High Thermal Dissipation Research Articles

Enhanced mechanical property, high-temperature oxidation and ablation resistance of carbon fiber/phenolic composites reinforced by attapulgite

To meet the thermal protection and load-bearing requirements of ultra-high-speed vehicles, it is urgent to improve the ablation resistance, high-temperature oxidation resistance and mechanical properties of carbon fiber/ boron phenolic resin (CF/BPR) composites simultaneously. Herein, polyhedral oligomeric silsesquioxane-modified attapulgite (ASP) with abundant porous structure was successfully introduced into the CF/BPR (CF/ASPBPR). The co-effect of ceramization, high infrared emissivity, and low thermal conductivity endowed the CF/ASPBPR with desirable ablation resistance, where the linear ablation rate and mass ablation rate reduced to 0.038 mm/s and 0.035 g/s, respectively. Meanwhile, due to the high thermal stability and energy dissipation of ASP, the CF/ASPBPR also presented the interlaminar shear strength of 35.40 and 9.79 MPa before and after high-temperature treatment, which were 24 % and 63 % higher than that of CF/BPR, respectively. This study provides a promising pathway for preparing advanced thermal protection materials that can adapt to severe mechanical spalling and thermochemical erosion environments.

Oscillatory onset of rotating thermal convection subject to spatially varying magnetic fields and stable stratification

Convective fluid motions in deep planetary cores induce spatially and temporally varying magnetic fields observable as secular variation. Oscillatory instabilities occurring as onset modes in rapidly rotating thermal convection influenced by heterogeneous magnetic fields and stratification, investigated in this study, can be potentially linked to such observations. A plane layer approximation to near-polar and near-equatorial regions of the Earth's outer core is considered. In addition to penetrative convection and flow suppression effects, the simultaneous interaction of convective instabilities with asymmetrical magnetic fields and stable stratification is the focus of this study. The fundamental modes of magnetoconvection onset are preserved even under stable stratification, although the convection threshold is lowered irrespective of the parameter regime. The axial invariance of rapidly rotating columnar convection loses its midplane symmetry with intense localization of kinetic energy in the unstably stratified regions. The parameter regimes supporting the onset of the magnetically modified viscous oscillatory (mVO) modes are further extended toward Earthlike conditions such as high thermal conductivity (low Prandlt number, Pr) and magnetic dissipation (low Roberts number, q). Moreover, compared to fully unstable stratification, partial stable stratification enhances the range of imposed magnetic field length scale (δ) over which the onset of mVO modes is favored. The critical field length scale (δ⋆), above which the onset regime of the mVO modes is bounded by a minimum q, is determined. Irrespective of the rotation rate, below δ=δ⋆, the onset of the mVO mode is supported for asymptotically small q for Pr values close to the Earth's outer core.

Experimental description of heat transfer processes at two-phase flow in microchannels towards the development of a heat sink for PV panels

The development of new and more effective cooling technologies is required for several high thermal power dissipation applications such as in electronics cooling or high concentrated photovoltaic panels. The present paper addresses an experimental study on the development of a microchannel based heat sink to cool photovoltaic panels. Experiments focus on the test of a microchannel, with geometry and dimensions optimized from previous work. The analysis performed here emphasizes the experimental characterization of flow boiling in the microchannel under different working conditions. The results include pressure drop and heat flux maps, obtained combining pressure sensors with high-speed imaging and time resolved thermography. The analysis performed was able to identify where nucleation sites were formed. Slug flow interfacial heat transfer could be observed and accurately described in the heat flux maps. Overall, results show the high potential of combining high-speed imaging with time resolved infrared thermography to characterize complex flows. These results also show that there is a good potential for this microchannel based flow cooling in removing the required heat fluxes for the application considered here, when compared to other liquid and air-cooling technologies.

Temperature dependency of impedance, dielectric, and conductivity properties for Si-p/beta-FeSi2-n heterostructures created through facing target sputtering

To connect thermal dependency with Si-p/beta-FeSi2-n heterostructure efficiency, this work explored the impedance characteristics accompanied by dielectric and conductivity properties under different temperatures of 160–400 K. The Nyquist impedance plots for the heterostructures showed a semicircular arc that shrank as the temperature increased. These can be equivalently interpreted as a loop of single resistance paralleled to single constant phase element representing the heterostucture which also paralleled to inductive elements representing the inductive effect, serially connected to electrode resistance. The dielectric properties implied a shift in behavior for the relaxation process since donor-acceptor deionization occurred when the temperatures reached 320 K or higher due to shorter relaxation time and higher thermal dissipation. The conductivity properties indicate that the transport mechanism at 180 K or lower involves a prolonged transitional movement before transitioning into localized hopping at higher temperatures, corresponding to faster carrier movement. The relaxation and activation energy of the heterostructure reveal drastic transition of the energy from a low temperature of 160–240 K to a higher temperature of 320–400 K, where the electrical mechanism of the heterostructures become highly dependent on the temperature likely due to the high carrier density based on unevenly high activation energy.

Conceptual cryostat design for cryogenic payload suspension studies for the Einstein Telescope

The Einstein Telescope (ET) is a third generation gravitational wave detector, combining a low-frequency (LF) and a high-frequency (HF) laser interferometer. Cryogenic operation of ET-LF in the temperature range of 10 K to 20 K is essential to suppress the suspension thermal noise, which dominates the detection sensitivity at frequencies below 10 Hz. This requires suspension materials with high thermal conductivity and low mechanical dissipation at cryogenic temperatures. Two possible suspension concepts are currently considered, using either monocrystalline suspension fibers made of silicon or sapphire, or titanium suspension tubes filled with static He-II. The dissipative behavior of these suspensions is characterized by the mechanical Q-factor. It can be measured by the ring-down method, exciting the suspensions to resonance vibrations on the nanometer scale and analyzing the decay time. For this purpose, a new cryogenic test facility is being planned, allowing the investigation of cryogenic payload suspensions for third-generation gravitational wave detectors. The test cryostat is equipped with a cryocooler and enables real-size studies with various suspension materials and geometries. The future integration of He-II is foreseen to enable He-II filled suspension studies. We describe the scope of experiments and the conceptual design of the test cryostat.

Boron nitride nanosheets from high shear exfoliation for high-performance thermal conductivity films

Boron nitride nanosheets (BNNSs) with intrinsically ultra-high thermal conductivity have attracted more and more attention and various methods have been proposed to prepare BNNSs-based thermally conductive adhesives. In this work, a liquid phase shear exfoliation process was proposed to prepare BNNSs. BNNSs can be directly prepared by exfoliating h-BN particles dispersed in isopropanol at a controlled rotational speed range of 16,000–22,000 rpm and the maximum yield of BNNSs is up to 32.1%. After the BNNSs were modified with polydopamine (M-BNNSs), the dispersion performance of BNNSs in water was significantly improved. BNNSs were incorporated into a cellulose nanofiber-based adhesive, and the highly thermally conductive films were prepared by a flow-delay process. A tested in-plane thermal conductivity of up to 23.23 W·m−1·K−1 and excellent mechanical properties are demonstrated and thermal infrared images provide a more visual representation of the high thermal conductivity and heat dissipation properties of the film, indicating the promising application of the film in the field of thermal conductivity.

A multi-layer fabric for high-efficiency solar-driven seawater desalination

Fiber-based photothermal materials for seawater desalination usage have garnered significant attention owing to their outstanding properties. However, traditional monolayer fabrics are prone to possess inherent inefficiencies such as high thermal dissipation and salt crystallization within the evaporation zone, especially reducing the evaporation efficiency during the long-term seawater desalination. Herein, a novel three-layered three-dimensional (3D) spacer carbon/polyester cotton spacer woven fabric (SWF) evaporator is designed. This SWF material was delineated into three distinct layers: an upper evaporate layer, a foundational water absorption layer, and a central water dedicated to water transition, thermal insulation, and salt crystallization. The rational three-layered 3D architecture guarantees the swift aqueous transition within SWF evaporator, simultaneously curtailing thermal losses from the top layer. The evaporation rate of 3D SWF, with 6 mm interval space, registered at 1.6721 kg · m−2·h−1 under a solar intensity of 1 kW · m−2. Furthermore, under conditions with a solar power of 1 kW · m−2 and a wind velocity of 2 m · s−1, the evaporation efficiency of liquid water from SWF, with a central layer height of 12 mm, culminated at 3.9742 kg · m−2·h−1, which validated its adeptness for the seawater desalination applications. The results of our research are helping to provide for efficient and stable methods of wastewater treatment, desalination, and drinking water collection.

A Comparative Thermodynamic Study of AlF3, ScF3, Al0.5Sc0.5F3, and In0.5Sc0.5F3 for Optical Coatings: A Computational Study

Optical coatings are thin layers of materials applied to optical components in order to modify the transmission, reflection, or polarization properties of light. The common materials used for optical coatings include magnesium fluoride (MgF2), scandium trifluoride (ScF3), and aluminum trifluoride (AlF3), owing to their desirable optical properties, spectral range, and compatibility with substrates. However, each of these materials has its own drawbacks. For instance, AlF3 has been found to exhibit limited resistance to attack by chemicals, as well as poor thermal stability, while MgF2 has low durability, as well as being hygroscopic. In this study, we undertook ab initio calculations in order to compare the thermal properties of AlF3, ScF3, Al0.5Sc0.5F3, and In0.5Sc0.5F3 in order to obtain the best material for optical coatings. MgF2 was also included in the study as a reference. The calculations used PBE pseudopotentials and the extended generalized gradient approximation within the quantum espresso algorithm. The study demonstrated that the computed results agree with the information found in the literature. ScF3 exhibited a negative coefficient of thermal expansion, unlike the other four. Moreover, AlF3 was found to be the best candidate for optical coatings that are used in high-power laser systems with high thermal dissipation, due to its superior thermal expansion coefficient as well as its better response to thermal stress. The large variation between the cp and cv of ScF3 is not desirable. Moreover, due to its negative thermal expansion coefficient, ScF3 is not thermally stable. The highest thermal stability was exhibited by In0.5Sc0.5F3. Since Al0.5Sc0.5F3 and In0.5Sc0.5F3 have been modeled in this study for the first time, experimental determination of their crystal structures needs to be investigated.

Uncooled 100-GBaud Directly Modulated Membrane Lasers on SiC Substrate

We investigate the temperature dependence of the dynamic characteristics of a 1.3-μm InGaAlAs-based directly modulated membrane laser on a SiC substrate. The laser is fabricated by combining direct wafer bonding of SiC and InP substrates using a very thin (∼10 nm) oxide layer and epitaxial regrowth of a membrane InP layer on the InP/SiC template. The membrane laser structure on SiC with a high thermal conductivity (490 Wm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) and a moderate refractive index (∼2.6) ensures both high thermal dissipation and a large optical confinement factor in the active region, which are ideal for increasing the relaxation oscillation frequency even at high operating temperatures. We further leverage the optical feedback effect from the output facet of a waveguide to enhance the bandwidth and enable signal modulation at 100 GBaud and beyond. Owing to the high relaxation oscillation frequency and the photon-photon resonance effect, it is possible to obtain a flat frequency response at temperatures ranging from 25 to 85°C. The fabricated membrane laser on SiC with an active-region length of 50 μm exhibits 3dB bandwidths of >110, 97, and 74 GHz at 25, 55, and 85°C, respectively. We successfully demonstrate 2-km transmissions of 100-Gbit/s NRZ signals under uncooled conditions (25 to 85°C). Furthermore, the laser is capable of 112-Gbit/s NRZ modulation at 85°C.

Salt‐Fingering Under the Thermal‐Wind and Lateral Shears in the Kuroshio Fronts

AbstractWe apply a linear normal mode stability analysis to identify instability in fronts stable to symmetric instability (SI). SI stable fronts appear in many of our observations in the Kuroshio current. These fronts consist of strong horizontal and vertical temperature and salinity gradients. Our stability analysis considers salt‐fingering instability in the presence of thermal‐wind and lateral shears along the isopycnal, which we term “geostrophic shear salt fingering (GSF).” When GSF grows faster than SI, the energy source is in the geostrophic and lateral shears, similar to SI. The results of the linear stability analysis are applied to evaluate temperature and salinity observations on the east coast of Japan in the Kuroshio current. The majority of our data do not support the growth of SI, as the measurements were taken in the fall when the fronts were stratified. Instead, our data indicate a preference for GSF growth. The total perturbation growth in GSF is determined by the source and sink terms in the scalar variance dissipation rates. The thermal and saline covariance dissipation rate (codissipation rate) serves as the primary energy source, while the thermal and saline variance dissipation rates function as the energy sink. This suggests that the presence of the GSF is detectable in microstructure measurements as patches of high thermal variance dissipation rate along the isopycnal slope at fronts in the absence of SI.

Preparation of Thermally Conductive Silicone Rubber-Based Ultra-Thin Sheets with Low Thermal Resistance and High Mechanical Properties

Thermally conductive silicone rubber (TCSR)-based thin sheets with low thermal resistance and high electrical insulation properties have been widely used in thermal management applications in the electronic and energy storage fields. The low thermal resistance is mainly attributed to the sheets’ small thickness. In order to further decrease the sheets’ thermal resistance, it is necessary to decrease their thickness. However, the sheets mostly have a thickness of at least 0.20 mm, and it is still a challenge to decrease the thickness to less than 0.10 mm mainly due to the difficulty of smooth calendering through a narrow roll-to-roll gap on calenders. Here, a low-viscosity calendering method has been developed to prepare TCSR-based ultra-thin sheets. The sheets present unprecedentedly small thickness (~0.08 mm), low thermal resistance (0.87 cm2K/W), high tensile strength (~8 MPa), high flexibility, high electrical resistance (&gt;1014 Ω·cm), and high thermal dissipation (&gt;30 °C decrease in LED working temperature). Comparison studies between this new method and the conventional preparation method have been carried out to understand the mechanism of the improvements.

Non-Darcy nanoliquid buoyant flow and entropy generation analysis in an inclined porous annulus: Effect of source-sink arrangement

In several engineering and industrial applications, the primary challenge in the design of thermal devices is to minimize the entropy production with maximum energy dissipation so that the system efficiency could be enhanced. In particular, an inclined partially heated annulus is far challenging due to the presence of both tangential and normal gravity components, which produces major impacts on the fluid movement and associated transport rates as well as entropy production. From several important applications point of view, the current investigation is mainly focused to address the combined impacts of source-sink arrangements as well as the annular inclination on buoyant nanoliquid motion, thermal dissipation along with irreversibility distribution in a tilted porous annulus. The governing model equations are numerically solved by utilizing the finite difference based time-splitting and relaxation techniques. Using second-order finite difference approximation, the partial derivatives are approximated and the resulting system of algebraic equations are inverted using Thomas algorithm. The influence of various controlling parameters such as geometric inclination angle, nanoparticle shape, Darcy number, length and position of source-sink on fluid movement, thermal and entropy distribution are scrutinized in detail. Through a wide range of numerical experiments, it has been found that the annular inclination angle and location of source-sink arrangement plays a vital role on fluidity and flow patterns of nanoliquid in the porous saturated annulus. For smaller size of source-sink pair, higher thermal dissipation with minimal entropy production could be achieved, which is an important observation for the design of thermally efficient systems. We have also noticed that a better thermal transport rate with minimum irreversibility rate could be attained for a particular source-sink arrangement, in particular for γ=0∘, the staggered positioning of source-sink pair is beneficial rather than in-line arrangement. Among the various parameters arising in this analysis, the nanoparticle shape has been one of the key parameters to test the thermal efficiency. It has been predicted that the blade shaped nanoparticle induces better thermal efficiency, among the five different shapes of nanoparticle. The outcomes of this analysis could be utilized in applications, such as solar systems, electronic equipment cooling and heat exchangers.

Current status of various coolant applications in machining of nickel-base superalloys

Nickel-chromium super-alloys are preferred over steel as they provide excellent performance over a broad temperature range of cryogenic temperature to 1400 Fahrenheit. These alloys possess both high impact and tensile strength, thus it is one of the most desirable raw material for aeronautical and marine industries. Apart from all these advantages, they are very hard to machine and a huge magnitude of heat arises during machining operations which directly affects the product quality and surface texture of the finished products. To overcome all these problems, many researchers have implemented different types of coolants to minimize temperature generation, surface roughness, and tool wear. Coolants also harm both human health and the ecosystem if it is not handled properly and their disposal remains a challenge to our civilization. To overcome these challenges most industries preferred biodegradable vegetable oil base coolants over conventional mineral oil coolants. Researchers are continuously working on different methods to intensify the thermal conductivity and heat-dissipating capability of the coolants. This gave birth to a new era of coolants, where nanoparticles are mixed in a base oil to intensify their lubricating and cooling properties. These types of coolants are known as nanofluids which are colloidal mixtures made by the combination of nanoparticles and a base fluid. Nanofluids are now renowned in the entire world because of their high thermal conductivity, lubrication, and heat dissipation abilities. These papers provides a concise review of the effects of the several cutting fluids such as synthetic oil, mineral oil, vegetable oil, and nanoparticle-based cutting fluid on various machining outputs such as surface roughness and wear on tool interface while machining of the nickel-based alloy under an MQL environment. A concise review of different nanofluid preparation techniques is also included in this paper to acquire close knowledge about the manufacturing of different nanofluids.

Si-IGBT and SiC-MOSFET hybrid switch-based 1.7 kV half-bridge power module

• Design guidelines, fabrication process, and evaluation of a 1.7-kV and 300-A multi-chip half bridge power module using the novel Si-IGBT and SiC-MOSFET hybrid switch in each switch position. • The module achieves its maximum DC current rating with a 6:1 current ratio of Si to SiC. • A novel custom-designed TPG-encapsulated metal base plate is proposed. • Silver clips for top-side interconnect in the module, facilitating a wire bond-less interconnection, high reliability, and low power loop inductance. • High thermal dissipation capability while maintaining a near-isolated thermal path for the SiC MOSFET to operate at a higher temperature than the Si-IGBT. This paper informs the design guidelines, fabrication process, and evaluation of a 1.7-kV and 300-A multi-chip half bridge power module using the novel Si-IGBT and SiC-MOSFET hybrid switch in each switch position. The module achieves its maximum DC current rating with a 6:1 current ratio of Si to SiC. This high current ratio yields significant cost savings compared to an all-SiC power module. The module employs high-reliability silver clips, which replaces conventional wire bonds for top-side interconnection, to partly enable a low power loop inductance of 12.38 nH. A novel thermal pyrolytic graphite-encapsulated metal baseplate is key to reducing the thermal coupling among the adjacent Si and SiC die, enabling higher junction temperature for SiC die relative to the Si die.

A Modeling and Simulation Method for Preliminary Design of an Electro-Variable Displacement Pump.

Electro-hydrostatic actuators (EHAs) have been considerably researched in academia, and their applications in various industrial fields are expanding. The variable-speed EHA has now taken priority over the variable-displacement EHA, but its driving motor and associated electronics encounter issues when applied in high-power applications: low-dynamics, high thermal dissipation, high price, etc. Therefore, a variable-displacement EHA equipped with an electro-variable displacement pump (EVDP) has been considered. The EVDP itself is a mechatronic system that integrates a piston pump, a ball screw, a gearbox, and a permanent magnet synchronous motor (PMSM). Consequently, the EVDP needs to be investigated to ensure its system-level performance when applied in an EHA. In addition to the previous research on the technical parameters of the EVDP, a dedicated design method is necessary for further reducing the cost of using the EVDP and exploring its performance potential. Here, a simulation based EVDP preliminary design method is selected for designing a 37 kW EVDP. Firstly, a previously proposed multidisciplinary model of the EVDP is extended by improving the parameter generation, including the EVDP life, reliability, control models, etc. Secondly, the proposed model is partially verified using a downsized prototype. Thirdly, the EVDP is simulated at a system level, supported by the proposed model. The EVDP performance is evaluated according to the specified design requirements. The temperature, bandwidth and accuracy, reliability and lifetime, etc., are all predicted for the EVDP. The simulation results demonstrate the EVDP's applicability in variable-displacement EHA. The proposed modeling and simulation method can be used to evaluate diverse EVDP performance and respond to general design requirements. The method can also support the resolution of the preliminary design challenges in terms of limited information and robustness. Therefore, the proposed method is appropriate for the realization of the simulation-based EVDP preliminary design method.

Partially-covered fractal induced turbulence on fins thermal dissipation

The impacts of partially-covered fractal grids induced turbulence on the forced convective heat transfer across plate-fin heat sink at Reynolds number ReDh = 22.0 × 103 were numerically and experimentally investigated. Results showed that partially covered grids rendered a higher thermal dissipation performance, with partially-covered square fractal grid (PCSFG) registering an outstanding increase of 43% in Nusselt number relative to the no grid configuration. The analyzation via an in-house developed single particle tracking velocimetry (SPTV) system displayed the findings of unique “Turbulence Annulus” formation, which provided a small degree of predictivity in the periodic annulus oscillations. Further assessments on PCSFG revealed the preferred inter-fin flow dynamics of (i) high flow velocity, (ii) strong turbulence intensity, (iii) vigorous flow fluctuations, (iv) small turbulence length scale, and (v) heightened decelerated flow events. These features stemmed from the coupling effects of multilength-scale fractal bar thicknesses in generating a veracity of eddy sizes, and a vertical segmentation producing heightened mass flow rate while inducing favourable wake-flow structures to penetrate inter-fin regions. Teeming effects of such energetic eddies within plate-fin array unveiled a powerful vortex shedding effect, with PCSFG achieving fluctuation frequency f = 18.5 Hz close to an optimal magnitude. The coaction of such traits limits the growth of fin boundary layers, providing superior thermal transfer capabilities which benefits the community in developing for higher efficiency heat transfer systems.

Microstructural characterization and oxidation performance of solution-annealed and precipitation hardened wire-arc additively manufactured Inconel 718 superalloys

This research work investigated the effects of standard solution-annealed (SA) treatment on microstructure and chemical characteristics of Inconel 718 (IN718) superalloys fabricated using tungsten inert gas welding based wire-arc additive manufacturing (WAAM) process. A commercial wrought IN718 product was also studied for comparison. It was observed that WAAM parts developed highly-textured large columnar austenite (γ) grains along the build-up direction due to the epitaxy and high thermal dissipation rate. The micro-segregation of Nb produced an inhomogeneous γ-matrix precipitating non-hardening laves phases as a result of constitutional undercooling, high energy input and slow cooling rate of WAAM process. After the solution treatment, SA sample remained to be highly-textured solid-solution of γ-matrix and formed non-hardening delta (δ) plates with undissolved residual laves phases in Nb-enriched regions. These deprived the precipitation of beneficial hardening phases of γ″ and γ′ particles in γ-matrix during SA treatment. The high-temperature oxidation study of SA-treated samples obeyed parabolic rate law which was independent of oxidation temperatures. The oxidation mechanisms in the formation of oxide scale were found to be temperature dependent. At 800 °C, only a thin and continuous layer of Cr2O3 scale was formed externally at the air-alloy interface. A multi-layer of external Cr2O3 at air-scale interface, inner Nb-rich complex Ti0.67Nb1.33O4 scale at scale-alloy interface and internal sub-scale of Al2O3 was formed at 900–1000 °C. Due to the high lattice diffusivity of Mn+2 and Ti+4 cations through Nb-rich complex layer and Cr2O3 scale, a thin layer of TiO2 and MnCr2O4 was formed at the outermost part of Cr2O3 scale at 1000 °C. The oxidation reaction process of scale growth in IN718 alloys was mainly dominated by the outward diffusion of Cr+3 cations through Cr2O3 layer at the air-scale interface as the activation energies were found to be in the range of 250–290 kJ/mol for Cr2O3 (chromia) forming Ni-based superalloys.

Thermal Protection by Integration of Vacuum Insulation Panel in Liquid-Cooled Active Thermal Management for Electronics Package Exposed to Thermal Radiation

Abstract Thermal management systems (TMSs) working for electronics packages under harsh environments like intense thermal radiation are challenging due to external thermal interactions. Thermal insulation protection for TMS is very critical in these harsh conditions. An experimental setup was developed to analyze the effect of insulation protection against thermal irradiation over a pumped liquid-cooling active thermal management system (ATMS) with varying heat dissipation rate (0–4.2 kW/m2), thermal irradiation (0.85–3.80 kW/m2), and coolant temperature (15–25 °C). Three configurations of ATMS are considered in the experimental study: ATMS without thermal insulation protection, ATMSs integrated with Cellulose Fibre Insulation (CFI), and Vacuum Insulation Panel (VIP). The effect of insulation on each parameter in all three ATMS configurations over the temperature of the electronics component, cooling load, and nature of heat flow in ATMS was analyzed. VIP outperformed CFI on achieving a significant reduction in the temperature of electronics systems (35.67%) and cooling load (45.64%) experienced by the ATMS. VIP effectively reduced the impact of temperature and cooling load change in ATMS against change in thermal irradiation. The study concluded that thermal insulation protection was most effective at high thermal irradiation and low heat dissipation rate. Heat Flow Direction Index (HFDI) concept was developed to find the nature of heat transfer direction in ATMS without temperature distribution trend. Heat generation rate and irradiation possess significant influence over the nature of heat flow direction.

Turbulence Properties of a Deep‐Sea Hydrothermal Plume in a Time‐Variable Cross‐Flow: Field and Model Comparisons for Dante in the Main Endeavour Field

AbstractA large eddy simulation is used to study a high temperature hydrothermal vent plume in a stratified and tidally modulated crossflow, in order to identify its turbulence and mixing characteristics. The model parameters and source conditions that are comparable to the vertical velocity and refractive index fluctuations measured 20 m above the Dante sulfide mound in the Main Endeavour vent Field are a heat transport of 50 MW over a cross‐sectional area of 4 × 4.5 m2. With these model source conditions and output results taken at 20 m above the source with 1 Hz sampling, the shear production of turbulent kinetic energy (TKE), the vertical transport of TKE, and the buoyancy production/dissipation are quantified showing that shear production dominates. Similarly, thermal variance production, and its vertical transport, is also quantified showing that the advective term dominates. Because of enhanced entrainment of ambient water into the plume during strong crossflows, all mean and turbulent quantities show tidally modulated values. Assuming steady state, the dissipation rates are evaluated. During strong crossflows, the tilting of the vertical velocity contours and isotherms plays a critical role in the stability of the plume and in creating high shear and thermal gradients on the upstream side of the plume center axis. These dissipation rates are used to quantify the refractive index fluctuations, and given the high thermal dissipation quantity it is the main contributing factor in acoustic forward scatter.

Optimization of the composition in a composite material for microelectronics application using the Ising model

Tailored material is necessary in many industrial applications since material properties directly determine the characteristics of components. However, the conventional trial and error approach is costly and time-consuming. Therefore, materials informatics is expected to overcome these drawbacks. Here, we show a new materials informatics approach applying the Ising model for solving discrete combinatorial optimization problems. In this study, the composition of the composite, aimed at developing a heat sink with three necessary properties: high thermal dissipation, attachability to Si, and a low weight, is optimized. We formulate an energy function equation concerning three objective terms with regard to the thermal conductivity, thermal expansion and specific gravity, with the composition variable and two constrained terms with a quadratic unconstrained binary optimization style equivalent to the Ising model and calculated by a simulated annealing algorithm. The composite properties of the composition selected from ten constituents are verified by the empirical mixture rule of the composite. As a result, an optimized composition with high thermal conductivity, thermal expansion close to that of Si, and a low specific gravity is acquired.