Pub Date : 2024-06-14DOI: 10.1016/j.ijthermalsci.2024.109210
Qingzhi Wang , Ruiqiang Bai , Zhiwei Zhou , Wancheng Zhu
The thermal property of the scum layer (soil-rock mixtures) has dominant influence on the heat exchange efficiency between the lower rock layer and the upper environment in the open-pit mines of the cold regions. This paper presents a series of thermal conductivity tests (560 samples) on the scum particle to investigate the coupling effects of ice (moisture) content, temperature, and particle size distribution on the thermal properties. Previously reported models (47 empirical or theoretical models) were adopted to predicate the thermal conductivity of soil-rock mixtures in order to validate the evaluation ability of these models under the wide testing ranges. The comparison results indicate that the theoretical models, normalized model and linear/non-linear models all can not fully predict experimental results under the wide testing conditions. Three machine learning algorithms were used in the assessment presentation for the thermal properties of soil-rock mixtures. The performance of three machine learning algorithms were contrastively examined by using three important indexes (the coefficient of determination (R2), the root mean square error (RMSE) and the relative error (RE)). Based on the evaluation results, the performance ranking of three machine learning algorithms can be listed (GA-BP > SVR > RFR). This investigation is a beneficial attempt for the large data analysis to introduce the machine learning method into the determination of the thermal conductivity of soil-rock mixture under complex conditions.
{"title":"Evaluating thermal conductivity of soil-rock mixtures in Qinghai-Tibet plateau based on theory models and machine learning methods","authors":"Qingzhi Wang , Ruiqiang Bai , Zhiwei Zhou , Wancheng Zhu","doi":"10.1016/j.ijthermalsci.2024.109210","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109210","url":null,"abstract":"<div><p>The thermal property of the scum layer (soil-rock mixtures) has dominant influence on the heat exchange efficiency between the lower rock layer and the upper environment in the open-pit mines of the cold regions. This paper presents a series of thermal conductivity tests (560 samples) on the scum particle to investigate the coupling effects of ice (moisture) content, temperature, and particle size distribution on the thermal properties. Previously reported models (47 empirical or theoretical models) were adopted to predicate the thermal conductivity of soil-rock mixtures in order to validate the evaluation ability of these models under the wide testing ranges. The comparison results indicate that the theoretical models, normalized model and linear/non-linear models all can not fully predict experimental results under the wide testing conditions. Three machine learning algorithms were used in the assessment presentation for the thermal properties of soil-rock mixtures. The performance of three machine learning algorithms were contrastively examined by using three important indexes (the coefficient of determination (R<sup>2</sup>), the root mean square error (RMSE) and the relative error (RE)). Based on the evaluation results, the performance ranking of three machine learning algorithms can be listed (GA-BP > SVR > RFR). This investigation is a beneficial attempt for the large data analysis to introduce the machine learning method into the determination of the thermal conductivity of soil-rock mixture under complex conditions.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141324189","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 : 2024-06-14DOI: 10.1016/j.ijthermalsci.2024.109215
Yansheng Zhang, Zhenlei Li, Yang Tang, Guo Yuan
Twin-roll casting (TRC) has seen a significant interest in recent years due to its short process, low energy consumption, and low emission. The research included both numerical simulation and experimental validation to examine the flow and temperature field distribution of the TRC process. The “U-shaped” buffer groove is identified as beneficial for maintaining a stable liquid level distribution in the molten pool through comparison with various flow distributor structures. The solidified billet shell dispersion around the casting roller in the molten pool is observed to undergo three distinct stages: stable growth, thickness fluctuation, and rapid growth. The inclusion of two circular side outlets, each with a diameter ranging from 8 to 10 mm, proves advantageous in maintaining a stable distribution of the liquid level within the molten pool. The edge outlet size ranges from 7 to 9 mm, and ensuring a U-shaped buffer groove width/flow distribution of 1.25–1.58 aids in enhancing casting stability.
{"title":"Research on flow, heat transfer, and solidification characteristics of flow distribution process in the twin-roll casting","authors":"Yansheng Zhang, Zhenlei Li, Yang Tang, Guo Yuan","doi":"10.1016/j.ijthermalsci.2024.109215","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109215","url":null,"abstract":"<div><p>Twin-roll casting (TRC) has seen a significant interest in recent years due to its short process, low energy consumption, and low emission. The research included both numerical simulation and experimental validation to examine the flow and temperature field distribution of the TRC process. The “U-shaped” buffer groove is identified as beneficial for maintaining a stable liquid level distribution in the molten pool through comparison with various flow distributor structures. The solidified billet shell dispersion around the casting roller in the molten pool is observed to undergo three distinct stages: stable growth, thickness fluctuation, and rapid growth. The inclusion of two circular side outlets, each with a diameter ranging from 8 to 10 mm, proves advantageous in maintaining a stable distribution of the liquid level within the molten pool. The edge outlet size ranges from 7 to 9 mm, and ensuring a U-shaped buffer groove width/flow distribution of 1.25–1.58 aids in enhancing casting stability.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141324187","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 : 2024-06-12DOI: 10.1016/j.ijthermalsci.2024.109181
Hai-Hui Wang , Shamima Aktar , Feng-Feng Yang , Bogdan Z. Dlugogorski , Chao-Peng Wu
The crossing-point temperature measurement is a classical thermal test method for ranking the propensity of coal towards self-heating and spontaneous combustion. Despite its longstanding use, it is still considered an empirical approach due to a lack of understanding on its working mechanism, preventing its wide use and standardization globally. In this paper, efforts were exerted to investigate the formation mechanism of the crossing-point temperature (CPT) and the impact of experimental settings on this parameter, aiming at the consolidation of the physical basis of this test method and paving the way for its further development. In light of the principles of heat and mass transfer, the thermal response of a coal sample stored in a cylindrical reactor exposed to linear heating environment was monitored. Fine coal particles were prepared and packed in the reactor with very thin wall, while the moisture content of a sample varied between 5 % and 20 %. The traced temperature histories are in agreement with the available experimental data. Observations indicated that the volume element at the sample center heats up by offsetting the heat sink term resulting from water evaporation. When the central temperature of the sample catches up with the environmental temperature, the heat sink term from water evaporation disappears, and the direction of heat flow via conduction is reversed, indicating the development of a self-heating domain. The impact of sample attributes and experimental settings on the measurement process is the actual reflection of the self-heating performance of a coal sample with specific physical properties and under defined environmental conditions. During the CPT measurement, the status of zero conductive heat flow at the central volume element can be monitored simultaneously, thereby extracting the apparent kinetic parameters of the sample oxidation at the same time. The established understanding sheds light on the broader application of this test method.
{"title":"Theoretical evaluation on the thermal response of coal during the conventional crossing-point temperature measurement","authors":"Hai-Hui Wang , Shamima Aktar , Feng-Feng Yang , Bogdan Z. Dlugogorski , Chao-Peng Wu","doi":"10.1016/j.ijthermalsci.2024.109181","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109181","url":null,"abstract":"<div><p>The crossing-point temperature measurement is a classical thermal test method for ranking the propensity of coal towards self-heating and spontaneous combustion. Despite its longstanding use, it is still considered an empirical approach due to a lack of understanding on its working mechanism, preventing its wide use and standardization globally. In this paper, efforts were exerted to investigate the formation mechanism of the crossing-point temperature (CPT) and the impact of experimental settings on this parameter, aiming at the consolidation of the physical basis of this test method and paving the way for its further development. In light of the principles of heat and mass transfer, the thermal response of a coal sample stored in a cylindrical reactor exposed to linear heating environment was monitored. Fine coal particles were prepared and packed in the reactor with very thin wall, while the moisture content of a sample varied between 5 % and 20 %. The traced temperature histories are in agreement with the available experimental data. Observations indicated that the volume element at the sample center heats up by offsetting the heat sink term resulting from water evaporation. When the central temperature of the sample catches up with the environmental temperature, the heat sink term from water evaporation disappears, and the direction of heat flow via conduction is reversed, indicating the development of a self-heating domain. The impact of sample attributes and experimental settings on the measurement process is the actual reflection of the self-heating performance of a coal sample with specific physical properties and under defined environmental conditions. During the CPT measurement, the status of zero conductive heat flow at the central volume element can be monitored simultaneously, thereby extracting the apparent kinetic parameters of the sample oxidation at the same time. The established understanding sheds light on the broader application of this test method.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141313574","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 : 2024-06-08DOI: 10.1016/j.ijthermalsci.2024.109205
Yanqiu Chen, Yifan Nie, Jiwei Zhang
As one of the most commonly used energy-saving methods in buildings, thermal insulation layer is widely used in building façade and it also endangers the human safety in buildings due to its combustibility. U-shaped facade is a commonly used structure in high-rise buildings since it could improve both the light and ventilation conditions indoors. This paper investigated the flame acceleration over the thermal insulation in u-shaped building facade fires. It was found that the flame spread rate over u-shaped facade had an exponential growth with time as the direction of preheating zone location is the same direction of the heat transfer from the pyrolysis zone. The air entrainment and the upward induced airflow played an important role in the acceleration. As the side wall length increased or the back wall length decreased, the flame spread rate accelerated more rapidly. Furthermore, a mathematical prediction model of the unsteady flame spread rate over u-shaped structure façade was established and validated through experiments. This study provides technical guidance for the fire safety design of building facade.
保温隔热层作为最常用的建筑节能方法之一,被广泛应用于建筑外墙,同时也因其可燃性而危及建筑中的人身安全。U 型外墙是高层建筑中常用的结构,因为它可以改善室内的采光和通风条件。本文研究了 U 型建筑外墙火灾中隔热层的火焰加速度。研究发现,由于预热区的位置方向与热解区的传热方向一致,u 形外墙的火焰蔓延速度随时间呈指数增长。空气夹带和向上的诱导气流在加速过程中发挥了重要作用。随着侧壁长度的增加或后壁长度的减少,火焰蔓延速度加快。此外,还建立了 U 型结构外墙非稳定火焰蔓延速率的数学预测模型,并通过实验进行了验证。该研究为建筑外墙的防火设计提供了技术指导。
{"title":"Acceleration analysis and unsteady mathematical prediction of flame spread over thermal insulation layer in u-shaped building façade fires","authors":"Yanqiu Chen, Yifan Nie, Jiwei Zhang","doi":"10.1016/j.ijthermalsci.2024.109205","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109205","url":null,"abstract":"<div><p>As one of the most commonly used energy-saving methods in buildings, thermal insulation layer is widely used in building façade and it also endangers the human safety in buildings due to its combustibility. U-shaped facade is a commonly used structure in high-rise buildings since it could improve both the light and ventilation conditions indoors. This paper investigated the flame acceleration over the thermal insulation in u-shaped building facade fires. It was found that the flame spread rate over u-shaped facade had an exponential growth with time as the direction of preheating zone location is the same direction of the heat transfer from the pyrolysis zone. The air entrainment and the upward induced airflow played an important role in the acceleration. As the side wall length increased or the back wall length decreased, the flame spread rate accelerated more rapidly. Furthermore, a mathematical prediction model of the unsteady flame spread rate over u-shaped structure façade was established and validated through experiments. This study provides technical guidance for the fire safety design of building facade.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141291232","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 : 2024-06-08DOI: 10.1016/j.ijthermalsci.2024.109211
Zhen Xiang , Shaohua Han , Shizhen Qi , Yibin Jia , Tairan Guo , Na An , Qilong Liu , Tianyi Huo , Jiangjiang Xing , Runsheng Zhang , Leping Zhou , Li Li , Hui Zhang , Xiaoze Du
The gas turbine blade tip might face substantial heat loads because of leakage flow between the blades and the casing. For blade tip cooling, a composite cooling structure with film holes and broken ribs is first used on GE-E3 blade in this work. The flow and cooling characteristics of the innovative structure are studied by numerical simulation under various blowing ratio (BR) conditions. Meanwhile, the impact of modifying both the rib angle and the rib height on the adiabatic film cooling effectiveness (AFCE) at the tip of the squealer is analyzed. According to the results, adding rib structures to the squealer tip can effectively regulate the paths of cavity vortices and kidney-shaped vortex pairs (KVP) at the tip. As a result, the averaged AFCE at the blade tip is improved. The notch pressure-side broken rib structure has good aerothermal performance, and the highest AFCE at BRs of 0.50, 1.00, and 1.50 basically occur under the “R60-100 %” condition (R60 refers to the rib structure of 60°, and 100 % is the ratio of rib height to notch depth), and the corresponding AFCE are 27.71 %, 26.00 %, and 32.47 % higher than those of the no-rib case, respectively. The corresponding AFCE increased by 27.71 %, 26.52 %, and 32.47 %, respectively, compared to the no-rib condition. The highest AFCE at a BR of 1.50 occurs at “R75-70 %“, which is a 38.20 % increase in AFCE compared to the no rib case. The improvement in AFCE is due to the difference in the flow of the cooling jets, which are subject to cavity vortices at different BRs. The analysis shows that the addition of ribs disrupts the formation of KVPs and weakens the influence of the cavity vortex, thus reducing the low AFCE region at the lower end of the tip groove and increasing the AFCE. However, due to the blocking effect of the ribs, the pressure loss at the blade tip is elevated. The proposed blade tip cooling structure is expected to provide new ideas for the next generation of advanced gas turbine cooling designs.
{"title":"Numerical study of cooling performance and flow characteristics of film hole-broken rib composite structure with squealer tip","authors":"Zhen Xiang , Shaohua Han , Shizhen Qi , Yibin Jia , Tairan Guo , Na An , Qilong Liu , Tianyi Huo , Jiangjiang Xing , Runsheng Zhang , Leping Zhou , Li Li , Hui Zhang , Xiaoze Du","doi":"10.1016/j.ijthermalsci.2024.109211","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109211","url":null,"abstract":"<div><p>The gas turbine blade tip might face substantial heat loads because of leakage flow between the blades and the casing. For blade tip cooling, a composite cooling structure with film holes and broken ribs is first used on GE-E<sup>3</sup> blade in this work. The flow and cooling characteristics of the innovative structure are studied by numerical simulation under various blowing ratio (BR) conditions. Meanwhile, the impact of modifying both the rib angle and the rib height on the adiabatic film cooling effectiveness (AFCE) at the tip of the squealer is analyzed. According to the results, adding rib structures to the squealer tip can effectively regulate the paths of cavity vortices and kidney-shaped vortex pairs (KVP) at the tip. As a result, the averaged AFCE at the blade tip is improved. The notch pressure-side broken rib structure has good aerothermal performance, and the highest AFCE at BRs of 0.50, 1.00, and 1.50 basically occur under the “R60-100 %” condition (R60 refers to the rib structure of 60°, and 100 % is the ratio of rib height to notch depth), and the corresponding AFCE are 27.71 %, 26.00 %, and 32.47 % higher than those of the no-rib case, respectively. The corresponding AFCE increased by 27.71 %, 26.52 %, and 32.47 %, respectively, compared to the no-rib condition. The highest AFCE at a BR of 1.50 occurs at “R75-70 %“, which is a 38.20 % increase in AFCE compared to the no rib case. The improvement in AFCE is due to the difference in the flow of the cooling jets, which are subject to cavity vortices at different BRs. The analysis shows that the addition of ribs disrupts the formation of KVPs and weakens the influence of the cavity vortex, thus reducing the low AFCE region at the lower end of the tip groove and increasing the AFCE. However, due to the blocking effect of the ribs, the pressure loss at the blade tip is elevated. The proposed blade tip cooling structure is expected to provide new ideas for the next generation of advanced gas turbine cooling designs.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141291230","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 : 2024-06-08DOI: 10.1016/j.ijthermalsci.2024.109182
Qinqin He , Yixin Xu , Haidong Wang , Zhigang Li , Yanguang Zhou
The interfaces between SiC and the corresponding substrate largely affect the performance of SiC-based electronics. Understanding and designing the interfacial thermal transport across the SiC/substrate interfaces is critical for the thermal management design of these SiC-based power electronics. In this work, we systematically investigate the heat transfer across the 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces using non-equilibrium molecular dynamics simulations and diffuse mismatch model. We find that the room temperature ITC for 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces is 932 MW/m2K, 759 MW/m2K, and 697 MW/m2K, respectively, which is among the highest values for all interfaces made up of semiconductors (Yue et al., 2011; Cheng et al., 2020; Wilson et al., 2015; Ziade et al., 2015) [[1], [2], [3], [4]]. The ultrahigh ITC of SiC/Si heterointerfaces at room temperature and high temperatures results from the dictating elastic scatterings at interfaces. We further find the ITC contributed by the elastic scattering decreases with the temperature but remains at a high ratio of 67%-78% even at an ultrahigh temperature of 1000 K. The reason for such a high elastic ITC is the large overlap between the vibrational density of states of Si and SiC at low and middle frequencies (<∼18 THz), which is also demonstrated by the diffuse mismatch model.
{"title":"Role of elastic phonon couplings in dictating the thermal transport across atomically sharp SiC/Si interfaces","authors":"Qinqin He , Yixin Xu , Haidong Wang , Zhigang Li , Yanguang Zhou","doi":"10.1016/j.ijthermalsci.2024.109182","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109182","url":null,"abstract":"<div><p>The interfaces between SiC and the corresponding substrate largely affect the performance of SiC-based electronics. Understanding and designing the interfacial thermal transport across the SiC/substrate interfaces is critical for the thermal management design of these SiC-based power electronics. In this work, we systematically investigate the heat transfer across the 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces using non-equilibrium molecular dynamics simulations and diffuse mismatch model. We find that the room temperature ITC for 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces is 932 MW/m<sup>2</sup>K, 759 MW/m<sup>2</sup>K, and 697 MW/m<sup>2</sup>K, respectively, which is among the highest values for all interfaces made up of semiconductors (Yue et al., 2011; Cheng et al., 2020; Wilson et al., 2015; Ziade et al., 2015) [<span>[1]</span>, <span>[2]</span>, <span>[3]</span>, <span>[4]</span>]. The ultrahigh ITC of SiC/Si heterointerfaces at room temperature and high temperatures results from the dictating elastic scatterings at interfaces. We further find the ITC contributed by the elastic scattering decreases with the temperature but remains at a high ratio of 67%-78% even at an ultrahigh temperature of 1000 K. The reason for such a high elastic ITC is the large overlap between the vibrational density of states of Si and SiC at low and middle frequencies (<∼18 THz), which is also demonstrated by the diffuse mismatch model.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141291231","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 : 2024-06-08DOI: 10.1016/j.ijthermalsci.2024.109208
Jian Chen , Linchuan Liu , Shengnan Fu , Jiaping Li , Xueling Fan , Xiaochao Jin
Quantitative analysis of the influence of thermal barrier coating spallation on the thermo-mechanical behaviors and creep lifetime of turbine vanes is crucial for their maintenance and reliability improvement. The temperature and stress distribution of vanes with preset coating spallation damage are investigated in this study, using the thermal-fluid-solid coupling method. Additionally, a further computational analysis is conducted to predict the hazardous regions and creep lifetime of the vanes. The results indicate that coating spallation leads to significant changes of the temperature and stress distribution at the spalled regions of vanes. The remaining coating on the unspalled regions continues to provide effective protection. Stress concentration primarily occurs at the upstream and downstream of the leading edge film holes, while high-stress regions are observed between adjacent rows of film holes, forming a serrated shape. The creep lifetime of the vanes decreases significantly at the region with coating spallation. When the same spallation area is considered, the coating spallation at the leading edge has a more serious influence on creep lifetime, which is more likely to cause the vanes failure. This study reveals the influence of coating spallation characteristics on the thermo-mechanical behaviors and creep lifetime of vanes, providing valuable insights for durability assessment of coated high-temperature components.
{"title":"Thermo-mechanical analysis and creep lifetime prediction of coated turbine vanes considering thermal barrier coating spallation characteristics","authors":"Jian Chen , Linchuan Liu , Shengnan Fu , Jiaping Li , Xueling Fan , Xiaochao Jin","doi":"10.1016/j.ijthermalsci.2024.109208","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109208","url":null,"abstract":"<div><p>Quantitative analysis of the influence of thermal barrier coating spallation on the thermo-mechanical behaviors and creep lifetime of turbine vanes is crucial for their maintenance and reliability improvement. The temperature and stress distribution of vanes with preset coating spallation damage are investigated in this study, using the thermal-fluid-solid coupling method. Additionally, a further computational analysis is conducted to predict the hazardous regions and creep lifetime of the vanes. The results indicate that coating spallation leads to significant changes of the temperature and stress distribution at the spalled regions of vanes. The remaining coating on the unspalled regions continues to provide effective protection. Stress concentration primarily occurs at the upstream and downstream of the leading edge film holes, while high-stress regions are observed between adjacent rows of film holes, forming a serrated shape. The creep lifetime of the vanes decreases significantly at the region with coating spallation. When the same spallation area is considered, the coating spallation at the leading edge has a more serious influence on creep lifetime, which is more likely to cause the vanes failure. This study reveals the influence of coating spallation characteristics on the thermo-mechanical behaviors and creep lifetime of vanes, providing valuable insights for durability assessment of coated high-temperature components.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141291233","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}
Accurate analysis of slab heat transfer characteristics is crucial for optimal control of reheating furnaces. This paper established a half furnace model to describe the heat and mass transfer and slab step heating processes in a walking beam reheating furnace. The contact heat conduction and beams misalignment are fully considered. The distribution of total heat transfer coefficient and the effect of stepping strategies on skid mark severity are investigated. The results show that the contact thermal resistance accounts for 1/8 of the conductivity thermal resistance of skid buttons and welding pads and has a lighter effect on the skid marks. The misalignment of the water-cooled beams effectively eliminated the original skid marks and minimized the range of the new ones, but the new skid mark severity before discharge from the furnace remains at 121 °C. The total heat transfer coefficient showed a wave distribution on the slab bottom surface and varied in the range of about −0.72 to 1.71 due to the beam shielding. On the slab top surface, it followed a stepped distribution. Stepping while advancing in soaking zone effectively improve the new skid mark temperature and reduce the skid mark severity by 24 °C. Increasing the stepping number can also reduce the influence of skid marks on the temperature of slab end, thus improving the temperature uniformity of the slab head and tail.
{"title":"Analysis of heat transfer coefficient and skid marks in a slab reheating furnace considering beam misalignment and contact heat conduction","authors":"Dijie Wang , Xinru Zhang , Youxin Zhu , Zeyi Jiang","doi":"10.1016/j.ijthermalsci.2024.109209","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109209","url":null,"abstract":"<div><p>Accurate analysis of slab heat transfer characteristics is crucial for optimal control of reheating furnaces. This paper established a half furnace model to describe the heat and mass transfer and slab step heating processes in a walking beam reheating furnace. The contact heat conduction and beams misalignment are fully considered. The distribution of total heat transfer coefficient and the effect of stepping strategies on skid mark severity are investigated. The results show that the contact thermal resistance accounts for 1/8 of the conductivity thermal resistance of skid buttons and welding pads and has a lighter effect on the skid marks. The misalignment of the water-cooled beams effectively eliminated the original skid marks and minimized the range of the new ones, but the new skid mark severity before discharge from the furnace remains at 121 °C. The total heat transfer coefficient showed a wave distribution on the slab bottom surface and varied in the range of about −0.72 to 1.71 due to the beam shielding. On the slab top surface, it followed a stepped distribution. Stepping while advancing in soaking zone effectively improve the new skid mark temperature and reduce the skid mark severity by 24 °C. Increasing the stepping number can also reduce the influence of skid marks on the temperature of slab end, thus improving the temperature uniformity of the slab head and tail.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141291227","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}
In this study, a stable hydrophilic thin layer resembling SiOx is formed on the copper surface by combining plasma polymerization using hexamethyldisiloxane (HMDSO) and Ar plasma activation. The effect of coating on the Heat Transfer Coefficient (HTC) and Critical Heat Flux (CHF) at two different subcooling temperatures is investigated through pool boiling experiments. It is found that the HTC and CHF of the modified surface improved by 42 % and 97 %, respectively. The chemical composition of the coating, as well as changes in surface roughness, wettability, and porosity, are studied using the Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectrometer (EDX), Fourier Transform Infrared (FT-IR) spectroscopy, and contact angle measurement. The boiling/cooling experiments for the plasma-coated surface show good stability, demonstrating that the surface characteristics remain stable even after three boiling/cooling cycles.
{"title":"Experimental investigation of pool boiling performance on a coated copper surface using a two-step non-thermal plasma process","authors":"Hamid Reza Mohammadi , Hamed Taghvaei , Ataollah Rabiee","doi":"10.1016/j.ijthermalsci.2024.109207","DOIUrl":"https://doi.org/10.1016/j.ijthermalsci.2024.109207","url":null,"abstract":"<div><p>In this study, a stable hydrophilic thin layer resembling SiO<sub>x</sub> is formed on the copper surface by combining plasma polymerization using hexamethyldisiloxane (HMDSO) and Ar plasma activation. The effect of coating on the Heat Transfer Coefficient (HTC) and Critical Heat Flux (CHF) at two different subcooling temperatures is investigated through pool boiling experiments. It is found that the HTC and CHF of the modified surface improved by 42 % and 97 %, respectively. The chemical composition of the coating, as well as changes in surface roughness, wettability, and porosity, are studied using the Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectrometer (EDX), Fourier Transform Infrared (FT-IR) spectroscopy, and contact angle measurement. The boiling/cooling experiments for the plasma-coated surface show good stability, demonstrating that the surface characteristics remain stable even after three boiling/cooling cycles.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141291229","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}
The authors regret that typos are in the original text and should be corrected in this corrigendum. These corrections do not influence the method, results and conclusions of the original article.
作者对原文中的错别字表示遗憾,并应在本更正中予以更正。这些更正并不影响原文的方法、结果和结论。
{"title":"Corrigendum to study on the heat transfer characteristics of CO2 and liquid desiccant CaCl2 aqueous solution in the gas cooler and evaporator [Int. J. Therm. Sci. 2024,197: 108830]","authors":"Dianhang Wei , Qi Cui , Enyuan Gao , Pengcheng Qi , Xiaosong Zhang","doi":"10.1016/j.ijthermalsci.2024.109183","DOIUrl":"10.1016/j.ijthermalsci.2024.109183","url":null,"abstract":"<div><p>The authors regret that typos are in the original text and should be corrected in this corrigendum. These corrections do not influence the method, results and conclusions of the original article.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1290072924003053/pdfft?md5=bc85c1f55c89b7d872041c80c2f56224&pid=1-s2.0-S1290072924003053-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141411155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}