Thermal Conductivity Enhancement Research Articles

Laser flash technique as an efficacious assessment approach for thermal conductivity of tungsten disulphide nanofluids

Two-dimensional tungsten disulphide (WS2) dispersed oil-based nanofluids are prepared by a two-step process and their stability and thermal properties are assessed. UV–visible spectrophotometry reveals marginal loss in relative absorbance over 15 days ensuring dispersion stability of the nano-additives. Thermal diffusivity of nanofluids is measured using the laser flash analyzer while specific heat capacity is studied by differential scanning calorimetry. The thermal diffusivity coupled with the specific heat capacity of the nanofluids provides an estimate of the thermal conductivity of the prepared nanofluids. Specific heat of the nanofluids is observed to increase with temperature and reduce with an increase in the concentration of the nano-additives. A statistical model is developed to predict the influence of density and temperature on the specific heat of the nanofluids. Higher thermal conductivity in comparison to the base fluid is observed which further enhances with an increment in concentration of the nano-additive. The parameters such as concentration of dispersoid and temperature reveal the effect on the thermal conductivity at elevated temperatures. Enhancement in thermal conductivity is observed between 3–12 % which is validated with an analytical model for thermal conductivity of composite nanofluids.

Eutectic phase change composites with MXene nanoparticles for enhanced photothermal absorption and conversion capacity

Phase change composite materials with uniform nanomaterial dispersion are potential solutions for improving thermophysical properties and enhancing latent heat capacity applicable in thermal management. In this study, various transitional carbide-based MXene samples were synthesised via acid etching to augment the heat transfer capacity and efficiency of the solar thermal energy storage (TES). These samples were then uniformly dispersed in a eutectic mixture (1:1) of paraffin wax (PW) and polyethylene glycol (PEG-6000), resulting in the formation of a MePCM composite. The controllable porous structure and hydrogen interactions with the external layer of MXene and long-chain PCM benefitted in the well impregnation of PCM and compatibility impregnated into the composite. An exceptionally higher mass fraction of 1 wt % Ti3C2Tx MXene-based phase change composite unveiled a higher phase change enthalpy of 138.66 J/g in the melting phase and 139.54 J/g in the solidification phase with 89.82 % energy storage efficiency. In contrast to pure eutectic PCM (0.2593 W/mK), the thermal conductivity of MePCM composite is relatively higher and provides a thermal conductivity of 0.9209 W/mK for Ti3C2Tx MXene-based composite. The enhancement of thermal conductivity is ascribed to the increased heat conduction pathway facilitated by the MXene arrangement. The utilisation of spatially constrained eutectic phase change material (PCM) assembly resulted in the development of MePCM, which exhibited enhanced thermal conductivity, chemical and physical stability, and thermal consistency across 500 melting-solidification cycles. Benefitting from the thermal conduction path, the MePCM exhibits an excellent photothermal conversion efficiency of 98.53 %. The thermal responsive tests of Ti3C2Tx and V2CTx MXene composite samples provide better thermal response than eutectic PCM without thermal reduction. With a higher thermal storage capacity and higher heat transfer property, thermally reliable MePCM composites exhibited tremendous potential for photothermal applications.

Enhancing thermal conductivity of sinterized bronze (Cu89/Sn11) by 3D printing and thermal post-treatment: Energy efficiency and environmental sustainability

Enhancing the thermal conductivity of bronze is essential to enhance the efficiency of heat transfer and reduce energy consumption in systems such as heating, cooling, and heat exchangers systems. This study investigates the feasibility of producing sinterized bronze (Cu89/Sn11) using low-cost 3D printing Fused Deposition Modeling (FDM) technology and thermal post-treatment processes. The intention is to identify optimal printing parameters and sintering temperatures to maximize thermal conductivity, while focusing on minimizing energy consumption, raw material usage, and environmental impact. The thermal conductivity of twenty-seven samples was evaluated according to the ASTM E1530:2019 standard. A statistical analysis revealed significant effects of nozzle diameter and flow rate on thermal conductivity and density. The optimal results were obtained with a sintering temperature of 845 °C, a 1.0 mm nozzle diameter, and a 110 % flow rate. These conditions yield the highest thermal conductivity (87.61 W/m·K) and density (7.52 g/cm3). The lowest values were observed at a sintering temperature of 865 °C, a 0.6 mm nozzle diameter, and a 100 % flow rate. A Life Cycle Assessment (LCA) using the ReCiPe Endpoint (E) methodology was employed to compare the environmental impact of the resulting thermal conductivities. The results suggest that sintered bronze produced by FDM and thermal post-treatment provide superior performance and a smaller environmental impact than conventional methods. This study underscores the potential for more efficient and sustainable manufacturing practices in the production of sintered bronze.

Synthesis of novel Stachytarpheta jamaicensis flower liked hexagonal boron nitride nanoribbons (SJF-BNNBs) to efficiently improve the thermal/mechanical/electrical properties of flexible polyimide films

Heat dissipation has become a bottleneck restricting large-scale integration and flexible electronic technologies. This study reports a novel fabrication strategy to prepare flexible stachytarpheta jamaicensis flower-like hexagonal boron nitride nanoribbons (SJF-BNNBs) and their composite films with polyimide (PI). The effect of synthesis conditions on the morphology of SJF-BNNBs was investigated, and the growth mechanism was proposed. The in-plane and through plane thermal conductivities of the 4 wt% SJF-BNNBs/PI composite film reach 5.98 W m−1 K−1 and 0.79 W m−1 K−1, which are 3047 % and 316 % higher than those of the pure PI film, respectively. The in-plane and through plane thermal conduction enhancement efficiencies reach 761.8 % and 78.9 %, respectively. The tensile strength of the composite film is 61.7 % higher than that of pure PI, and maintains excellent electrical insulating and thermal stability properties. Infrared imaging tests verified the excellent heat dissipation performance of the composite film as a thermal interface material and a flexible copper clad laminate substrate, where the operating temperature of device could be reduced by 17.3 °C. To the best of our knowledge, SJF-BNNBs outperform the most efficient thermally conductive electrically insulating filler and are to break the overcome of polymer composites in heat dissipation applications.

Construction of three-dimensional network using boron nitride microspheres and the thermal conductivity/stability of epoxy resin composites

Efficient heat dissipation has become the focus of electronic packaging materials, constructing three-dimensional thermally conductive filler networks to prepare composites can realize efficient heat transfer. However, there are few studies comparing the effects of different ways of constructing three-dimensional networks on the thermal conductivity enhancement of polymers. In this study, BNMS self-assembled from BNNSs was used as a thermally conductive filler, and the three-dimensional skeleton was constructed by both the powder mixing pressing method and the ice template method, and scanned to analyze the morphological and structural characteristics. At the same time, the epoxy composites were prepared, and the advantages and disadvantages of the thermal conductivity of the composites prepared in different ways were analyzed by combining the SEM structures. In the powder mixing pressing method, the in-plane and through-plane thermal conductivity of the epoxy composites with the BNMS additive amount of 53.92 wt% reached 10.961 W·m−1·K−1 and 9.955 W·m−1·K−1, respectively, which was increased by 58 and 52 times. The thermal stability has been improved significantly that the T60 was in creased by 60.89°C compared to pure epoxy. Using the ice template method with 7.67 wt% of BNMS addition, the through-plane thermal conductivity of the epoxy composites reaches 0.977 W·m−1·K−1, which is an improvement of 428.1 % compared with pure EP. In addition, both composites maintain low dielectric constants and dielectric losses. It is instructive for the preparation method of subsequent construction of three-dimensional thermally conductive filler networks.

Enhancement of thermal conductivity in PDMS/CFP composites using a dredging-plugging thermal network

In the preparation of thermally conductive polymer composites (TCPC), it is necessary to incorporate a filler network in the polymer matrix. Further enhancement of the thermal conductivity (TC) of TCPCs is challenging due to the exceptional heat absorption of the polymer matrix, which results in heat flow losses in the network. To address this issue, a novel procedure, termed thermal network dredging-plugging, has been proposed. In this study, polydimethylsiloxane (PDMS) composites with a carbon fiber powder (CFP) network and a CFP/glass ball (GB) network enhanced by dredging-plugging were prepared by a coating method. The TC of the PDMS/CFP system increased with an increase in CFP loading from 0 to 12 wt% and a decrease in sample thickness from 0.4 to 0.2 mm. At a 12 wt% CFP loading, the PDMS/CFP composites exhibited a maximum TC of 4.687 W/(mK). With the addition of GBs ranging from 0 to 2 wt%, the dredging-plugging CFP/GB network increased the maximum TC by a factor of 1.26 relative to the dredged CFP network. In conjunction with the thermal resistance method, a mathematical model that considers both the plugging and dilution effects of GBs was constructed. The calculated TCs were validated by using the prepared PDMS/CFP/GB composites, with average absolute relative errors ranging from 0.5 % to 4.19 %. In addition to TC enhancement, the mechanical properties and thermal management of the PDMS composites were evaluated.

Covalent vs. Non covalent chemical modification of multiwalled carbon nanotubes based-nanofluids: Stability and thermal conductivity steadiness over temperature

Thermal conductivity enhancement coupled to nanoparticle dispersion stability over time are the two main conflicting requirements to overcome to develop carbon nanomaterial-based nanofluids. Both covalent and non-covalent approaches, having their own advantages and disadvantages, are commonly used for carbon nanotube based nanofluids development. However, they are rarely compared regarding their impact on stability and thermal conductivity performances for the same kind of nanofluid. In this work, multiwalled carbon nanotubes have been chemically modified by both covalent and non-covalent functionalization. For the covalent functionalization, a simple oxidation method is applied. It consists of refluxing the powdered MWCNTs in H2SO4/HNO3 at 5 M concentration. For the non-covalent approach, both an anionic (sodium dodecyl sulfate) and a non-ionic (Pluronic P123, comprising poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) in an alternating linear fashion, PEO-PPO-PEO) surfactants were employed at a concentration of 1 wt%. Nanofluids were prepared with multiwalled carbon nanotubes at a fixed concentration of 0.2 wt% for both chemical modification approaches. The oxidation reaction occurs without significant structure damaging as shown by transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. UV–visible spectrophotometry analysis shows a remarkable stability with temperature in the 293.15–303.15 K range over one-week and for a longer period of 49 days for all the three types of nanofluids. Their thermal conductivity has been investigated in the same temperature range. For all the three nanofluid series prepared with a fixed concentration of carbon nanomaterials, a thermal conductivity enhancement compared to that of the base fluid has been observed. The thermal conductivity evolution with temperature is different for each type of nanofluid. The covalently oxidized multiwalled carbon nanotube based nanofluids showed the better thermal conductivity enhancement steadiness (around 7 %) with temperature. The discussion on the surfactant-based nanofluid behavior proposes the possible involved mechanisms as temperature increases for each surfactant.

Techniques for Enhancing Thermal Conductivity and Heat Transfer in Phase Change Materials in Hybrid Phase Change Material–Water Storage Tanks

In recent years, extensive research has been dedicated to enhancing energy efficiency and promoting environmental sustainability in heating and cooling systems. Among the promising solutions, phase change materials (PCM) technology stands out as a key area of exploration. This study focuses on improving the thermal performance of PCM–water hybrid tanks by investigating methods to enhance thermal conductivity and heat transfer. Through experimental testing using techniques such as copper matrices, steel twisted matrices, and copper spirals, this study demonstrates significant improvements in thermal conductivity, particularly with the use of copper matrices. The integration of a copper matrix placed in the PCM reservoir increased the heat transfer coefficient and thermal conductivity of the PCM, and thus, the total phase transformation time for solidification was reduced by 79.19% and for melting by 54.7%. Our experimental results demonstrate that the integration of a copper matrix can increase latent heat transfer from 55,677.6 J up to 125,274.6 J, marking a 125% enhancement over the experiment with pure PCM. Additionally, comparisons of the energy storage potentials for different PCMs underscore the benefits of integrating PCMs into hybrid storage tanks. These findings highlight the immense potential of PCM technology to increase energy storage efficiency in heating and cooling applications.

A novel candidate shape-stabilized phase change material for building energy conservation based on lauric acid/roasted iron tailings-expanded graphite

This study presents the fabrication of a novel shape-stabilized phase change material (SSPCM) characterized by high thermal capacity and heat transfer efficiency. The material was composed of lauric acid (LA) embedded in roasted iron tailings (RIT) and expanded graphite (EG), utilizing a straightforward, low-cost, and direct impregnation method. The as-prepared LA/RIT-EG SSPCM underwent a comprehensive analysis of leakage tests, surface morphology, chemical compatibility, phase change properties, thermal stability, and reliability. Furthermore, the heat transfer efficiency and thermal conductivity were measured through cooling tests and a laser thermal conductivity analyzer, respectively. The LA/RIT-EG formulation demonstrated an ability to absorb 61.57 wt% LA without leakage, maintaining excellent form-stability with a mass fraction proportion of 29:9.43 for RIT and EG. DSC results revealed phase temperatures and latent heats of 42.49–46.31 °C and 108.1–113.1 J/g, respectively. Compared to pure LA, LA/RIT-EG exhibited a 489.7 % increase in thermal conductivity. Additionally, heat storage and release rates were improved by 81.25 % and 88.24 %, respectively. The study elucidated the mechanism behind the enhancement in encapsulation capacity and thermal conductivity by RIT-EG, validated through specific surface area and wettability tests. Overall, the results suggest that LA/RIT-EG, characterized by high thermal capacity and heat transfer efficiency, holds promise as a potential candidate for thermal energy storage, particularly in the context of energy conservation in buildings.

Layer-by-layer assembly of boron arsenide and copper nanoflake-based aramid nanofibers for thermoconductive electromagnetic interference shielding materials with superior mechanical flexibility and flame retardancy

Flexible and wearable electronics represent an emerging frontier, but realizing their potential requires addressing challenges like electromagnetic interference (EMI) shielding, electrical insulating thermal management, and mechanical flexibility. Layer-by-layer structure with alternating conductive and insulating layers offers a promising solution. In this work, we fabricated layer-by-layer structured papers combining boron arsenide (BA) as insulating layers and two-dimensional copper nanoflake (CuF) as conductive layers based on aramid nanofiber (ANF) film via alternating vacuum filtration. The resultant paper (BA4/CuF3) consists of 3 layers of CuF (50 wt%) based ANF (CuF@ANF) conductive layers sandwiched between 4 layers of BA (50 wt%) based ANF (BA/ANF) insulating layers providing exceptional EMI shielding effectiveness (SE) up to 52 dB in the X-band frequency, and in-plane thermal conductivity up to 32.8 W/mK. Meanwhile, the composite papers also demonstrate excellent mechanical flexibility, with the BA4/CuF3 papers exhibiting a tensile strength of 92.38 MPa and EMI SE above 50 dB. Moreover, the composites impart thermal stability up to 500 °C and reduce flammability. The concurrent enhancement of EMI shielding, thermal conductivity, and mechanical properties confirms the potential of layer-by-layer BA/CuF papers for next-generation flexible electronics demanding electromagnetic protection and thermal management.

In situ three-roll mill exfoliation approach for fabricating asphalt/graphite nanoplatelet composites as thermal interface materials

Thermal interface materials (TIMs) are vital to dissipate excess heat generated by electronic components with ever-growing power density to ensure their reliability and performance. However, the limited dispersibility of nano-sized thermal conductive fillers hinders further enhancement of thermal conductivity in TIMs. It remains challenging to manufacture high-performance TIMs with simultaneous high thermal conductivity, low cost, and capability of large-scale production. Herein, a solvent-free and scalable approach was adopted to fabricate asphalt/graphite nanoplatelets (GNPs) composites by in situ exfoliating graphite in asphalt melt using a three-roll mill. During exfoliation, asphalt was adsorbed onto the surface of GNPs via π-π interaction and improved their dispersibility. Hence, GNPs formed integrated thermal conductive pathways with reduced interfacial thermal resistance, which significantly improved the thermal conductivity of asphalt/GNP composites. At 25 vol% loading, the asphalt/GNP composite displayed a thermal conductivity of 1.95 W m−1 K−1, showing a 114 % increase compared to the asphalt/commercial GNP (c-GNP) composite prepared by conventional mechanical mixing. Moreover, the heat-resistant and mechanical properties of the asphalt/GNP composites were also enhanced due to the improved filler dispersion and filler-matrix interactions. Thus, the asphalt/GNP composites fabricated by in situ three-roll milling possessed remarkable advantages as TIMs compared with asphalt/c-GNP composites and commercial silicone rubber thermal pads.

Enhanced thermal conductivity in thermoplastic polyether ester elastomer vitrimer composite foams via cell growth-induced orientation and lap of hybrid fillers

Lightweight thermal conductive polymer foams own a great potential application in some weight sensitive fields such as aerospace and encapsulation. Herein, the enhancement of thermal conductivity of thermoplastic polyether ester elastomer (TPEE) vitrimer composites foams caused by cell growth inducing fillers orientation and lap was investigated with hybrid fillers of fixed 15 vol% h-BN and various SiC nanowires. First, the hybrid fillers orientation in TPEE vitrimer composites (TVC) characterized by SEM and XRD patterns showed that the hybrid fillers were induced to be through-plane orientation and no interfacial defects were observed owing to the increasing contact area among fillers caused by large specific area and length of SiC nanowires. Based on that, cells were generated into TVC through scCO2 foaming. The effect of through-plane orientation and lap of hybrid fillers caused by cell growth of different cell structures on the thermal conductivity of TVC foams was investigated using extended Hashin-Shtrikman model and Maxwell-Eucken I model. The results showed that the thermal conductivity of TVC foams could greatly be enhanced to be higher than that of TVC by cell growth of continuous cell structures as it contributed to the through-plane orientation and lap of hybrid fillers to increase the contact and lap ratio among fillers. Thereby, the thermal conductive networks favorable to heat transfer were constructed in TVC foams to enhance the thermal conductivity as well as merit of lightweight.

Sugar‐template method to construct a boron nitride filler network to enhance the thermal conductivity of epoxy composites

AbstractIn this work, a technique for constructing a three‐dimensional (3D) skeleton of hexagonal boron nitride (h‐BN) using sugar as the fulcrum and preparing composites by embedding in the epoxy (EP) in a vacuum environment is proposed. The study of thermal conductivity (TC) in polymer composites is conducted through a blend of techniques: laser flashing, theoretical modeling, and finite element simulation. The h‐BN skeleton exhibits a honeycomb structure through the scanning electron microscopy findings. Further investigation using finite element simulation demonstrates that conductive networks are formed by the h‐BN skeleton within the composites, leading to a notable enhancement in TC. Specifically, the composite for h‐BN/EP reaches a TC of 2.25 W/m K when composed of 52 vol% h‐BN. A dielectric loss of 0.008 for the composite with the same h‐BN loading shows a considerable improvement. The compressive yield strength of the 3D h‐BN/EP composites reached 312 MPa at 5 vol% h‐BN loading.

Simultaneous Enhancement of Thermal Conductivity and Mechanical Properties of EZ42 Magnesium Alloy by Ca Microalloying

Simultaneous Enhancement of Thermal Conductivity and Mechanical Properties of EZ42 Magnesium Alloy by Ca Microalloying

A comprehensive experimental study on the effects of hexagonal boron nitride particle size and loading ratio on thermal and mechanical performance in epoxy composites

Harnessing the potential of hexagonal boron nitride (h-BN) in epoxy composites for tailoring thermal conductivity is a promising avenue in materials science. However, achieving balanced enhancements in both in-plane and through-plane directions remains a challenge that requires innovative solutions. The primary objective of this research is to evaluate how thermal and mechanical characteristics of an epoxy matrix are affected by the size and amount of h-BN particles. To achieve this goal, h-BN particles with varying sizes (micro and nano) are incorporated into the epoxy matrix at different weight ratios spanning from 0.5 wt % to 20 wt % using a pre-dispersion technique. The epoxy composites reinforced with h-BN through a molding process exhibits enhanced mechanical and thermal performance in contrast to the pristine epoxy material. During the flexural test, acoustic emission data is collected to identify the initiation and progression of damage within the specimens under testing conditions. The most notable enhancement in thermal conductivity is observed when incorporating 20 wt% of micron-sized h-BN particles. This leads to a remarkable 107% increase in the in-plane direction and an impressive 112% increase in the through-plane direction. These results can be attributed to the formation of a three-dimensional thermally conductive network by the larger h-BN particles, which extends the path of phonon scattering. Furthermore, there are significant improvements in both flexural modulus and tensile modulus. Epoxy composites containing 10 wt% of micron-sized h-BN experiences an approximate 42% increase, while those with 20 wt% of the same particles displays a substantial 47% rise in these properties. This study effectively addresses the challenges associated with tailoring the thermal properties of epoxy composites, opening up new opportunities for applications in various industries, including electronics, aerospace and thermal management systems.

Enhancing Thermal Conductivity in Polymer Composites through Molding-Assisted Orientation of Boron Nitride.

Incrementing thermal conductivity in polymer composites through the incorporation of inorganic thermally conductive fillers is typically constrained by the requirement of high filler content. This necessity often complicates processing and adversely affects mechanical properties. This study presents the fabrication of a polystyrene (PS)/boron nitride (BN) composite exhibiting elevated thermal conductivity with a modest 10 wt% BN content, achieved through optimized compression molding. Adjustments to molding parameters, including molding-cycle numbers, temperature, and pressure, were explored. The molding process, conducted above the glass transition temperature of PS, facilitated orientational alignment of BN within the PS matrix predominantly in the in-plane direction. This orientation, achieved at low filler loading, resulted in a threefold enhancement of thermal conductivity following a single molding time. Furthermore, the in-plane alignment of BN within the PS matrix was found to intensify with increased molding time and pressure, markedly boosting the in-plane thermal conductivity of the PS/BN molded composites. Within the range of molding parameters examined, the highest thermal conductivity (1.6 W/m·K) was observed in PS/BN composites subjected to five molding cycles at 140 °C and 10 MPa, without compromising mechanical properties. This study suggests that compression molding, which allows low filler content and straightforward operation, offers a viable approach for the mass production of polymer composites with superior thermal conductivity.

Development and comparison of multi-walled carbon nanotubes and graphite nanoflakes dispersed solar salt: Structural formation and thermophysical properties

A molten salt energy storage has proven to be a promising candidate for medium and high-temperature thermal energy storage (TES) applications. Improving the thermophysical properties, such as specific heat capacity (Cp) and thermal conductivity (k) is crucial to deciding the charging/discharging characteristics of the energy storage system. In this study, 1 wt% of two variant carbon allotropes, such as multi-walled carbon nanotubes (MWCNTs) and graphite nanoflakes (GNFs), were dispersed in solar salt (i.e., MWCNTs nanosalt and GNFs nanosalt) using wet preparation method. Thermophysical properties of the prepared nanosalts were evaluated using different analytical techniques and compared with pristine solar salt. The specific heat capacity was measured from 50 °C to 350 °C, and the maximum specific heat capacity enhancement in 1 wt% of MWCNTs dispersed solar salt was 18 %. The enhancement in 1 wt% of GNFs dispersed solar salt was 12.5 % at 200 °C (in solid phase). Similarly, in the liquid phase (at 350 °C), MWCNTs dispersed solar salt improves Cp by 6.2 %, while GNFs dispersed solar salt exhibits negligible improvement in Cp. Further, a modified transient plane source (MTPS) technique was used to measure the thermal conductivity of both carbon nanosalts in the solid phase (30–100 °C). The maximum thermal conductivity enhancement observed for MWCNTs dispersed solar salt and GNFs dispersed solar salt was 5.8 % and 11.7 %. Finally, thermogravimetric analysis was conducted to evaluate the thermal stability of the MWCNTs nanosalt and GNFs nanosalt at a maximum temperature of 700 °C, and found that the MWCNTs nanosalt show better thermal stability than the GNFs nanosalt.

A novel PCM/expanded graphite composite sphere with high thermal conductivity and excellent shape stability used for a packed-bed thermal energy system

In this research, a novel phase change material (NPCM) sphere was developed and its application in a packed-bed thermal energy storage (PBTES) system during thermal energy storage was studied. Paraffin wax (PW) with a melting point of 40 °C was selected as phase change material (PCM), expanded graphite (EG) as thermal conductivity enhancement material, and epoxy resin (ER) as a surface coating. The results show that the three-dimensional heat conduction network constructed by EG foam improves the thermal conductivity of PW/EG. The thermal conductivity of NPCM is anisotropic. The thermal conductivities perpendicular and parallel to the EG compression direction are 9.03 (W/m·K) and 5.58 W/(m·K). NPCM has excellent shape stability with a leakage rate of only 2.95 %. Then, a PBTE system was built to record the temperature evolution of NPCM spheres at various inlet temperatures and volume flow rates during thermal energy storage, and thermodynamic analysis was performed. The results are as follows. (1) The temperature of the NPCM sphere near the inlet rises more rapidly and the melting time of PCM is shorter. (2) Increasing the inlet temperature improves the heat transfer and shortens the melting time of PCM while increasing the temperature inhomogeneity of the NPCM spheres. Increasing the inlet temperature increases the energy storage capacity. However, higher inlet temperature leads to lower energy efficiency and exergy efficiency. The energy efficiency and exergy efficiency are 49.66 % and 67.64 % for the inlet temperature of 60 °C, respectively. When the inlet temperature increases from 60 °C to 80 °C, the energy efficiency and exergy efficiency decrease by 16.13 % and 16.22 %, respectively. (3) Higher inlet volume flow rate also promotes heat transfer and reduces the melting time of the PCM, but has little effect on the temperature inhomogeneity of the NPCM spheres. Increasing the inlet volume flow rate does not increase the energy storage capacity. Similarly, increasing the inlet volume flow rate also results in a decrease in energy efficiency and exergy efficiency. At the inlet volume flow rate of 19.28 m3/h, the energy efficiency and exergy efficiency are 41.65 % and 56.67 %, respectively. When the inlet volume flow rate increases from 19.28 m3/h to 25.16 m3/h, the energy efficiency reduces by 7.80 % while the exergy efficiency reduces by 7.41 %. This research provides a foundation for the application of the NPCM sphere.

Numerical investigation and optimisation of solid–solid phase change material composite-based plate-fin heat sink for thermal management of electronic package

Phase Change Material based Thermal Management Systems show promise in electronic packaging systems for safe operation, acting as a thermal storage element to prevent sudden temperature surges, enhancing operational time and mitigating electronic system failures. Therefore, the meticulous design of a solid–solid phase change material (SSPCM) based heat sink with fins is imperative for effective electronic thermal management by improving its safe operational time. This study performs a numerical analysis of two-dimensional transient heat transfer for the SSPCM-based plate-fin heat sink using the modified enthalpy porosity method, where the plate fins serve as Thermal Conductivity Enhancers (TCEs). Neopentyl glycol with 6% (w/w) Copper oxide nanoparticle is used as the SSPCM composite. Enhancement ratio based on safe operational time at different power levels (2–6 W) with different percentages of TCE and fin count recorded variation from 1.32 to 13.7. The TCE integration is more effective at higher power levels. The optimisation of SSPCM-based heat sink design for maximum safe operational time is accomplished through Response Surface Methodology. The significance of the TCE fraction, number of fins, heat generation rate, and interaction effects over the safe operational time are observed. The correlation for safe operational time as a function of TCE volume fraction, fin count and heat generation rate is developed. TCE volume fraction possesses the highest influencing factor over safe operational time at lower and higher power levels compared to fin count. At 2 W and 6 W, a maximum change in safe operational time is observed from 72.7% at 2 W to 83.45% at 6 W. The heat sink with 0.262 volume fraction of TCE and 11 fins is the optimised design that can provide the desirable safe operational time for the tested range of power levels.

Unlocking enhanced thermal conductivity in polymer blends through active learning

Polymers play an integral role in various applications, from everyday use to advanced technologies. In the era of machine learning (ML), polymer informatics has become a vital field for efficiently designing and developing polymeric materials. However, the focus of polymer informatics has predominantly centered on single-component polymers, leaving the vast chemical space of polymer blends relatively unexplored. This study employs a high-throughput molecular dynamics (MD) simulation combined with active learning (AL) to uncover polymer blends with enhanced thermal conductivity (TC) compared to the constituent single-component polymers. Initially, the TC of about 600 amorphous single-component polymers and 200 amorphous polymer blends with varying blending ratios are determined through MD simulations. The optimal representation method for polymer blends is identified, which involves a weighted sum approach that extends existing polymer representation from single-component polymers to polymer blends. An AL framework, combining MD simulation and ML, is employed to explore the TC of approximately 550,000 unlabeled polymer blends. The AL framework proves highly effective in accelerating the discovery of high-performance polymer blends for thermal transport. Additionally, we delve into the relationship between TC, radius of gyration (Rg), and hydrogen bonding, highlighting the roles of inter- and intra-chain interactions in thermal transport in amorphous polymer blends. A significant positive association between TC and Rg improvement and an indirect contribution from H-bond interaction to TC enhancement are revealed through a log-linear model and an odds ratio calculation, emphasizing the impact of increasing Rg and H-bond interactions on enhancing polymer blend TC.