Search

This paper established a three-dimensional transient MHD model of a high-current multi-component vacuum arc under a transverse magnetic field (TMF) to simulate the dynamic characteristics of plasma parameters in the uniform motion mode of a contracted arc under lower TMF. The model considered the ionization–recombination process among the multi-components and used the P1 model to calculate the thermal radiation losses. The simulation results show that the ion number density of The TMF arc is on the order 1024 m−3, and when the plasma temperature reaches 4.3 eV, the effects of thermal radiation cannot be ignored. The majority of the plasma from the cathode and anode undergo acceleration and then deceleration before finally intersecting at the center of the arc, creating an extreme value of the density and the pressure, where a large amount of kinetic energy is converted into internal energy. The arc will be bent and deflected under the action of the ampere force, and the deflection of Cu3+ is especially obvious. The TMF affects the collision strength of the jet in the intersection area and, thus, affects the ion density, in which the change of Cu2+ is dominant. The ionization–recombination process of ions is mainly determined by the electron temperature, which is affected by the arc current. As the current decreases, Cu1+ increases and Cu2+ and Cu3+ decrease, and the change in ionization rate is the main reason for the change in the proportion of each ionic component; the heat flux density to the anode and cathode is on the order of 1010 W/m2, which heats the front of the arc and ensures the stable movement of the arc. Meanwhile, due to the high ion number density, the ion heat flux accounts for the main part of the heat flux, and the anode exhibits a higher proportion of ion heat flux. [ABSTRACT FROM AUTHOR]

This paper presents BubbleID, a sophisticated deep learning architecture designed to comprehensively identify both static and dynamic attributes of bubbles within sequences of boiling images. By amalgamating segmentation powered by Mask R-CNN with SORT-based tracking techniques, the framework is capable of analyzing each bubble's location, dimensions, interface shape, and velocity over its lifetime and capturing dynamic events such as bubble departure. BubbleID is trained and tested on boiling images across diverse heater surfaces and operational settings. This paper also offers a comparative analysis of bubble interface dynamics prior to and post-critical heat flux conditions. [ABSTRACT FROM AUTHOR]

To address the challenges faced by designers of multi-field coupled cooling systems for high heat flux chips, this paper proposes a "near-source" microchannel cooling strategy and establishes a thermal–flow-force electrically coupled model for chips. The effects of chip Joule heat and cooling water flow rate on the cooling performance with respect to multi-field coupling effects were studied. The impact of multi-field coupling effects was revealed, and a method for enhancing microchannel cooling performance in light of multi-field coupling effects is proposed. The results indicated that considering multi-field coupling effects in the microchannel cooling process leads to a deterioration in the thermal performance of chips, accompanied by a significant increase in electrical fluctuations and thermal deformation amplitude. Compared to chips upstream of the cooling water, chips downstream subjected to thermal cascade effects were more sensitive to multi-field coupling effects. Moreover, the temperature variance index, output current, and strain energy density of high heat flux chips were positively correlated with Joule heat but inversely proportional to the Reynolds number of the cooling water for cases in respect of multi-field coupling effects. Additionally, serpentine microchannels maximized the operational performance of high heat flux chips by reducing temperature of chip by up to 55.1%, decreasing strain energy density by 96.7%, and increasing input potential by 120%. [ABSTRACT FROM AUTHOR]

Machine-learning potentials provide computationally efficient and accurate approximations of the Born–Oppenheimer potential energy surface. This potential determines many materials properties and simulation techniques usually require its gradients, in particular forces and stress for molecular dynamics, and heat flux for thermal transport properties. Recently developed potentials feature high body order and can include equivariant semi-local interactions through message-passing mechanisms. Due to their complex functional forms, they rely on automatic differentiation (AD), overcoming the need for manual implementations or finite-difference schemes to evaluate gradients. This study discusses how to use AD to efficiently obtain forces, stress, and heat flux for such potentials, and provides a model-independent implementation. The method is tested on the Lennard-Jones potential, and then applied to predict cohesive properties and thermal conductivity of tin selenide using an equivariant message-passing neural network potential. [ABSTRACT FROM AUTHOR]

This work presents a method for calculating the difference in temperature jumps observed at the solid–water and water–solid interfaces when heat is flowing under steady state conditions from a hot to a cold solid separated by an intermediate water phase. The method is based on a hypothesis stating that the entropy flux is maximized where the heat flux is constrained, i.e., at the solid–water interfaces. By focusing on the entropy rather than the heat flux and by maximizing its value vs the magnitude of the temperature jump over the interfaces where the latter is constrained, simple analytical expressions for the jump differences independent of the actual heat flux are established only depending on the absolute temperature of the hot and cold solid. The results show that the temperature jump at the hotter interface, therefore, must be higher than the jump at the colder because of the differences in absolute temperature between the two interfaces, supported by many observations. The results, furthermore, show that the temperature jump asymmetry between the two interfaces should increase with decreasing absolute temperature of the system. The work, therefore, finally indicates that there are two quantities contributing to the magnitude of any temperature jump, the heat and entropy flux. More investigations about their relationship under different conditions are encouraged since the topic is not systematically acknowledged and, therefore, investigated in the literature. [ABSTRACT FROM AUTHOR]

The carbon fiber (CF) reinforced boron phenolic resin (BPR) matrix composite, renowned for its exceptional ablation resistance, represents a promising material for high-temperature applications. However, hypersonic vehicles are subjected to increasingly challenging service environments, which necessitate materials capable of enduring even more extreme temperatures. Consequently, there is a growing need for composites that exhibit superior ablation resistance. To tackle these demanding requirements, this research initiative introduces the integration of ceramizable fillers, including TiB2, B4C, and ZrC, into the composite structure to create a high-temperature ceramizable system. The experimental findings indicate that the composites formulated with this innovative system demonstrate extraordinary ablation resistance, even when exposed to oxyacetylene flames with a heat flux of 4364 kW/m2. Notably, the measured linear ablation rate and mass ablation rate were recorded at −0.012 mm/s and 0.0268 g/s, respectively. These values are exceptionally low. Subsequent analysis utilizing X-ray diffraction (XRD) and additional characterization techniques has confirmed the formation of a dense ceramic layer with a B-C-O-Ti-Zr composition on the composite surface at elevated temperatures. This ceramic layer acts as a formidable barrier, significantly mitigating the ablation effects caused by high-temperature exposure. Meanwhile, it is pertinent to note that the formation of the ceramic layer is accompanied by an endothermic reaction, which consequently leads to a reduction in the thermal conduction of the composite to some extent. [ABSTRACT FROM AUTHOR]

Mercury's low obliquity and 3:2 spin‐orbit resonance create a surface temperature distribution with large latitudinal and longitudinal variations. These propagate via thermal conduction through the thin silicate shell influencing the interior temperature distribution. We use 3‐D thermal evolution models to investigate the effects of lateral variations of surface temperature and crustal thickness on the surface and core‐mantle boundary (CMB) heat fluxes, and elastic thickness distribution. Surface temperature variations cause a long‐wavelength perturbation of the heat fluxes, as well as of the elastic lithosphere thickness, while variations in crustal thickness affect these quantities at small spatial scales. Like the surface temperature, the present‐day CMB heat flux pattern is characterized primarily by spherical harmonics of degrees two and four, which could affect dynamo generation. Placing robust constraints on the thermal evolution based on the available estimates of the age and thickness of the elastic lithosphere remains challenging due to their large uncertainties. Plain Language Summary: The orbit of Mercury around the Sun leads to a specific surface temperature distribution, with some regions receiving more insolation than others. The thickness of Mercury's crust has been derived using gravity and topography data acquired by the MESSENGER mission. Since the rocky mantle of Mercury is rather thin (≈ ${\approx} $400 km), temperature variations driven by the insolation and by crustal properties (i.e., crustal heat sources and thermal conductivity) can affect the entire mantle, down to the core‐mantle boundary. Here we model the global thermal evolution of Mercury, and investigate the influence of surface temperature and crustal thickness variations on the history and present‐day state of the interior. We find that the surface temperature variations are reflected in the variations of Mercury's surface and core‐mantle boundary heat fluxes, as well as in the thickness of the elastic part of its lithosphere. Crustal thickness variations lead to more local temperature differences, thus resulting in smaller scale variations in the lithosphere thickness and heat fluxes. The heat flux pattern at the core mantle boundary induced by the surface temperature distribution could affect magnetic field generation and should be tested by future dynamo models. Key Points: The distribution of Mercury's mantle temperature is strongly influenced by surface temperature and crustal thickness variationsSurface heat flux and elastic thickness are controlled at large scales by surface temperature, and at small scales by crustal thicknessSurface temperature variations influence the CMB heat flux distribution, which we make readily available to test dynamo models [ABSTRACT FROM AUTHOR]

The synergistic interactions between urban heat islands (UHI) and heat waves (HW) continue to be debated. Despite the expectations of UHI intensification during HW, several studies have demonstrated variations. Notably, there is a dearth of investigations concerning the UHI–HW synergy in tropical climate cities amidst the escalating trend of more frequent and severe HW in Southeast Asia. To address this gap, our study aimed to investigate the synergies between the UHI and HW phenomena in Greater Kuala Lumpur (GKL) and its surrounding areas. We employed the advanced research version 4.2.2 of the Weather Research and Forecasting (WRF) model, coupled with a single‐layer Urban Canopy Model (UCM), to examine the impact of UHI during two heat wave events in 2016 (Case 1) and 2020 (Case 2), against the periods immediately before and after these events, which we refer to as Pre‐Post HW (PPHW), in GKL. An elevated UHI intensity (UHII) was evident during the HW in both observations and simulations, with a noticeable distinction particularly observed in Case 1. During HW, observed data indicates average UHII peaks at 1.8°C (0100 LST (UTC+8)) and 1.7°C (1500 LST) in Cases 1 and 2, respectively. In contrast, those for PPHW days for Cases 1 and 2 are 1.5°C (0000 LST) and 1.2°C (0100 LST), respectively. The maximum observed heat loads are likely to occur at noon, reaching 2.3°C at 1600 LST in Case 1 and 3.7°C at 1500 LST in Case 2. LST stands for local standard time. Heat flux component analysis from the surface energy balance model confirmed the UHI–HW synergy. A notable difference in the Bowen Ratio between urban and rural areas highlights the effect of urbanisation on heat fluxes, potentially exacerbating urban discomfort during HW. Consistent across all measurement methods, the evidence indicates a clear and positive synergy between the UHI and HW in the GKL. This study can potentially deliver valuable insights, especially in urban planning, where the implications of weather events are substantial. [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) have adverse impacts on marine ecosystems and fisheries, yet extreme MHWs in the western tropical Pacific Ocean remain largely unexplored. Here, we investigate the evolution and drivers of the two strongest subsurface MHWs in the western tropical Pacific Ocean on record, in 2008 (MHW-08) and 2010–11 (MHW-11). The two events have similar evolutions, as they were both initiated and developed locally in tropical regions during their onset phase and gradually dissipated with multiple cores during the decay phase. We examined the physical processes during the evolution of MHW-08 and MHW-11 and performed a heat budget analysis for the subsurface layer in each case. We find that the onset of both events were mainly controlled by convergence and vertical heat advection due to anomalous Ekman downwelling, while the decay of both events was mainly controlled by horizontal heat advection due to anomalous horizontal currents and withdrawal of anomalous convergence. The relationship between the subsurface MHWs and El Niño–Southern Oscillation is discussed. We suggest that the anomalous heat advections plus the La Niña–related background warming lead to the extreme subsurface MHW events. Our findings may have important implications for environmental change and marine life in the western tropical Pacific Ocean. [ABSTRACT FROM AUTHOR]

This study examined Baltic Sea Marine Heatwaves (MHWs) using 42 years of satellite-derived sea surface temperature (SST) data. We found that MHWs in warmer months are more intense but shorter compared to MHWs in cooler months. Also, MHWs predominantly affect offshore areas in warmer months, whereas MHWs predominantly impacting coastal seas in cooler months, especially along the eastern coast. Our analysis of interannual variability revealed that, unlike in many other basins worldwide, Baltic MHWs tend to maintain a constant intensity, while their spatial extent has significantly increased over the last few decades. Shortwave radiation notably influences MHW intensity and spatial extent, with additional impacts from longwave radiation in cooler months and latent heat flux in warmer months. Northern Hemisphere teleconnections exhibit stronger correlations with MHWs in the Baltic Sea compared to global-scale climate oscillations, with the Eastern Atlantic pattern having a particularly significant effect on MHW variability in the region. [ABSTRACT FROM AUTHOR]

Product selectivity of solar‐driven CO2 reduction and H2O oxidation reactions has been successfully controlled by tuning the spatial distance between Pt/Au bimetallic active sites on different crystal facets of CeO2 catalysts. The replacement depth of Ce atoms by monatomic Pt determines the distance between bimetallic sites, while Au clusters are deposited on the surface. This space configuration creates a favourable microenvironment for the migration of active hydrogen species (*H). The *H is generated via the activation of H2O on monatomic Pt sites and migrate towards Au clusters with a strong capacity for CO2 adsorption. Under concentrated solar irradiation, selectivity of the (100) facet towards CO is 100 %, and the selectivity of the (110) and (111) facets towards CH4 is 33.5 % and 97.6 %, respectively. Notably, the CH4 yield on the (111) facet is as high as 369.4 μmol/g/h, and the solar‐to‐chemical energy efficiency of 0.23 % is 33.8 times higher than that under non‐concentrated solar irradiation. The impacts of high‐density flux photon and thermal effects on carriers and *H migration at the microscale are comprehensively discussed. This study provides a new avenue for tuning the spatial distance between active sites to achieve optimal product selectivity. [ABSTRACT FROM AUTHOR]

Polar 2D materials hold the emerging functionalities such as ferro‐, piezo‐, and pyro‐electric properties. On account of infrared‐active low bandgap and polar nature at reduced dimensionality, they served as an ideal choice of pyroelectric material. It can cover up a diverse range of applications, such as waste thermal energy harvesting, IR imaging, photodetector, temperature sensors, and several catalytic processes due to the abundance of dynamic thermal fluxes. Recently, 2D pyroelectric materials have manifested a substantial role in thermal energy harvesting. Consequently, it is realized that there are plenty of scopes available to diversify its applicability. Thus, the challenges are spotlighted in this perspective to envision the desired 2D pyroelectric materials to achieve the effective thermal energy harvesting, sensing, and catalytic efficacy. Particularly, the emphasis is given to elucidate the role of spontaneous polarization in 2D materials to ascertain the giant pyroelectricity. [ABSTRACT FROM AUTHOR]

This primary goal of this analysis is to investigate how several slips affect the flow, heat, and mass performance of Darcy–Forchheimer unstable behavior beyond a stretching sheet using a numerical analysis of the Soret effect. The novel constitutive model Cattaneo–Christov is illustrated to analyze the features of thermal relaxation time. The Cattaneo–Christov method is used to predict heat and mass transport. A surface that slanders and has varying thicknesses propels the flow. Through the use of local similarity transformations, the governing nonlinear partial differential equations reduce to the coupled ordinary differential equations and include the momentum, energy, and concentration equations. The altered ODEs are calculated numerically using the Runge–Kutta Fehlberg scheme and an efficient shooting procedure. The physical properties of the temperature, concentration, and fluid velocity profiles are shown visually and shed light on the change of several governing parameters. For example, in comparison to the classical Fourier's heat model, our result suggests that the Cattaneo–Christov heat flux constitution has lower temperature and thermal boundary layer thickness. In the meantime, a high wall thickness parameter greatly upgrades the rate of heat transfer, and thermal relaxation has the opposite effect. Discussion is held regarding the effects of various miscellaneous variables on temperature, concentration, and velocity. [ABSTRACT FROM AUTHOR]

In the present work, the laminar burning velocities of NH3 + hydrous C2H5OH + air flames were measured using the heat flux method at 1 atm with varied equivalence ratios and mixing ratios (with hydrous ethanol molar fractions of 45%–75%). The measurements were carried out at unburned temperatures of 358 and 378 K. The results show that the laminar burning velocities increase with the increase of hydrous ethanol mixing ratio and temperature, indicating that hydrous ethanol contributes to the combustion of NH3 flames. Based on Wang et al.'s CEU‐NH3 mechanism, sensitivity, reaction pathways, and product formation rate analyses were conducted. The results show that the addition of water reduces the laminar burning velocities of mixed fuel. Intermediate radicals such as NH and HNO are crucial for the formation of NO. After adding water, in the preheating zone, the total production rates of key species such as NH3, H, O, and OH radicals and intermediate species like NH2, NH, HNO, and N decrease, leading to a reduction in the total NO generation rate and the peak mole fraction of NO in the reaction zone. [ABSTRACT FROM AUTHOR]

As a high heat flux linear plasma device designed for studying divertor materials in future fusion reactors, HIT-PSI(Plasma Surface Interaction device at Harbin Institute of Technology) has been successfully constructed and has maintained stable operation since its completion. The characteristics of He plasma beams in HIT-PSI are investigated by emission spectroscopy and an infrared camera, with preliminary irradiation experiments conducted by bombarding tungsten with the beam. For relatively conservative discharge parameters, HIT-PSI achieved a steady-state heat flux capacity of ∼40 MW/m2 using infrared measurements, with the full width at half maximum (FWHM) of the heat flux beam reaching 4 mm. These characteristics make HIT-PSI an advanced platform for testing divertor materials and plasma-facing components, providing essential experimental supports for research and development of high-performance divertor materials. [ABSTRACT FROM AUTHOR]

Solid state semiconductor based neutron detectors have the potential to be energy efficient and compact, making them suitable for applications where low power consumption and size constraints are important considerations. Herein, neutron detection devices based on PIN structures consisting of BGaN/GaN superlattice (SL) are demonstrated. These SL structures enable to incorporate significant boron (B) content and achieve good crystalline quality epilayers crucial for better neutron detection. Further, by leveraging the built‐in electric field generated by the PIN structure, these devices can be operated without any applied bias, simplifying overall operation and enabling a more compact size system for detection. Their performance is evaluated by measuring real‐time current response under neutron irradiation (IN) and without it (ID). The neutron induced current density (ΔJ = JN − JD) is determined, reaching an impressive value of 0.67 pA cm−2 (two times JD) under thermal neutron flux of 1.2 × 104 n cm−2 s−1 without biasing, demonstrating their self‐powered capability. They exhibit a linear response to varying thermal neutron flux levels. Additionally, the detectors successfully detect low thermal neutron fluxes down to 300 n cm−2 s−1, showcasing their potential for diverse applications, including in low neutron environments, screening nuclear warheads, and preventing illegal trafficking of radiological materials. [ABSTRACT FROM AUTHOR]

The simultaneous concentration of electromagnetic (EM) waves and heat fluxes in the same target region within an on‐chip system has substantial academic research importance and practical application value. However, the existing research is primarily aimed at the design and experimentation of concentrators for individual EM waves or temperature fields. In this study, a thermal‐EM concentrator capable of simultaneously concentrating EM waves and heat fluxes is designed using transformation optics and thermodynamics and fabricated using engineered thermal‐EM metamaterials. Both the numerically simulated and experimentally measured results demonstrate the concentrating capability of the proposed thermal‐EM concentrator, which can concentrate broadband transverse magnetic (TM)‐polarized EM waves ranging from 8 to 12 GHz and heat flux to the same target region within an on‐chip operating environment. The proposed thermal‐EM concentrator can be utilized for the efficient cooling of the specified component and for simultaneously enhancing the radiation and reception efficiency of the EM antenna within an on‐chip system. [ABSTRACT FROM AUTHOR]

The paper discusses potential hazards at hydrogen refueling stations for transportation vehicles: cars and trucks. The main hazard analyzed here is an uncontrolled gas release due to a failure in one of the structures in the station: storage tanks of different pressure levels or a dispenser. This may lead to a hydrogen cloud occurring near the source of the release or at a given distance. The range of the cloud was analyzed in connection to the amount of the released gas and the wind velocity. The results of the calculations were compared for chosen structures in the station. Then potential fires and explosions were investigated. The hazard zones were calculated with respect to heat fluxes generated in the fires and the overpressure generated in explosions. The maximum ranges of these zones vary from about 14 to 30 m and from about 9 to 14 m for a fires and an explosions of hydrogen, respectively. Finally, human death probabilities are presented as functions of the distance from the sources of the uncontrolled hydrogen releases. These are shown for different amounts and pressures of the released gas. In addition, the risk of human death is determined along with the area, where it reaches the highest value in the whole station. The risk of human death in this area is 1.63 × 10−5 [1/year]. The area is approximately 8 square meters. [ABSTRACT FROM AUTHOR]

We studied a candidate TPS (thermal protection system) material for reusable re-entry space vehicle applications. The material was based on a high-temperature-resistant material called Cerakwool. A total of six specimens were fabricated with substrate densities of 0.45 g/cm3, 0.40 g/cm3, and 0.35 g/cm3, with two specimens for each density. All specimens were coated with high-emissivity TUFI (toughened unpiece fibrous insulation), with coating thicknesses ranging from 445 to 1606 µm. The specimens were tested using an HVOF (high-velocity oxygen fuel) material ablation test facility. For each density specimen pair, one specimen was tested at 1 MW/m2 and the remaining one was tested at 0.65 MW/m2. The average stagnation point temperature for specimens tested at 1 MW/m2 was ~893 °C, approximately 200 °C higher than those tested at 0.65 MW/m2. This suggests a ~200 °C increase in stagnation point temperature for a 0.35 MW/m2 rise in incident heat flux. During the tests, internal temperatures were measured at three locations. For all tested specimens, regardless of heat flux test conditions and density, the temperature at ~40 mm from each specimen's stagnation point remained around or below 50 °C, well within the 180 °C design limit set for the TPS back face temperature. Post-test visual inspections revealed no signs of ablation or internal damage, confirming the material's reusability. [ABSTRACT FROM AUTHOR]

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant (Tween 20) and asymmetric structures (expanding microchannel) to enhance the boiling performances of deionized water under sub-atmospheric pressure. The research examines the effects of pressure (8.8~38.5 kPa), surfactant concentration (0.1~0.5 mL/L), and heat flux density (10~180 W/cm2) on the boiling heat transfer characteristics and analyzes the mechanism of unusual temperature oscillations induced by surfactants. It was found that the trade-off between the sub-atmospheric pressure, surface tension coefficient, and reduced static contact angle results in pronounced intermittent boiling on the heated surface. Even with the addition of surfactants, the improvement in heat transfer requires demanding conditions. Boiling enhancement throughout all heat flux conditions was achieved when the surfactant concentration was higher than 0.2 mL/L for the expanding microchanneled surface. The heat transfer coefficient reached 6.89 W·cm−2·K−1 under 8.8 kPa, which was 45% higher than without the surfactant. Under the same heat flux and sub-atmospheric pressure, as the concentration increased from 0.1 to 0.5 mL/L, the amplitudes of temperature fluctuation of the plane surface and expanding microchanneled surface decreased from 10 K to 2 K and 18 K to 1 K, respectively. The onset of nucleate boiling and wall superheat of the expanding microchanneled surface gradually decreased with the increase in surfactant concentration, where the onset of nucleate boiling decreased by 10.54 K. When the heat flux is 160 W/cm2, the wall superheat is reduced by 12.8 K. [ABSTRACT FROM AUTHOR]

High‐repetition‐rate free‐electron lasers impose stringent requirements on the thermal deformation of beamline optics. The Shanghai HIgh‐repetition‐rate XFEL aNd Extreme light facility (SHINE) experiences high average thermal power and demands wavefront preservation. To deeply study the thermal field of the first reflection mirror M1 at the FEL‐II beamline of SHINE, thermal analysis under a photon energy of 400 eV was executed by fluid and solid heat transfer method. According to the thermal analysis results and the reference cooling water temperature of 30 °C, the temperature of the cooling water at the flow outlet is raised by 0.15 °C, and the wall temperature of the cooling tube increases by a maximum of 0.5 °C. The maximum temperature position of the footprint centerline in the meridian direction deviates away from the central position, and this asymmetrical temperature distribution will directly affect the thermal deformation of the mirror and indirectly affect the focus spot of the beam at the sample. [ABSTRACT FROM AUTHOR]

We offer a modern interpretation of Lagrangian hydrodynamics as employed in Lagrangian simulations of compressible fluid flow. Our main result is to show that artificial viscosity, traditionally viewed as a numerical artifice to control unphysical oscillations in flows with shocks, actually represents a physical process and is necessary to derive accurate simulations in any compressible flow. We begin by reviewing the origins of two numerical devices, artificial viscosity and finite‐volume methods. We proceed to construct a mathematical (PDE) model that incorporates those numerics and in which a new length scale, the observer, arises representing the discretization. Associated with that length scale, there are new inviscid fluxes that are the artificial viscosity as first formulated by Richtmyer and an artificial heat flux postulated by Noh but typically not included in Lagrangian codes. We discuss the connection of our results to bivelocity hydrodynamics. We conclude with some speculation as to the direction of future developments in multidimensional Lagrangian codes as computers get faster and have larger memories. [ABSTRACT FROM AUTHOR]

Dry devolatilization is a promising method for saving energy, but understanding the devolatilization process has been challenging. A static devolatilizer was designed to study the devolatilization process of a Styrene-butadiene-styrene (SBS) block copolymer solution at different temperatures using visualization technology. The study found that temperature, Reynolds number, and heat flux are key factors influencing the devolatilization process. The optimal residence time was determined to be 196 s and the suitable feed coefficient is 0.17. Additionally, a new dimensionless parameter (the LZ number) was introduced. A value closer to 1 indicated a more effective devolatilization process. The obtained thermodynamic parameters and LZ number can guide the design of industrial devolatilization devices. [ABSTRACT FROM AUTHOR]

Microchannel heat sink is widely applied in high-density heat flux devices for its high efficiency in heat dissipation. However, the most effective geometrical configuration of microchannels for best heat transfer augmentation with least pump power penalty is still unknown. In this research, the heat transfer augmentation in a microchannel heat sink with different shaped periodic reentrant cavities on channel sidewalls are numerically studied. Three different kinds of channel structures are introduced, including convex quarter-circular, concave quarter-circular, and inclined shaped reentrant cavities. The comprehensive performances of the proposed microchannels are compared with that of the smooth straight channel, with respect to the pressure drop, friction coefficient, Nusselt number, and performance factor. The results indicate that the comprehensive performance of the microchannel heat sink with periodic reentrant cavities is superior to the smooth straight channel, because its reentrant cavities can strengthen the mixing of fluids and lower the pressure loss. The proposed microchannels can enhance the heat transfer by 1.7 times, reduce the pressure drop by 3.7%–22.4% at Re 648.2, with the heat transfer entropy production decreased by 15.9%–48.2%. The inclined shaped microchannel has the best overall performance factor among the three proposed channels, which achieves up to 1.59 at Re 648.2. [ABSTRACT FROM AUTHOR]

Escalations in wildfire activity are of significant global concern, particularly within vulnerable wetland ecosystems integral to natural carbon sequestration and climate change mitigation. Our understanding and management of future wildfire activity may be better contextualised through the study of historic and ancient fire records, independent of human influence. Methods of study include 'geothermometry' - approximating ancient fire intensity from temperature-dependent changes in the chemistry of fossil charcoal. Though well established in their relation to experimental charcoalification, these methods still fail to quantify the true intensity of ancient fires, as a measure of energy release. As a result, their applicability, and contributions to the characterisation of modern fire activity, remain uncertain. Here, we present a novel measure of wildfire energy release, as a proxy for true intensity, through the co-application of cone calorimetry and Raman spectroscopy of charcoal. By applying a range of wildfire heat fluxes to variable peatland fuel mixes, this research demonstrates the complexity in correlating fire behaviour and charcoal microstructure. Further statistical analyses suggest a correlation between spectroscopic results, measures of CO and CO2 release, and fire severity. This offers a principal measure of ancient wildfire intensity, consistent with modern practices in wildfire modelling, monitoring, and management. [ABSTRACT FROM AUTHOR]

Numerical investigations were conducted to analyze the heat transfer characteristics in a single square minichannel with supercritical C10H22 (sC10H22) and supercritical CO2 (sCO2). A single symmetric minichannel with a square cross-section of 1 mm × 1 mm and a length of 400 mm was selected, the top surface of which is applied with a uniform heat flux from 100 to 300 kW/m2. The inlet temperatures are varied from 20 to 150 °C and the inlet mass fluxes are ranged from 300 to 500 kg/(m2·s) in the physical model. The flow and heat transfer processes of the fluids were simulated in COMOSOL Multiphysics® software with RANS k-ω low-Reynolds number turbulence model. Results show that the heat removal capacity of sCO2 at 8 MPa is superior, which is 8 times that of sC10H22 at 3 MPa at the inlet temperature of 20 °C. When the inlet temperature and heat flux increase, the heat transfer performance of sCO2 drops sharply, while the overall performance of sC10H22 rises steadily. It suggests that sCO2 is more suitable for the heat transfer process with high-efficient cooling system at a lower inlet temperature, while sC10H22 is capable of a stable and long-time heat transfer process at a higher inlet temperature. [ABSTRACT FROM AUTHOR]

Purpose: This study is to examine the impact of viscous dissipation, thermal radiation and Ohmic heating on the magnetohydrodynamic (MHD) flow with thermal and mass transport over a horizontally stretching surface. Cattaneo–Christov heat flux model on a non-Newtonian viscous fluid along with two viscosity models and convective boundary condition has been employed. Tri-hybrid nanofluid has been used to increase thermal performance. Design/methodology/approach: Governing mathematical model has been transposed into a dimensionless system of ordinary differential equations (ODEs) by applying suitable similarity transformation. Numerical solution has been found by applying the bvp4c shooting method in MATLAB software. Findings: Velocity and thermal profiles of Model-I dominate the profiles of Model-II whereas opposite behavior is noticed for concentration profiles. It is concluded that there is an increase in temperature due to thermal radiation, viscous dissipation and convective boundary condition. Originality/value: The novelty of presented work is to examine the impact of Ohmic heating, viscous dissipation, thermal radiation, chemical reaction and two models of viscosity on Cattaneo–Christov heat flux model of tri-hybrid non-Newtonian nanofluid with convective boundary constraint. The accuracy and effectiveness of presented model have been compared with already published research. [ABSTRACT FROM AUTHOR]

Purpose: Recent advancements in technology have led to the exploration of solar-based thermal radiation and nanotechnology in the field of fluid dynamics. Solar energy is captured through sunlight absorption, acting as the primary source of heat. Various solar technologies, such as solar water heating and photovoltaic cells, rely on solar energy for heat generation. This study focuses on investigating heat transfer mechanisms by utilizing a hybrid nanofluid within a parabolic trough solar collector (PTSC) to advance research in solar ship technology. The model incorporates multiple effects that are detailed in the formulation. Design/methodology/approach: The mathematical model is transformed using suitable similarity transformations into a system of higher-order nonlinear differential equations. The model was solved by implementing a numerical procedure based on the Wavelets and Chebyshev wavelet method for simulating the outcome. Findings: The velocity profile is reduced by Deborah's number and velocity slip parameter. The Ag-EG nanoparticles mixture demonstrates less smooth fluid flow compared to the significantly smoother fluid flow of the Ag-Fe3O4/EG hybrid nanofluids (HNFs). Additionally, the Ag-Ethylene Glycol nanofluids (NFs) exhibit higher radiative performance compared to the Ag-Fe3O4/Ethylene Glycol hybrid nanofluids (HNFs). Practical implications: Additionally, the Oldroyd-B hybrid nanofluid demonstrates improved thermal conductivity compared to traditional fluids, making it suitable for use in cooling systems and energy applications in the maritime industry. Originality/value: The originality of the study lies in the exploration of the thermal transport enhancement in sun-powered energy ships through the incorporation of silver-magnetite hybrid nanoparticles within the heat transfer fluid circulating in parabolic trough solar collectors. This particular aspect has not been thoroughly researched previously. The findings have been validated and provide a highly positive comparison with the research papers. [ABSTRACT FROM AUTHOR]

In the field of composite materials, many reports have shown that catastrophic structural damage is caused by lightning strikes. In this study, new design concepts were proposed for the lightning-strike protection of nickel-coated glass/epoxy foam-core composites. Instead of using a neat metal mesh, glass fibers were modified with nickel particles via a plating technique to improve their thermal and electrical conductivities. In addition, a thin Invar plate was inserted at the middle of the structure and a foam core was introduced to reduce damage to the structure. Three models with different materials and stacking sequences were used in this study. Severe damage was experimentally observed following artificial lightning at a peak current of approximately 150 kA when considering a waveform A. Furthermore, numerical prediction was performed to identify the damage mechanisms of the structures. Besides the heat flux source, a mechanical source known as the shock wave overpressure was investigated separately as a new factor for dielectric materials. These two sources of lightning were determined as minor reasons for the structural damage. The failure modes were analyzed for further discussion about the failure mechanism in this study. [ABSTRACT FROM AUTHOR]

Based on the EAST equilibrium, the effects of boron (B) and neon (Ne) injected at different locations on the target heat load, and the distributions of B and Ne particles were investigated by transport code SOLPS-ITER. It was found that the B injection was more sensitive to the injection location for heat flux control than impurity Ne. The high electron and ion densities near the inner target in the discharge with impurity B injected from over X -point (R 1) led to plasma detachment only at the inner target, and the localized B ions in the cases with injection from outer target location (R 2) and upstream location (R 3) led to far-SOL detachment at the outer target, but not at the inner target. In contrast, for Ne, the spatial distributions of Ne ions and electrons were found to be similar in all the cases at the three injection locations, and the detached plasma was achieved at the inner target and the electron temperature was reduced at the outer target. For locations R 2 and R 3, impurity B showed a more pronounced effect on the heat flux at the far-SOL of the outer target. Further analysis indicated that Ne atoms came mainly from the recycling sources, whereas B atoms came mainly from injection, and that their distinct atomic distributions resulted from the difference in the ionization threshold and ionization mean free path. In addition, the radiation proportion of B in the divertor region was larger than that of Ne when the total radiation power was similar, which suggests that B has less influence on the core region. [ABSTRACT FROM AUTHOR]

We present direct eddy covariance measurements of the surface heat flux in sea ice over a wide range of conditions across the Arctic Ocean made during two research cruises. Photographic imagery of the surface around the ship provides a local, in situ estimate of the ice fraction. Aerodynamically rough conditions prevail for the majority of the time in the consolidated pack ice. The results are analyzed in the framework of a recently-developed parameterization scheme in which the exchange coefficients over ice are functions of a roughness Reynolds number, R*, hence account for aerodynamic roughness variability. This parameterization accurately represents the measured fluxes under all conditions, while under aerodynamically rough conditions the existing parameterizations from both the Met Office Unified Model, and ECMWF Integrated Forecast System overestimate the fluxes. The results corroborate those of a previous airborne study over the marginal ice zone, and encompass a wider range of atmospheric stability conditions. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the salinity barrier layer (BL) on the upper ocean response to Super Typhoon Mangkhut (2018) in the western North Pacific. After the passage of Mangkhut, a noticeable increase (∼0.6 psu) in sea surface salinity and a weak decrease (< 1°C) in sea surface temperature (SST) were observed on the right side of the typhoon track. Mangkhut-induced SST change can be divided into the three stages, corresponding to the variations in BL thickness and SST before, during, and after the passage of Mangkhut. During the pre-typhoon stage, SST slightly warmed due to the entrainment of BL warm water, which suppressed the cooling induced by surface heat fluxes and horizontal advection. During the forced stage, SST cooling was controlled by entrainment, and the preexisting BL reduced the total cooling by 0.89°C d−1, thus significantly weakening the overall SST cooling induced by Mangkhut. During the relaxation stage, the SST cooling was primarily caused by the entrainment. Our results indicate that a preexisting BL can limit typhoon-induced SST cooling by suppressing the entrainment of cold thermocline water, which contributed to Mangkhut becoming the strongest typhoon in 2018. [ABSTRACT FROM AUTHOR]

This study introduced a novel numerical modeling for the evaluation of a hybrid heat sink design by replacing the solid fins with aluminum foam fins (AFF) for the same thickness of 2 mm within a phase change material (PCM). This innovation is designed to enhance thermal performance in electronic cooling applications. Heat fluxes of 2, 3, and 4 kW/m2 were applied to the base. The performance has been verified at set point temperatures (SPT) of 60°C, 70°C, and 80°C, encompassing a range relevant to various applications. Different AFF thicknesses (4 and 6 mm) and foam porosities (0.85, 0.90, and 0.95) were investigated. The study demonstrated that AFFs improve heat transfer by increasing fin surface area and by effectively raising the thermal conductivity of the PCM. Compared to the SF heat sink, the results show that the AFF design extended the operational time by 5%–8% for the range of heat fluxes. Notably, AFFs with a thickness of 6 mm achieved a significant 41% improvement in the operation time at a lower SPT (60°C). The metal foam porosity of ε = 0.85 exhibited superior thermal performance within the investigated temperature range. This research paves the way for optimizing hybrid heat sink designs using metal foam for efficient thermal management and reduction of weight. [ABSTRACT FROM AUTHOR]

Experimental investigations have been conducted to study the convective heat transfer from a cylindrical solar cavity receiver with vertical fins. The experiments were performed under varying surface heat flux levels and at seven inclination angles, ranging from −90° (upward facing) to +90° (downward facing) at 30° intervals. The impact of fins on the heat transfer process was studied by conducting experiments in two scenarios, namely, finned and unfinned cavities. The findings of the study showed that with an increase in cavity inclination, the magnitude of convective heat loss decreased in both finned and unfinned cavities, while the cavity surface temperature increased. At +90° inclination, the convective heat loss and Nusselt number were observed to have the lowest value, while the surface temperature had the highest value. For a downward‐facing cavity, the fins reduced convective heat loss, leading to an increase in cavity surface temperature. The finned cavity performed better for a vertically downward‐facing inclination (+90°) as it had a contribution of only 11% for convection heat loss compared with the unfinned cavity, which had a contribution of 21% for the same. Furthermore, an empirical model was developed based on the experimental results for the Nusselt number, which correlates experimental data with an error margin of ±15%. This model can be used to predict the Nusselt number for different inclination angles and surface heat flux levels. The presence of vertical fins in the cavity was found to be effective in reducing convective heat loss, especially for downward‐facing cavities. Understanding the influence of fin and cavity inclination on convective heat transfer can lead to enhanced efficiency and performance of solar receivers, thereby increasing the overall energy output of the system. [ABSTRACT FROM AUTHOR]

The improvement in the efficiency of the thermal system can be achieved by disrupting the laminar flow of fluid and boundary layer separators. Passive techniques are already incorporated by industries because it increases heat transfer rate up to many folds. The numerical investigation purpose is to find techniques for heat transfer augmentation in the square duct in the laminar flow regime. The thermo-hydraulic characteristics of ribs and helical screw tape (HST) insert fitted in the square ducts have been presented. The effect of rib orientations on the Nusselt number has been analyzed by the Finite volume-based commercial software ANSYS "Fluent". A SIMPLE algorithm has been used. The fluids having different Prandtl numbers are investigated under an imposed uniform wall heat flux boundary condition. The combination performance is better than the bare and ribbed square ducts. The 45° angled ribs with HST performance is better than the combination of transverse ribs with HST. At Reynolds number 200, the Nusselt number achieved by 45° angled ribs with HST is 4.3% higher than the 30° angled ribs with HST, 22.26% higher than the 60° angled ribs, and 35.82% higher than the transverse ribs with HST. Among the three working fluids, the Nusselt number for Servo-therm oil is the highest because Servo-therm oil minimizes entropy generation. Also, the thermal enhancement factor is greater than one for all considered cases and it is the highest for Servo-therm oil is the highest. [ABSTRACT FROM AUTHOR]

The current study explores the thermal performance and geometric optimization of radial heat sinks manufactured through selective laser melting process of AlSi10Mg material, primarily intended for cooling applications in light-emitting diodes (LEDs). Few studies have systematically approached the geometric optimization of radial heat sink designs, particularly considering variable fin heights (both fin outer and fin inner height), in conjunction with other geometric parameters like fin length, fin thickness, and the number of fins tested across a broad spectrum of heat flux values. Through comprehensive experimentation and numerical simulations, the independent and combined impact of these considered key geometric parameters was investigated on the heat sink performance. The experimental design, guided by Response Surface Methodology, encompasses a wide range of heat flux levels, varying from 300 to 1800 W/m2, to ensure the broad applicability of the findings. The results underscore the significance of fin thickness, which notably influences the base temperature of the heat sink, particularly at higher heat flux levels. The interaction between heat flux and fin length also plays a pivotal role in base temperature control, with additional fins contributing to lower temperatures. Furthermore, it was revealed that higher fin outer heights, combined with lower fin inner heights, lead to superior heat sink performance, aligning with practical LED cooling requirements. The optimization process results in configurations that consistently maintain base temperatures below the critical 70 °C threshold, thus contributing to effective thermal management in LED devices. [ABSTRACT FROM AUTHOR]

• New data of jet impingement boiling on surface modified metal foam were obtained. • Effects of metal foam wettability on boiling heat transfer were analyzed. • Influence on bubble dynamics behavior was analyzed. • New heat transfer coefficient correlation considering wettability was developed. Wettability may have significant influence on jet impingement boiling on metal foam, but the effect mechanism of metal foam wettability remains unclear. In this study, the boiling heat transfer characteristics of distributed jet array impingement on hydrophobic and hydrophilic metal foam covers were experimentally researched and compared with those on uncoated metal foam covers to analyze the influence of wettability. The experimental conditions cover contact angles of 14.0–158.7°, pore densities of 20–40 PPI, porosities of 92 %-97 %, thicknesses of 3.0–5.0 mm, and jet velocities of 0.5–4.0 m·s−1. The results show that, the obtained maximum heat flux and maximum heat transfer coefficient are up to 538.1 W cm−2 and 57.9 Kw m−2 K−1, respectively; the hydrophobic metal foam cover has a 4.8 K lower surface superheated degree at the onset of nucleate boiling, but a 7.5 % lower maximum heat transfer coefficient compared with the uncoated one; the hydrophilic metal foam cover shows a less deterioration after the departure from nucleate boiling but a 5.3 K higher surface superheated degree at the onset of nucleate boiling than those of the uncoated one. A new correlation for boiling heat transfer coefficients was developed with a mean relative error of 9.75 %. [ABSTRACT FROM AUTHOR]

The objective of this work is to measure the heat transfer of a liquid metal in a cylindrical cell under the conjugate effects of a temperature difference and a Lorentz force generated by an alternating current in a coil. The experimental results are compared to recent direct numerical simulations (DNS) (Guillou et al., 2022). 25 experiments are performed for a large range of frequency f , ac intensity amplitude I 0 and temperature difference between the top and bottom walls Δ T 0 : 15 ≤ f ≤ 1000 Hz , 2 ≤ I 0 ≤ 67 A and 6 ≤ Δ T 0 ≤ 11 K. In these experiments, the Hartmann number H a , the shielding parameter S ω and Rayleigh number R a vary in the following range: 6 ≤ H a ≤ 200 , 1 ≤ S ω ≤ 70 , 2. 3 × 1 0 6 ≤ R a ≤ 4. 1 × 1 0 6 . The experiments with an ac magnetic field are compared with the Rayleigh–Bénard convection (RBC) experiments under the same thermal conditions. Three rings of thermocouples allow characterizing the fluid temperature distribution during the convection. The heat flux at the bottom and top walls are also measured. We observe a very good agreement between the experimental results and the DNS results. As previously shown by numerical simulations, a master curve of N u / P e ω vs. Q J / Q c allows predicting the evolution of the heat transfer under different conditions of temperature difference and Lorentz force. Here N u and P e ω are the Nusselt number and a Péclet number based on the Lorentz force, and Q J and Q c are the total power deposited by the Joule effect and the total conduction heat flux without motion, respectively. The experiments show that N u / P e ω ∼ (Q J / Q c) − 2 / 5 . [ABSTRACT FROM AUTHOR]

This paper presents an experimental inverse approach to simultaneously estimate the temperature-dependent thermal properties of AISI 316 stainless steel. The heat flux conducted to the sample was corrected by using a transducer, evaluating contact resistance at microscopic level, and performing experiments under vacuum. Estimates were severely biased when heat flux correction was not applied. Metaheuristics were used to enlarge the search space, which can cover the thermal properties of all known metallic materials, thereby taking advantage of better thermal modeling adequacy. The estimation reliability was shown by comparison with literature data, statistical significance, uncertainty analysis, and inverse heat flux retrieval. [ABSTRACT FROM AUTHOR]

Flow boiling heat transfer is a promising technology for thermal management. In this paper, flow boiling heat transfer characteristics in a rectangular vertical flow channel are experimentally and numerically investigated at low flow rate. Visualization results provide guidance for the prediction of flow patterns. The flow boiling correlation at low flow rates is improved with an error of less than 30%. Numerical results reveal vortices enhanced local heat transfer. Absolute vorticity is introduced to quantify the secondary flow. The results indicate that the secondary flow intensity increases with heat flux, verifying that boiling flow produces the local convection enhancement. [ABSTRACT FROM AUTHOR]

The current paper reports the impact of variation of ribs' pitch distance in the case of laminar flow and forced convection heat transfer upon flow characteristics in a rectangular channel experimentally and numerically. The thermal behavior of the ribbed channel with water as a working fluid was measured experimentally and compared to numerical simulations performed using Galerkin finite element method under the same operating and boundary conditions. Numerical analysis has been extended to investigate the entire ribbed channel with the presence of nano-particles in the base fluid to predict the performance of the heat transfer process with interaction with extended geometries. The analysis was done keeping heat flux constant at the bottom boundary condition. The impacts of the rib pitch-to-height ratio (p/e = 2.5, 3.125, 3.75, 4.375, and 5), nano-particle volume concentration (0% ≤ φ ≤ 4%), also Reynolds numbers (427.44 to 1282. 9), were all examined in the present study. The results show a good coincidence between the numerical and experimental study with a maximum deviation was nearly 3%. The main findings show that when the nano-fluid volume fraction increases from 0% to 4%, the average Nusselt number for all aspect ratios increases too. Meanwhile, the average skin friction decreases as the Reynolds number increase for different values of AR. Furthermore, the results revealed that the water – aluminum oxide nano-fluid with the concentration φ = 0.04 aid to improve the coefficient of heat transfer by 5% higher than the case of φ = 0.02, and up to 9.4% compared to pure water (φ = 0) due to an increase in viscosity. Finally, the current work shows that these extended surfaces with the use of nano-fluids can remarkably improve heat transfer properties with barely increased friction, making them suitable candidates for the development of efficient heat exchanger devices. [ABSTRACT FROM AUTHOR]

The continued depreciation of electronic components presents severe challenges for thermal management. Regarding this issue, the current experimental study targets to propose and assess two passive cooling (using a heat sink and rough surface) and two active cooling (air and water cooling) for improving the cooling efficiency of aluminum heat sink heat pipes (HSHPs). In roughening process, the fins are chemically etched using a lab-made simple, cost-efficient, and environmental-friendly method to achieve better cooling performance synergistically. Scanning electron microscopy and atomic force microscopy characterizations are executed to investigate the heat sink surfaces' micro/nano roughened structure. Current results and related comparative studies of the three cooling modules (typical, liquid-based, and liquid-based micro/nano roughened HSHPs) are presented as well, where effects of constant/intermittent heat fluxes (4000–12000 W/m2) and the volume flow rates of testing fluid on heat transfer characteristics, thermal resistance, and temperature behavior are disclosed. Based on findings, at a constant heat flux, roughening the HSHP fins led to an enhancement in cooling through fins and a reduction in cooling through the water. Moreover, it is found that the modified HSHP without testing fluid and with water at volume flow rates of 100 and 200 ml/min decreases the thermal resistance by 11.9, 13.7, and 3.6%, in order, compared with the typical HSHP. [ABSTRACT FROM AUTHOR]

The objectives of NSTX-U research are to reinforce the advantages of STs while addressing the challenges. To extend confinement physics of low- A, high beta plasmas to lower collisionality levels, understanding of the transport mechanisms that set confinement performance and pedestal profiles is being advanced through gyrokinetic simulations, reduced model development, and comparison to NSTX experiment, as well as improved simulation of RF heating. To develop stable non-inductive scenarios needed for steady-state operation, various performance-limiting modes of instability were studied, including MHD, tearing modes, and energetic particle instabilities. Predictive tools were developed, covering disruptions, runaway electrons, equilibrium reconstruction, and control tools. To develop power and particle handling techniques to optimize plasma exhaust in high performance scenarios, innovative lithium-based solutions are being developed to handle the very high heat flux levels that the increased heating power and compact geometry of NSTX-U will produce, and will be seen in future STs. Predictive capabilities accounting for plasma phenomena, like edge harmonic oscillations, ELMs, and blobs, are being tested and improved. In these ways, NSTX-U researchers are advancing the physics understanding of ST plasmas to maximize the benefit that will be gained from further NSTX-U experiments and to increase confidence in projections to future devices. [ABSTRACT FROM AUTHOR]

After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed for the first long-pulse operation campaign. A maximum discharge length of 8 min was achieved with a total heating energy of 1.3 GJ. Safe divertor operation was demonstrated in attached and detached mode. Stable detachment is readily achieved in some magnetic configurations but requires impurity seeding in configurations with small magnetic pitch angle within the edge islands. Progress was made in the characterization of transport mechanisms across edge magnetic islands: Measurement of the potential distribution and flow pattern reveals that the islands are associated with a strong poloidal drift, which leads to rapid convection of energy and particles from the last closed flux surface into the scrape-off layer. Using the upgraded plasma heating systems, advanced heating scenarios were developed, which provide improved energy confinement comparable to the scenario, in which the record triple product for stellarators was achieved in the previous operation campaign. However, a magnetic configuration-dependent critical heating power limit of the electron cyclotron resonance heating was observed. Exceeding the respective power limit leads to a degradation of the confinement. [ABSTRACT FROM AUTHOR]

The present examination focuses on the Falkner-Skan flow of micropolar hybridized nanofluid via a wedge surface. The proposed study examines thermal radiative fluxing and heat dissipation in hybridized nanoparticle aqueous solutions. Simulations of uni-directional radiative transport in optically dense fluids use Rosseland's diffusion model. This study created a Cu-TiO 2 /water hybrid nanofluid by mixing Cu and TiO 2 nanomolecules with H 2 O. Partial differential equations from Naiver-Stokes theory are used to generate the regulating flow phenomena, then convert them into ordinary differentiation equations using an appropriate similarity approach. Additionally, the three-stage Lobatto IIIA method is used to compute the formulae. Calculations are done using MATLAB's built-in bvp5c function. We found that increasing material characteristics slows fluid flow because micropolar nanofluids minimize drag. These alterations alter fluid flow and boost temperature. However, boosting thermal radiation and Eckert number slows heat movement but improves temperature profiles. Much prior research ignored thermal radiative fluxing and heat dissipation in the aqueous solution of hybrid nanomolecules (Cu and TiO 2) in Falkner-Skan micropolar flow via a wedge surface. Tables show wall frictional factor and Nusselt quantity results. Micropolar fluid characteristic decreases velocity but increases micro-rotational velocity. Power-law parameters, volume fractions, radiation, heat source, and Eckert amount affect thermal contours. [ABSTRACT FROM AUTHOR]

There is great interest in developing methods to predict full‐scale fire performance of mattresses and upholstered furniture for design and regulatory purposes using cone calorimeter and other small‐scale test results. One method used in the past is a model developed during the European Combustion Behavior of Upholstered Furniture (CBUF) project. To support the further development of this model, cone calorimeter tests of polyurethane (PU) foam specimens 5–10 cm thick were conducted using incident heat fluxes between 5 and 35 kW/m2. Temperatures were measured using thermocouples located on the surface and at four depths within 10 cm thick foam specimens to determine the effects of heat flux on heat transfer and foam degradation. Peak and average heat release rate (HRR) values for a particular thickness of foam increased with an increase in heat flux. An increase in heat flux decreased the times to reach the two peaks in the HRR curve, which represent the collapse of foam and burning of liquid products, as well as burning duration. Heat flux had a larger effect on the second HRR peak than the first peak. Significant temperature gradients were initially confined to the top portion of the foam. A surface temperature of 150–200°C was shown to be indicative of the onset of ignition, while a temperature of 150°C at a particular location was indicative of when temperatures began to more rapidly increase at deeper locations within the foam. Infrared video records were also used to examine three‐dimensional burning behavior of the foam. [ABSTRACT FROM AUTHOR]

This study employed the Japanese Ocean flux data sets with use of remote sensing observations version 2 (JOFURO2) to examine global-scale seasonal variations and trends in Latent heat flux (LHF) over a 19-year period. Furthermore, additional analysis has been conducted to determine the response of LHF to the El Niño Southern Oscillation (ENSO) phenomenon. To assess variability, trends, and strength of relationships with ENSO, statistical score analysis was employed using seasonal means, standard deviations, linear trends, and linear correlations, respectively. In this study, the seasons were classified as December-January-February (DJF), March-April-May (MAM), June-July-August (JJA), and September-October-November (SON). The result of the study revealed that the highest LHF values tracked the annual movement of the sun. In the Northern Hemisphere, the highest spatial trends occurred during DJF, while JJA exhibited the peak values in the Southern Hemisphere. This spatial pattern aligns with the seasonal means of LHF, where the highest and lowest standard deviations and trends coincide with the corresponding regions of high and low LHF. This finding suggests that the standard deviation patterns support the observed variability in seasonal LHF means. The strongest spatial correlations between LHF and ENSO were observed over the Indian Ocean during the SON season. In contrast, the correlations between LHF and ENSO in the Atlantic Ocean exhibited spatial heterogeneity, with a significant correlation only during the DJF season. In general, the seasonal spatio-temporal patterns suggest a dynamic link between LHF and ENSO, potentially linked to large-scale monsoon system changes, the specific locations and distributions of positive/negative trends and standard deviations in LHF reveal a spatial response that appears independent of the ENSO phenomenon. [ABSTRACT FROM AUTHOR]

Development of a model that allows performance and combustion characteristics for a supercharged diesel engine was the main objective sought by the present work. Thus, the developed model is used, to examine the impact of start combustion, combustion duration, compression ratio, and heat flux, as well as intake conditions such as pressure and temperature, on the combustion characteristics of the supercharged diesel. For this purpose, a one zone thermodynamic prediction model was adopted with Wiebe function for combustion sub-model. The heat transfer was correlated using Woschni correlation. A numerical simulation is developed considering the crankshaft angle as the independent variable. Validation of the computational code has been favorably evaluated using our experimental data. To give a more general aspect to the developed model, experimental data found in the literature, are also used for this purpose. The results show that the addition of a turbocharger increases low-speed airflow and hence fuel consumption. In addition, an increase in intake pressure contributes to the rise of the heat flux released during combustion, while an increase in intake temperature leads to a strong increase in combustion temperature. Moreover, an increase in the compression ratio leads in a remarkable increase in all parameters simultaneously. However, maximum combustion pressure limits must not be exceeded. This is because the pressure has an effect with the engine mechanical strength. [ABSTRACT FROM AUTHOR]

The thermally anisotropic building envelope (TABE) is an active building envelope that redistributes thermal loads in response to weather conditions and building energy demand. Conductive layers throughout the TABE distribute low-grade heat among hydronic loops, altering heat flow direction and intensity. Finite element models of TABE roof and wall panels were developed and calibrated using field evaluation data. The calibration results showed that heat flux differences between the experimental data and finite element models averaged −0.42% and 3.57%, with a maximum mean square error of 1.78 and 3.96 for roof and wall panels, respectively. A reduction in heat flux from the environment to the building living space over the entire testing period (weeks in July/August) was found to be 85% for roof panels and 335% (load reversed) for wall panels. These results indicate TABE can effectively harness low-grade thermal energy sources to achieve high energy efficiency and promote demand-side management. [ABSTRACT FROM AUTHOR]