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Effective thermal conductivity of composites using homogenization 使用均质化的复合材料的有效导热系数
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103078
Ilige S. Hage
Composite materials are extensively used in engineering applications due to their customizable properties and high performance. Determining the equivalent homogenized properties of composites, such as thermal conductivity, is crucial for their effective use. Various theoretical, analytical, and experimental methods have been developed to assess these properties. This study investigates the effective thermal conductivity of composites using a deterministically based procedure for thermal analysis. This procedure accounts for the combined influences of the inclusions’ volume fractions, shapes, orientations, and locations within the matrix to determine the effective thermal conductivity of composites. The specific composite analyzed consists of a cubical PLA matrix with a single spherical or elliptical void inclusion with perfect interfaces. For that purpose, an analytical approach was developed, and MATLAB® code was created to calculate the effective thermal conductivity tensor. To benchmark the analytical results, comparisons were made against numerical finite element modeling (FEM) results conducted using ANSYS®; in addition, to previously reported analytical models from the literature. Corroboration was also obtained by comparing the results against experimental data from the literature. The accuracy of the proposed homogenization scheme was demonstrated by achieving a low mean absolute percentage error (MAPE) compared to FEM (2.88%) and to the experimental results (2.72% for void inclusion and 6.99% for filled inclusion). Additionally, a high R-squared (R2) value of 0.986 was achieved compared to FEM, and values of 0.97 and 0.998 were achieved compared to the experimental results for void and filled inclusions, respectively.
复合材料因其可定制性和高性能而广泛应用于工程领域。确定复合材料的等效均质性,如导热性,对其有效使用至关重要。各种理论的、分析的和实验的方法被开发出来评估这些特性。本研究使用基于确定性的热分析程序来研究复合材料的有效导热系数。该程序考虑了夹杂物体积分数、形状、取向和基体内位置的综合影响,以确定复合材料的有效导热系数。所分析的特定复合材料由立方体聚乳酸基体和具有完美界面的单个球形或椭圆形空洞包裹体组成。为此,开发了一种分析方法,并创建了MATLAB®代码来计算有效导热张量。为了对分析结果进行基准测试,将分析结果与ANSYS®的数值有限元模拟结果进行了比较;此外,以前报道的分析模型从文献。通过将结果与文献中的实验数据进行比较,也得到了确证。与有限元法(2.88%)和实验结果(空隙包裹体的2.72%和填充包裹体的6.99%)相比,所提出的均匀化方案的平均绝对百分比误差(MAPE)较低,证明了该方案的准确性。与有限元相比,该方法的r平方(R2)值较高,为0.986;与实验结果相比,空心夹杂物和充填夹杂物的r平方(R2)值分别为0.97和0.998。
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引用次数: 0
Numerical exploration of heat transfer and friction factor in corrugated dual-pipe heat exchangers using SiO2 and CuO nanofluids 基于SiO2和CuO纳米流体的波纹双管换热器传热和摩擦系数数值研究
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103076
Prem Kumar Chaurasiya , Jatoth Heeraman , Anoop Pratap Singh , K. Sudha Madhuri , Vinod Kumar Sharma
Numerical simulations are conducted to explore influence of corrugation on internal tube surfaces of the double pipe heat exchanger (DPHE). The study comparing the performance of liquid water, SiO2 (Silicon dioxide) and CuO (Copper oxide) as working fluids, with CuO showing promising outcomes. The configuration employed for investigation are inner tube corrugated externally (ECIT) and inner tube corrugated internally (ICIT), at helix angles (α) of 15°, 20°, and 25° is analysed using k-ε turbulence model within a Reynolds number (Re) range of 4000 to 20,000 under constant temperature conditions along the tube wall. Insights is gained from numerical simulations on heat transfer coefficient, pressure drop, frictional loss, and heat transfer rate [HTR]. The results revealed that ECIT outperformed ICIT, particularly at α = 15°, with higher performance evaluation criteria (PEC). This investigation provides valuable insights for optimizing heat exchanger design and operation by emphasizing the importance of corrugations for improved efficiency in industrial heat transfer processes. This study reveals that using CuO nanofluid in corrugated double pipe heat exchangers significantly enhances heat transfer performance, with a maximum Nusselt number increase of up to 35 %, while maintaining superior friction factors and performance evaluation criteria (PEC) values ranging from 0.89 to 2.09 at varying Reynolds numbers.
通过数值模拟研究了波纹对双管换热器内管表面的影响。该研究比较了液态水、SiO2(二氧化硅)和CuO(氧化铜)作为工质的性能,其中CuO表现出良好的效果。采用k-ε湍流模型分析了沿管壁在恒定温度条件下,螺旋角(α)分别为15°、20°和25°时的内管外波纹(ECIT)和内管内波纹(ICIT)结构。通过对传热系数、压降、摩擦损失和传热速率[HTR]的数值模拟,获得了新的见解。结果表明,ECIT在α = 15°时表现更好,具有更高的性能评价标准(PEC)。本研究通过强调波纹对提高工业传热过程效率的重要性,为优化热交换器的设计和操作提供了有价值的见解。研究表明,在波纹双管换热器中使用CuO纳米流体可以显著提高换热性能,在不同雷诺数下,Nusselt数最大可提高35%,同时保持了优异的摩擦因数和性能评价标准(PEC)值,范围在0.89 ~ 2.09之间。
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引用次数: 0
Heat transfer phenomena and performance investigations for 3D fin-and-tube pulsating heat pipe heat exchanger under vertical and horizontal orientations 三维翅片管脉动热管换热器在垂直和水平方向下的传热现象及性能研究
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103077
Po-Shen Cheng , Shwin-Chung Wong , Shih-Kuo Wu
The present heat exchanger is modified from an inexpensive commercial heat exchanger composed of three connected tube layers with an internal tube diameter of 5.6 mm. Under the vertical orientation, methanol with weaker surface tension can surprisingly achieve pulsation-like motion in the large ID with Bo numbers ranging between 3.37 and 3.73, well beyond the widely accepted criterion of Bo = 1.8 or 2.0. Under the horizontal orientation, the multi-layered structure greatly helps the pulsation in that liquid slug trains tend to drain down to the lower layer, thereby not only trigger but sustain continuous pulsation motion. Also, the low-surface-tension working fluid, like methanol, also activated a dynamic flowing behavior over the PHPHX unit. In terms of the thermal performance, the effectiveness increases by up to 50 % compared to the system with independent tube layers, even though both have the same total number of tubes. The system can accommodate up to three sets of PHPHX units, and the maximum effectiveness appears with the methanol for the filling ratio of 35 % under the horizontal orientation. With methanol overcoming local dry-out by installing multiple sets of PHPHX unit, the smooth movement of liquid slug trains, due to its lighter weight and lower viscosity, achieve more heat delivery even with a 2.2 times lower latent heat and a 3.51–3.64 times lower thermal conductivity than water.
本发明的热交换器是由一种廉价的商用热交换器改进而来,该热交换器由三个相连的管层组成,其内管直径为5.6 mm。在垂直取向下,表面张力较弱的甲醇出人意料地在大内径内实现了脉动运动,其Bo值在3.37 ~ 3.73之间,远远超出了广为接受的Bo = 1.8或2.0的标准。在水平方向下,多层结构极大地促进了脉动,液体段塞流会向下层流动,从而触发并维持了连续的脉动运动。此外,低表面张力的工作流体,如甲醇,也激活了PHPHX装置上的动态流动行为。在热性能方面,与具有独立管层的系统相比,效率提高了50%,即使两者具有相同的管总数。该系统最多可容纳三套PHPHX装置,在水平方向下,甲醇填充率为35%时,效率最高。甲醇通过安装多套PHPHX装置克服了局部干燥,由于其重量更轻,粘度更低,液体段塞流运动平稳,即使潜热比水低2.2倍,导热系数比水低3.51-3.64倍,也能实现更多的热量传递。
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引用次数: 0
Real-Time prediction of pool fire burning rates under complex heat transfer effects influenced by ullage height: A comparative study of BPNN and SVR 高度影响下复杂换热效应下池火燃烧速率的实时预测:BPNN与SVR的对比研究
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103060
Chaolan Gao , Wei Ji , Jiyun Wang , Xianli Zhu , Chunxiang Liu , Zhongyu Yin , Ping Huang , Longxing Yu
This research utilizes machine learning methods to forecast the complex, non-linear thermal phenomena, along with heat transfer mechanisms, that influence the burning rate of pool fires, especially with changes in ullage height. Experiments involving pool fires were systematically designed and carried out, incorporating different diameters and ullage heights. Heptane was used as the representative alkane fuels. A dataset containing more than 70,000 sets of data was created as a training dataset for training the Backpropagation Neural Network (BPNN) and Support Vector Regression (SVR) models. During the optimization of machine learning model parameters, this study is based on Particle Swarm Optimization (PSO) with the principle of intelligent optimization to efficiently and accurately screen and optimize the key parameters of the model. The combustion duration, pool dimensions, and non-dimensional ullage height were input into a machine-learning model to predict the burning rate. By comparing against experimental data, the model was found to be able to predict the dynamic evolution of the burning rate of the pool fire in a real-time manner. The SVR model demonstrates greater predictive accuracy in comparison to the BPNN model, and the relative prediction error remains within ± 20 %, which fully proves its effectiveness and generalization ability in the prediction of pool fire burning rate. The insights gained will offer substantial scientific backing for enhanced fire monitoring systems, while highlighting the capability of advanced machine learning methodologies to predict the intricate, real-time thermal dynamics and heat transfer characteristics of burning liquid fuels.
本研究利用机器学习方法来预测复杂的非线性热现象,以及传热机制,这些现象会影响池火的燃烧速度,特别是随着高度的变化。系统地设计和进行了涉及池火的实验,包括不同的直径和高度。以庚烷为代表的烷烃燃料。创建了一个包含超过70,000组数据的数据集作为训练数据集,用于训练反向传播神经网络(BPNN)和支持向量回归(SVR)模型。在机器学习模型参数优化过程中,本研究基于粒子群算法(Particle Swarm optimization, PSO),采用智能优化的原理对模型的关键参数进行高效、准确的筛选和优化。燃烧持续时间、池尺寸和无量纲高度被输入到机器学习模型中,以预测燃烧速度。通过与实验数据的对比,发现该模型能够实时预测池火燃烧速率的动态演变。与BPNN模型相比,SVR模型的预测精度更高,相对预测误差保持在±20%以内,充分证明了其在池火燃烧速率预测中的有效性和泛化能力。所获得的见解将为增强的火灾监测系统提供实质性的科学支持,同时突出先进的机器学习方法的能力,以预测复杂的实时热动力学和燃烧液体燃料的传热特性。
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引用次数: 0
Enhancing Part-Load performance of the simple recuperated supercritical carbon dioxide cycle through shaft separation 通过轴分离提高简单回收超临界二氧化碳循环的部分负荷性能
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103074
Seongmin Son
In this study, the operability of a simple recuperated supercritical carbon dioxide (S-CO2) cycle under off-design conditions, specifically during part-load operation, was quantitatively analyzed by implementing shaft separation to place a compressor-driving turbine (CDT). For off-design evaluation, both the heat exchanger and turbomachinery were designed in one dimension before being inserted into the off-design platform of the system. To ensure physical consistency, all turbines were designed using the same set of loss models. The analysis results revealed that the efficiency of the single-shaft configuration decreased by about 12 %p at 10 % output, while that of the separated-shaft configuration decreased by < 8 %p under the same conditions. The arrangement of the CDT and power turbine had minimal impacts on off-design performance. The power required to drive the CDT–compressor operating at the optimal Revolution Per Minuate was found to be less than 5 % of the design output. These findings imply that layout modifications can enhance overall off-design efficiency and that the incorporation of a motor that supplies about 5 % of the design output for the CDT–compressor set significantly improves part-load operability. This requirement is practical, as such a motor is typically required for startup procedures. Although these results were obtained from the simplest recuperated S-CO2 cycle, similar approaches could enhance off-design performance in more complex cycles such as waste heat recovery or S-CO2 recompression cycles. The findings of this study demonstrate that altering the shaft arrangement while considering off-design operability can significantly enhance the operability of S-CO2 systems.
在本研究中,通过实施轴分离放置压缩机驱动涡轮(CDT),定量分析了在非设计条件下,特别是在部分负荷运行期间,简单回收超临界二氧化碳(S-CO2)循环的可操作性。对于非设计评价,换热器和涡轮机械均进行一维设计,然后插入系统的非设计平台。为了确保物理一致性,所有涡轮机都使用同一套损失模型进行设计。分析结果表明,当输出功率为10%时,单轴结构的效率下降了约12% p,而分离轴结构的效率下降了<;8% p在相同条件下。CDT和动力涡轮的布置对非设计性能的影响最小。驱动cdt压缩机以最佳每分钟转数运行所需的功率小于设计输出的5%。这些发现表明,布局调整可以提高整体非设计效率,并且为cdt压缩机组提供约5%的设计输出的电机显着提高了部分负载的可操作性。这个要求是实际的,因为这样的电机通常需要启动程序。虽然这些结果是从最简单的S-CO2回收循环中获得的,但类似的方法可以提高更复杂循环(如废热回收或S-CO2再压缩循环)的非设计性能。研究结果表明,在考虑非设计可操作性的情况下,改变轴的布置方式可以显著提高S-CO2系统的可操作性。
{"title":"Enhancing Part-Load performance of the simple recuperated supercritical carbon dioxide cycle through shaft separation","authors":"Seongmin Son","doi":"10.1016/j.tsep.2024.103074","DOIUrl":"10.1016/j.tsep.2024.103074","url":null,"abstract":"<div><div>In this study, the operability of a simple recuperated supercritical carbon dioxide (S-CO<sub>2</sub>) cycle under off-design conditions, specifically during part-load operation, was quantitatively analyzed by implementing shaft separation to place a compressor-driving turbine (CDT). For off-design evaluation, both the heat exchanger and turbomachinery were designed in one dimension before being inserted into the off-design platform of the system. To ensure physical consistency, all turbines were designed using the same set of loss models. The analysis results revealed that the efficiency of the single-shaft configuration decreased by about 12 %p at 10 % output, while that of the separated-shaft configuration decreased by &lt; 8 %p under the same conditions. The arrangement of the CDT and power turbine had minimal impacts on off-design performance. The power required to drive the CDT–compressor operating at the optimal Revolution Per Minuate was found to be less than 5 % of the design output. These findings imply that layout modifications can enhance overall off-design efficiency and that the incorporation of a motor that supplies about 5 % of the design output for the CDT–compressor set significantly improves part-load operability. This requirement is practical, as such a motor is typically required for startup procedures. Although these results were obtained from the simplest recuperated S-CO<sub>2</sub> cycle, similar approaches could enhance off-design performance in more complex cycles such as waste heat recovery or S-CO<sub>2</sub> recompression cycles. The findings of this study demonstrate that altering the shaft arrangement while considering off-design operability can significantly enhance the operability of S-CO<sub>2</sub> systems.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"56 ","pages":"Article 103074"},"PeriodicalIF":5.1,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The influence of microgrooves on the dynamics of drop spreading on textured surfaces 微槽对织构表面液滴扩散动力学的影响
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103058
S.V. Syrodoy, G.V. Kuznetsov, K.A. Voytkova, Zh.A. Kostoreva, N.Yu. Gutareva, A.S. Poznaharev, M.S. Tamashevich
In years of intensive development of electronic and microelectronic equipment, the problem of ensuring the scheduled thermal mode of both individual elements of such equipment and large-sized products, such as data storage databases, has become increasingly acute. Therefore, researchers from many countries are currently making active attempts to develop new systems for ensuring scheduled operating modes of electronic computer elements. One of the options for solving this problem is the drop cooling of surfaces of electronic and microelectronic equipment heated to high temperatures. This technology involves the formation of a cluster on the heat-removal surface of highly loaded computer elements. This allows extreme heat fluxes to be removed through phase change. However, despite a fairly large volume of research on this topic, there are still many unsolved problems in this area of knowledge. For example, the parameters (deposition height, drop feed rate, etc.) of water drop deposition on the surface of substrates used for cooling have not been determined yet. Moreover, the efficiency of drop cooling increases if the surface from which heat is removed is modified (roughness is formed). However, the patterns of spreading and evaporation of coolant drops on rough surfaces have not been sufficiently studied yet. Therefore, the aim of the work was to establish, based on the results of the experiments, the scale of the influence of the fall height of water drops on the characteristics and conditions of their spreading on a textured and polished surface. The paper presents the experimental results of the process of water drop impact on a textured surface. The main characteristics of a liquid drop spreading over a textured surface have been investigated. To establish the characteristics and conditions of spreading (drop spreading speed and time, drop shape stabilization time), typical shapes (in the midsection) of a drop spreading over the surface have been established. It is shown that the characteristic time of formation of the equilibrium state of the “water drop – substrate” system is no more than 0.1 s. This is significantly less than the drop evaporation time, even on high-temperature surfaces. The effect of surface anisotropy on the characteristics and conditions of spreading has been analyzed. It is shown that when water moves across the grooves, drop spreading is higher than along the grooves. A hypothesis has been developed to describe this effect.
随着电子和微电子设备的密集发展,保证这些设备的单个元件和大型产品(如数据存储数据库)的预定热模式的问题变得越来越尖锐。因此,目前许多国家的研究人员正在积极尝试开发新的系统,以确保电子计算机元件的预定工作模式。解决这一问题的选择之一是对加热到高温的电子和微电子设备表面进行滴冷却。该技术涉及在高负荷计算机元件的散热表面形成一个簇。这允许通过相变去除极端的热通量。然而,尽管对这一主题进行了相当大量的研究,但在这一知识领域仍有许多未解决的问题。例如,用于冷却的基板表面水滴沉积的参数(沉积高度、水滴进给量等)尚未确定。此外,如果对除去热量的表面进行修饰(形成粗糙度),液滴冷却的效率就会提高。然而,冷却剂液滴在粗糙表面上的扩散和蒸发模式尚未得到充分的研究。因此,这项工作的目的是在实验结果的基础上,确定水滴下落高度对其在纹理和抛光表面上扩散的特性和条件的影响程度。本文给出了水滴在织构表面上撞击过程的实验结果。研究了液滴在织构表面上扩散的主要特性。为了确定液滴扩散的特征和条件(液滴扩散速度和时间、液滴形状稳定时间),建立了液滴在表面上扩散的典型形状(在中部)。结果表明,“水滴-衬底”体系平衡态形成的特征时间不大于0.1 s。即使在高温表面上,这也明显小于液滴蒸发时间。分析了表面各向异性对扩散特性和条件的影响。结果表明,当水穿过沟槽时,水滴的扩散比沿着沟槽的扩散要大。人们提出了一种假说来描述这种效应。
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引用次数: 0
Pyrolysis kinetics and reaction mechanism of waste medical masks by sectional heating process 废医用口罩分段加热热解动力学及反应机理
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-12-01 DOI: 10.1016/j.tsep.2024.103065
Yong Li, Shuo Liu, Fengfu Yin, Dong Liang
The COVID-19 epidemic has led to a significant upsurge in the accumulation of waste medical masks. This work focuses on the detailed examination of waste medical masks’ pyrolysis kinetic and reaction mechanism, employing a sectional heating process. The degradation properties were analyzed via thermal gravimetric analysis and pyrolysis reactor. The comprehensive kinetic process was studied using model-free and model-fitting methods, which determined the apparent activation energy and pre-exponential factor. The calculated average value for these parameters was 221.32 kJ/mol and 2.6 × 1014 min−1, respectively. The pyrolysis process was carried out at three distinct temperatures: 380, 470, and 490 ℃, corresponding to the initial peak degradation rate and final degradation temperatures determined by TGA results. The total yield of oil, gas and tar was 88.6 %, 11.3 % and 0.1 %, respectively. The identification and quantification of pyrolysis products were achieved through GC–MS and FTIR. It was observed that higher pyrolysis temperature facilitated the generation of alkanes and hydrocarbons with lower carbon chain lengths in oil products and propylene monomers in gas products. The dominant pyrolysis products in oil under 380 ℃, 470 ℃ and 490 ℃ were C20, C20 and C12 with the yield of 36.17 %, 48.96 % and 43.35 %, respectively. And the corresponding dominant products in gas all were propylene with the yield of 34.74 %, 53.02 % and 54.55 %, respectively. Furthermore, a reaction mechanism was postulated to elucidate the pyrolysis process under varying temperature conditions.
新冠肺炎疫情导致废弃医用口罩的积累大幅增加。本文采用分段加热工艺,对废弃医用口罩的热解动力学和反应机理进行了详细的研究。通过热重分析和热解反应器对其降解性能进行了分析。采用无模型法和模型拟合法研究了综合动力学过程,确定了表观活化能和指前因子。这些参数的计算平均值分别为221.32 kJ/mol和2.6 × 1014 min−1。热解过程在380、470和490℃三个不同的温度下进行,对应于TGA结果确定的初始峰值降解速率和最终降解温度。石油、天然气和焦油的总收率分别为88.6%、11.3%和0.1%。通过GC-MS和FTIR对热解产物进行了鉴定和定量。研究发现,较高的热解温度有利于成品油生成低碳链长的烷烃和烃类,气生成丙烯单体。380℃、470℃和490℃条件下,原油的主要热解产物为C20、C20和C12,产率分别为36.17%、48.96%和43.35%。气体中相应的优势产物均为丙烯,产率分别为34.74%、53.02%和54.55%。在此基础上,对不同温度条件下的热解过程进行了反应机理分析。
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引用次数: 0
Model-based analysis of the effective pressure on effective thermal conductivity of porous media 基于模型的有效压力对多孔介质有效热导率的影响分析
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-11-26 DOI: 10.1016/j.tsep.2024.103069
Gang Lei , Jiadi Tang , Kaixuan Qiu , Shiming Wei , Wan Cheng , Liangliang Zhang , Xianmin Zhou
Accurate characterization of the effective thermal conductivity (ETC) of porous media is crucial for analyzing heat transfer involved in the scientific, technological, and engineering fields. For example, ETC is a fundamental parameter for characterizing energy exploitation and utilization, such as the coupled thermo-hydro-mechanical-chemical process. During the energy extraction from the deep subsurface, the effective pressure (the difference between the confining pressure and the pore pressure) will alter the microstructure of the porous medium, which will then change its ETC value. In light of the intrinsic randomness and disorder in the distribution of grains and pores in the deep subsurface, many researchers have focused on heat conduction to develop theoretical models of ETC. Less attention has been paid to the thermal and mechanical coupling processes. In this paper, a novel analytical model was derived to study the effect of effective pressure on ETC of porous materials based on fractal theory, Laplace′s equation and the theory of elastic mechanics. The newly developed ETC model considered the effective pressure, the liquid saturation, and the microstructure parameters. The model has also been validated against the experimental results. The model demonstrated that effective pressure increases the ETC of a given porous medium. Moreover, there is a larger change in ETC in porous materials with a smaller initial porosity compared to porous materials with a larger initial porosity. This work constitutes a comprehensive investigation of pressure-dependent ETC, which is a key issue in heat transfer in porous media.
准确表征多孔介质的有效热导率(ETC)对于分析科学、技术和工程领域的传热至关重要。例如,ETC 是表征能源开发和利用(如热-水-机械-化学耦合过程)的基本参数。在从深层地下提取能源的过程中,有效压力(约束压力与孔隙压力之差)会改变多孔介质的微观结构,进而改变其 ETC 值。鉴于深层地下晶粒和孔隙分布的内在随机性和无序性,许多研究人员将重点放在热传导方面,以建立 ETC 理论模型。对热和机械耦合过程关注较少。本文基于分形理论、拉普拉斯方程和弹性力学理论,推导出一个新的分析模型,研究有效压力对多孔材料 ETC 的影响。新建立的 ETC 模型考虑了有效压力、液体饱和度和微观结构参数。该模型还根据实验结果进行了验证。该模型表明,有效压力会增加特定多孔介质的 ETC。此外,与初始孔隙率较大的多孔材料相比,初始孔隙率较小的多孔材料的 ETC 变化更大。这项工作全面研究了与压力有关的 ETC,这是多孔介质传热中的一个关键问题。
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引用次数: 0
Thermal radiation optical motion capture based on depth camera perception for basketball fatigue detection simulation 基于深度摄像头感知的热辐射光学运动捕捉,用于篮球疲劳检测模拟
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-11-26 DOI: 10.1016/j.tsep.2024.103072
Zeyang Yin , Zheng Li , Hongbo Li
Traditional fatigue detection methods usually rely on physiological indicators and subjective evaluation, which has certain limitations. Because of its non-contact and high sensitivity, thermal radiation optical motion capture technology has gradually become a research hotspot in fatigue detection. This paper aims to explore the application of thermal radiation optical motion capture technology based on depth camera perception in the fatigue detection of basketball players, so as to provide a new method for improving sports load management and reducing the risk of sports injuries. In this paper, depth camera and thermal imaging technology are used to collect the thermal radiation information of basketball players under different fatigue states. Through data preprocessing and feature extraction, a fatigue recognition model based on machine learning was constructed. In the experiment, the athletes completed standardized basketball training sessions, during which the heat radiation data was recorded in real time and compared with physiological indicators (such as heart rate and breathing rate). The experimental results show that the fatigue detection model based on thermal radiation optical motion capture has higher accuracy than the traditional method, and can reflect the change of fatigue state of athletes in time. There is a significant correlation between thermal imaging data and physiological indicators, which verifies the effectiveness of the method. Thermal radiation optical motion capture technology based on depth camera perception provides an effective solution for fatigue detection of basketball players.
传统的疲劳检测方法通常依赖于生理指标和主观评价,具有一定的局限性。热辐射光学运动捕捉技术因其非接触、灵敏度高等特点,逐渐成为疲劳检测的研究热点。本文旨在探索基于深度相机感知的热辐射光学运动捕捉技术在篮球运动员疲劳检测中的应用,从而为改善运动负荷管理、降低运动损伤风险提供一种新方法。本文利用深度相机和热成像技术采集篮球运动员在不同疲劳状态下的热辐射信息。通过数据预处理和特征提取,构建了基于机器学习的疲劳识别模型。在实验中,运动员完成了标准化的篮球训练,其间热辐射数据被实时记录并与生理指标(如心率和呼吸频率)进行对比。实验结果表明,基于热辐射光学运动捕捉的疲劳检测模型比传统方法具有更高的准确性,能及时反映运动员疲劳状态的变化。热成像数据与生理指标之间存在明显的相关性,验证了该方法的有效性。基于深度相机感知的热辐射光学运动捕捉技术为篮球运动员的疲劳检测提供了有效的解决方案。
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引用次数: 0
Thermal performance enhancement with solidification effect of nickel foam and MXene nanoenhanced PCM composite based thermal energy storages 利用泡沫镍和 MXene 纳米增强 PCM 复合材料的凝固效应提高热能储存器的热性能
IF 5.1 3区 工程技术 Q2 ENERGY & FUELS Pub Date : 2024-11-24 DOI: 10.1016/j.tsep.2024.103068
Utkarsh Srivastava, Rashmi Rekha Sahoo
This paper presents a numerical investigation into the solidification behavior of phase change material (PCM) in duplex and triplex-tube latent heat thermal energy storage (LHTES) systems enhanced with nickel foam and MXene nanoparticles. The study aims to investigate how nickel foam integration enhances heat transfer during PCM solidification, aiming for faster, more uniform solidification, and to analyse energy and exergy efficiency for optimizing thermal energy storage systems. The study also assesses the impact of nickel foam on enhancing PCM thermal conductivity, improving solidification rates, and overall thermal management. Focusing on a nickel foam/PCM/MXene (5 % v/v.) composite, the study explores the effects of solidification characteristics, as well as the Stefan and Fourier numbers, in both duplex tube thermal energy storage (DuT-TES) and triplex tube thermal energy storage (TrT-TES) systems. It provides detailed insights into the thermal performance of these systems by evaluating key factors such as liquid fraction, solidification temperature profiles, exergy destruction, exergetic efficiency, system efficiency, and discharged energy.
The findings reveal that systems incorporating nickel foam/PCM-MXene composites significantly outperformed those using nickel foam/PCM and pure PCM alone, achieving notably faster solidification. Specifically, the nickel foam/PCM composite demonstrated higher discharge exergy than pure cetyl alcohol PCM. The TrT-TES system with the nickel foam/PCM composite solidified 48.40% faster than the DuT-TES system. Additionally, the discharge energy of the TrT-TES system with nickel foam/PCM and nickel foam/PCM/MXene composites was 2.26 % and 3.65 % greater, respectively, than that of the DuT-TES system. At 90 s, the DuT-TES with nickel foam/PCM/MXene showed a 2.91 % improvement in system efficiency. Overall, the TrT-TES system using the nickel foam/PCM/MXene composite exhibited a 48.39 % faster solidification rate than the DuT-TES system. Thus, this study highlights the superior potential of the TrT-TES system with nickel foam/PCM/MXene composite for enhancing latent heat thermal energy storage, outperforming the DuT-TES system in terms of solidification speed, discharge energy, and efficiency.
本文对使用泡沫镍和 MXene 纳米粒子增强的双联管和三联管潜热热能存储(LHTES)系统中相变材料(PCM)的凝固行为进行了数值研究。该研究旨在探讨泡沫镍如何在 PCM 固化过程中增强传热,从而实现更快、更均匀的固化,并分析能量和放能效率,以优化热能存储系统。研究还评估了泡沫镍对增强 PCM 热传导性、提高凝固速率和整体热管理的影响。该研究以泡沫镍/PCM/MXene(5% v/v.)复合材料为重点,探讨了凝固特性以及斯特凡数和傅里叶数在双联管热能储存(DuT-TES)和三联管热能储存(TrT-TES)系统中的影响。研究结果表明,采用泡沫镍/PCM-MXene 复合材料的系统明显优于单独使用泡沫镍/PCM 和纯 PCM 的系统,凝固速度明显更快。具体来说,泡沫镍/PCM 复合材料比纯鲸蜡醇 PCM 显示出更高的放电能。使用泡沫镍/PCM 复合材料的 TrT-TES 系统的凝固速度比 DuT-TES 系统快 48.40%。此外,带有泡沫镍/PCM 和泡沫镍/PCM/MXene 复合材料的 TrT-TES 系统的放电能量分别比 DuT-TES 系统高 2.26% 和 3.65%。在 90 秒时,使用泡沫镍/PCM/MXene 的 DuT-TES 系统效率提高了 2.91%。总体而言,使用泡沫镍/PCM/MXene 复合材料的 TrT-TES 系统的凝固速度比 DuT-TES 系统快 48.39%。因此,本研究强调了使用泡沫镍/PCM/MXene 复合材料的 TrT-TES 系统在提高潜热热能存储方面的卓越潜力,在凝固速度、放电能量和效率方面均优于 DuT-TES 系统。
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Thermal Science and Engineering Progress
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