Thermal Load Research Articles

Cost-Effective Planning of Hybrid Energy Systems Using Improved Horse Herd Optimizer and Cloud Theory under Uncertainty

In this paper, an intelligent stochastic model is recommended for the optimization of a hybrid system that encompasses wind energy sources, battery storage, combined heat and power generation, and thermal energy storage (Wind/Battery/CHP/TES), with the inclusion of electric and thermal storages through the cloud theory model. The framework aims to minimize the costs of planning, such as construction, maintenance, operation, and environmental pollution costs, to determine the best configuration of the resources and storage units to ensure efficient electricity and heat supply simultaneously. A novel meta-heuristic optimization algorithm named improved horse herd optimizer (IHHO) is applied to find the decision variables. Rosenbrock’s direct rotational technique is applied to the conventional horse herd optimizer (HHO) to improve the algorithm’s performance against premature convergence in the optimization due to the complexity of the problem, and its capability is evaluated with particle swarm optimization (PSO) and manta ray foraging optimization (MRFO) methods. Also, the cloud theory-based stochastic model is recommended for solving problems with uncertainties of system generation and demand. The obtained results are evaluated in three simulation scenarios including (1) Wind/Battery, (2) Wind/Battery/CHP, and (3) Wind/Battery/CHP/TES systems to implement the proposed methodology and evaluate its effectiveness. The results show that scenario 3 is the best configuration to meet electrical and thermal loads, with the lowest planning cost (12.98% less than scenario 1). Also, the superiority of the IHHO is proven with more accurate answers and higher convergence rates in contrast to the conventional HHO, PSO, and MRFO. Moreover, the results show that when considering the cloud theory-based stochastic model, the costs of annual planning are increased for scenarios 1 to 3 by 4.00%, 4.20%, and 3.96%, respectively, compared to the deterministic model.

Numerical Study of Coolant Flow Phenomena and Heat Transfer at the Cutting-Edge of Twist Drill

Cutting tool coolant channels play a pivotal role in machining processes, facilitating the efficient supply of cooling agents to high-stress areas and effective heat dissipation. Achieving optimal cooling at the tool’s cutting-edge is essential for enhancing production processes. Experimental investigations into tribological stress analysis can be limited in accessing complex tool–workpiece contact zones, prompting the use of numerical modelling to explore fluid dynamics and tribology. In this study, the coolant flow dynamics and heat dissipation in drilling operations were comprehensively investigated through computational fluid dynamics (CFD) modelling. Four twist drill models with varying coolant channel arrangements were studied: standard model drill, standard model drill with notch, profile model drill, and profile model drill with notch. Two distinct approaches are applied to the coolant inlet to assess the impact of operating conditions on fluid flow and heat dissipation at the cutting-edge. The findings emphasize that cutting-edge zones have insufficient coolant supply, particularly in modified drill models such as the standard model drill with notch and profile model drills with and without notch. Moreover, enhanced coolant supply at the cutting-edge is achieved under high-pressure inlet conditions. The standard model drill with a notch exhibited exceptional performance in reducing thermal load, facilitating efficient coolant escape to the flute for improved heat dissipation at the cutting-edge. Despite challenges like dead zones in profile models, the standard-with-notch model yielded the most promising results. Further analyses under constant pressure conditions at 40 and 60 bar exhibited enhanced fluid flow rates, particularly at the cutting-edge, leading to improved heat dissipation. The temperature distribution along the cutting-edge and outer corner demonstrated a decrease as the pressure increased. This study underscores the critical role of both coolant channel design and inlet pressure in optimizing coolant flow dynamics and heat transfer during drilling operations. The findings provide valuable insights for designing and enhancing coolant systems in machining processes, emphasizing the significance of not only coolant channel geometry but also inlet pressure for effective heat dissipation and enhanced tool performance.

Thermal and structural evaluation of an asphalt pavement with an embedded inductive power transfer pad for stationary charging of EVs

A key strategy for increasing sustainability in transportation is to increase the use of Electric Vehicles (EVs) worldwide. Charging EVs wirelessly utilizing Inductive Power Transfer (IPT) pads eliminates most of the current limitations of EVs, such as range anxiety. In this study, the effect of an IPT pad on the temperature and strain response of an asphalt mixture was evaluated. A scaled IPT pad was placed into an experimental asphalt slab and the IPT-asphalt temperature, while energizing the IPT pad, was determined by a thermal camera, Fibre Bragg Grating (FBG) sensors, and thermistors. Moreover, a static wheel load was applied on the surface of the asphalt slab, with and without an IPT pad, and the horizontal tensile strain adjacent to the bottom of the asphalt slab was measured using an FBG sensor. ANSYS simulations were conducted and were validated using the experimental results. The results showed that embedding an energized IPT pad into the asphalt slab at 20 °C increased the asphalt’s surface temperature (approximately 32 mm offset from the pad) by 8.3 °C in the experiment. Raising the ambient temperature from 20 to 50 °C resulted in an elevation of the asphalt surface temperature from 28.3 to 56.7 °C in the experimental analysis. Placement of the IPT pad into the asphalt slab was seen to decrease the asphalt strain by 41 % in the experiment. Placing the static wheel load on the edge of the pad increases the maximum tensile strain by 16 % and moving the load 66.4 mm from the edge increases the maximum tensile strain by 54 %. Significantly, applying both the thermal load and the static wheel load increased the maximum tensile strain by 53 % compared to the asphalt slab without an IPT pad.

Impact of temporal resolution on the design and reliability of residential energy systems

Future energy systems incorporating high shares of intermittent renewable energy sources are often designed using optimization-based, bottom-up energy system models. However, such models are generally limited to single years and hourly resolutions. This study quantifies the precision loss between hourly and sub-hourly-resolved data for the design and operation of a self-sufficient residential multi-energy system with respect to total costs, system design, and reliability using both averaging and sampling data methods. In this case study, the total annual cost is underestimated by 1.7% with the average hourly data relative to the fully-resolved minute resolution data, mainly due to the sizing of the photovoltaic inverter and battery. This is a result of the sub-hourly peaks in the supply and demand data that are evened out, significantly impacting the sub-electrical system. The results show up to 89 kWh of the annual lost load of the total electrical and thermal load, and a penalty cost of up to €894 (+24%) based on the value of the lost load. Another method, which employs regular sampling of the original time series, shows unpredictable behavior with respect to the tendency of either over- or underestimating system costs and components’ capacities depending on the selected samples. Both the sampling and averaging methods highlight that while hourly resolution may suffice for total system cost approximations, it falls short of sizing dynamically-operated components and meeting stringent reliability requirements. Future research may aim to enhance the temporal resolution of global intermittent renewable energy sources and reduce the computational expenses associated with minute-level resolutions.

Stored energy density solution for TSV-Cu structure deformation under thermal cyclic loading based on PINN

TSV-Cu is widely used for chip interconnects, where high testing costs and complex crystal plasticity finite element (CPFE) limit the research of its deep microplastic evolution process. Considering the stored energy density (SED) based on dislocation density and plastic work as a fatigue indicator factor (FIP), this paper proposes for the first time a physics-informed neural network (PINN) framework based on SED, which aims to achieve the solution of SED distributions quickly and efficiently to save computational time and cost. The grain orientation, geometrical compatibility factor, back stress, and effective plastic strain are taken into account as inputs to the PINN model. The total dislocation density is used as an indirect solution variable to construct the associated loss boundary terms, which results in the solution of the SED. The results of the two real EBSD tests show that the PINN model is able to accurately and sensitively predict the SED concentration distribution for different thermal cycle loadings, and maintains a high degree of agreement with the CPFE calculation results. Moreover, The superiority of PINN over other machine learning algorithms in terms of physical model interpretation and prediction accuracy is verified. These make it a reality for PINN to solve for the FIP distribution for the first time, and to accurately and quickly predict the location of crack initiation.

Research on the thermal runaway mechanism and eruption flame dynamics of NCM811 lithium-ion battery stimulated by the coupling abuse of heat and penetration

Thermal abuse and mechanical abuse are the main triggers of thermal runaway (TR) in lithium-ion batteries (LIBs). With the emergence of stimulus superposition application scenarios makes the TR mechanism of LIBs under a single stimulus no longer applicable, and the TR characteristics of LIBs induced by heat-penetration coupled stimulation has become one of the key bottlenecks constraining the intrinsic safety design and control of LIBs. In this paper, an experimental platform for heat-penetration coupled stimulation on LIBs was built, and an experimental research on the TR mechanism and eruption dynamics of LIBs under penetration with different initial thermal load was carried out. The results show that the maximum temperature of cell induced by penetration increases from 537.4 °C to 746 °C, an increase of 38.8 %, as the initial thermal load of the cell increases from 10 °C to 130 °C. When the initial thermal load is further increased to 160 °C, the penetration stimulation no longer induces TR, which is closely related to the “separator melt protection channel”. Based on this, a “kebab” micro-short circuit model is proposed. At 10 °C, 40 °C, 70 °C, and 100 °C, the cell safety valve is destroyed and a “column fire” is formed above the positive electrode. And at 100 °C, the flame eruption height is the largest, up to 185.10 cm, and the jet flame area is the largest, up to 5687.62 cm2.And with the initial thermal load increases, the eruption particles are smaller in size. Increasing content of O in eruption particles, which characterizes the strength of the reaction within the cell, and F elements characterizing toxicity are detected in the eruption particles. The results enrich the theory of TR induced by thermal–mechanical abuse, which is of great guiding significance for the intrinsic safety design of LIBs and the prevention and control of TR risk.

The potential of utilizing vertical borehole heat exchangers in residential buildings for the various climate zones of Saudi Arabia

Most of the literature concerning geothermal energy in Saudi Arabia has focused on power generation applications. This paper investigates the potential of utilizing ground-source heat pump (GSHP) with vertical borehole heat exchangers in residential buildings in the various climate zones and subsurface geologies of Saudi Arabia. Thermal loads of a typical residential building in Saudi Arabia were generated using eQuest software, then used in a model of GSHP system in TRNSYS. The performance and economics of the GSHP system was evaluated and compared with a typical air-source heat pump (ASHP) system for each location. The total borehole lengths in all zones were determined using the cooling load (the dominant load). The potential for employing GSHP systems was found to be not uniform across Saudi Arabia. The required length of the GHE ranged between 12 and 148 m/kW of cooling. The annual energy saving when employing GSHP instead of ASHP systems varied between 3 % to 19 %, and the building's electricity peak demand could be reduced between 5 % to 43 %. Although GSHPs reduced electrical and maintenance costs, their high drilling cost makes them economically unattractive under the present electric utility charge in Saudi Arabia.

УПРОЧНЕНИЕ МЕТАЛЛОРЕЖУЩЕГО ИНСТРУМЕНТА ЭЛЕКТРОИСКРОВОЙ ОБРАБОТКОЙ

Metal-cutting tools during the machining of parts by cutting experience high strength and thermal loads, causing wear of the cutting edges. Increasing the wear resistance of the cutting edges of a metal-cutting tool is an urgent task. (Research purpose) The research purpose is analyzing the causes of wear of end mills and drills and proposing the most rational method of hardening metal-cutting tools. (Materials and methods) End mills and drills were chosen as the object of research. The BIG-5 installation with the use of electrodes made of hard alloys VK8 and T15K6 was used to harden metal-cutting tools. It was pointed out that relatively mild electrical modes with pulse energy from 0.05 to 0.2 joules are used to harden drills and end mills, the thickness of the applied coating layer in such modes is 10-30 micrometers. (Results and discussion) It was noted that the performed analysis of the applied hardening methods confirmed the feasibility of using electric spark processing for these purposes. The optimal modes of electric spark processing were selected on the basis of previous studies. Comparative tests for wear resistance of samples from materials of end mills (P18) and drills (P6M5) were performed. It was shown that when using electrodes made of T15K6, the wear resistance of the samples increases by 1.85 times for P18 and by 8 times for P6M5. Comparative tests of hardened end mills and drills for wear resistance were carried out. The indicator was the number of processed parts. (Conclusions) The result of using the electric spark processing method to harden the cutting tool was an increase in the life of end mills by 3.8 times, drills by 2.25 times. The productivity of manufacturing parts has increased.

Multi-factor thermal analysis of phase change material integrated roofing elements

In the present study, the PCM layer is integrated into the roof, analyzed, and compared for its thermal behaviour in terms of Indoor Air Temperature Reduction (IATR), Thermal Load Levelling (TLL), and Lag Time (LT) to determine the ideal position, thickness, and type of PCM. The observations from the experimental analysis were validated using COMSOL Multiphysics v6.0 with available literature. The results showed that PCM-integrated roofs reduced the interior temperature by around 30%. Furthermore, the fluctuations in the interior temperatures were reduced to 6.1% with PCM integration within the roof. A lag time of 5–8.25 h was observed for the PCM roofs. The study also found that the material properties impact the overall thermal behaviour of the PCM-integrated roofs. These properties were further explored using continuous cyclic thermal loading and variation of latent heat over a period of four days for three climatic zones in India. Abbreviations: PCM: Phase Change Material; CC: Conventional Concrete; AAC: Autoclaved Aerated Cement; TMY: Typical Meteorological Years; epw file: Energy Plus Weather File; mPCM: Microencapsulated Phase Change Material; PTC: Positive Temperature Coefficient; DHT: Digital Temperature And Humidity; IATR: Indoor Air Temperature Reduction (%); TLL: Thermal Load Levelling (%); LT: Lag Time (hours)

Smoothed particle hydrodynamics simulation of transient heat transfer within rotary kiln

Rotary kilns are widely used in industries to heat or cool various materials. Previously the heat efficiency of rotary kiln is often evaluated by assuming the temperature is uniformly distributed within the particle bed, while lacking insights into the recirculating particle flows and the resulted non-uniform heat transfer. Here a smoothed particle hydrodynamics (SPH) approach is deployed to study the particle flow and particle–particle, particle–wall heat transfer in the rotary kilns. The results reveal that there exist low-temperature regimes in the core of rotary kilns depending on the filling levels. The temperature distribution is thus nonuniform and closely related to the particle flow pattern. In terms of heating efficiency, the thermal conductivity of particles exerts the greatest influence on the total heat transfer in rotary kiln. Other material and operational parameters, including the rotating speed, filling level, thermal load, and internal friction of particles, also remarkably affect the heat transfer according to the present simulation results, which are of significance to optimize the heating efficiency of rotary kiln.

Підхід до визначення напружено-деформованого стану стрижнів з композиційних матеріалів з урахуванням внутрішнього самоврівноваженого напруженого стану

The subject of this research is methods of stress-strain state analysis of composite structures. The goal is to develop a mechanism to explain the phenomenon of warping of thin-walled composite sections with a non-uniform cross-section under thermal loading and to synthesize a model to determine the forces in the section elements. The objectives of this study are to predict the deformed states of composite sections at the manufacturing stage and to determine the temperature stresses that occur at the manufacturing stage, as well as after the assembly of the structure. The methods used are related to the mechanics of materials and structures. The following results were obtained. The possible deformation forms of composite plates with an asymmetric structure are analyzed and the rationale for the appearance of such deformations is given. A model of the force interaction of elements in a folded section is proposed. The proposed model can be extended to most sections of load-carrying aircraft structures. Based on the analysis of the mechanics of thin-walled folded sections, the mechanism of the occurrence of complex bending-torsional deformation of long-dimensional sections made of composites with a non-uniform cross-section under the action of an internal self-equilibrium stress state caused by a change in temperature or shrinkage of the binder or both is explained. The analysis of this mechanism makes it possible to design composite sections with minimal warping and to propose engineering methods to compensate for unwanted spatial movements in the case of arbitrary loading of section elements. Conclusions. The scientific novelty of the obtained results can be summarized as follows. A mechanism for the deformation of rods made of dissimilar composite materials when the temperature changes (after extraction from the tool or during operation) is proposed considering the difference in Poisson's coefficients. A model for determining the forces acting on the perimeter of section elements was synthesized, and the corresponding formulas were obtained, which form the basis for the theory of off-center compression of rods. The direction of further research in this field is currently being planned.

Numerical investigation of printed circuit board response during solder float test: Influence of thermal boundary conditions

During qualification, a Printed Circuit Board (PCB) must pass several electrical and thermomechanical tests. Among the tests required by the European Cooperation for Space Standardization (ECSS), the solder float test consists in resting a sample on a 288 °C solder bath. In order to simulate and better understand the latter, the heat transfer coefficient (HTC) of the PCB/solder bath interface has to be characterized.In this work, an experimental setup has been developed to measure the HTC of the interface between SnPb and a horizontal surface. In addition, a finite element model of the solder float test has been developed in order to study the temperature and stress fields inside the PCB. The temperature field is highly heterogeneous at the beginning of the heating. A direct consequence of this early temperature heterogeneity is the development of stress fields that can be correlated to the observed failure modes. A parametric study revealed the sensitivity of the stress and strain development to changes in the HTC value. The difference observed in finite element simulations between isothermal assumptions and transient regime holds true for any maximum temperature in the range of 100 °C to 288 °C. The present work highlights the importance of considering exact thermal boundary conditions when studying the reliability of PCBs under thermal loading (especially with fast changes).

Increasing the Working Time of Forging Tools Used in the Industrial Process of Producing a Disk-Type Forging Assigned for a Gearbox through the Application of Hybrid Layers.

The article discusses the phenomena and destructive mechanisms occurring on the surface of 1.2344 steel dies used during the hot forging of disc-type forgings. Preliminary research has shown that gas nitriding alone, used so far, is insufficient due to the occurrence of destructive mechanisms other than abrasive wear, such as thermal and thermomechanical fatigue, which cause the average durability of such tools to be approximately 5000 forgings. Analyses were also carried out to assess the load on forging tools using numerical modeling (Forge 3.0NxT), which confirmed the occurrence of large and cyclically changing thermal and mechanical loads during the forging process. Therefore, in order to increase operational durability, it was decided to use two types of hybrid layers, differing in the PVD coating used: TiCrAlN and CrN, and then subjected to gas nitriding (GN). The obtained results showed that, depending on the area of the tool and the current working conditions, the applied PVD coatings protect the surface layer of the tool against the dominant destructive mechanisms. In both cases, the strength increased to the level of 7000 forgings, the tools could continue to work, and globally, slightly better results were obtained for the GN+TiCrAlN layer. The CrN-type layer protects the tool more against thermal fatigue, while the TiCrAlN layer is more resistant to abrasive wear. In areas where the hybrid layer was worn, a decrease in hardness was observed from 1300 HV to 600-700 HV, and in places of intense material flow (front-point 2 and tool bridge-point 9) the hardness dropped to below 400 HV, which may indicate local tempering of the material. Moreover, the research has shown that each process and tool should be analyzed individually, and the areas in the tool where particular destructive mechanisms dominate should be identified, so as to further protect the forging tool by using appropriate protective coatings in these areas.

Dynamic responses of a plate on layered transversely isotropic poroelastic subgrade under moving thermal and mechanical loads

In this paper, the dynamic responses of a plate on layered transversely isotropic (TI) poroelastic subgrade under moving thermo-mechanical loads are investigated. Based on the thermodynamics, poroelastic mechanics and the Kirchhoff's thin plate theory, the governing equations of the plate and layered TI saturated subgrade are derived in the wavenumber domain. Then, by introducing the flexibility coefficient of the layered TI poroelastic subgrade and the plate-subgrade interface condition, the solution of the plate-subgrade dynamic interaction is obtained through the extended precise integration method. After the presented method is validated, parametric studies are carried out to confirm the influences of the thermal load, plate-subgrade modulus ratio, plate thickness, and the speed of moving load. Parametric analysis shows that the effect of the thermal load cannot be ignored when considering the plate-subgrade dynamic interaction. In addition, the plate-subgrade modulus ratio, plate thickness, and the speed of moving load have a significant effect on the plate-subgrade dynamic interaction.

Effect of thermomechanical ageing on force transmission by orthodontic aligners made of different thermoformed materials: An experimental study.

Investigating the impact of thermal and mechanical loading on the force generation of orthodontic aligners made from various thermoplastic materials and different compositions. Five distinct materials were utilized including, three multi-layer (Zendura FLX, Zendura VIVA, CA Pro) and two single-layer (Zendura A and Duran). A total of 50 thermoformed aligners (n = 10) underwent a 48-hour ageing protocol, which involved mechanical loading resulting from a 0.2 mm facial malalignment of the upper right central incisor (Tooth 11) and thermal ageing through storage in warm distilled water at 37°C. The force exerted on Tooth 11 of a resin model was measured both before and after ageing using pressure-sensitive films and a biomechanical setup. Before ageing, pressure-sensitive films recorded normal contact forces ranging from 83.1 to 149.7 N, while the biomechanical setup measured resultant forces ranging from 0.1 to 0.5 N, with lingual forces exceeding facial forces. Multi-layer materials exhibited lower force magnitudes compared to single-layer materials. After ageing, a significant reduction in force was observed, with some materials experiencing up to a 50% decrease. Notably, multi-layer materials, especially Zendura VIVA, exhibited lower force decay. The force generated by aligners is influenced by both the aligner material and the direction of movement. Multi-layer materials exhibit superior performance compared to single-layer materials, primarily because of their lower initial force, which enhances patient comfort, and their capability to maintain consistent force application even after undergoing ageing.

Coupled modeling of thermal-fluid-solid and chemo-mechanical behaviors in thermal barrier coatings under flowing gas environment

This study proposes a modeling approach to simulate the thermo-chemo-mechanical responses of thermal barrier coatings (TBCs) exposed to flowing high-temperature gas. A thermal-fluid-solid analysis was performed to simulate temperature fields of the coatings under flowing gas environment, while finite element analysis was carried out to study the oxidation and stress evolutions of the coatings using a developed chemo-mechanical constitutive model. Thermal loads from thermal-fluid-solid analysis were imposed on the finite element model, by which the factors associated with flowing gas were incorporated into the thermo-chemo-mechanical modeling. The study systematically investigated the effects of flowing gas and coolant on the chemo-mechanical responses of the coatings. The results revealed that the enhanced gas factors (temperature, velocity, angle of attack, and pressure) and coolant temperatures accelerate oxidation and induce higher residual stresses, while higher coolant velocity mitigates both oxidation and stresses. The volume fraction of oxygen in the gas was found to have a negligible influence. Dimensional analysis and multiple regression were performed to derive mathematical expressions for assessing out-of-plane stress and oxidation dynamics. Design maps were proposed to guide the durable design of the coatings.

Early-Detection of EVA Encapsulant Degradation in PV Modules Based on Vibration Frequency Analysis

In engineering applications, the frequency analysis represents a first and practical step to collect relevant parameters for structural and mechanical diagnostics. Any possible material / component degradation and deterioration can be prematurely detected by frequency modifications that exceed a certain alert value. In this paper, the attention is given to the dynamic mechanical analysis of commercial photovoltaic (PV) modules, in which the solar cells are typically encapsulated in thin viscoelastic interlayers made of Ethylene-Vinyl Acetate (EVA), which are primarily responsible for the load-bearing capacity of the sandwich PV system. As a major effect of ageing, ambient conditions, non-uniform / cyclic thermal gradients, humidity and even extreme mechanical / thermal loads, the rigidity of these films can largely modify and decrease, thus possibly affecting the mechanical capacity of the PV module, and even exposing the solar cells to fault. Knowledge of the effective bonding level is an important step for diagnostic purposes. In this regard, the present study is based on a preliminary but extensive parametric Finite Element (FE) numerical investigation of full-scale commercial PV modules of typical use in buildings. The attention is given – for PV module arrangements of technical interest – to the effect of EVA stiffness in terms of vibration modes and especially frequency sensitivity. As shown, when compared to newly installed PV modules, any kind of stiffness decrease is associated to major frequency modifications for the composite system, and in the worst configuration, such a frequency scatter can decrease down to -40% the original condition. Such a marked stiffness decrease would be implicitly associated to a weak mechanical performance of the sandwich section, with major stress peaks and deflections in the PV system, even under ordinary loads. The presented results, in this sense, suggest that major consequences can be prevented and minimized by monitoring the vibration frequency of PV modules.

A new ventilation performance index considering relative changes in environmental parameters: A numerical study

The ventilation index plays a crucial role in evaluating and selecting ventilation systems. However, existing studies focus only on the "effectiveness" of ventilation systems but usually ignore the "extent of the effect" caused by ventilation, and no relevant indexes are available. To address this issue, this study aims to propose a new ventilation index named the equivalent ventilation number (EVN), which considers the relative change in environmental parameters. The application potential of the EVN index was numerically examined in a virtual hospital ward setting with varying air changes per hour (ACH), thermal loads, air distribution patterns, contaminant source intensities, and local air supply rates. The results demonstrate that the highest average temperature-based EVN and CO2-based EVN are obtained when ACH increases from 6 h−1 to 12 h−1 and local supply air velocity increases from 0 m/s to 1 m/s, with values of 0.66 and 1.49 respectively. Furthermore, EVN values differ across different ventilation conditions and locations. The effect of changing ventilation conditions on ventilation performance assessed by heat removal effectiveness and temperature-based EVN, as well as contaminant removal effectiveness and CO2-based EVN, is opposite in 4 out of 10 cases and 3 out of 10 cases, respectively. The average EVN values calculated based on temperature and contaminant changes differ among all cases, with the largest difference of 1.2. The proposed EVN is anticipated to be an effective index for quantifying and comparing the "extent of the effect" caused by ventilation systems under various ventilation conditions.

Effects of the Slotted-Cavity Tip on the Vortices and Aerothermal Performance in the High-Pressure Turbine

To enhance aerodynamic performance in high-pressure turbines, cavity tips are commonly employed. However, these cavity tips tend to generate more vortices than flat tips, leading to an increased thermal load on the blade tips. This study introduces a novel configuration aimed at suppressing vortex intensity by incorporating a slot at the cavity bottom. Through numerical simulations, the impact of slot geometry parameters on vortices and aerothermal performance is investigated. The findings reveal that a slot height of 0–0.1 mm effectively suppresses the pressure side corner vortex within the cavity, while a slot height of 0.2–0.3 mm eliminates it. A slot height of 0.3 mm reduced average heat transfer and the high heat transfer region at the cavity bottom by 22.6% and 92.6%, respectively; however, it was observed that the leakage flow increased by 15.9%. Therefore, this study further combines the slot structure with a winglet to control the leakage flow. The combined structures exhibit superior overall performance compared to the single-slot cavity tip. Compared to the conventional cavity tips, the combined structure achieves a maximum reduction of 27.3% in average heat transfer and 7.9% in leakage flow, along with a decline of 1.9% in total pressure loss.

Discovering tungsten-based composites as plasma facing materials for future high-duty cycle nuclear fusion reactors

Despite of excellent thermal properties and high sputtering resistance, pure tungsten cannot fully satisfy the requirements for plasma facing materials in future high-duty cycle nuclear fusion reactions due to the coupled extreme environments, including the high thermal loads, plasma exposure, and radiation damage. Here, we demonstrated that tungsten-based composite materials fabricated using spark-plasma sintering (SPS) present promising solutions to these challenges. Through the examination of two model systems, i.e., tungsten-zirconium composite for producing porous tungsten near the surface and dispersoid-strengthened tungsten, we discussed both the strengths and limitations of the SPS-fabricated materials. Our findings point towards the need for future studies aimed at optimizing the SPS process to achieve desired microstructures and effective control of oxygen impurities in the tungsten-based composite materials.