The present numerical study explores the flow physics and heat transfer characteristics around three unconfined inline horizontally placed cylinders arranged in a vertical array subjected to ambient air. It investigates the effect of Rayleigh number (i.e., 102 ≤ Ra ≤ 106) and the center-to-center spacing (1≤ S/D ≤ 9). The study shows that the augmentation or reduction of heat transfer rate from an individual cylinder in the array to that of a single unconfined cylinder under identical conditions strongly depends on the separation distance and Rayleigh number. Moreover, the average Nu from the bottom cylinder deteriorates only at very close spacing, whereas after S/D ≥ 3, it attains an asymptotic value to that of a single cylinder. The heat transfer rates from the middle and top cylinders relative to a single cylinder also deteriorate drastically at close spacing. In contrast, a slight enhancement is observed at relatively large spacing and higher Ra.
本数值研究探讨了在环境空气作用下，三个以垂直阵列排列的无约束直列水平放置圆柱体周围的流动物理和传热特性。它研究了瑞利数（即 102 ≤ Ra ≤ 106）和中心到中心间距（1≤ S/D ≤ 9）的影响。研究表明，在相同条件下，从阵列中的单个圆柱体到单个非封闭圆柱体的传热速率的增加或减少很大程度上取决于分离距离和雷利数。此外，来自底部圆柱体的平均 Nu 只有在间距非常近时才会变差，而在 S/D ≥ 3 后，则会达到与单个圆柱体相同的渐近值。相对于单个圆柱体，中间和顶部圆柱体的传热率在间距很近时也会急剧下降。相反，在间距相对较大和 Ra 较高的情况下，传热率会略有提高。
{"title":"Natural Convection Around Three Horizontal Cylinders in Vertical Array: A Numerical Approach","authors":"Manoj Kumar Dash, Santosh Kumar Senapati, Aurovinda Mohanty","doi":"10.2514/1.t6925","DOIUrl":"https://doi.org/10.2514/1.t6925","url":null,"abstract":"<p>The present numerical study explores the flow physics and heat transfer characteristics around three unconfined inline horizontally placed cylinders arranged in a vertical array subjected to ambient air. It investigates the effect of Rayleigh number (i.e., 10<sup>2</sup> ≤ <i>Ra</i> ≤ 10<sup>6</sup>) and the center-to-center spacing (1≤ <i>S/D</i> ≤ 9). The study shows that the augmentation or reduction of heat transfer rate from an individual cylinder in the array to that of a single unconfined cylinder under identical conditions strongly depends on the separation distance and Rayleigh number. Moreover, the average <i>Nu</i> from the bottom cylinder deteriorates only at very close spacing, whereas after <i>S/D</i> ≥ 3, it attains an asymptotic value to that of a single cylinder. The heat transfer rates from the middle and top cylinders relative to a single cylinder also deteriorate drastically at close spacing. In contrast, a slight enhancement is observed at relatively large spacing and higher <i>Ra</i>.</p>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"51 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140570434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents a method for estimating the space-dependent thermal contact resistance between the two-layer walls of a furnace using the boundary element method (BEM) and conjugate gradient method (CGM) for the heat conduction problem. The global solution equation in matrix form is derived using the interface conditions, and the BEM is used to solve the direct problem. The CGM minimizes the objective function and calculates the sensitivity coefficients with the complex variable derivation method (CVDM). Comparative results show that the present approach is more accurate, stable, and efficient than the conventional CGM, which is attributed to the calculation of the sensitivity coefficients by CVDM. The effects of the value of thermal contact resistance, thermal conductivity ratio, Biot number, initial guess, measurement error, and the number and position of measurement points on the inversion results are also analyzed. Finally, the effectiveness of this approach is demonstrated through numerical examples, and the inversion results show its stability, efficiency, and accuracy in identifying different and complex distributions of thermal contact resistance. Furthermore, this approach is feasible for nonintrusive measurement, which is very meaningful in practical applications.
本研究提出了一种方法，利用边界元法（BEM）和共轭梯度法（CGM）估算热传导问题中炉子两层壁之间与空间有关的热接触电阻。利用界面条件推导出矩阵形式的全局求解方程，并使用 BEM 解决直接问题。CGM 使目标函数最小化，并用复变推导法（CVDM）计算敏感系数。比较结果表明，本方法比传统 CGM 更精确、稳定和高效，这归功于 CVDM 对灵敏度系数的计算。此外，还分析了热接触电阻值、导热比、比奥特数、初始猜测、测量误差以及测量点的数量和位置对反演结果的影响。最后，通过数值示例证明了该方法的有效性，反演结果表明，该方法在识别不同的复杂热接触电阻分布方面具有稳定性、高效性和准确性。此外，这种方法适用于非侵入式测量，在实际应用中非常有意义。
{"title":"Inverse Estimation of Thermal Contact Resistance Between Two Layers of Cylindrical Wall","authors":"Bin Li, Qiang Liu, Keli He","doi":"10.2514/1.t6952","DOIUrl":"https://doi.org/10.2514/1.t6952","url":null,"abstract":"<p>This study presents a method for estimating the space-dependent thermal contact resistance between the two-layer walls of a furnace using the boundary element method (BEM) and conjugate gradient method (CGM) for the heat conduction problem. The global solution equation in matrix form is derived using the interface conditions, and the BEM is used to solve the direct problem. The CGM minimizes the objective function and calculates the sensitivity coefficients with the complex variable derivation method (CVDM). Comparative results show that the present approach is more accurate, stable, and efficient than the conventional CGM, which is attributed to the calculation of the sensitivity coefficients by CVDM. The effects of the value of thermal contact resistance, thermal conductivity ratio, Biot number, initial guess, measurement error, and the number and position of measurement points on the inversion results are also analyzed. Finally, the effectiveness of this approach is demonstrated through numerical examples, and the inversion results show its stability, efficiency, and accuracy in identifying different and complex distributions of thermal contact resistance. Furthermore, this approach is feasible for nonintrusive measurement, which is very meaningful in practical applications.</p>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"51 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140570359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A material response solver that predicts the response of charring ablative materials under different degrees of physical modeling complexity is developed. The solver provides a versatile environment for engineering analyses and incorporates a third-party library for the evaluation of thermodynamic/transport properties of pyrolysis gas mixture and chemical kinetics, if necessary. Thermal nonequilibrium between the solid and the gas phases is considered using the two-equation model. A novel reactor network approach is used for modeling pyrolysis gas flow inside the porous ablative material, allowing simulations with various gas compositions and reaction mechanisms. Effects of chemical and thermal nonequilibrium and influences of the porosity and permeability of the porous structure on the response of charring ablative materials are explored. It is observed that higher porosity and smaller permeability values induce local thermal equilibrium, and chemical reactions increase the temperature differences between the phases.
{"title":"Effects of Thermal and Chemical Nonequilibrium on Response of Charring Ablative Materials","authors":"Volkan Coskun, Cuneyt Sert","doi":"10.2514/1.t6786","DOIUrl":"https://doi.org/10.2514/1.t6786","url":null,"abstract":"<p>A material response solver that predicts the response of charring ablative materials under different degrees of physical modeling complexity is developed. The solver provides a versatile environment for engineering analyses and incorporates a third-party library for the evaluation of thermodynamic/transport properties of pyrolysis gas mixture and chemical kinetics, if necessary. Thermal nonequilibrium between the solid and the gas phases is considered using the two-equation model. A novel reactor network approach is used for modeling pyrolysis gas flow inside the porous ablative material, allowing simulations with various gas compositions and reaction mechanisms. Effects of chemical and thermal nonequilibrium and influences of the porosity and permeability of the porous structure on the response of charring ablative materials are explored. It is observed that higher porosity and smaller permeability values induce local thermal equilibrium, and chemical reactions increase the temperature differences between the phases.</p>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"60 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140570343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Contact Angles of Water on Different Metals","authors":"Muhammed Murat Aksoy, Yildiz Bayazitoglu","doi":"10.2514/1.t6935","DOIUrl":"https://doi.org/10.2514/1.t6935","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"42 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140107319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Comment on “Unsteady Flow of a Nanofluid over a Sphere with Nonlinear Boussinesq Approximation”","authors":"Asterios Pantokratoras","doi":"10.2514/1.t6929","DOIUrl":"https://doi.org/10.2514/1.t6929","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"163 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139950654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Uncertainty Analysis of Slug Calorimeters in the NASA HyMETS Arc-Jet Facility","authors":"Andrew J. Brune, Chelsey C. Morrow","doi":"10.2514/1.t6883","DOIUrl":"https://doi.org/10.2514/1.t6883","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"255 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139950484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Radiative Transfer in Finite Concentric Cylinders by the Zonal Monte Carlo Method","authors":"Walter W. Yuen","doi":"10.2514/1.t6923","DOIUrl":"https://doi.org/10.2514/1.t6923","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"31 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139921232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hui Wang, Tao Zhu, Xinxin Zhu, Xiaojuan Bai, Kai Yang, Qingtao Yang
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Inverse Estimation of Dynamic Heat Flux Using Proportional Integral Derivative Control","authors":"Hui Wang, Tao Zhu, Xinxin Zhu, Xiaojuan Bai, Kai Yang, Qingtao Yang","doi":"10.2514/1.t6855","DOIUrl":"https://doi.org/10.2514/1.t6855","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"18 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Nonlinear Estimators for Hypersonic Heat Flux Reconstruction","authors":"Nhat M. Nguyen, Mathew L. Ruda, Luca Massa","doi":"10.2514/1.t6888","DOIUrl":"https://doi.org/10.2514/1.t6888","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"145 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Journal of Thermophysics and Heat Transfer, Ahead of Print.
热物理学和传热学杂志》，提前出版。
{"title":"Experiment on Heat Exchanger Using Innovative Coils and Phase Change Material/MXene Nanofluids","authors":"Jahar Sarkar, Rashmi Rekha Sahoo","doi":"10.2514/1.t6897","DOIUrl":"https://doi.org/10.2514/1.t6897","url":null,"abstract":"Journal of Thermophysics and Heat Transfer, Ahead of Print. <br/>","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":"18 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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