Edge Heat Research Articles

Collaborative role of warm pool edge and ocean heat content in El Niño development: implications for the 1982/83 extreme El Niño

Collaborative role of warm pool edge and ocean heat content in El Niño development: implications for the 1982/83 extreme El Niño

Rotating Flow and Heat Transfer Characteristics of a Novel Cooling Channel for Gas Turbine Blade Trailing Edge With Diamond-Type TPMS Structures

Abstract This work designs a Diamond-type triply periodic minimal surface (TPMS) structure that exhibits excellent thermomechanical properties in a gas turbine blade trailing edge to enhance thermal performance and improve heat transfer uniformity. Since the velocity and temperature distributions are altered in the rotating trailing edge channel, the flow and heat transfer characteristics of the baseline pin fin and Diamond TPMS models are numerically investigated at the Reynolds number of 10,000 and the rotation numbers of 0.0–0.28. Compared to the baseline model, the Diamond TPMS network significantly decreases recirculation flow at the inner wall, improving heat transfer, especially at the tip and outlet regions. Although the Diamond TPMS model incurs substantial pressure losses from 191% to 234%, it yields significantly higher overall heat transfer than the pin fins by 179%. Consequently, the thermal performance increased by 93.4%. The flow fluctuations due to the rotating effects are minor in the Diamond TPMS architecture, considerably reducing the differences in heat transfer between the leading and trailing walls. The differences in the wetted-area averaged Nusselt number of the baseline and Diamond TPMS models within the studied rotation numbers are 8.5–14.4% and about 8.5%, respectively. Moreover, the Diamond TPMS structure reduces the differences in heat transfer between the root and tip regions at the outlet by up to 80% compared to the pin fins. This improvement helps protect the trailing edge from thermal failure, thereby potentially prolonging the gas turbine blade's lifetime.

Experimental analyses of temperature and pressure oscillation frequencies of a flat plate pulsating heat pipe tested under various edge orientation angles and heat loads

Experimental analyses of temperature and pressure oscillation frequencies of a flat plate pulsating heat pipe tested under various edge orientation angles and heat loads

Influence of temperature and pressure gradient on power deposition and field pattern in High Magnetic field Helicon eXperiment

AbstractBased on High Magnetic field Helicon eXperiment, considering the parabolic distribution and Gaussian distribution of radial plasma density, HELIC code was used to study the influence of temperature and pressure gradient on power deposition, electric field, and current density of Helicon Wave Plasma. Three different gradients (positive, negative, and zero gradient) were selected. The results show that positive temperature gradient is beneficial to increase the relative absorption power at the center of plasma. Compared with negative and zero pressure gradients, positive pressure gradient increases the relative absorption power and weakens the current density at the center of plasma, and increases the electric field intensity at the edge of plasma. Larger edge heating will cause the relative absorption power at edge to rise rapidly, which is not conducive to the coupling at the center of plasma. In practical experiments, it is particularly important to reduce the heating effect at edge by cooling the antenna itself. Three different gradients of temperature and pressure have little effect on electric field intensity and current density in plasma, and the variation trend is basically similar, which proves the stability of the antenna mode: m = 1.

Computational fluid dynamic simulation of packed bed drying process: impact of particle properties, drying conditions, and lateral edge heating modes on drying kinetics

In this work, a two-dimensional computational fluid dynamic (CFD) model is developed to describe the drying process of a packed bed made of spherical particles. The volumetrical evaporation rate inside the bed is computed from the pressure difference between the particle surface and the airflow. By using the thermal equilibrium assumption, the heat conservation equation is derived. The CFD model is solved in the COMSOL Multiphysics environment. The obtained results indicate remarkable maldistributions of temperature and moisture content. These maldistributions can be explained by the impact of lateral edges on thermo-hydraulic behavior. Additionally, the impact of particle diameter, air velocity, and bed width on the spatial-temporal moisture content and temperature distribution is investigated. It shows that the CFD model can be simplified to the receding front drying model for a bed made of small particles. Furthermore, by changing the thermal boundary conditions at the lateral edges, the influence of the heating mode at the lateral edges on the drying behavior is explored. The results indicate that contact heating at the bed wall can help to accelerate the drying process significantly.

Vectorizing planar roof structure from very high resolution remote sensing images using transformers

ABSTRACT Accurately predicting the geometric structure of a building's roof as a vectorized representation from a raster image is a challenging task in building reconstruction. In this paper, we propose an efficient and precise parsing method called Roof-Former, based on a vision Transformer. Our method involves three steps: (1) Image encoder and edge node initialization, (2) Image feature fusion with an enhanced segmentation refinement branch, and (3) Edge filtering and structural reasoning. Our method outperforms previous works on the vectorizing world building dataset and the Enschede dataset, with vertex and edge heat map F1-scores increasing from 87.1 % , 76.2 % to 89.1 % , 78.1 % , and from 69.7 % , 68.8 % to 71.2 % , 69.5 % , respectively. Furthermore, our method demonstrates superior performance compared to the current state-of-the-art based on qualitative evaluations, indicating its effectiveness in extracting global image information while maintaining the consistency and topological validity of the roof structure.

Investigation on the heat transfer characteristics of flexible vacuum glass based on cross-laminated microcavities

Vacuum glass is a key component of energy-efficient buildings. At present, the traditional vacuum glass (VG) has some problems, such as side edge heat transfer, poor thermal insulation in small sizes, high cost of indium alloy edge sealing, and poor adaptability to the rigid structure to environments, which limits its application in buildings. Vacuum interlayer heat transfer is thickness-independent. Therefore, increasing the transfer path and thermal resistance of the support structure under micrometer gaps achieves effective thermal insulation. In this study, a vacuum glass with a cross-laminated microcavity structure was proposed. The cross-laminated structure has a total thickness of several hundred micrometers and is made of polycarbonate. The heat transfer and stress-strain of the cross-laminated vacuum glass (CLVG) and VG are investigated. The results indicate that the CLVG accomplished a lower heat transfer coefficient compared with the VG at a size smaller than 30 × 30 cm2. In addition, the CLVG is edge-effect-free. As a flexible structure, the CLVG can be easily applied to existing buildings. This study contributes to the exploration of new structures for the vacuum glass.

Convective heat transfer from a spherical concave surface due to swirling impinging jets issuing from a circular pipe

Impinging jet heat transfer from curved surfaces is available in many industrial applications, such as cooling of gas turbine leading edge and deicing of airplane wing leading edge (heating). Most of the published studies on this topic involve non-swirling jet impingement from flat surfaces. Swirling jets are also used in some applications with the anticipation of heat transfer augmentation. Swirling impinging jet flow characteristics are significantly different from that of the non-swirling jet. However, fundamental studies of swirling jet impingement onto curved surfaces are very limited. As such, flow dynamics and convective heat transfer from a heated concave surface due to swirling impinging jets from a circular nozzle are numerically investigated using the RANS approach and the realizable k-ε turbulence model. Various flow and geometric parameters, such as the jet Reynolds number (Re) in the range of 11,600–35,000; the swirl number (Sw) in the range of 0–2.4; and the jet-to-surface separation distance (H) of 0.5–8 times the nozzle diameter, at a fixed impingement surface curvature (diameter) are studied. The results show that two counter-rotating recirculation zones appear near the target surface for near-field impingement (H ≤ 1) and higher swirl numbers (Sw ≥ 1.2), whereas for far-field impingements (H > 2), they are formed inside and outside of the main jet stream. An intense surface heat transfer zone develops only for near-field impingement in the range 1 ≤ S ≤ 3 at higher swirl numbers, where S is the distance along the impingement surface from the domain axis. More uniform thermal distribution along the curved surface is found for far-field impingement at Sw ≥ 0.8. Whilst the transitional Sw and H for Re = 11,600 are 0.8 and 2 respectively, the transitional Sw and H for Re = 35,000 are 0.8–1.2 and 4, respectively. Maximum heat transfer zones are found to be correlated with strong turbulence. Correlations are developed for the average Nusselt number as a function of the jet Reynolds number, jet exit to impingement surface separation distance, and swirling strength.

Effect of Microstructural Transformation upon Edge Heat Treatment on Stretch Flangeability of Ultrahigh-Strength Steel with Sheared Edge

Effect of Microstructural Transformation upon Edge Heat Treatment on Stretch Flangeability of Ultrahigh-Strength Steel with Sheared Edge

Формирование секторных полей остаточных термопластических напряжений в полотне круглой пилы

The efficiency of a stationary circular saw is determined by the performance and operational reliability of the woodcutting unit. During operation, the circular saw blade is exposed to a variety of complex loads and thermal conditions. The rigidity and stability of the saw blade determine its capacity to resist the perturbing cutting forces. The cutting compound itself is a thin disc made of steel with a hole in the middle that has a serrated cutting edge. It consists of three areas: peripheral, middle, and central. The stability of the saw blade is determined by the middle and peripheral parts. The increase in durability is achieved by plastic deformation to form the strip boundaries of the radial sections. These parts are treated by forging in both national and international practice. Normalization of loads on the blade in case of local mechanical contact with the working body is formed in the strip boundaries of the radial sections through the formation of places with plastic deformation of the metal, which rearrange the loads and place them in the radial direction. At the same time, countertension appears from the adjoining sections, leading to mutual “repulsion” of them and the creation of compressive tension that compensates for the forces of centrifugal acceleration, thermal heating of separate areas of the saw blade, external longitudinal and transverse bending tension that arise during wood processing. The combined interaction of all adjoining sections provides the tension and stability of the saw blade. The creation of the radial sections by forging has some significant disadvantages. Their elimination requires a fundamentally new approach, such as the formation of the residual stress sections in the saw blade by thermal exposure. It creates a normalized residual thermoplastic tension in the saw blade by a short-time (1–2 s) focused thermal influence on the strip boundaries of the radial sections. The results of the conducted research determined the boundaries of the sections for thermal treatment and the temperature range, which ensure the formation of normalized residual thermoplastic tension in the circular saw blade through concentrated pulsed heating of the strip edges of radial sections. For citation: Melekhov V.I., Solovev I.I. Formation of Sectoral Residual Thermoplastic Tension Fields in Circular Saw Blade. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 146–154. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-146-154

Buckling behavior of non‐uniformly heated 3D printed plain and functionally graded nanocomposites

AbstractThe functionalized multi‐walled carbon nanotubes (MWCNTs) (0.5–5 wt.%) are compounded with high density polyethylene (HDPE), and, subsequently, used for extruding nanocomposite filaments to fabricate nanocomposites (NCs) and functionally graded nanocomposites (FGNCs) through 3D printing. The 3D printed NCs are investigated for coefficient of thermal expansion (CTE), and buckling under different non‐uniform temperature distributions (case‐1: left edge heating, case‐2: centre heating, and case‐3: left and right edge heating). A significant reduction in CTE is observed with MWCNT addition and gradation. The highest reduction in CTE is observed for H5 (5 wt.% of MWCNT in HDPE) NC and H1 ⟶ H3 ⟶ H5 (FGNC‐2) among the NCs and the FGNCs. It is noted that Tcr (critical buckling temperature) is highest for case‐3 and lowest for case‐2. The highest deflection is noticed in case‐2, while no significant difference is observed in case‐1 and case‐3 heating conditions. It is also observed that Tcr increases with gradation and MWCNTs addition. The H5 NC and FGNC‐2 exhibited the highest Tcr among the NCs and FGNCs, respectively. The maximum deflection is noticed for HDPE, whereas the minimum deflection is noticed for FGNC‐2 and H‐5 NC among the tested samples. The results also revealed that Tcr is very sensitive to type of heating.

Optimization of divertor design for Pakistan spherical tokamak

Abstract Handling the power deposition, reducing erosion effects, and plasma configuration are the key factors in the design of a divertor. The design of Pakistan Spherical Tokamak (PST) is based on double-null divertor configuration with actively cooled graphite targets at outer/inner strike point and peak heat flux range capacity of 0.1–0.3 MW/m2. The configuration of PST divertor module is designed with mock-up (used flat type tiles on baffles and dome) and cassette (support PFC and cooling channels) technology. Helium-cooled stage and water-cooled stage are two options for divertor. Therefore, one part of this research is focused on water-cooling system for the divertor. This paper presents the divertor design for PST with cooling channel and material analysis of the divertor, which is carried out in three phases. In the first phase, the plasma edge temperature, density, particle velocity, input power, heat flux, and surface temperature are estimated. In second phase, physics and engineering design of divertor system has been performed. In the third phase, COMSOL simulation has been performed to analyses the material properties, surface temperature rise (∆T °C) at stable heat flux, and thermal hydraulic system for the divertor. It is found from the analysis that the specific heat flux of 0.3 MW/m2 up to 3 s is the safe zone limit. The R & D work ratifies that manufacturing and installation processes are plausible for the proposed divertor design. This design is able to meet the requirement of PST. However, increasing time or specific heat flux beyond these limits would require redesigning of the cooling channel.

Effects of Edge Heating and Strain Gradient on Stretch Flange Deformation Limit of Steel Sheet

To improve the stretch flange deformation limit of ultrahigh-strength steels, a partial edge heating method was investigated. The effect of the strain gradient on the stretch flange deformation limit when a partial edge heating method was applied was investigated by the hole expansion test and FEM analysis. The stretch flange formability was improved by application of a partial edge heating method because of the recovery of the shearing microstructure and the reduction of the hardness difference of microstructure. It was found that the improvement of the deformation limit strain for the strain gradient with edge heating depends on the strain gradient region. In the low strain gradient region, the improvement margin of the deformation limit strain with edge heating was small. On the other hand, in the high strain gradient region, the deformation limit strain was markedly improved compared with that without heating. It was confirmed that the strain gradient in the direction perpendicular to the maximum principal strain could be used for the prediction of the deformation limit and also the determination of the stretch flange fracture by the FEM analysis of actual parts even under edge heating conditions.

Short-Circuit Capability Optimization of Press-Pack IGBT by Improving Active Edge Heat Dissipation

Press-pack insulated gate bipolar transistor (PP-IGBT) device has been widely used in VSC-HVDC converters. Research on the optimization method of short-circuit capability is crucial to improve the short-circuit robustness and reliability of PP-IGBT. Aiming at the problem of device failure due to transient overstress induced by press-pack packaging, this paper proposes a short-circuit capability optimization method of PP-IGBT that improving the active edge heat dissipation by using silver conductive adhesive (SCA). Firstly, the short-circuit capability is evaluated by experimental test, and the failure conditions and positions are obtained. Secondly, based on the finite element method simulation, the electrical-thermal-mechanical stress of PP-IGBT under short-circuit transients is analyzed and the optimization method by using SCA is proposed. Thirdly, the short-circuit capability of PP-IGBT with SCA coating is tested and verified. Lastly, the potential of SCA coating under different short-circuit voltage levels is discussed. The results indicate that the transient thermal shock at the active corner of the chip that is not in direct contact with the emitter molybdenum plate causes device failure and improving the active edge heat dissipation by SCA could be an effective approach to improve the short-circuit capability of PP-IGBT.

Effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field

The effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field was investigated in this work. The neutral pressure was set to 0.08 Pa, 0.36 Pa, and 0.68 Pa. A Nikon camera, intensified charge-coupled device (ICCD), optical emission spectrometer (OES), and Langmuir probe were used to diagnose the blue core in helicon plasma. Helicon plasma discharges experienced density jumps from the E mode, H mode to W mode before power just rose to 200 W. The plasma density increased and maintained a central peak with the increase of neutral pressure. However, the brightness of the blue core gradually decreased. It is demonstrated that the relative intensity of Ar II spectral lines and the ionization rate in the central area were reduced. Radial electron temperature profiles were flattened and became hollow as neutral pressure increased. It is demonstrated that increasing the neutral pressure weakened the central heating efficiency dominated by the helicon wave and strengthened the edge heating efficiency governed by the TG wave and skin effect. Therefore, the present experiment successfully reveals how the neutral pressure affects the heating mechanism of helicon plasma in an inhomogeneous magnetic field.

ASSURANCE OF THE QUALITY OF THE ASPHALT CONCRETE COATING IN THE ZONE OF THE LONGITUDINAL JOINT OF STRIPS

The article deals with the issue of high-quality compaction of the asphalt concrete mixture during the arrangement of coatings separately along the traffic lanes. It was determined that the main causes of defects in the operation of such coatings are insufficient density and excessive porosity of asphalt concrete in the joint area. The paper analyzes the results of studies that show that the temperature distribution of the mixture along the width of the coating strip is uneven. The coldest and most enriched with large crushed stone areas are found in the zone of joints. The article considers a model of heating a cold joint due to heat from a layer of hot mixture that is placed on the adjacent strip. Depending on the temperature difference between the layers, the increase in the temperature of the edge of the previously laid grip is from 15 °C to 20 °C. However, this is not enough for high-quality sealing of the layer. Thus, it was concluded that during the organization of work on laying asphalt concrete mixtures of connected lanes by one asphalt paver with its displacement from one lane to another, it is necessary to apply edge heating systems without fail.

Determination of limiter design and material composition of MT-II spherical tokamak

Abstract MT-II is a spherical tokamak with a major radius of 0.15 m and a minor radius of 0.09 m, currently under development at the Pakistan Tokamak Plasma Research Institute. It is designed with a higher elongation of 2.67. This paper presents the design and material analysis of the limiter configuration for the MT-II tokamak, which is being carried out in two phases. In the first phase, theoretical studies and calculations are performed to estimate the plasma edge temperature, density, particle velocity, input power, heat flux, heat load and surface temperature on the limiter tile. In the second phase, computational techniques are applied to analyses the material properties, the maximum/minimum surface temperature rise (∆T °C) at stable heat load and power deposition based on theoretical calculations that will help optimize the design parameters of the limiter. The type of material and the surface temperature of the limiter as well as the general design parameters of MT-II are included in the proposed poloidal limiter. The results suggest that crystalline vein graphite is a suitable candidate for the proposed poloidal limiter. A combination of mechanical and electrical feedthrough techniques are used to improve the performance of the limiter. The proposed limiter is able to meet the requirements of MT-II.

The automized fracture edge detection and generation of three-dimensional fracture probability heat maps

With proven impact of statistical fracture analysis on fracture classifications, it is desirable to minimize the manual work and to maximize repeatability of this approach. We address this with an algorithm that reduces the manual effort to segmentation, fragment identification and reduction. The fracture edge detection and heat map generation are performed automatically. With the same input, the algorithm always delivers the same output. The tool transforms one intact template consecutively onto each fractured specimen by linear least square optimization, detects the fragment edges in the template and then superimposes them to generate a fracture probability heat map. We hypothesized that the algorithm runs faster than the manual evaluation and with low (< 5mm) deviation. We tested the hypothesis in 10 fractured proximal humeri and found that it performs with good accuracy (2.5mm ± 2.4mm averaged Euclidean distance) and speed (23 times faster). When applied to a distal humerus, a tibia plateau, and a scaphoid fracture, the run times were low (1-2min), and the detected edges correct by visual judgement. In the geometrically complex acetabulum, at a run time of 78min some outliers were considered acceptable. An automatically generated fracture probability heat map based on 50 proximal humerus fractures matches the areas of high risk of fracture reported in medical literature. Such automation of the fracture analysis method is advantageous and could be extended to reduce the manual effort even further.

Reducing the L-H transition power threshold in ITER-similar-shape DIII-D hydrogen plasmas

Recent dedicated DIII-D experiments in low-torque, ITER-similar-shape (ISS) hydrogen plasmas (at a plasma current I p ∼ 1.5 MA and ITER-similar edge safety factor q 95 ∼ 3.6) show that the L-H transition power threshold P LH can be reduced substantially (∼30%) with L-mode helium admixtures n He/n e ⩽ 25%. In the ensuing H-mode, helium ion fractions n He/n H remain below 25%. H-mode normalized pressure and confinement quality are only slightly affected by helium seeding, and Z eff ⩽ 2.15 (including helium and carbon content). The plasmas investigated here are electron-heat dominated, with temperatures T e(0)/T i(0) ⩾ 1 and edge heat flux ratio Q e/Q i(ρ = 0.95) ∼ 1.2–1.5. Without mitigation, P LH is higher by a factor of 2–3 in comparison to similar ISS deuterium plasmas. ISS hydrogen plasmas with lower plasma current I p ∼ 1 MA (increased edge safety factor q 95 ∼ 5.1) exhibit a substantially lower power threshold. This plasma current dependence, also observed previously on ASDEX-U and in JET, is not accounted for by the commonly used 2008 ITPA multi-machine threshold scaling, but could potentially allow H-mode access at marginal heating power during the initial plasma current ramp-up. Attempts to reduce P LH with low-field- and high-field-side hydrogen pellet injection, using 1.7 mm diameter pellets, have not demonstrated a robust threshold reduction, in contrast to successful earlier experiments with larger 2.7 mm pellets. Techniques for reducing P LH are very important for ITER, in particular for accessing H-mode in hydrogen plasmas during the Pre-Fusion Power Operation-1 (PFPO-1) campaign with marginal auxiliary heating power (20–30 MW of ECH).

Schmid factor crack propagation and tracking crystallographic texture markers of microstructural condition in direct energy deposition additive manufacturing of Ti-6Al-4V

Metallic additive manufacturing (AM) provides a customizable and tailorable manufacturing process for new engineering designs and technologies. The greatest challenge currently facing metallic AM is maintaining control of microstructural evolution during solidification and any solid state phase transformations during the build process. Ti-6Al-4V has been extensively surveyed in this regard, with the potential solid state and solidification microstructures explored at length. This work evaluates the applicability of previously determined crystallographic markers of microstructural condition observed in electron beam melting powder bed fusion (PBF-EB) builds of Ti-6Al-4V in a directed energy deposition (DED) build process. The aim of this effort is to elucidate whether or not these specific crystallographic textures are useful tools for indicating microstructural conditions in AM variants beyond PBF-EB. Parent β -Ti grain size was determined to be directly related to α -Ti textures in the DED build process, and the solid state microstructural condition could be inferred from the intensity of specific α -Ti orientations. Qualitative trends on the as-solidified β -Ti grain size were also determined to be related to the presence of a fiber texture, and proposed as a marker for as-solidified grain size in any cubic metal melted by AM. Analysis of the DED Ti-6Al-4V build also demonstrated a near complete fracture of the build volume, suspected to originate from accumulated thermal stresses in the solid state. Crack propagation was found to only appreciably occur in regions of slow cooling with large α + β colonies. Schmid factors for the basal and prismatic α -Ti systems explained the observed crack pathway, including slower bifurcation in colonies with lower Schmid factors of both slip systems. Colony morphologies and localized equiaxed β -Ti solidification were also found to originate from build pauses during production and uneven heating of the build edges during deposition. Tailoring of DED Ti-6Al-4V microstructures with the insight gained here is proposed, along with cautionary insight on preventing unplanned build pauses to maintain an informed and controlled thermal environment for microstructural control.