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Gradient-based image generation for thermographic material inspection
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-18 DOI: 10.1016/j.applthermaleng.2025.125900
Valentino Razza , Luca Santoro , Manuela De Maddis
Infrared thermography is a non-contact, cost-effective, and non-destructive technique for defect inspection. Analyzing the surface temperature behavior of an object excited by a suitably designed heat source provides information on the internal structure of the object. The thermal diffusion coefficient of the material is the main physical parameter determining the surface temperature profile. Defects are typically characterized by a different thermal diffusion coefficient than the base material, leading to changes in the heat transfer model.
If defect identification from thermography analysis is possible and computationally efficient, interpreting the results often requires trained users. In this work, we propose an algorithm for active thermography data analysis that generates images enabling the detection of the position and size of internal defects. Experimental results validate the approach, showing its ability to detect blind flat-top holes of 3 mm diameter and depths of 0.5 mm and 0.8 mm in a 1 mm thick DP600 steel plate. In addition, tests of the proposed technique show promising results in highlighting embedded defects in a 3D-printed polylactic acid object, proving the algorithm efficacy for the inspection of materials with different heat diffusion coefficients. These findings highlight the robustness and practicality of the proposed method for industrial applications.
{"title":"Gradient-based image generation for thermographic material inspection","authors":"Valentino Razza ,&nbsp;Luca Santoro ,&nbsp;Manuela De Maddis","doi":"10.1016/j.applthermaleng.2025.125900","DOIUrl":"10.1016/j.applthermaleng.2025.125900","url":null,"abstract":"<div><div>Infrared thermography is a non-contact, cost-effective, and non-destructive technique for defect inspection. Analyzing the surface temperature behavior of an object excited by a suitably designed heat source provides information on the internal structure of the object. The thermal diffusion coefficient of the material is the main physical parameter determining the surface temperature profile. Defects are typically characterized by a different thermal diffusion coefficient than the base material, leading to changes in the heat transfer model.</div><div>If defect identification from thermography analysis is possible and computationally efficient, interpreting the results often requires trained users. In this work, we propose an algorithm for active thermography data analysis that generates images enabling the detection of the position and size of internal defects. Experimental results validate the approach, showing its ability to detect blind flat-top holes of 3 mm diameter and depths of 0.5 mm and 0.8 mm in a 1 mm thick DP600 steel plate. In addition, tests of the proposed technique show promising results in highlighting embedded defects in a 3D-printed polylactic acid object, proving the algorithm efficacy for the inspection of materials with different heat diffusion coefficients. These findings highlight the robustness and practicality of the proposed method for industrial applications.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"268 ","pages":"Article 125900"},"PeriodicalIF":6.1,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437123","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}
引用次数: 0
A radiative heat network method for accurate indoor radiant field and thermal comfort evaluation
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125910
Huaiyuan Wang , Yuanwei Lu , Xuefeng Tian , Baiqi Zhang , Meiqi Wang , Wei Zhou , Jihui Gao
Solar radiation entering the interior through windows has a significant impact on the indoor radiation environment. Previous studies have proposed models to quantify the effects of direct solar radiation on the radiation environment and human thermal comfort. However, little attention has been given to the additional long-wave radiation effects generated by sunlight-heated wall surfaces. To address this gap, this study developed a radiative heat network model combined with a one-dimensional finite volume method. By dividing walls into multiple surface units, the model enhances resolution, improves the ability to capture localized heating effects from solar radiation, and significantly increases the accuracy of wall temperature distribution calculations. Model validation shows that the surface temperature error is less than 0.32 °C, and the ΔMRT error induced by solar radiation is below 1.9 °C. The results indicate that under high-resolution conditions, wall temperatures can increase by up to 16.6 °C, resulting in localized MRT and SMRT increases of 7.3 °C and 8.8 °C, respectively. Based on this model, the study further explored the combined effects of thermochromic and Low-E glass on regulating radiation environments. The results demonstrate that this combination effectively reduces summer cooling energy consumption by 57.8 %, increases thermal comfort probabilities by 4 %, and significantly improves the uniformity of indoor thermal comfort distribution. This work provides foundational technical support for the evaluation and design of indoor thermal environments.
{"title":"A radiative heat network method for accurate indoor radiant field and thermal comfort evaluation","authors":"Huaiyuan Wang ,&nbsp;Yuanwei Lu ,&nbsp;Xuefeng Tian ,&nbsp;Baiqi Zhang ,&nbsp;Meiqi Wang ,&nbsp;Wei Zhou ,&nbsp;Jihui Gao","doi":"10.1016/j.applthermaleng.2025.125910","DOIUrl":"10.1016/j.applthermaleng.2025.125910","url":null,"abstract":"<div><div>Solar radiation entering the interior through windows has a significant impact on the indoor radiation environment. Previous studies have proposed models to quantify the effects of direct solar radiation on the radiation environment and human thermal comfort. However, little attention has been given to the additional long-wave radiation effects generated by sunlight-heated wall surfaces. To address this gap, this study developed a radiative heat network model combined with a one-dimensional finite volume method. By dividing walls into multiple surface units, the model enhances resolution, improves the ability to capture localized heating effects from solar radiation, and significantly increases the accuracy of wall temperature distribution calculations. Model validation shows that the surface temperature error is less than 0.32 °C, and the ΔMRT error induced by solar radiation is below 1.9 °C. The results indicate that under high-resolution conditions, wall temperatures can increase by up to 16.6 °C, resulting in localized MRT and SMRT increases of 7.3 °C and 8.8 °C, respectively. Based on this model, the study further explored the combined effects of thermochromic and Low-E glass on regulating radiation environments. The results demonstrate that this combination effectively reduces summer cooling energy consumption by 57.8 %, increases thermal comfort probabilities by 4 %, and significantly improves the uniformity of indoor thermal comfort distribution. This work provides foundational technical support for the evaluation and design of indoor thermal environments.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"268 ","pages":"Article 125910"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Evaluation of thermal performance and efficiency enhancement potential of low-temperature operation strategies in solar district heating systems
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125980
Ruichao Zhang , Dengjia Wang , Zhelong Mo , Qingtai Jiao , Xia Liu , Meng Gao , Jianhua Fan
A defining innovation in fourth- and fifth-generation district heating systems is the emphasis on low-temperature operation, which is crucial for advancing the efficiency of modern systems. While considerable attention has been given to low-temperature operation in traditional district heating systems, its application and quantification in solar district heating systems remain underexplored. In the context of solar district heating systems, adopting low-temperature operation is pivotal for unlocking substantial improvements in overall energy efficiency. This study addresses this gap by systematically evaluating and comparing several low-temperature operation strategies, including reductions in supply and return temperatures, integration of water-to-water heat pumps, and dynamic regulation of solar collector field outlet temperatures—strategies that have not been comprehensively studied together within solar heating systems. A comprehensive thermodynamic model was developed in Matlab, with the Langkazi solar district heating system serving as a case study to validate and quantify the effectiveness of these proposed strategies. Results demonstrate that reducing return water temperature and integrating water-to-water heat pumps significantly lower solar collector field inlet temperatures, with the integration of the water-to-water heat pump yielding the most pronounced improvements in system performance. This led to a notable increase in solar fraction and heat collection efficiency, from 66.4 % and 35.2 % to 78.7 % and 40.3 %, respectively. Importantly, the dynamic regulation of solar collector field outlet temperature emerges as an especially effective and innovative approach that significantly reduces operating temperatures and further boosting system thermal efficiency. Notably, in non-direct supply mode with integrated water-to-water heat pumps, dynamic regulation based on heat storage temperature provided an additional improvement, increasing annual heat collection efficiency and solar fraction by over 2.0 % and 4.0 %, respectively, compared to the direct supply mode with WWHP integration. When all low-temperature strategies were applied, the system’s solar fraction and heat collection efficiency increased by an average of 16.51 % and 7.15 %, with maximum gains of 18.56 % and 8.06 %. Additionally, the potential for efficiency improvements is greater in regions with weaker solar radiation, and under low-temperature operation strategies, the system shows improved economic performance and carbon emission reductions. These findings offer valuable insights for optimizing low-temperature solar district heating systems.
{"title":"Evaluation of thermal performance and efficiency enhancement potential of low-temperature operation strategies in solar district heating systems","authors":"Ruichao Zhang ,&nbsp;Dengjia Wang ,&nbsp;Zhelong Mo ,&nbsp;Qingtai Jiao ,&nbsp;Xia Liu ,&nbsp;Meng Gao ,&nbsp;Jianhua Fan","doi":"10.1016/j.applthermaleng.2025.125980","DOIUrl":"10.1016/j.applthermaleng.2025.125980","url":null,"abstract":"<div><div>A defining innovation in fourth- and fifth-generation district heating systems is the emphasis on low-temperature operation, which is crucial for advancing the efficiency of modern systems. While considerable attention has been given to low-temperature operation in traditional district heating systems, its application and quantification in solar district heating systems remain underexplored. In the context of solar district heating systems, adopting low-temperature operation is pivotal for unlocking substantial improvements in overall energy efficiency. This study addresses this gap by systematically evaluating and comparing several low-temperature operation strategies, including reductions in supply and return temperatures, integration of water-to-water heat pumps, and dynamic regulation of solar collector field outlet temperatures—strategies that have not been comprehensively studied together within solar heating systems. A comprehensive thermodynamic model was developed in <em>Matlab</em>, with the <em>Langkazi</em> solar district heating system serving as a case study to validate and quantify the effectiveness of these proposed strategies. Results demonstrate that reducing return water temperature and integrating water-to-water heat pumps significantly lower solar collector field inlet temperatures, with the integration of the water-to-water heat pump yielding the most pronounced improvements in system performance. This led to a notable increase in solar fraction and heat collection efficiency, from 66.4 % and 35.2 % to 78.7 % and 40.3 %, respectively. Importantly, the dynamic regulation of solar collector field outlet temperature emerges as an especially effective and innovative approach that significantly reduces operating temperatures and further boosting system thermal efficiency. Notably, in non-direct supply mode with integrated water-to-water heat pumps, dynamic regulation based on heat storage temperature provided an additional improvement, increasing annual heat collection efficiency and solar fraction by over 2.0 % and 4.0 %, respectively, compared to the direct supply mode with WWHP integration. When all low-temperature strategies were applied, the system’s solar fraction and heat collection efficiency increased by an average of 16.51 % and 7.15 %, with maximum gains of 18.56 % and 8.06 %. Additionally, the potential for efficiency improvements is greater in regions with weaker solar radiation, and under low-temperature operation strategies, the system shows improved economic performance and carbon emission reductions. These findings offer valuable insights for optimizing low-temperature solar district heating systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125980"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fault detection and diagnosis algorithm for multiple simultaneous faults in residential air-conditioning systems: Development, validation study and critical analysis
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125975
Belén Llopis-Mengual , David P. Yuill , Emilio Navarro-Peris
Detecting and diagnosing faults in residential air conditioning (AC) systems is crucial for preventing critical failures and ensuring efficient operation. Some of these soft faults are refrigerant undercharge (UC), overcharge (OC), inadequate evaporator airflow (EA), or liquid line restrictions (LL). Data-driven methodologies have proven effective in achieving reliable detection but require a large amount of data. This paper proposes utilizing a model based on vapor compression cycles capable of simulating a wide range of indoor/outdoor operating conditions and faults imposed individually and several co-occurring (multiple combinations) for a residential AC unit. This simulated dataset is used to train a Support Vector Machine (SVM) classification algorithm to distinguish between fault, non-fault, and multiple fault states. The SVM uses features obtained from a small number of sensors, making this methodology adequate for residential AC units that typically have limited instrumentation. The proposed method is applied to the same simulated unit, which is experimentally tested in the laboratory with imposed faults, resulting in a balanced accuracy of 82% and a weighted F1-score of 84%. These results demonstrate the feasibility of training a fault detection and diagnosis algorithm with simulation data without requiring an extensive experimental campaign.
{"title":"Fault detection and diagnosis algorithm for multiple simultaneous faults in residential air-conditioning systems: Development, validation study and critical analysis","authors":"Belén Llopis-Mengual ,&nbsp;David P. Yuill ,&nbsp;Emilio Navarro-Peris","doi":"10.1016/j.applthermaleng.2025.125975","DOIUrl":"10.1016/j.applthermaleng.2025.125975","url":null,"abstract":"<div><div>Detecting and diagnosing faults in residential air conditioning (AC) systems is crucial for preventing critical failures and ensuring efficient operation. Some of these soft faults are refrigerant undercharge (UC), overcharge (OC), inadequate evaporator airflow (EA), or liquid line restrictions (LL). Data-driven methodologies have proven effective in achieving reliable detection but require a large amount of data. This paper proposes utilizing a model based on vapor compression cycles capable of simulating a wide range of indoor/outdoor operating conditions and faults imposed individually and several co-occurring (multiple combinations) for a residential AC unit. This simulated dataset is used to train a Support Vector Machine (SVM) classification algorithm to distinguish between fault, non-fault, and multiple fault states. The SVM uses features obtained from a small number of sensors, making this methodology adequate for residential AC units that typically have limited instrumentation. The proposed method is applied to the same simulated unit, which is experimentally tested in the laboratory with imposed faults, resulting in a balanced accuracy of 82% and a weighted F1-score of 84%. These results demonstrate the feasibility of training a fault detection and diagnosis algorithm with simulation data without requiring an extensive experimental campaign.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125975"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Performance analysis of heat extraction in a multi-well EGS using a DFN-based modeling scheme
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125988
Xinxin Li, Junchao Wang, Cheng Du, Jin Luo, Wenping Gong
Enhanced geothermal system is currently the most efficient technology for extracting geothermal energy from deep earth, utilizing the heat exchange between circulating fluids and high-temperature rock reservoirs. However, accurately modeling fluid flow and heat transfer within a multi-well enhanced geothermal system, characterized by a large-scale porous rock matrix, densely distributed fracture networks, and highly varying well configurations, poses significant computational challenges. Moreover, the subsequent evaluation of geothermal energy for various multi-well arrangement modes may bring about additional complexity and uncertainty, particularly in economic analysis. In this study, a discrete fracture network-based modeling scheme is developed to simulate fluid flow and heat transfer behaviors in multi-well enhanced geothermal system containing multiple main wells, multiple lateral wells, rock matrix and complex fracture networks. Based on the developed model, different well layouts for 7 scenarios totaling 41 cases are employed to assess how geometric parameters (number, spacing, length and diameter) of both main and lateral wells influence the heat extraction performance. The results indicate that increasing the number and length of wells improves heat production efficiency but shortens the lifetime of the system. In contrast, increased well spacing has the opposite effect, while well diameter has a negligible effect. From both economic and environmental perspectives, the well configuration consisting of three injection and two production wells represents the most optimal scenario owing to its lowest levelized cost of electricity, accompanied by a substantial reduction in greenhouse gas emissions by 0.543–1.877 Mt.
{"title":"Performance analysis of heat extraction in a multi-well EGS using a DFN-based modeling scheme","authors":"Xinxin Li,&nbsp;Junchao Wang,&nbsp;Cheng Du,&nbsp;Jin Luo,&nbsp;Wenping Gong","doi":"10.1016/j.applthermaleng.2025.125988","DOIUrl":"10.1016/j.applthermaleng.2025.125988","url":null,"abstract":"<div><div>Enhanced geothermal system is currently the most efficient technology for extracting geothermal energy from deep earth, utilizing the heat exchange between circulating fluids and high-temperature rock reservoirs. However, accurately modeling fluid flow and heat transfer within a multi-well enhanced geothermal system, characterized by a large-scale porous rock matrix, densely distributed fracture networks, and highly varying well configurations, poses significant computational challenges. Moreover, the subsequent evaluation of geothermal energy for various multi-well arrangement modes may bring about additional complexity and uncertainty, particularly in economic analysis. In this study, a discrete fracture network-based modeling scheme is developed to simulate fluid flow and heat transfer behaviors in multi-well enhanced geothermal system containing multiple main wells, multiple lateral wells, rock matrix and complex fracture networks. Based on the developed model, different well layouts for 7 scenarios totaling 41 cases are employed to assess how geometric parameters (number, spacing, length and diameter) of both main and lateral wells influence the heat extraction performance. The results indicate that increasing the number and length of wells improves heat production efficiency but shortens the lifetime of the system. In contrast, increased well spacing has the opposite effect, while well diameter has a negligible effect. From both economic and environmental perspectives, the well configuration consisting of three injection and two production wells represents the most optimal scenario owing to its lowest levelized cost of electricity, accompanied by a substantial reduction in greenhouse gas emissions by 0.543–1.877 Mt.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125988"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A double-ridged waveguide for low-power microwave thermal fracture cutting of low-loss glass and ceramic materials
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125985
Yuehao Ma , Fengming Yang , Shuang Song , Yang Yang , Long Gao , Huacheng Zhu
This paper proposes an innovative microwave technology-based approach for the precision cutting of low-loss materials, such as glass and alumina ceramics. A novel double-ridged waveguide is designed to optimize energy coupling and generate localized strong electric fields, thereby enhancing cutting efficiency. A multiphysics simulation model for microwave heating is established, incorporating a transformation optics algorithm to simulate the continuous movement of the waveguide’s sliding short-circuit surface during the cutting process. Simulation results show that the proposed waveguide achieves an electric field strength of 5.51 × 105 V/m at 400 W input power, resulting in a 32-fold improvement in energy coupling compared to conventional WR340 waveguides. Microwave cutting experiments on ceramics and glass are conducted and compared with WR340 waveguide heating, with the double-ridged waveguide exhibiting significantly higher heating performance, showing a 93-fold increase in maximum temperature rise. This enables the precise cutting of alumina ceramics and glass sheets. A microwave heating simulation analysis of the temperature distribution on the cutting cross-section reveals that the heat source is concentrated in the center of the section, showing a more uniform and symmetrical temperature distribution compared to traditional thermal cutting. This study not only demonstrates the efficacy of the double-ridged waveguide in generating high-intensity electric fields but also offers a promising solution for low-power thermal fracture cutting of brittle materials, providing new insights for the future of advanced manufacturing technologies.
{"title":"A double-ridged waveguide for low-power microwave thermal fracture cutting of low-loss glass and ceramic materials","authors":"Yuehao Ma ,&nbsp;Fengming Yang ,&nbsp;Shuang Song ,&nbsp;Yang Yang ,&nbsp;Long Gao ,&nbsp;Huacheng Zhu","doi":"10.1016/j.applthermaleng.2025.125985","DOIUrl":"10.1016/j.applthermaleng.2025.125985","url":null,"abstract":"<div><div>This paper proposes an innovative microwave technology-based approach for the precision cutting of low-loss materials, such as glass and alumina ceramics. A novel double-ridged waveguide is designed to optimize energy coupling and generate localized strong electric fields, thereby enhancing cutting efficiency. A multiphysics simulation model for microwave heating is established, incorporating a transformation optics algorithm to simulate the continuous movement of the waveguide’s sliding short-circuit surface during the cutting process. Simulation results show that the proposed waveguide achieves an electric field strength of 5.51 × 10<sup>5</sup> V/m at 400 W input power, resulting in a 32-fold improvement in energy coupling compared to conventional WR340 waveguides. Microwave cutting experiments on ceramics and glass are conducted and compared with WR340 waveguide heating, with the double-ridged waveguide exhibiting significantly higher heating performance, showing a 93-fold increase in maximum temperature rise. This enables the precise cutting of alumina ceramics and glass sheets. A microwave heating simulation analysis of the temperature distribution on the cutting cross-section reveals that the heat source is concentrated in the center of the section, showing a more uniform and symmetrical temperature distribution compared to traditional thermal cutting. This study not only demonstrates the efficacy of the double-ridged waveguide in generating high-intensity electric fields but also offers a promising solution for low-power thermal fracture cutting of brittle materials, providing new insights for the future of advanced manufacturing technologies.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"268 ","pages":"Article 125985"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Investigation on hydrodynamic characteristic and flow instability in regenerative cooling channels
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125983
Wendi Du, Yu Pan, Ning Wang, Kai Yang
Flow instability poses a significant risk of structural failure in regenerative cooling channels. To investigate dynamic behaviors under supercritical pressure, a one-dimensional transient model based on the finite volume method is developed. After validating the flow resistance model and instability boundary prediction, a single channel, consisting of connected and uniformly heated sections, is modeled using n-Decane as the coolant. By analyzing friction loss and acceleration effect, the multi-valued characteristic between pressure drop and mass flow rate is demonstrated, with particular emphasis on the impact of the acceleration effect. The results, obtained under four inlet temperatures and six heat flux conditions, indicate that the outlet temperature is close to each other for different local minimum points. At varying initial flow rates, flow behaviors following pressure perturbations are investigated. Consequently, the hydrodynamic characteristic curve is divided into five regions based on flow behaviors: backflow, interaction of density wave oscillation and Ledinegg instability, density wave oscillation, Ledinegg instability, and stable state. Two types of oscillations, with periods of 2.480 s and 0.908 s, are observed. The feasibility of these classifications is further validated by varying the driving force. Additionally, the effects of inlet and outlet local losses on system stability are investigated. The outlet local losses at varying flow rates exhibit a multi-valued characteristic, which can be mitigated by tripling the inlet local losses. To analyze the cause of the negative slope region, a formula based on linear assumptions is proposed with reasonable accuracy and efficiency. For inlet local losses, the monotonic variation for flow rates effectively mitigates the negative slope of the hydrodynamic characteristic curve and dynamic instability simultaneously.
{"title":"Investigation on hydrodynamic characteristic and flow instability in regenerative cooling channels","authors":"Wendi Du,&nbsp;Yu Pan,&nbsp;Ning Wang,&nbsp;Kai Yang","doi":"10.1016/j.applthermaleng.2025.125983","DOIUrl":"10.1016/j.applthermaleng.2025.125983","url":null,"abstract":"<div><div>Flow instability poses a significant risk of structural failure in regenerative cooling channels. To investigate dynamic behaviors under supercritical pressure, a one-dimensional transient model based on the finite volume method is developed. After validating the flow resistance model and instability boundary prediction, a single channel, consisting of connected and uniformly heated sections, is modeled using n-Decane as the coolant. By analyzing friction loss and acceleration effect, the multi-valued characteristic between pressure drop and mass flow rate is demonstrated, with particular emphasis on the impact of the acceleration effect. The results, obtained under four inlet temperatures and six heat flux conditions, indicate that the outlet temperature is close to each other for different local minimum points. At varying initial flow rates, flow behaviors following pressure perturbations are investigated. Consequently, the hydrodynamic characteristic curve is divided into five regions based on flow behaviors: backflow, interaction of density wave oscillation and Ledinegg instability, density wave oscillation, Ledinegg instability, and stable state. Two types of oscillations, with periods of 2.480 s and 0.908 s, are observed. The feasibility of these classifications is further validated by varying the driving force. Additionally, the effects of inlet and outlet local losses on system stability are investigated. The outlet local losses at varying flow rates exhibit a multi-valued characteristic, which can be mitigated by tripling the inlet local losses. To analyze the cause of the negative slope region, a formula based on linear assumptions is proposed with reasonable accuracy and efficiency. For inlet local losses, the monotonic variation for flow rates effectively mitigates the negative slope of the hydrodynamic characteristic curve and dynamic instability simultaneously.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125983"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A numerical approach to enhance the performance of double-pass solar collectors with finned photovoltaic/thermal integration
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125974
Mohammed El Hadi Attia , Moataz M. Abdel-Aziz , Abdelkrim Khelifa
The increasing demand for sustainable energy solutions underscores the importance of optimizing photovoltaic (PV) systems to enhance energy efficiency and output. This study addresses the challenge of excessive heat in PV systems, which adversely impacts their performance, by investigating an innovative integration of finned photovoltaic-thermal (PVT) panels with a double-pass solar water collector. The research compares two configurations: a standard PV module without thermal enhancements and an optimized PVT system incorporating fins and a double-pass collector for improved thermal management. Numerical simulations were conducted using PV panels of standardized dimensions (54 cm × 120 cm) with controlled water circulation at a flow rate of 0.01 kg/s. Results demonstrate that the optimized PVT system achieves an average thermal power output of 994.45 W, a 48.6 % increase over the standard setup (669.15 W), and an electrical power output of 60.52 W, reflecting an 8.61 % improvement. The optimized system also exhibits a significant boost in thermal efficiency, reaching 61.00 %, compared to 40.37 % for the conventional configuration, alongside enhanced electrical efficiency of 14.57 %, up from 13.63 %. These findings highlight the efficacy of the innovative design in reducing operating temperatures and improving energy conversion rates. This study offers a novel approach by integrating fins and a double-pass collector in PVT systems, advancing the literature on solar energy technologies and demonstrating practical improvements in energy efficiency. The results underline the potential of enhanced thermal management to drive advancements in renewable energy applications.
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引用次数: 0
Beyond traditional PV system: An annual study on incorporating thermal, phase change material, and thermoelectric generator technologies for performance optimization under various climatic conditions
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125967
Z. Benseddik , M. Mortadi , A. Derraz , M. Ahachad , H. Radoine , M. Mahdaoui
Photovoltaic (PV) systems play a pivotal role in the global transition to sustainable energy systems and reducing greenhouse gas emissions. The enhancement of the systems’ electrical performance has been an intriguing research topic addressed through the development of various cooling technologies. However, the evaluation of these technologies under dissimilar real-world operating conditions to support informed decision-making remains limited, leading to mixed conclusions about their actual potential. This study conducts a year-round assessment of common PV cooling technologies—Phase Change Material (PCM), Thermal Absorber (TA), and Thermoelectric Generators (TEG)—across diverse climates (cold to desert). Six configurations were tested: PV-only, PV-PCM, PV-TEG, PVT, PVT-TEG, and PVT-PCM. An optimized PCM model enabled annual simulations balancing computational efficiency and accuracy, while computing cold inlet water temperature variations based on weather data. Mathematical models were developed and validated in MATLAB using hourly meteorological data. Annually, the PVT-PCM system achieved the highest total energy efficiency (83 %), outperforming other configurations. In terms of average electrical efficiencies, PVT-TEG and PV-PCM systems ranked first and second, with a range of 11.4–12.2 %. However, TEG integration was limited by insufficient temperature gradients, underscoring the need for advanced materials or cooling approaches. These findings offer key insights into the performance of optimized PV configurations across various climate conditions over a full year period.
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引用次数: 0
Investigation on the influence of structural parameters on the performance of double wall turbine blade leading edge
IF 6.1 2区 工程技术 Q2 ENERGY & FUELS Pub Date : 2025-02-17 DOI: 10.1016/j.applthermaleng.2025.125989
Zhonghao Tang , Gongnan Xie , Honglin Li , Sichen Dong , Yajie Bao , Lei Li
This paper investigates the effects of structural parameters on the cooling performance and structural strength of double wall turbine blade leading edge. A one-way coupling method was employed to perform fluid-thermal-structural analysis on the double wall leading-edge structure. First, a detailed conjugate heat transfer analysis was performed to explore the effects of impingement hole diameter, pin fin diameter, and film hole diameter on Nusselt number, cooling effectiveness, and flow resistance coefficient. Subsequently, the temperature field obtained from the heat transfer analysis was interpolated and coupled into structural strength model to analyze the impact of structural parameters on Von Mises stress. The findings reveal that impingement hole diameter has a pronounced impact on the Nusselt number of the impingement target surface, while film hole diameter significantly influences cooling effectiveness. Specifically, within a diameter range of 0.75 to 1.00, the area-averaged Nusselt number at a diameter of 0.75 is 26.54% higher than that at 1.00. At a blowing ratio of 2.5, a film hole diameter of 1.00 offers highest cooling effectiveness and the lowest pressure loss coefficient. The maximum Von Mises stress tends to increase when the temperature field boundary condition is applied to the double wall leading edge, although the thermal expansion of the outer wall can partially offset the compressive stress. Moreover, the average Von Mises stress increases with larger impingement and film hole diameters but decreases with larger pin fin diameters. Considering the cooling performance and structural strength, within the parameter range studied, the double-wall leading edge structure has better comprehensive performance under high blowing ratio when the impingement hole diameter, pin fin diameter and film hole diameter are 0.75, 1.00 and 1.00 respectively.
{"title":"Investigation on the influence of structural parameters on the performance of double wall turbine blade leading edge","authors":"Zhonghao Tang ,&nbsp;Gongnan Xie ,&nbsp;Honglin Li ,&nbsp;Sichen Dong ,&nbsp;Yajie Bao ,&nbsp;Lei Li","doi":"10.1016/j.applthermaleng.2025.125989","DOIUrl":"10.1016/j.applthermaleng.2025.125989","url":null,"abstract":"<div><div>This paper investigates the effects of structural parameters on the cooling performance and structural strength of double wall turbine blade leading edge. A one-way coupling method was employed to perform fluid-thermal-structural analysis on the double wall leading-edge structure. First, a detailed conjugate heat transfer analysis was performed to explore the effects of impingement hole diameter, pin fin diameter, and film hole diameter on Nusselt number, cooling effectiveness, and flow resistance coefficient. Subsequently, the temperature field obtained from the heat transfer analysis was interpolated and coupled into structural strength model to analyze the impact of structural parameters on Von Mises stress. The findings reveal that impingement hole diameter has a pronounced impact on the Nusselt number of the impingement target surface, while film hole diameter significantly influences cooling effectiveness. Specifically, within a diameter range of 0.75 to 1.00, the area-averaged Nusselt number at a diameter of 0.75 is 26.54% higher than that at 1.00. At a blowing ratio of 2.5, a film hole diameter of 1.00 offers highest cooling effectiveness and the lowest pressure loss coefficient. The maximum Von Mises stress tends to increase when the temperature field boundary condition is applied to the double wall leading edge, although the thermal expansion of the outer wall can partially offset the compressive stress. Moreover, the average Von Mises stress increases with larger impingement and film hole diameters but decreases with larger pin fin diameters. Considering the cooling performance and structural strength, within the parameter range studied, the double-wall leading edge structure has better comprehensive performance under high blowing ratio when the impingement hole diameter, pin fin diameter and film hole diameter are 0.75, 1.00 and 1.00 respectively.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125989"},"PeriodicalIF":6.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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Applied Thermal Engineering
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