular material (PCM) cores are carried out at a similar porosity level. For a given Reynolds number, the highly porous X-lattice cored sandwich panel provides up to 38% higher overall Nusselt number than tetrahedral lattice cored sandwich panel, while exhibits comparable heat transfer performance to Kagome lattice cored sandwich panel. Although brazed joints between the lattice core and the facesheets induce both transverse and longitudinal vortices, limited flow mixing asa result of smooth mainstream in the X-lattice leads to inferior average Nusslet number on both the facesheets and ligaments relative to tetrahedral lattice cored sandwich panel. However, the X-lattice has a 66% higher surface area density than tetrahedral lattice, which acts as the main heat transfer enhancement mechanism. Relative to the reference ones, the X-lattice cored sandwich not only provides an overall Nusselt number up to 77% higher for a given pumping power, but also exhibits evidently lower pressure drop for a given Reynolds number. Therefore, such metallic lattices fabricated using the simple metal sheet folding method are superior for lightweight thermal management systems where a cooling fluid with small specific heat is driven by limited pumping power in a long cooling channel.

자연대류상의 LED 모듈의 경량열관리를 위한 하이브리드 휜 히트싱크의 수치적으로 조사된 열성능

자연대류상의 LED 모듈의 경량열관리를 위한 하이브리드 휜 히트싱크의 수치적으로 조사된 열성능

Modelling of effective thermal conductivity of polymer matrix composite foams with biaxially aligned filler networks

Recent research revealed potentials to develop polymer matrix composite foams filled with thermally conductive filler network as light-weight thermal management materials. Since polymeric foams are commonly used for thermal insulation, the concept of thermally conductive polymer matrix composite foams seems to be counter-intuitive, and the underlying factors that govern polymer matrix composite foam’s effective thermal conductivity ( keff) were not clear. In this context, this paper develops new models to predict polymer matrix composite foams’ keff and to elucidate the dependence of keff on their cellular morphology. Linear low density polyethylene–hexagonal boron nitride composite foams were used as case examples to verify the model. The model demonstrated that the composite foam’s keff would be promoted when the volume expansion was over a threshold percentage. At low hexagonal boron nitride loadings (e.g. 10 vol.%) and fixed cell size, linear low density polyethylene–hexagonal boron nitride foams’ keff increased with volume expansion percent through an increase in cell population density. Constrained foaming with preferential expansion in the heat flow direction also enhanced their keff.

Characterization and Modeling of the Heat Transfer Performance of Nanostructured Cu Micropost Wicks

Micro heat pipes incorporating advanced wicks are promising for the thermal management of power electronics. We report the heat transfer performance of superhydrophilic Cu micropost wicks fabricated on thin silicon substrates using electrochemical deposition and controlled chemical oxidation. For a fixed post diameter, the interpost spacing and hence solid fraction is found to be a main design factor affecting the effective heat transfer coefficient and critical heat flux. The effective heat transfer coefficient >10 W/cm2 K and the critical heat flux >500 W/cm2 over 2 mm × 2 mm heating areas are demonstrated. Copper oxide nanostructures formed on the micropost surfaces significantly enhance the critical heat flux without compromising the effective heat transfer coefficient. An approximate numerical model is developed to help interpret the experimental data. A surface energy minimization algorithm is used to predict the static equilibrium shape of a liquid meniscus, which is then imported into a finite element model to predict the effective heat transfer coefficient. The advanced wick structures and experimental and modeling approaches developed in this work will help develop thin and lightweight thermal management solutions for high-power-density semiconductor devices.

Performance of a Jet-Pumped Cryogenic Refrigeration System

Efficient, lightweight thermal management and power systems are crucial for successful exploration of space. This paper provides an analysis of a novel solar-integrated thermal management and power system, which is comprised of a thermally actuated heat pump with power and refrigeration subsystems and having a jet pump serving as the compression device. The analysis allows calculation of on an overall system mass ratio that compares the overall active system mass to an idealized passive counterpart. In this study liquid nitrogen, which is common on many space missions, is the working fluid. This achieves a significant mass advantage as the use of cryocoolers is eliminated. By applying the techniques demonstrated in this paper, designers can identify and optimize conceptual configurations during the initial prototype development stages to reduce payload weight and increase financial savings.