International Communications in Heat and Mass Transfer最新文献_第4页

Fabrication and enhanced thermal performance of a self-rewetting wick of silicon-based loop heat pipe 硅基环形热管自润湿芯的制造与热性能提升

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-22 DOI: 10.1016/j.icheatmasstransfer.2024.108378

Dongfang Zhou , Lin Guo , Xin Lan , Jingzhi Zhang , Xinyu Wang , Wenjing Du , Gongming Xin

The improvement of chip integration has led to increased heat flux, making heat dissipation in confined spaces increasingly challenging. Silicon-based loop heat pipes (sLHPs) offer a simple, reliable, and easily integrated thermal management solution. Still, problems like dry-out, limited heat exchange area, and flow instability hinder further heat transfer improvements of sLHP. Therefore, a novel composite MCC wick (Microchannel-micropillar Composite Cell arrays wick) incorporating microchannels into the micropillar arrays has been designed and experimentally studied in this work. The results indicate that micropillar arrays provide fluid flow freedom and a high heat exchange area, benefiting the efficient evaporation of the working fluid. The microchannels enhance fluid flow stability by providing continuous adhesion, promoting the directional supplement of working fluid. Moreover, liquid-replenishment microchannels have been introduced to the proposed MCC wick, enabling self-rewetting of the wick and enhance liquid film evaporation. The highest effective thermal conductivity of the sLHP reaches 856 W/(m·K) after structural optimization, which is significantly higher than that of other sLHPs. This work is expected to provide valuable insights for the optimal design of LHPs and chip heat dissipation.

芯片集成度的提高导致热通量增加，使得在狭小空间内散热变得越来越具有挑战性。硅基环形热管（sLHP）提供了一种简单、可靠、易于集成的热管理解决方案。然而，干涸、有限的热交换面积和流动不稳定性等问题阻碍了 sLHP 热传导性能的进一步提高。因此，本研究设计了一种新型复合 MCC 烛芯（微通道-微柱复合电池阵列烛芯），并对其进行了实验研究。结果表明，微柱阵列提供了流体流动自由度和高热交换面积，有利于工作流体的高效蒸发。微通道通过提供连续的附着力，提高了流体流动的稳定性，促进了工作流体的定向补充。此外，拟议的 MCC 烛芯还引入了液体补充微通道，实现了烛芯的自润湿，增强了液膜蒸发。结构优化后，sLHP 的最高有效热导率达到 856 W/(m-K)，明显高于其他 sLHP。这项工作有望为 LHP 的优化设计和芯片散热提供有价值的见解。

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引用次数: 0

A dynamic characteristic on the boiling crisis in downward facing flow boiling, Part II: Model development and validation 下向流沸腾中沸腾危机的动态特性，第二部分：模型开发与验证

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-22 DOI: 10.1016/j.icheatmasstransfer.2024.108360

Shixian Wang , Kai Wang , Chen Zeng , Shuichiro Miwa , Koji Okamoto

This paper advances our understanding of boiling dynamics at the Critical Heat Flux (CHF) level within a downward flow boiling scenario. Building on initial visual observations, this study clarifies the mechanisms driving CHF front motion and introduces a model to track its progression. It reveals that the CHF front advances when the evaporation rate in the microlayer surpasses the liquid inflow. This insight has facilitated further modeling of the relationship between the CHF threshold and CHF front velocity using a balance model in the microlayer. We observe an inverse yet linear relationship where the ratios

R_{m} / δ_{0}

-

the microlayer radius to its thickness

-

and

{\bar{U}}_{X}

-

the mean liquid inflow rate

-

show negligible variation despite changes in surface roughness and flow rates. Additionally, we have refined our CHF prediction model to incorporate effects of surface roughness and flow rate, linking it with the CHF front velocity model. This model, which balances three velocity terms at the CHF front, demonstrates substantial predictive accuracy and suggests that enhancements to the CHF threshold improve rewetting flow, thereby delaying surface dry-out, reducing CHF front velocity and enhancing CHF performance. These findings provide crucial insights for advancing thermal management technologies.

本文加深了我们对向下流动沸腾情景中临界热通量（CHF）水平沸腾动力学的理解。在初步目测观察的基础上，本研究阐明了驱动 CHF 前端运动的机制，并引入了一个模型来跟踪其进展。研究发现，当微层中的蒸发率超过液体流入量时，CHF 前沿就会前进。这一洞察力有助于利用微层中的平衡模型进一步模拟 CHF 临界值与 CHF 锋速度之间的关系。我们观察到一种反比但线性的关系，其中 Rm/δ0（微层半径与厚度之比）和 ŪX（平均液体流入率）的变化可以忽略不计，尽管表面粗糙度和流速发生了变化。此外，我们还改进了 CHF 预测模型，将表面粗糙度和流速的影响纳入其中，并将其与 CHF 前线速度模型联系起来。该模型平衡了 CHF 前端的三个速度项，显示出很高的预测准确性，并表明 CHF 临界值的提高可改善再湿流动，从而延迟表面干燥、降低 CHF 前端速度并提高 CHF 性能。这些发现为热管理技术的进步提供了重要启示。

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引用次数: 0

Characterizing thermal distribution of electric heating plates for power battery 动力电池电热板的热分布特征

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-22 DOI: 10.1016/j.icheatmasstransfer.2024.108329

Guanqing Wang, Zhiyu Li, Junhua Zhang, Shuai Wang, Guanghua Zheng, Jiangrong Xu

Electric preheating of power batteries within specific temperature ranges is recognized as a promising technology for enabling fast charging and discharging. Among various methods, electric heating plate (EHP) has gained widespread attention. Nevertheless, its performance remains insufficiently understood. In this study, the EHP is comprehensively characterized through the construction of a realistic three-dimensional transient model, which is experimentally validated. Detailed analysis is conducted on the influence of resistance wire (RW) width and thermal power, with a particular focus on temperature profiles and uniformity. The results show that a circular fillet structure is recommended to ensure uniform current distribution in RW instead of the traditional right-angle fillet structure. The temperature of the EHP gradually decreases from its center to the outwards, forming an O-shape distribution of isotherm. The temperature uniformity and maximum temperature difference are primarily determined by the width and spacing of RW, demonstrating a positive correlation. Our finding also reveals that an EHP with a RW width of 1 mm displays a maximum temperature difference within ±0.5 K, meeting the requirements imposed by major industrial power battery producers. These results not only provide guidance for optimizing EHP architecture but also support enhanced performance in the fast charging and discharging of power batteries.

在特定温度范围内对动力电池进行电预热被认为是实现快速充放电的一项前景广阔的技术。在各种方法中，电加热板（EHP）受到了广泛关注。然而，人们对其性能的了解仍然不够。在本研究中，通过构建一个逼真的三维瞬态模型对 EHP 进行了全面描述，并通过实验进行了验证。详细分析了电阻丝 (RW) 宽度和热功率的影响，尤其关注温度曲线和均匀性。结果表明，建议采用圆形圆角结构，而不是传统的直角圆角结构，以确保电阻丝中的电流分布均匀。EHP 的温度从中心向外逐渐降低，形成 O 型等温线分布。温度均匀性和最大温差主要取决于 RW 的宽度和间距，两者呈正相关。我们的研究结果还表明，RW 宽度为 1 毫米的 EHP 显示的最大温差在 ±0.5 K 以内，符合主要工业动力电池生产商的要求。这些结果不仅为优化 EHP 结构提供了指导，还有助于提高动力电池的快速充放电性能。

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引用次数: 0

Comprehensive revelation of the influence mechanism for the thermal decomposition of ammonium perchlorate by ammonium oxalate 全面揭示草酸铵热分解高氯酸铵的影响机理

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108358

Ronghuan Yang , Yong Kou , Jiao Wei , Qiangqiang Lu , Weihai Zhang , Zhongwu Chen , Cheng Zhang , Hongxu Gao , Fengqi Zhao , Wei Jiang , Gazi Hao

Rate inhibitors for combustion are crucial to decrease the burning rate and prolong the working time of solid propellants. Ammonium oxalate (AO), the most frequently utilized and effective rate inhibitor in propellants, faces the challenge of an unclear influence mechanism regarding ammonium perchlorate (AP). Therefore, it is necessary to elucidate the influence mechanism of AO on the thermal decomposition of AP. This study fabricated AP/AO composites with varying AO content via wet milling, the structural, thermal decomposition processes and products of these composites were investigated. Additionally, the adsorption between AP and NH₃ was simulated. The findings indicate that the inclusion of AO inhibits the low-temperature decomposition (LTD) of AP while enhancing its high-temperature decomposition (HTD). Furthermore, it was observed that the heat release of AP/AO composites was lower than that of AP. The Gibbs free energy (ΔG^≠) of the AP/AO composites exceeded that of the AP at the LTD stage and was lower than that of AP at the HTD stage. Further study using molecular dynamics simulations revealed that as the increase of NH₃ concentration, its adsorption on the AP surface intensifies during LTD, inhibiting the forward progress of the AP decomposition reaction. However, NH₃ molecules desorbed from the AP surface and actively participated in gas-phase reactions with increasing temperature, thereby promoting the HTD of AP. This work is helpful to fully understanding the mechanism of AO in the process of the LTD and the HTD of AP but also contributes to the exploration of novel inhibitors and advances the development of low-burning rate solid propellants.

燃烧速率抑制剂对于降低固体推进剂的燃烧速率和延长其工作时间至关重要。草酸铵（AO）是推进剂中最常用、最有效的速率抑制剂，但它面临的挑战是对高氯酸铵（AP）的影响机制不明确。因此，有必要阐明 AO 对 AP 热分解的影响机制。本研究通过湿法研磨制备了不同 AO 含量的 AP/AO 复合材料，并对这些复合材料的结构、热分解过程和产物进行了研究。此外，还模拟了 AP 与 NH3 之间的吸附。研究结果表明，AO 的加入抑制了 AP 的低温分解（LTD），同时增强了其高温分解（HTD）。此外，还观察到 AP/AO 复合材料的热释放量低于 AP。AP/AO 复合材料的吉布斯自由能（ΔG≠）在 LTD 阶段超过 AP，在 HTD 阶段低于 AP。利用分子动力学模拟进行的进一步研究表明，随着 NH3 浓度的增加，在 LTD 阶段 NH3 在 AP 表面的吸附增强，抑制了 AP 分解反应的进行。然而，随着温度的升高，NH3 分子从 AP 表面解吸并积极参与气相反应，从而促进了 AP 的 HTD。这项工作不仅有助于全面了解 AO 在 AP 的 LTD 和 HTD 过程中的作用机理，还有助于探索新型抑制剂，推动低燃耗固体推进剂的发展。

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引用次数: 0

Mechanical performance evaluation of optimal hybrid composite fabricated with glass and carbon fibers and thermoplastic polypropylene matrix or fencing sports athletes 用玻璃纤维和碳纤维以及热塑性聚丙烯基体制造的最佳混合复合材料或击剑运动运动员的机械性能评估

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108346

Xiaomin Zhu , Jie Deng , A. Heidari , M. Jamei , As'ad Alizadeh

Fibers in composite materials intended for athletic equipment applications can exhibit superior mechanical properties, such as tensile strength, in comparison to the polymer matrix. In this study, glass fibers were combined with a polypropylene matrix, with six layers of glass fibers placed alternately between the polypropylene layers. The polypropylene matrix was melted using a hot-press machine, which covered the glass fibers by applying pressure and heat simultaneously. After fabrication, the mechanical performance of the composite was evaluated using various tests, including tensile, compressive, flexural, and shear tests. The mechanical characteristics related to each test, such as tensile strength and elastic modulus, were measured. The same process was repeated to produce composite sheets with a combination of carbon fibers and polypropylene matrix. Additionally, digital image correlation analysis was used to measure the shear characteristics of composites with 45-degree fiber orientation. Finally, the mechanical properties of glass fibers and carbon fibers were used to simulate hybrid composites, which combined carbon and glass fibers in the ABAQUS software. By moving the glass and carbon layers symmetrically and simulating the tensile test, the optimal hybrid composite was identified. The results show that placing carbon layers in the core of the composites led to a tensile strength of 155.4 MPa, while placing the carbon layers in the outer layer or middle of the composite resulted in tensile strengths of 145.7 MPa and 136 MPa, respectively. Therefore, the optimal hybrid composite was achieved by placing the carbon layer in the core.

与聚合物基体相比，用于运动器材的复合材料中的纤维可表现出更优越的机械性能，如抗拉强度。在这项研究中，玻璃纤维与聚丙烯基体相结合，在聚丙烯层之间交替放置六层玻璃纤维。使用热压机熔化聚丙烯基体，通过同时施加压力和热量将玻璃纤维覆盖。制作完成后，复合材料的机械性能通过各种测试进行了评估，包括拉伸、压缩、弯曲和剪切测试。测量了与各项测试相关的机械特性，如拉伸强度和弹性模量。在生产碳纤维和聚丙烯基质复合片材时，重复了相同的过程。此外，还使用数字图像相关分析法测量了 45 度纤维取向复合材料的剪切特性。最后，利用玻璃纤维和碳纤维的机械特性，在 ABAQUS 软件中模拟了碳纤维和玻璃纤维的混合复合材料。通过对称移动玻璃层和碳层并模拟拉伸试验，确定了最佳混合复合材料。结果表明，将碳层置于复合材料的核心层可获得 155.4 兆帕的拉伸强度，而将碳层置于复合材料的外层或中间层则可分别获得 145.7 兆帕和 136 兆帕的拉伸强度。因此，将碳层置于芯部可获得最佳混合复合材料。

{"title":"Mechanical performance evaluation of optimal hybrid composite fabricated with glass and carbon fibers and thermoplastic polypropylene matrix or fencing sports athletes","authors":"Xiaomin Zhu , Jie Deng , A. Heidari , M. Jamei , As'ad Alizadeh","doi":"10.1016/j.icheatmasstransfer.2024.108346","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108346","url":null,"abstract":"<div><div>Fibers in composite materials intended for athletic equipment applications can exhibit superior mechanical properties, such as tensile strength, in comparison to the polymer matrix. In this study, glass fibers were combined with a polypropylene matrix, with six layers of glass fibers placed alternately between the polypropylene layers. The polypropylene matrix was melted using a hot-press machine, which covered the glass fibers by applying pressure and heat simultaneously. After fabrication, the mechanical performance of the composite was evaluated using various tests, including tensile, compressive, flexural, and shear tests. The mechanical characteristics related to each test, such as tensile strength and elastic modulus, were measured. The same process was repeated to produce composite sheets with a combination of carbon fibers and polypropylene matrix. Additionally, digital image correlation analysis was used to measure the shear characteristics of composites with 45-degree fiber orientation. Finally, the mechanical properties of glass fibers and carbon fibers were used to simulate hybrid composites, which combined carbon and glass fibers in the ABAQUS software. By moving the glass and carbon layers symmetrically and simulating the tensile test, the optimal hybrid composite was identified. The results show that placing carbon layers in the core of the composites led to a tensile strength of 155.4 MPa, while placing the carbon layers in the outer layer or middle of the composite resulted in tensile strengths of 145.7 MPa and 136 MPa, respectively. Therefore, the optimal hybrid composite was achieved by placing the carbon layer in the core.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"160 ","pages":"Article 108346"},"PeriodicalIF":6.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

Experimental study on condensation-free radiant cooling panel with low-temperature for local cooling in vehicles - Part 2: Demonstration with passengers for thermal comfort analysis 用于车内局部降温的低温无结露辐射冷却板实验研究 - 第 2 部分：乘客热舒适度分析演示

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108368

Suet Man Wong , Gineesh Gopi , Jung Kyung Kim , Dongchan Lee

Radiant cooling is highly energy efficient and provides excellent thermal comfort; however, owing to the large area required, it has primarily been applied to indoor space cooling. In this study, a low-temperature condensation-free radiant cooling panel (RCP), proposed in a related paper (Part 1: Design process and feasibility evaluation with performance test), was applied to an actual vehicle to study its effect and impact on thermal comfort. Thermal satisfaction and sensation were assessed using a subjective survey, and skin temperature was investigated using objective measurements in 17 participants. The results showed that the proposed RCP provided the passengers with better thermal comfort under solar radiation; furthermore, 95 % of participants found it more satisfying when the RCP was turned on, and the overall thermal sensation vote tended to be neutral (0) from warm (2) after operating the RCP for 5 min. In addition, thermal sensation in the head and upper body had a major effect on the overall thermal sensation, whereas thermal sensation in the lower body was of no importance to the overall thermal sensation. The RCP used in this study can maximize the energy-saving effect through local cooling, particularly in vehicles with large spaces.

辐射冷却具有很高的能效，并能提供极佳的热舒适性，但由于所需面积较大，因此主要应用于室内空间冷却。在本研究中，相关论文（第 1 部分：设计过程和可行性评估与性能测试）中提出的低温无冷凝辐射冷却板（RCP）被应用于实际车辆，以研究其效果和对热舒适度的影响。通过主观调查对热满意度和感觉进行了评估，并对 17 名参与者的皮肤温度进行了客观测量。结果表明，在太阳辐射下，拟议的 RCP 为乘客提供了更好的热舒适度；此外，95% 的参与者认为打开 RCP 后会更令人满意，并且在操作 RCP 5 分钟后，整体热感觉投票从温暖（2）趋向于中性（0）。此外，头部和上半身的热感觉对整体热感觉有很大影响，而下半身的热感觉对整体热感觉并不重要。本研究中使用的 RCP 可以通过局部冷却最大限度地发挥节能效果，尤其是在空间较大的车辆中。

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引用次数: 0

Numerical contact line behavior prediction for droplet-wall impact by the modified Hoffman-function-based dynamic contact angle model 基于修正霍夫曼函数的动态接触角模型对液滴壁撞击的接触线行为进行数值预测

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108372

I.S. Vozhakov , S.Y. Misyura , A.M. Shain , R.I. Mullyadzhanov , M.V. Piskunov , P.A. Strizhak

The droplet-wall impact phenomenon is observed in numerous applications such as spray cooling, coatings, wetting, and inkjet printing. To date, there are still unresolved issues related to the effect of wettability and hysteresis on droplet spreading along a wall and rim fingering. This research deals with the effects of dynamic and static contact angles on droplet spreading evolution, as well as with droplet rim fingering characterization. Experiments and direct numerical simulations are performed in a wide range of Weber numbers (We = 1–375). At high We numbers, the droplet rim loses stability and begins to deform, forming fingers. The critical disturbances resulting in the formation of fingers occur in times of around 1 ms, which are significantly smaller than those typical of maximum droplet spreading. Moreover, a certain shape of the droplet meniscus is shown to be necessary for the growth of fingers. When the contact line receding takes place, the contact angle depends only on the initial contact line acceleration. Considering the contact angle hysteresis and its dependence on We ensures a better agreement with experimental data during the droplet advancing-to-receding transition and the receding phase.

在喷雾冷却、涂料、润湿和喷墨打印等众多应用中，都能观察到液滴-壁冲击现象。迄今为止，与润湿性和滞后对液滴沿壁扩散和边缘指状的影响有关的问题仍未得到解决。本研究涉及动态和静态接触角对液滴扩散演变的影响，以及液滴边缘指状化的表征。实验和直接数值模拟在很大的韦伯数（We = 1-375）范围内进行。在高韦伯数下，液滴边缘失去稳定性并开始变形，形成指状。形成指状的临界扰动时间约为 1 毫秒，明显小于液滴扩散最大时的典型时间。此外，研究还表明，液滴半月板的特定形状是形成液指的必要条件。当接触线后退时，接触角只取决于最初的接触线加速度。考虑到接触角滞后及其与 We 的依赖关系，可以确保在液滴前进到后退的过渡阶段和后退阶段与实验数据更加一致。

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引用次数: 0

Numerical analysis of heat exchanger with inclined finned semicircular tubes 带倾斜翅片半圆管热交换器的数值分析

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108326

Mateusz Szydłowski, Artur Gutkowski

This article will examine the numerical analysis of airflow and heat transfer occurring in a heat exchanger with staggered finned semicircular tubes. Efficiency comparison between various inclined finned and plain tube banks provides a unique contribution to the heat exchanger design. Calculations were performed in five sets with separately applied variables– four with different degrees of finned tube inclination angle (0°, 15°, 30°, 45°) and one with unturned plain semicircular tubes. Each set consisted of 10 simulations ranging in the Reynolds number from 1000 to 10,000. The behaviour of the fluid was presented in the form of contours of normalised: velocity, pressure and temperature; the results of all simulations were presented on graphs. The outcomes showed an improvement in the heat transfer rate from 6 % to 58 % with increasing the tube inclination angle. At the same time, rising pressure drops were observed. The highest value was recorded for the 45° inclination angle. The conclusion of the study is the validity of using inclined finned tubes in heat exchangers that focus on increased heat transfer without concentrating on pressure drops.

本文将对交错翅片半圆管热交换器中的气流和传热进行数值分析。各种倾斜翅片管组和普通管组之间的效率比较为热交换器设计提供了独特的贡献。计算分为五组，分别采用不同的变量--四组采用不同的翅片管倾斜角度（0°、15°、30°、45°），一组采用未翻转的普通半圆管。每组包括 10 次模拟，雷诺数从 1000 到 10,000 不等。流体的行为以速度、压力和温度归一化等值线的形式呈现；所有模拟结果均以图表形式呈现。结果显示，随着管道倾角的增大，传热率从 6% 提高到 58%。同时，还观察到压降上升。倾角为 45°时的压降值最高。这项研究的结论是，在热交换器中使用倾斜翅片管是有效的，其重点是提高传热率，而不是关注压降。

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引用次数: 0

Calculation of the temperature field in the thermal sensitive disc-pad couple during multiple braking 计算多重制动时热敏制动盘-衬垫耦合的温度场

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108352

Katarzyna Topczewska , Michal Kuciej , Aleksander Yevtushenko , Adolfo Senatore

An analytical model of frictional heating in a railway disc brake system during a multiple braking process is proposed. It considers the thermal sensitivity of the friction coefficient and the thermophysical properties of the materials. The developed model accounts for convective cooling of the brake disc only during the intervals between consecutive braking applications. The theoretical outcomes were compared with experimental data obtained from simulation on a full-scale inertia dynamometer for a friction node consisting of a cast iron railway brake disc combined with a composite friction material. An increase in temperature (by 30–50 °C) at each subsequent braking, accompanied by a simultaneous decrease in the friction coefficient, was observed. The analysis indicated that the relative difference between the maximum temperature values at each braking stage, derived from the model and the data recorded by the thermocouple system during testing, was less than 5 %. The good agreement of the theoretical results with the experimental data confirms the validity of the proposed model, which can be used to estimate the temperature of a disc brake operating in multiple braking modes with non-uniform cycles. Previously, such schemes have only been developed and validated for single and repetitive short-term braking modes.

本文提出了铁路盘式制动系统在多重制动过程中摩擦发热的分析模型。该模型考虑了摩擦系数的热敏感性和材料的热物理性质。所建立的模型仅考虑了连续制动之间制动盘的对流冷却。理论结果与在全尺寸惯性测功机上对由铸铁铁路制动盘和复合摩擦材料组成的摩擦节点进行模拟获得的实验数据进行了比较。在随后的每次制动中都观察到温度升高（30-50 °C），同时摩擦系数下降。分析表明，根据模型得出的每个制动阶段的最高温度值与测试期间热电偶系统记录的数据之间的相对差异小于 5%。理论结果与实验数据的良好一致性证实了所提模型的有效性，该模型可用于估算盘式制动器在非均匀循环的多种制动模式下的工作温度。此前，此类方案仅针对单一和重复的短期制动模式进行了开发和验证。

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引用次数: 0

Drag reduction characteristics of RJD-suitable surfactant-polymer composite fluids under high shear 适合 RJD 的表面活性剂-聚合物复合流体在高剪切下的减阻特性

IF 6.4 2区工程技术 Q1 MECHANICS

International Communications in Heat and Mass Transfer

Pub Date : 2024-11-21 DOI: 10.1016/j.icheatmasstransfer.2024.108341

Zhe Zhou , Mengli Li , Zhaolong Ge , Xu Zhang , Yilong Tang , Jinming Cui , Shihui Gong

Radial Jet Drilling (RJD) provides favorable conditions for exploitation of coalbed methane (CBM). However, the jetting medium always remains in a high-shear state (Re>> 1 × 10⁵) during the construction of RJD, with significant pressure loss that is difficult to control. In this paper, two surfactant-polymer composite systems for high-shear conditions are firstly preferred: CTAC-PEO and OTAC-PEO, with drag reduction rates (DR) of 31.92 % and 21.97 %, respectively. Secondly, three fluids were further optimized by adjusting the ratio and concentration of drag reducers: CP11–1000, OP41–1000, and OP41–3000. Their drag reduction characteristics were investigated at different temperatures and shear durations. Among them, the average DR of OP41–3000 at 55 °C is 2.28 and 2.95 times that of CP11–1000 and OP41–1000, respectively. Moreover, terminated DR after 30 mins of cyclic shear is 4.74 and 7.5 times greater than that of them, with a drag reduction retention rate exceeding 80 %. Finally, the “laminae encapsulate chains-network structure” was proposed to explain the mechanism of drag reduction under high shear. This study is the first to investigate drag reduction from the perspective of the jetting medium. The research findings will improve the future advancement of CBM mining utilizing RJD. Additionally, this study can assist in the selection of appropriate drag reducers for high-shear environment and the exploration of drag reduction mechanism.

径向喷射钻井（RJD）为煤层气（CBM）的开采提供了有利条件。然而，在 RJD 施工过程中，喷射介质始终处于高剪切状态（Re>> 1 × 105），压力损失大，难以控制。本文首先优选了两种适用于高剪切条件的表面活性剂-聚合物复合体系：CTAC-PEO 和 OTAC-PEO，其阻力降低率（DR）分别为 31.92 % 和 21.97 %。其次，通过调整减阻剂的比例和浓度，进一步优化了三种流体：CP11-1000、OP41-1000 和 OP41-3000。研究了它们在不同温度和剪切持续时间下的减阻特性。其中，OP41-3000 在 55 °C 时的平均减阻效果分别是 CP11-1000 和 OP41-1000 的 2.28 倍和 2.95 倍。此外，循环剪切 30 分钟后终止的 DR 分别是它们的 4.74 倍和 7.5 倍，阻力减少保持率超过 80%。最后，研究人员提出了 "层状包链网状结构 "来解释高剪切下阻力降低的机理。这项研究是首次从喷射介质的角度研究减阻问题。研究结果将有助于今后利用 RJD 开采煤层气。此外，这项研究还有助于为高剪切力环境选择合适的减阻剂和探索减阻机理。

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引用次数: 0