Pub Date : 2024-10-13DOI: 10.1016/j.ijthermalsci.2024.109469
Yuxuan Chen , Jianye Yang , Xiaokang Liu , Xiuliang Liu
Vapor condensation is widely adopted in thermal management technology and condenser of energy power plant, benefiting from its high heat transfer coefficient. Contact angle is the key factor to regulate vapor condensation rate, leading to the rapid development of surfaces with various wettability fabricated by micro/nanoengineering. However, the nucleated nanodroplets (1–100 nm) at the beginning of condensation exhibit different wetting dynamics from macroscopic droplets, the mechanisms of which are not well understood. In this work, we perform molecular dynamic (MD) simulations to study the evolution of contact angle during nanodroplet nucleation processes. The results show the nucleated contact angle of a nanodroplet is smaller than the contact angle predicted by the classical Young equation on a hydrophobic surface, while it is opposite for nanodroplet nucleating on hydrophilic surface. Moreover, we have calculated line tension for the nucleated nanodroplet on the surfaces with different wettability to explain this discovery, and found positive line tension on hydrophobic surface, while negative line tension for nucleated nanodroplet on hydrophilic surface. Furthermore, the calculated line tension, which is at the order magnitude of 10−11 J/m, aligns well with the data documented in the literature.
蒸汽冷凝因其传热系数高而被广泛应用于热管理技术和能源发电厂的冷凝器中。接触角是调节蒸汽冷凝速率的关键因素，因此微/纳米工程制造的各种润湿性表面得到了快速发展。然而，凝结初期的成核纳米液滴（1-100 nm）表现出与宏观液滴不同的润湿动力学，其机理尚不十分清楚。在这项工作中，我们进行了分子动力学（MD）模拟，研究纳米液滴成核过程中接触角的演变。结果表明，在疏水表面上，纳米液滴的成核接触角小于经典 Young 方程预测的接触角，而在亲水表面上，纳米液滴的成核接触角则与之相反。此外，为了解释这一发现，我们还计算了在不同润湿性表面上成核纳米液滴的线拉力，结果发现在疏水表面上成核纳米液滴的线拉力为正，而在亲水表面上成核纳米液滴的线拉力为负。此外，计算出的线拉力在 10-11 J/m 的数量级，与文献记载的数据非常吻合。
{"title":"Contact angle evolution during nanodroplet nucleation","authors":"Yuxuan Chen , Jianye Yang , Xiaokang Liu , Xiuliang Liu","doi":"10.1016/j.ijthermalsci.2024.109469","DOIUrl":"10.1016/j.ijthermalsci.2024.109469","url":null,"abstract":"<div><div>Vapor condensation is widely adopted in thermal management technology and condenser of energy power plant, benefiting from its high heat transfer coefficient. Contact angle is the key factor to regulate vapor condensation rate, leading to the rapid development of surfaces with various wettability fabricated by micro/nanoengineering. However, the nucleated nanodroplets (1–100 nm) at the beginning of condensation exhibit different wetting dynamics from macroscopic droplets, the mechanisms of which are not well understood. In this work, we perform molecular dynamic (MD) simulations to study the evolution of contact angle during nanodroplet nucleation processes. The results show the nucleated contact angle of a nanodroplet is smaller than the contact angle predicted by the classical Young equation on a hydrophobic surface, while it is opposite for nanodroplet nucleating on hydrophilic surface. Moreover, we have calculated line tension for the nucleated nanodroplet on the surfaces with different wettability to explain this discovery, and found positive line tension on hydrophobic surface, while negative line tension for nucleated nanodroplet on hydrophilic surface. Furthermore, the calculated line tension, which is at the order magnitude of 10<sup>−11</sup> J/m, aligns well with the data documented in the literature.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421695","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}
Pub Date : 2024-10-13DOI: 10.1016/j.ijthermalsci.2024.109476
Bowen Yu , Zhiguo Xu , Zhaolin Li , Jingxiang Wang
The velocity and temperature fields of droplet evaporation on bio-inspired surfaces are investigated based on the single-component multiphase pseudopotential lattice Boltzmann method and liquid-vapor phase-change model. The morphology of the surface is inspired by the hierarchical cuticle of springtails which have the feature of doubly reentrant pillars. The dynamic mechanism of droplet collision and evaporation is revealed in the study. The effects of Jakob number, solid thermal conductivity, and pillar spacing on the behavior of the droplet collision on superheated bio-inspired surfaces are statistically analyzed. The study provides detailed snapshots depicting the evolution of droplet morphology. The trends of substrate heat flux, droplet lifetime, and droplet volume with time are presented. For the doubly re-entrant superheated surface, the droplet is easier to split and the droplet lifetime is shorter compared to that on smooth substrates. The reduction ratio of droplet lifetime is 66.2 % when Jakob number equals 0.12. When Jakob number increases, Leidenfrost vapor layer is generated on the surface and it deteriorates droplet evaporation. The lifetime of droplets does not consistently decrease with increasing solid-liquid thermal conductivity ratio across different Jakob numbers, primarily due to variations in droplet morphology under different conditions. Moreover, an increase in pillar spacing leads to an enhancement in the evaporation rate under the same superheating conditions. The droplet lifetime of 20 pillar spacing is 58.72 % of 8 pillar spacing.
基于单组分多相伪势晶格玻尔兹曼法和液气相变模型，研究了液滴在生物启发表面上蒸发的速度场和温度场。表面形态的灵感来自于具有双重内倾柱特征的春蜱分层角质层。研究揭示了液滴碰撞和蒸发的动态机制。通过统计分析了雅各布数、固体热导率和柱间距对过热生物启发表面液滴碰撞行为的影响。研究提供了描绘液滴形态演变的详细快照。研究还给出了基底热通量、液滴寿命和液滴体积随时间变化的趋势。与光滑基底上的液滴相比，双重再入式过热表面上的液滴更容易分裂，液滴寿命更短。当 Jakob 数等于 0.12 时，液滴寿命的缩短率为 66.2%。当 Jakob 数增大时，表面会产生 Leidenfrost 蒸汽层，从而使液滴蒸发变差。在不同的雅各布数下，液滴的寿命并不会随着固液导热比的增加而持续缩短，这主要是由于在不同条件下液滴形态的变化。此外，在相同的过热条件下，柱间距的增加会导致蒸发率的提高。20 柱间距的液滴寿命是 8 柱间距的 58.72%。
{"title":"Numerical study on heat and mass transfer of droplet collision on superheated bio-inspired surfaces","authors":"Bowen Yu , Zhiguo Xu , Zhaolin Li , Jingxiang Wang","doi":"10.1016/j.ijthermalsci.2024.109476","DOIUrl":"10.1016/j.ijthermalsci.2024.109476","url":null,"abstract":"<div><div>The velocity and temperature fields of droplet evaporation on bio-inspired surfaces are investigated based on the single-component multiphase pseudopotential lattice Boltzmann method and liquid-vapor phase-change model. The morphology of the surface is inspired by the hierarchical cuticle of springtails which have the feature of doubly reentrant pillars. The dynamic mechanism of droplet collision and evaporation is revealed in the study. The effects of Jakob number, solid thermal conductivity, and pillar spacing on the behavior of the droplet collision on superheated bio-inspired surfaces are statistically analyzed. The study provides detailed snapshots depicting the evolution of droplet morphology. The trends of substrate heat flux, droplet lifetime, and droplet volume with time are presented. For the doubly re-entrant superheated surface, the droplet is easier to split and the droplet lifetime is shorter compared to that on smooth substrates. The reduction ratio of droplet lifetime is 66.2 % when Jakob number equals 0.12. When Jakob number increases, Leidenfrost vapor layer is generated on the surface and it deteriorates droplet evaporation. The lifetime of droplets does not consistently decrease with increasing solid-liquid thermal conductivity ratio across different Jakob numbers, primarily due to variations in droplet morphology under different conditions. Moreover, an increase in pillar spacing leads to an enhancement in the evaporation rate under the same superheating conditions. The droplet lifetime of 20 pillar spacing is 58.72 % of 8 pillar spacing.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109476"},"PeriodicalIF":4.9,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432735","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}
Pub Date : 2024-10-13DOI: 10.1016/j.ijthermalsci.2024.109474
Ya-Zhou Song , Dong Liu , Si-Liang Sun , Hyoung-Bum Kim
Heat transfer performance and power consumption of Taylor-Couette flow with helical slit wall are analyzed. Slit number, width, and spacing are selected for multi-objective optimization of heat transfer performance and power consumption. Energy loss within the coaxial cylinder is analyzed using the entropy generation principle. Different Machine learning methods are applied to predict the heat transfer and power consumption of Taylor-Couette flow. A comparison made between the predictive findings of the XGBoost model and other three different models. The XGBoost prediction model for heat transfer and power consumption not only exhibits the highest determination coefficient, but also achieves the lowest mean absolute percentage error, root mean squared error, mean absolute error, which has the best predictive performance. Finally, the NSGA-II algorithm is used to optimize the elliptical helical slit structure, and obtained the Pareto front of the optimized design of the helical slit structure. Comparing results with the original model, the maximum improvement in heat transfer performance is 18.68 % and maximum reduction in power consumption is 15.28 %. In practical design, reasonable slit structure parameters can be selected from the obtained set of optimal parameter solutions based on design requirements.
{"title":"Multi-objective optimization of heat transfer performance and power consumption of Taylor-Couette flow with elliptical helical slits wall","authors":"Ya-Zhou Song , Dong Liu , Si-Liang Sun , Hyoung-Bum Kim","doi":"10.1016/j.ijthermalsci.2024.109474","DOIUrl":"10.1016/j.ijthermalsci.2024.109474","url":null,"abstract":"<div><div>Heat transfer performance and power consumption of Taylor-Couette flow with helical slit wall are analyzed. Slit number, width, and spacing are selected for multi-objective optimization of heat transfer performance and power consumption. Energy loss within the coaxial cylinder is analyzed using the entropy generation principle. Different Machine learning methods are applied to predict the heat transfer and power consumption of Taylor-Couette flow. A comparison made between the predictive findings of the XGBoost model and other three different models. The XGBoost prediction model for heat transfer and power consumption not only exhibits the highest determination coefficient, but also achieves the lowest mean absolute percentage error, root mean squared error, mean absolute error, which has the best predictive performance. Finally, the NSGA-II algorithm is used to optimize the elliptical helical slit structure, and obtained the Pareto front of the optimized design of the helical slit structure. Comparing results with the original model, the maximum improvement in heat transfer performance is 18.68 % and maximum reduction in power consumption is 15.28 %. In practical design, reasonable slit structure parameters can be selected from the obtained set of optimal parameter solutions based on design requirements.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421693","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}
Pub Date : 2024-10-12DOI: 10.1016/j.ijthermalsci.2024.109463
Safaa Lahayrech , Anas El Maakoul , Alain Degiovanni , Ismail Khay , Monica Siroux
This research proposes a fast and accurate method for modeling transient heat transfer in ventilated double-skin façades (VDFs) with forced ventilation to predict their energy-saving potential. Using the thermal quadrupole formalism, the method solves the VDF problem in the Laplace domain while considering the full transient nature of the heat transfer; the only approximation is in space. The solution involves obtaining a general transfer function that predicts heat transfer rates or air temperatures at ventilated cavity's exit. The quadrupole method is validated against computational fluid dynamic numerical simulations conducted under similar meteorological, design and boundary conditions. A very good agreement was found (less than 3 % average deviation) with a significant reduction in computation time (less than 3s against 6h for CFD calculations). The model is computationally efficient and can consider important factors such as the opacity of the walls, construction materials, and air cavity design parameters. Finally, the model allows the assessment of the energy-saving potential of VDFs under various scenarios compared to conventional systems, which helps contributing to more sustainable building design practices. The energy efficiency of a VDF configuration was compared against a conventional wall system. Energy savings of 8.4 and 5.2 % were obtained, in cold and hot climates respectively.
{"title":"A fast quadrupole-based analytical model for solving transient heat transfer in ventilated double-skin walls and assessing their energy saving potential","authors":"Safaa Lahayrech , Anas El Maakoul , Alain Degiovanni , Ismail Khay , Monica Siroux","doi":"10.1016/j.ijthermalsci.2024.109463","DOIUrl":"10.1016/j.ijthermalsci.2024.109463","url":null,"abstract":"<div><div>This research proposes a fast and accurate method for modeling transient heat transfer in ventilated double-skin façades (VDFs) with forced ventilation to predict their energy-saving potential. Using the thermal quadrupole formalism, the method solves the VDF problem in the Laplace domain while considering the full transient nature of the heat transfer; the only approximation is in space. The solution involves obtaining a general transfer function that predicts heat transfer rates or air temperatures at ventilated cavity's exit. The quadrupole method is validated against computational fluid dynamic numerical simulations conducted under similar meteorological, design and boundary conditions. A very good agreement was found (less than 3 % average deviation) with a significant reduction in computation time (less than 3s against 6h for CFD calculations). The model is computationally efficient and can consider important factors such as the opacity of the walls, construction materials, and air cavity design parameters. Finally, the model allows the assessment of the energy-saving potential of VDFs under various scenarios compared to conventional systems, which helps contributing to more sustainable building design practices. The energy efficiency of a VDF configuration was compared against a conventional wall system. Energy savings of 8.4 and 5.2 % were obtained, in cold and hot climates respectively.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109463"},"PeriodicalIF":4.9,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421692","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}
Pub Date : 2024-10-12DOI: 10.1016/j.ijthermalsci.2024.109456
Liang Du , Ningkang Deng , Jin Yuan , Yongfeng Qu , Zhaoyang Zhang , Wenbo Hu , Hongxing Wang
In order to effectively reduce the operating temperature of electronic devices and improve their working stability and service life, this study has designed the microchannel with stacked combinations of ribs and cavities. The thermal-hydraulic characteristics of microchannel with stacked combinations of cuboid cavities and various rib shapes (1/4 ellipsoid, triangular prism, 1/4 cylinder, trapezoidal prism, and cuboid) were investigated using numerical simulation. Subsequently, their comprehensive performance and energy saving effect were assessed. It is shown that the microchannel with stacked combinations of ribs and cavities not only increases the solid-liquid contact area, but also enhance the mixing efficiency between cold water in the channel center and hot water along the side walls. This improvement helps to reduce temperature and thermal resistance, leading to enhanced heat transfer within the microchannel. As a result, it exhibits excellent comprehensive performance and energy saving effects. When the relative rib width and height ratio of rib to cavity of microchannel with stacked combinations of cuboid cavity and cuboid rib are 0.733 and 0.765, respectively, the figure of merit reaches 2.23, which has high comprehensive performance.
{"title":"Thermal-hydraulic analysis and geometric optimization on a microchannel with stacked combinations of ribs and cavities","authors":"Liang Du , Ningkang Deng , Jin Yuan , Yongfeng Qu , Zhaoyang Zhang , Wenbo Hu , Hongxing Wang","doi":"10.1016/j.ijthermalsci.2024.109456","DOIUrl":"10.1016/j.ijthermalsci.2024.109456","url":null,"abstract":"<div><div>In order to effectively reduce the operating temperature of electronic devices and improve their working stability and service life, this study has designed the microchannel with stacked combinations of ribs and cavities. The thermal-hydraulic characteristics of microchannel with stacked combinations of cuboid cavities and various rib shapes (1/4 ellipsoid, triangular prism, 1/4 cylinder, trapezoidal prism, and cuboid) were investigated using numerical simulation. Subsequently, their comprehensive performance and energy saving effect were assessed. It is shown that the microchannel with stacked combinations of ribs and cavities not only increases the solid-liquid contact area, but also enhance the mixing efficiency between cold water in the channel center and hot water along the side walls. This improvement helps to reduce temperature and thermal resistance, leading to enhanced heat transfer within the microchannel. As a result, it exhibits excellent comprehensive performance and energy saving effects. When the relative rib width and height ratio of rib to cavity of microchannel with stacked combinations of cuboid cavity and cuboid rib are 0.733 and 0.765, respectively, the figure of merit reaches 2.23, which has high comprehensive performance.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109456"},"PeriodicalIF":4.9,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421696","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}
Pub Date : 2024-10-10DOI: 10.1016/j.ijthermalsci.2024.109465
Man Li , Yize Shen , Zhongkun Cai , Qishen Xiao , Haowei Hu
This paper presents an experimental investigation of the feedback effect with smoke acceleration on flame behaviors in the U shaped shaft of a high-rise building. Heat release rate of the fire, depths and widths of the U shaped shaft are changed. The flame height, vertical maximum temperature in the open shaft and the heat flux distribution on the façade are studied. Results show that the flame height is elongated by the smoke acceleration effect in the U shaped shaft and larger than that in the open space. Correlations for the flame height are established by taking into account the geometries of the U shaped shaft. The vertical maximum temperature in the U shaped shaft first decreases rapidly then keeps room temperature, which are compared with that under stack effect in the staircase. The exponential decay law between the vertical maximum temperature and height is modified. The total heat flux is mainly affected by the width and heat release rate. Radiation heat transfer fraction is larger than 80 % in the continuous and intermittent flame regions, of which the flame emissivity is about 0.53.
本文介绍了烟雾加速对高层建筑 U 型竖井中火焰行为的反馈效应的实验研究。火灾的热释放率、U 型竖井的深度和宽度都发生了变化。研究了火焰高度、开口竖井中的垂直最高温度以及立面上的热通量分布。结果表明，U 型竖井中的火焰高度受烟雾加速效应的影响而拉长，大于开放空间中的火焰高度。考虑到 U 型竖井的几何形状，建立了火焰高度的相关性。U 型竖井中的垂直最高温度先是迅速下降，然后保持室温，这与楼梯中烟囱效应下的温度进行了比较。垂直最高温度与高度之间的指数衰减规律被修正。总热流量主要受宽度和放热率的影响。在连续和间歇火焰区域，辐射传热系数大于 80%，其中火焰发射率约为 0.53。
{"title":"Experimental studies on the influence of smoke acceleration effect feedback to the flame behavior in the U shaped shaft of a high-rise building","authors":"Man Li , Yize Shen , Zhongkun Cai , Qishen Xiao , Haowei Hu","doi":"10.1016/j.ijthermalsci.2024.109465","DOIUrl":"10.1016/j.ijthermalsci.2024.109465","url":null,"abstract":"<div><div>This paper presents an experimental investigation of the feedback effect with smoke acceleration on flame behaviors in the U shaped shaft of a high-rise building. Heat release rate of the fire, depths and widths of the U shaped shaft are changed. The flame height, vertical maximum temperature in the open shaft and the heat flux distribution on the façade are studied. Results show that the flame height is elongated by the smoke acceleration effect in the U shaped shaft and larger than that in the open space. Correlations for the flame height are established by taking into account the geometries of the U shaped shaft. The vertical maximum temperature in the U shaped shaft first decreases rapidly then keeps room temperature, which are compared with that under stack effect in the staircase. The exponential decay law between the vertical maximum temperature and height is modified. The total heat flux is mainly affected by the width and heat release rate. Radiation heat transfer fraction is larger than 80 % in the continuous and intermittent flame regions, of which the flame emissivity is about 0.53.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109465"},"PeriodicalIF":4.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421691","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}
Pub Date : 2024-10-10DOI: 10.1016/j.ijthermalsci.2024.109462
Lan Bo, Qiang Wang, Haiyang Hu
An integration of collaborative optimization (CO) strategy was undertaken to improve aerodynamic performance and mitigate the infrared signature of the axisymmetric exhaust system. The Optimal Latin Hypercube method was utilized to construct a kriging surrogate model, considering influential factors such as nozzle geometric parameters, thermodynamic parameters, and material properties of nozzle components. The aerodynamic performance of the nozzle was computed using the Computational Fluid Dynamics (CFD) method, while the assessment of infrared characteristics of the exhaust system was conducted using the multiscale multigroup wide band k-distribution model (MSMGWB) and the Ray Tracing Method. Following a comprehensive evaluation and selection process of optimized results, improvements were observed: the discharge coefficient experienced an increase of up to 1.72 %, the thrust coefficient showed an increase of up to 1.19 %, and a notable reduction of up to 31.23 % in tail direction dimensionless infrared radiation intensity was achieved among all optimized outcomes. The CO method successfully decouples these two tightly coupled disciplines, enabling independent optimization while ensuring consistency between them. By transforming the multi-objective optimization problem into a single-objective optimization within the system and optimizer, this method allows for the rapid and accurate identification of the optimal design that balances aerodynamic performance and infrared stealth according to mission requirements.
为了提高空气动力性能并减轻轴对称排气系统的红外特征，研究人员采用了集成协同优化（CO）策略。考虑到喷嘴几何参数、热力学参数和喷嘴部件的材料属性等影响因素，利用最优拉丁超立方法构建了克里金替代模型。使用计算流体动力学（CFD）方法计算了喷嘴的空气动力学性能，同时使用多尺度多组宽带 k 分布模型（MSMGWB）和光线跟踪方法对排气系统的红外特性进行了评估。在对优化结果进行综合评估和选择后，观察到了一些改进：排放系数增加了 1.72%，推力系数增加了 1.19%，在所有优化结果中，尾部方向无量纲红外辐射强度显著降低了 31.23%。CO 方法成功地解耦了这两个紧密耦合的学科，实现了独立优化，同时确保了它们之间的一致性。通过将多目标优化问题转化为系统和优化器内的单目标优化，该方法可根据任务要求快速准确地确定兼顾气动性能和红外隐身的最佳设计。
{"title":"Multidisciplinary design optimization of axisymmetric exhaust systems: Integrating aerodynamic performance and infrared stealth capabilities","authors":"Lan Bo, Qiang Wang, Haiyang Hu","doi":"10.1016/j.ijthermalsci.2024.109462","DOIUrl":"10.1016/j.ijthermalsci.2024.109462","url":null,"abstract":"<div><div>An integration of collaborative optimization (CO) strategy was undertaken to improve aerodynamic performance and mitigate the infrared signature of the axisymmetric exhaust system. The Optimal Latin Hypercube method was utilized to construct a kriging surrogate model, considering influential factors such as nozzle geometric parameters, thermodynamic parameters, and material properties of nozzle components. The aerodynamic performance of the nozzle was computed using the Computational Fluid Dynamics (CFD) method, while the assessment of infrared characteristics of the exhaust system was conducted using the multiscale multigroup wide band k-distribution model (MSMGWB) and the Ray Tracing Method. Following a comprehensive evaluation and selection process of optimized results, improvements were observed: the discharge coefficient experienced an increase of up to 1.72 %, the thrust coefficient showed an increase of up to 1.19 %, and a notable reduction of up to 31.23 % in tail direction dimensionless infrared radiation intensity was achieved among all optimized outcomes. The CO method successfully decouples these two tightly coupled disciplines, enabling independent optimization while ensuring consistency between them. By transforming the multi-objective optimization problem into a single-objective optimization within the system and optimizer, this method allows for the rapid and accurate identification of the optimal design that balances aerodynamic performance and infrared stealth according to mission requirements.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109462"},"PeriodicalIF":4.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421690","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}
Pub Date : 2024-10-10DOI: 10.1016/j.ijthermalsci.2024.109439
Zeyu Wu , Nan Cao , Jiahua Liu , Xiang Luo
Turbine blade cooling air is facilitated in part by the pre-swirl system, a crucial part of the aero-engine secondary air system. This article primarily focuses on the pre-swirl angle and the turbine co-rotating cavity in order to improve the pre-swirl system's temperature drop. It also employs the thermochromic liquid crystal test method to investigate the pre-swirl system's temperature drop characteristics and the cavity's cooling effect. The experimental parameters are measured at different flow rates when the rotational Reynolds number is between 2.97 × 106 and 4.23 × 106. The results indicate that within the experimental operating range, for the axial pre-swirl structure, the fluid velocity is fast and the static temperature is significantly reduced after pre-rotation. The higher the rotational Reynolds number, the lower the static temperature of the fluid passing through the receiving hole, and the higher the outlet temperature rise. The tangential velocity of the 15-degree preswirl structure is low, the static temperature of the receiving hole is high, and the average outlet temperature increases. In terms of pressure loss, the higher the rotational Reynolds number, the lower the fluid static pressure. The larger the pre-swirl flow rate, the higher the static pressure inside the cavity. The outlet static pressure of the 15-degree structure is higher than that of the 10-degree structure. The swirl ratio increases with an increasing flow rate. The swirl ratio decreases as the rotational Reynolds number increases. The 15-degree structure's swirl ratio is significantly lower than that of the 10-degree structure. Entropy generation is mostly produced along the trailing edge of the blade and in the vicinity of the wall, and the entropy generation of the 15-degree preswirl structure is higher than that of the 10-degree structure. On the disc's surface, the convective heat transfer coefficient rises with a rising dimensionless flow rate and falls with an increasing rotational Reynolds number.
{"title":"Study on flow and heat transfer characteristics of two axial preswirl structures","authors":"Zeyu Wu , Nan Cao , Jiahua Liu , Xiang Luo","doi":"10.1016/j.ijthermalsci.2024.109439","DOIUrl":"10.1016/j.ijthermalsci.2024.109439","url":null,"abstract":"<div><div>Turbine blade cooling air is facilitated in part by the pre-swirl system, a crucial part of the aero-engine secondary air system. This article primarily focuses on the pre-swirl angle and the turbine co-rotating cavity in order to improve the pre-swirl system's temperature drop. It also employs the thermochromic liquid crystal test method to investigate the pre-swirl system's temperature drop characteristics and the cavity's cooling effect. The experimental parameters are measured at different flow rates when the rotational Reynolds number is between 2.97 × 10<sup>6</sup> and 4.23 × 10<sup>6</sup>. The results indicate that within the experimental operating range, for the axial pre-swirl structure, the fluid velocity is fast and the static temperature is significantly reduced after pre-rotation. The higher the rotational Reynolds number, the lower the static temperature of the fluid passing through the receiving hole, and the higher the outlet temperature rise. The tangential velocity of the 15-degree preswirl structure is low, the static temperature of the receiving hole is high, and the average outlet temperature increases. In terms of pressure loss, the higher the rotational Reynolds number, the lower the fluid static pressure. The larger the pre-swirl flow rate, the higher the static pressure inside the cavity. The outlet static pressure of the 15-degree structure is higher than that of the 10-degree structure. The swirl ratio increases with an increasing flow rate. The swirl ratio decreases as the rotational Reynolds number increases. The 15-degree structure's swirl ratio is significantly lower than that of the 10-degree structure. Entropy generation is mostly produced along the trailing edge of the blade and in the vicinity of the wall, and the entropy generation of the 15-degree preswirl structure is higher than that of the 10-degree structure. On the disc's surface, the convective heat transfer coefficient rises with a rising dimensionless flow rate and falls with an increasing rotational Reynolds number.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109439"},"PeriodicalIF":4.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421694","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}
Pub Date : 2024-10-09DOI: 10.1016/j.ijthermalsci.2024.109468
Hanxu Xia, Jun Wang, Yan Shen, Kai Fang
With the rapid development of lithium-ion (Li-ion) batteries, battery thermal management (BTMS) is increasingly essential for the temperature control of Li-ion batteries. The energy required to control temperature is coming into focus. In order to consume less energy to control temperature and improve temperature uniformity, the liquid-cooled plate (LCP) based on bionic flow channels evolved from the shape of leaf veins and tree roots is proposed. In this BLCP, different from the others BLCPs, it is divided into a reinforced heat exchange area located in the middle and back part of the plate and a normal area located in the front part of the plate. Firstly, 16 sets of orthogonal tests are conducted based on four parameters: the distance of the hexagon from the outlet (a), the distance from the inlet (b), the distance between two adjacent hexagons (c) and the size of the hexagon (d). Secondly, Optimization was investigated based on NSGA-II for two objectives: temperature and pressure drop. The simulation results are analyzed based on the optimized structural parameters (a = 30 mm, b = 8 mm, c = 50 mm and d = 90 mm). After Comparing the optimization results with the simulation results, the temperature and pressure drop errors were 0.56 percent and 3.8 percent, respectively. The effects of flow rate and thickness of the fluid domain on temperature and pressure drop are next discussed separately. Finally, after comparing the optimized bionic liquid cooling plate (BLCP) with the conventional liquid cooling plate (CLCP) based on temperature pressure drop, velocity, and synergy angle, conclusions are made at the same inlet width, height, flow rate, and velocity (V = 0.2 m/s). This leads to the criterion of energy loss becoming only the pressure drop. The BLCP for pressure drop is 14.2 percent lower than the CLCP, which means less energy loss. The maximum temperature of the BLCP is 0.7 °C lower than that of the CLCP. Furthermore, the former has a better ability to suppress the rate of temperature rise and better temperature uniformity. In addition, this proposed new structure and research methods can be applied to the subsequent study of LCP.
{"title":"A liquid-cooled plate based on bionic flow channels evolved from the shape of leaf veins and tree roots","authors":"Hanxu Xia, Jun Wang, Yan Shen, Kai Fang","doi":"10.1016/j.ijthermalsci.2024.109468","DOIUrl":"10.1016/j.ijthermalsci.2024.109468","url":null,"abstract":"<div><div>With the rapid development of lithium-ion (Li-ion) batteries, battery thermal management (BTMS) is increasingly essential for the temperature control of Li-ion batteries. The energy required to control temperature is coming into focus. In order to consume less energy to control temperature and improve temperature uniformity, the liquid-cooled plate (LCP) based on bionic flow channels evolved from the shape of leaf veins and tree roots is proposed. In this BLCP, different from the others BLCPs, it is divided into a reinforced heat exchange area located in the middle and back part of the plate and a normal area located in the front part of the plate. Firstly, 16 sets of orthogonal tests are conducted based on four parameters: the distance of the hexagon from the outlet (a), the distance from the inlet (b), the distance between two adjacent hexagons (c) and the size of the hexagon (d). Secondly, Optimization was investigated based on NSGA-II for two objectives: temperature and pressure drop. The simulation results are analyzed based on the optimized structural parameters (a = 30 mm, b = 8 mm, c = 50 mm and d = 90 mm). After Comparing the optimization results with the simulation results, the temperature and pressure drop errors were 0.56 percent and 3.8 percent, respectively. The effects of flow rate and thickness of the fluid domain on temperature and pressure drop are next discussed separately. Finally, after comparing the optimized bionic liquid cooling plate (BLCP) with the conventional liquid cooling plate (CLCP) based on temperature pressure drop, velocity, and synergy angle, conclusions are made at the same inlet width, height, flow rate, and velocity (V = 0.2 m/s). This leads to the criterion of energy loss becoming only the pressure drop. The BLCP for pressure drop is 14.2 percent lower than the CLCP, which means less energy loss. The maximum temperature of the BLCP is 0.7 °C lower than that of the CLCP. Furthermore, the former has a better ability to suppress the rate of temperature rise and better temperature uniformity. In addition, this proposed new structure and research methods can be applied to the subsequent study of LCP.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109468"},"PeriodicalIF":4.9,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421689","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}
Pub Date : 2024-10-08DOI: 10.1016/j.ijthermalsci.2024.109450
Yuanji Li , Xinyu Huang , Tao Lai , Youruo Wu , Xiaohu Yang , Bengt Sundén
The heat storage efficiency of heat storage tank is a challenge to optimize the utilization of solar energy. Therefore, improving the efficiency of heat storage tank has become the main research focus. In this study, the conical tank design optimized for natural convection and the metal foam addition enhanced for thermal conduction are combined. However, there are some mutual constraints between two optimization methods. Therefore, the single factor analysis coupled response surface optimization method was used in this study to optimize the conical heat storage tank filled with metal foam. Firstly, the influence and optimization interval of each factor are discussed through single factor analysis. Then, the comprehensive influence of three factors is analyzed by response surface method. Finally, the heat storage characteristics, natural convection characteristics, melting fraction and temperature uniformity of the optimized model were evaluated. The results show that the optimized heat storage tank has stronger natural convection intensity and stronger melting heat storage performance than three comparative heat storage tanks.
{"title":"Thermal characteristics of conical heat storage tank filled by metal foam: Optimization by response surface analysis","authors":"Yuanji Li , Xinyu Huang , Tao Lai , Youruo Wu , Xiaohu Yang , Bengt Sundén","doi":"10.1016/j.ijthermalsci.2024.109450","DOIUrl":"10.1016/j.ijthermalsci.2024.109450","url":null,"abstract":"<div><div>The heat storage efficiency of heat storage tank is a challenge to optimize the utilization of solar energy. Therefore, improving the efficiency of heat storage tank has become the main research focus. In this study, the conical tank design optimized for natural convection and the metal foam addition enhanced for thermal conduction are combined. However, there are some mutual constraints between two optimization methods. Therefore, the single factor analysis coupled response surface optimization method was used in this study to optimize the conical heat storage tank filled with metal foam. Firstly, the influence and optimization interval of each factor are discussed through single factor analysis. Then, the comprehensive influence of three factors is analyzed by response surface method. Finally, the heat storage characteristics, natural convection characteristics, melting fraction and temperature uniformity of the optimized model were evaluated. The results show that the optimized heat storage tank has stronger natural convection intensity and stronger melting heat storage performance than three comparative heat storage tanks.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109450"},"PeriodicalIF":4.9,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421688","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}
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