Pub Date : 2026-01-12DOI: 10.1016/j.applthermaleng.2026.129760
Ina Jeong , Seongpil An , Changwoo Kang
The thermal behaviors of the LiFePO4 battery are examined to understand how C-rate and convective heat transfer rate (h) influence thermal stability. A heat generation model, including side reaction heat, is utilized for numerical simulations. Temperature behaviors and the onset of thermal runaway are studied under different C-rates and convective heat transfer coefficients. The thermal stability is categorized into three levels to assess battery safety. When thermal runaway occurs, the onset time and peak temperature are analyzed to evaluate stability. The contributions from each heat source are also measured. Side reactions start above 8C during charging and above 10C during discharging, while thermal runaway happens above 10C and 12C for charging and discharging, respectively. Higher C-rates and lower convective heat transfer coefficients reduce thermal safety. Furthermore, electro-thermal heat is the main heat source before thermal runaway, whereas the heat from reaction between the cathode and electrolyte dominates afterward until the maximum temperature is reached.
{"title":"Thermal runaway behaviors in 18,650 LiFePO4 batteries under high C-rate charge/discharge operations","authors":"Ina Jeong , Seongpil An , Changwoo Kang","doi":"10.1016/j.applthermaleng.2026.129760","DOIUrl":"10.1016/j.applthermaleng.2026.129760","url":null,"abstract":"<div><div>The thermal behaviors of the LiFePO<sub>4</sub> battery are examined to understand how C-rate and convective heat transfer rate (<em>h</em>) influence thermal stability. A heat generation model, including side reaction heat, is utilized for numerical simulations. Temperature behaviors and the onset of thermal runaway are studied under different C-rates and convective heat transfer coefficients. The thermal stability is categorized into three levels to assess battery safety. When thermal runaway occurs, the onset time and peak temperature are analyzed to evaluate stability. The contributions from each heat source are also measured. Side reactions start above 8C during charging and above 10C during discharging, while thermal runaway happens above 10C and 12C for charging and discharging, respectively. Higher C-rates and lower convective heat transfer coefficients reduce thermal safety. Furthermore, electro-thermal heat is the main heat source before thermal runaway, whereas the heat from reaction between the cathode and electrolyte dominates afterward until the maximum temperature is reached.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129760"},"PeriodicalIF":6.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975298","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 : 2026-01-12DOI: 10.1016/j.applthermaleng.2026.129781
Shiyu Lai , Tieyu Gao , Xiangrui Meng , Zhihui Zhang , Jianying Gong , Lulu Zhu
The fourth-generation nuclear systems are vital to global energy transition and sustainable development. This study introduces rib structures into a helium-cooling printed circuit heat exchanger to investigate the effects of rib arrangements on thermal-hydraulic characteristics by numerical simulation combined with a multi-objective optimization algorithm. Based on previous operating conditions, the Reynolds number ranges from 450 to 5300, the inlet temperatures of the hot and cold channels are 823.15 K and 473.15 K, and the system pressure is 3 MPa. Results show that, the transverse ribs exhibit the optimal thermal performance, followed by the hybrid and longitudinal configurations. Distinct mechanisms are observed: smaller vortices dominate around the longitudinal ribs, whereas in the transverse channel, persistent large vortices (T₃) form a heart-shaped high turbulence kinetic energy region and exhibit an enhanced field synergy effect. To further identify the optimal rib parameters, the correlations between rib dimensions (l, w and h) and Nusselt number and friction factor are established. Four optimized configurations (A-D) are obtained using a multi-objective optimization algorithm. The rib geometry exhibits an evolutionary trend, and the concept of a flow rate dominance region is proposed to describe the optimal balance among different thermal objectives. Moreover, the performance of the optimized configurations is examined to extend the evaluation to a broader flow range (10–80 kg/h), showing stable and significant enhancement. Configuration C demonstrates the best overall performance with the PEC increased by 97.35%, while configuration D achieves the highest heat exchanger effectiveness improvement of 18.07%, together with a system efficiency gain of 41.21% and a compactness enhancement of 29.18%. These findings elucidate that the thermal-hydraulic characteristics of helium in PCHE ribbed channels, providing a methodological guidance for high efficiency heat exchanger designs.
{"title":"Numerical study and multi-objective optimization of helium-cooled printed circuit heat exchangers with ribs","authors":"Shiyu Lai , Tieyu Gao , Xiangrui Meng , Zhihui Zhang , Jianying Gong , Lulu Zhu","doi":"10.1016/j.applthermaleng.2026.129781","DOIUrl":"10.1016/j.applthermaleng.2026.129781","url":null,"abstract":"<div><div>The fourth-generation nuclear systems are vital to global energy transition and sustainable development. This study introduces rib structures into a helium-cooling printed circuit heat exchanger to investigate the effects of rib arrangements on thermal-hydraulic characteristics by numerical simulation combined with a multi-objective optimization algorithm. Based on previous operating conditions, the Reynolds number ranges from 450 to 5300, the inlet temperatures of the hot and cold channels are 823.15 K and 473.15 K, and the system pressure is 3 MPa. Results show that, the transverse ribs exhibit the optimal thermal performance, followed by the hybrid and longitudinal configurations. Distinct mechanisms are observed: smaller vortices dominate around the longitudinal ribs, whereas in the transverse channel, persistent large vortices (T₃) form a heart-shaped high turbulence kinetic energy region and exhibit an enhanced field synergy effect. To further identify the optimal rib parameters, the correlations between rib dimensions (<em>l</em>, <em>w</em> and <em>h</em>) and Nusselt number and friction factor are established. Four optimized configurations (A-D) are obtained using a multi-objective optimization algorithm. The rib geometry exhibits an evolutionary trend, and the concept of a flow rate dominance region is proposed to describe the optimal balance among different thermal objectives. Moreover, the performance of the optimized configurations is examined to extend the evaluation to a broader flow range (10–80 kg/h), showing stable and significant enhancement. Configuration C demonstrates the best overall performance with the PEC increased by 97.35%, while configuration D achieves the highest heat exchanger effectiveness improvement of 18.07%, together with a system efficiency gain of 41.21% and a compactness enhancement of 29.18%. These findings elucidate that the thermal-hydraulic characteristics of helium in PCHE ribbed channels, providing a methodological guidance for high efficiency heat exchanger designs.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129781"},"PeriodicalIF":6.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975244","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 : 2026-01-12DOI: 10.1016/j.applthermaleng.2026.129791
Muyao Wu , Changpeng Tan , Li Wang
The strong cross-coupling among electrical, thermal, and mechanical behaviors in lithium-ion batteries pose significant challenges to accurate dynamic mathematical characterization. The core innovation lies in developing an incremental integration of existing electro, thermal, mechanical models, to dynamically characterize of electro-thermal-mechanical coupling behaviors of lithium-ion batteries. The electrical behaviors are captured by a first-order RC equivalent circuit model, the thermal behaviors are captured by a lumped-parameter thermal model, and the mechanical behaviors are captured by an equivalent strain model based on the solid-state diffusion theory and the thermal expansion theory. The coupling model parameters are identified online via the Forgetting Factor Recursive Least Squares. Experimental results under FUDS and WLTC, across various ambient temperatures and battery aging levels indicate that, the Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) of the voltage estimation results remain below 20 mV and 35 mV, the MAE and RMSE of the temperature estimation results remain below 0.1 °C and 0.15 °C, the MAE and RMSE of the strain estimation results remain below 2.5 and 3.0. Furthermore, the more innovation conclusion is that, the thermal resistance exhibits an overall increasing trend as the battery aging, but no clear dependence of it on the ambient temperature is identified. The dynamic temperature strain coefficient shows a notable dependence on the battery aging level, the average standard deviations of the it for fresh and aged batteries are 0.12 and 0.25, respectively, representing a more than twofold difference. In contrast, the dynamic SOC strain coefficient does not demonstrate such a trend.
{"title":"Dynamic mathematical characterization of electro-thermo-mechanical coupling behaviors in lithium-ion batteries","authors":"Muyao Wu , Changpeng Tan , Li Wang","doi":"10.1016/j.applthermaleng.2026.129791","DOIUrl":"10.1016/j.applthermaleng.2026.129791","url":null,"abstract":"<div><div>The strong cross-coupling among electrical, thermal, and mechanical behaviors in lithium-ion batteries pose significant challenges to accurate dynamic mathematical characterization. The core innovation lies in developing an incremental integration of existing electro, thermal, mechanical models, to dynamically characterize of electro-thermal-mechanical coupling behaviors of lithium-ion batteries. The electrical behaviors are captured by a first-order RC equivalent circuit model, the thermal behaviors are captured by a lumped-parameter thermal model, and the mechanical behaviors are captured by an equivalent strain model based on the solid-state diffusion theory and the thermal expansion theory. The coupling model parameters are identified online via the Forgetting Factor Recursive Least Squares. Experimental results under FUDS and WLTC, across various ambient temperatures and battery aging levels indicate that, the Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) of the voltage estimation results remain below 20 mV and 35 mV, the MAE and RMSE of the temperature estimation results remain below 0.1 °C and 0.15 °C, the MAE and RMSE of the strain estimation results remain below 2.5<span><math><mi>με</mi></math></span> and 3.0<span><math><mi>με</mi></math></span>. Furthermore, the more innovation conclusion is that, the thermal resistance exhibits an overall increasing trend as the battery aging, but no clear dependence of it on the ambient temperature is identified. The dynamic temperature strain coefficient shows a notable dependence on the battery aging level, the average standard deviations of the it for fresh and aged batteries are 0.12<span><math><mi>με</mi></math></span> and 0.25<span><math><mi>με</mi></math></span>, respectively, representing a more than twofold difference. In contrast, the dynamic SOC strain coefficient does not demonstrate such a trend.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129791"},"PeriodicalIF":6.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975307","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 : 2026-01-12DOI: 10.1016/j.applthermaleng.2026.129783
Jie Li , Xiaobing Sun , Yiming Li , Minggao Liu , Xiaoqin Sun , Quan Zhang
Embedding metal foam into phase change materials is an effective approach to enhance the thermal performance of latent heat thermal energy storage systems. However, heat transfer mismatches caused by coupling between conduction and natural convection remain a challenge. Unlike most existing studies focusing on uniform or one-dimensional porosity-gradient structures, this work investigates the effect of the inclination angle of the porosity-gradient interface on melting behavior and heat transfer performance. A three-dimensional pore-scale numerical simulation is employed to analyze the melting process of gradient-porosity metal foam composite PCMs. The effects of the inclination angle (θ), porosity gradient magnitude (Δε), and thermal energy storage temperature difference (ΔT) are evaluated. The results show that melting performance first improves and then deteriorates with increasing inclination angle, with optimal performance at θ = 30°. Compared with a uniform-porosity structure, this configuration reduces the total melting time by 12.16% and increases the thermal energy storage rate by 11.66% by suppressing melting dead zones and improving the balance between heat conduction and natural convection. The effect of porosity gradient depends strongly on interface orientation: a moderate gradient (Δε = 0.12) is optimal for θ = 0° and 30°, whereas smaller gradients are preferable at θ = 90°. Increasing ΔT consistently accelerates melting, for the optimal structure (θ = 30°, Δε = 0.12), increasing ΔT from 25 K to 40 K reduces melting time by 29.06% and enhances the energy storage rate by 55.14%. Overall, this study provides new insight into pore-scale heat transfer regulation in gradient-porosity LHTES structures and offers practical guidance for optimal design.
{"title":"Melting performance of gradient-porosity metal foam composite phase change materials: A pore-scale numerical study","authors":"Jie Li , Xiaobing Sun , Yiming Li , Minggao Liu , Xiaoqin Sun , Quan Zhang","doi":"10.1016/j.applthermaleng.2026.129783","DOIUrl":"10.1016/j.applthermaleng.2026.129783","url":null,"abstract":"<div><div>Embedding metal foam into phase change materials is an effective approach to enhance the thermal performance of latent heat thermal energy storage systems. However, heat transfer mismatches caused by coupling between conduction and natural convection remain a challenge. Unlike most existing studies focusing on uniform or one-dimensional porosity-gradient structures, this work investigates the effect of the inclination angle of the porosity-gradient interface on melting behavior and heat transfer performance. A three-dimensional pore-scale numerical simulation is employed to analyze the melting process of gradient-porosity metal foam composite PCMs. The effects of the inclination angle (<em>θ</em>), porosity gradient magnitude (Δ<em>ε</em>), and thermal energy storage temperature difference (Δ<em>T</em>) are evaluated. The results show that melting performance first improves and then deteriorates with increasing inclination angle, with optimal performance at <em>θ</em> = 30°. Compared with a uniform-porosity structure, this configuration reduces the total melting time by 12.16% and increases the thermal energy storage rate by 11.66% by suppressing melting dead zones and improving the balance between heat conduction and natural convection. The effect of porosity gradient depends strongly on interface orientation: a moderate gradient (Δ<em>ε</em> = 0.12) is optimal for <em>θ</em> = 0° and 30°, whereas smaller gradients are preferable at <em>θ</em> = 90°. Increasing Δ<em>T</em> consistently accelerates melting, for the optimal structure (<em>θ</em> = 30°, Δ<em>ε</em> = 0.12), increasing ΔT from 25 K to 40 K reduces melting time by 29.06% and enhances the energy storage rate by 55.14%. Overall, this study provides new insight into pore-scale heat transfer regulation in gradient-porosity LHTES structures and offers practical guidance for optimal design.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129783"},"PeriodicalIF":6.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974993","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 : 2026-01-12DOI: 10.1016/j.applthermaleng.2026.129777
Chaocheng Zhao , Guangtao Ni , Wei Han , Ming Liu , Zhenzhen Wang , Junjie Yan
Compressed air energy storage (CAES) is a promising technology for large-scale energy storage, where operational flexibility is critical for accommodating high penetration of intermittent renewable energy in modern power grids. This study systematically investigates a CAES system integrated with molten salt thermal storage, with particular emphasis on flexibility enhancement and efficiency improvement under partial-load and off-design conditions. An intrinsically flexible CAES configuration featuring four operation modes—corresponding to high, upper-middle, lower-middle, and low power output—is proposed, and key design parameters are optimized to improve energy efficiency during partial-load operation. When the pressure of the air storage cavern drops below the design value, rated output power is maintained through air injection. This enables full-load operation and high round-trip efficiency (RTE) even under low cavern pressure conditions, significantly enhancing operational flexibility and extending the effective operating pressure range of the cavern. Off-design thermodynamic models are developed, and air consumption together with exergy loss distribution are employed to evaluate system performance. The results demonstrate that the air injection location plays a critical role in the upper-middle power operation mode. When the injection point is located at the outlet of expander E1, the system can sustain rated output power at 50% of the design cavern pressure, achieving a minimum average air consumption of 48.34 kg/s and a maximum RTE of 59.23%. At this condition, the exergy loss of the combustion chamber is also minimized to 32.01 MW, and the lowest air consumption coincides with the highest RTE. By contrast, the air injection location has a less pronounced influence on the lower-middle power operation mode. The system remains capable of full-load operation at 60% of the design cavern pressure. The minimum average air consumption of 30.45 kg/s occurs when the injection point is located at 8 MPa, whereas the maximum RTE of 78.74% is achieved at the outlet of expander E4. In this case, the minimum air consumption does not correspond to the maximum RTE.
{"title":"Operational flexibility enhancement for the compressed air energy storage system integrated with molten salt thermal energy storage","authors":"Chaocheng Zhao , Guangtao Ni , Wei Han , Ming Liu , Zhenzhen Wang , Junjie Yan","doi":"10.1016/j.applthermaleng.2026.129777","DOIUrl":"10.1016/j.applthermaleng.2026.129777","url":null,"abstract":"<div><div>Compressed air energy storage (CAES) is a promising technology for large-scale energy storage, where operational flexibility is critical for accommodating high penetration of intermittent renewable energy in modern power grids. This study systematically investigates a CAES system integrated with molten salt thermal storage, with particular emphasis on flexibility enhancement and efficiency improvement under partial-load and off-design conditions. An intrinsically flexible CAES configuration featuring four operation modes—corresponding to high, upper-middle, lower-middle, and low power output—is proposed, and key design parameters are optimized to improve energy efficiency during partial-load operation. When the pressure of the air storage cavern drops below the design value, rated output power is maintained through air injection. This enables full-load operation and high round-trip efficiency (RTE) even under low cavern pressure conditions, significantly enhancing operational flexibility and extending the effective operating pressure range of the cavern. Off-design thermodynamic models are developed, and air consumption together with exergy loss distribution are employed to evaluate system performance. The results demonstrate that the air injection location plays a critical role in the upper-middle power operation mode. When the injection point is located at the outlet of expander E1, the system can sustain rated output power at 50% of the design cavern pressure, achieving a minimum average air consumption of 48.34 kg/s and a maximum RTE of 59.23%. At this condition, the exergy loss of the combustion chamber is also minimized to 32.01 MW, and the lowest air consumption coincides with the highest RTE. By contrast, the air injection location has a less pronounced influence on the lower-middle power operation mode. The system remains capable of full-load operation at 60% of the design cavern pressure. The minimum average air consumption of 30.45 kg/s occurs when the injection point is located at 8 MPa, whereas the maximum RTE of 78.74% is achieved at the outlet of expander E4. In this case, the minimum air consumption does not correspond to the maximum RTE.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129777"},"PeriodicalIF":6.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975245","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 : 2026-01-11DOI: 10.1016/j.applthermaleng.2026.129769
Jianchen Wang , Lichuan Zhang , Meng Han , Haoqi Ren , Chi Zhang , Quanhong Xu
This study experimentally investigates self-excited azimuthal instabilities in a full-scale annular reverse-flow combustor for micro gas turbines, featuring arrayed micro-tubes designed for hydrogen micro-diffusion flames. The results characterize a distinct instability region (Φ ≈ 0.26–0.41) where pressure pulsation amplitudes initially rise and subsequently fall, reaching a peak of approximately 1.9 kPa. The dominant instability frequency (≈ 0.9–1.3 kHz) exhibits a strong linear correlation with the square root of the adiabatic flame temperature, which, supported by Helmholtz solver results, confirms that the resonance mechanism comprises both 1 A (azimuthal) and 1 L (longitudinal) components. Although the instability physically manifests as a mixed 1A1L mode, this study focuses on the azimuthal dynamics and modal transitions inherent to the annular architecture. A prominent feature is the path-dependent hysteresis observed in modal symmetry breaking. Specifically, the instability onset during the ascending path is marked by a transition from ST to CW, while the cessation during the descending path involves a transition from CCW to ST. This path dependence suggests that intrinsic nonlinear dynamics play a critical role in mode selection, potentially overriding fixed geometrical asymmetries in the developed instability regime. Additionally, transient analysis identifies distinct dynamic states within the high-amplitude region: a quasi-stable state during ascension and a large-amplitude periodic switching state during descension. The latter provides experimental evidence of slow-fast dynamic coupling, where a low-frequency physical process (≈ 11 Hz) periodically modulates the high-frequency acoustic oscillations (≈ 1.17 kHz). These findings, likely influenced by the specific hydrogen flame characteristics and intrinsic convective timescales, provide an experimental data and reference for the investigation of azimuthal combustion instabilities and modal transitions in hydrogen annular combustors.
{"title":"Experimental investigation of azimuthal instability characteristics in a hydrogen annular combustor","authors":"Jianchen Wang , Lichuan Zhang , Meng Han , Haoqi Ren , Chi Zhang , Quanhong Xu","doi":"10.1016/j.applthermaleng.2026.129769","DOIUrl":"10.1016/j.applthermaleng.2026.129769","url":null,"abstract":"<div><div>This study experimentally investigates self-excited azimuthal instabilities in a full-scale annular reverse-flow combustor for micro gas turbines, featuring arrayed micro-tubes designed for hydrogen micro-diffusion flames. The results characterize a distinct instability region (<em>Φ</em> ≈ 0.26–0.41) where pressure pulsation amplitudes initially rise and subsequently fall, reaching a peak of approximately 1.9 kPa. The dominant instability frequency (≈ 0.9–1.3 kHz) exhibits a strong linear correlation with the square root of the adiabatic flame temperature, which, supported by Helmholtz solver results, confirms that the resonance mechanism comprises both 1 A (azimuthal) and 1 L (longitudinal) components. Although the instability physically manifests as a mixed 1A1L mode, this study focuses on the azimuthal dynamics and modal transitions inherent to the annular architecture. A prominent feature is the path-dependent hysteresis observed in modal symmetry breaking. Specifically, the instability onset during the ascending path is marked by a transition from ST to CW, while the cessation during the descending path involves a transition from CCW to ST. This path dependence suggests that intrinsic nonlinear dynamics play a critical role in mode selection, potentially overriding fixed geometrical asymmetries in the developed instability regime. Additionally, transient analysis identifies distinct dynamic states within the high-amplitude region: a quasi-stable state during ascension and a large-amplitude periodic switching state during descension. The latter provides experimental evidence of slow-fast dynamic coupling, where a low-frequency physical process (≈ 11 Hz) periodically modulates the high-frequency acoustic oscillations (≈ 1.17 kHz). These findings, likely influenced by the specific hydrogen flame characteristics and intrinsic convective timescales, provide an experimental data and reference for the investigation of azimuthal combustion instabilities and modal transitions in hydrogen annular combustors.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129769"},"PeriodicalIF":6.9,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975241","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 : 2026-01-11DOI: 10.1016/j.applthermaleng.2026.129752
Mingxuan Hao , Fan Zhang , Nanpei Li , Zelinlan Wang , Yixiao Liu , Zhihong Rao , Jinghui Ling , Kai Chen , Ruiqi Wang , Dongliang Guo , Junfeng Li , YongAn Huang
The optimal hydrodynamic performance of autonomous underwater vehicles in complex flow fields is critically dependent on the dynamic power density of their propulsion motors, demanding active regulation of heat dissipation guided by advanced thermal monitoring and intelligent cooling technologies. To meet this demand, an intelligent flexible sensing system deployed on motor surfaces for active flow control is introduced, which integrates precise flow-field sensing with adaptive hydrodynamic regulation. By acquiring regional coolant flow information via flexible dual-mode sensing skins, the system generates real-time actuation commands to adjust the angle of attack of vortex generator arrays, thereby enhancing local heat transfer through the induction of longitudinal vortices. Compared to the conventional forced undisturbed water-cooling baseline (flat wall, no vortex generator arrays), the proposed approach achieves up to a 25.4% improvement in cooling efficiency at a flow velocity of 6 m/s while maintaining precise and intelligent thermal control. This closed-loop sensing-actuation paradigm offers an intelligent, shape-adaptive solution for AUV thermal management and demonstrates strong potential for broader application in autonomous flow control within complex fluidic environments.
{"title":"Conformable sensing and adaptive vortex generating for active flow control of AUV propulsion systems","authors":"Mingxuan Hao , Fan Zhang , Nanpei Li , Zelinlan Wang , Yixiao Liu , Zhihong Rao , Jinghui Ling , Kai Chen , Ruiqi Wang , Dongliang Guo , Junfeng Li , YongAn Huang","doi":"10.1016/j.applthermaleng.2026.129752","DOIUrl":"10.1016/j.applthermaleng.2026.129752","url":null,"abstract":"<div><div>The optimal hydrodynamic performance of autonomous underwater vehicles in complex flow fields is critically dependent on the dynamic power density of their propulsion motors, demanding active regulation of heat dissipation guided by advanced thermal monitoring and intelligent cooling technologies. To meet this demand, an intelligent flexible sensing system deployed on motor surfaces for active flow control is introduced, which integrates precise flow-field sensing with adaptive hydrodynamic regulation. By acquiring regional coolant flow information via flexible dual-mode sensing skins, the system generates real-time actuation commands to adjust the angle of attack of vortex generator arrays, thereby enhancing local heat transfer through the induction of longitudinal vortices. Compared to the conventional forced undisturbed water-cooling baseline (flat wall, no vortex generator arrays), the proposed approach achieves up to a 25.4% improvement in cooling efficiency at a flow velocity of 6 m/s while maintaining precise and intelligent thermal control. This closed-loop sensing-actuation paradigm offers an intelligent, shape-adaptive solution for AUV thermal management and demonstrates strong potential for broader application in autonomous flow control within complex fluidic environments.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129752"},"PeriodicalIF":6.9,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974991","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 : 2026-01-11DOI: 10.1016/j.applthermaleng.2026.129716
Shen Gao , Yue Ren , Yanxing Zhao , Jiayu Zhang , Yunxiao Wang , Kun Wang , Yong Li , Jiangtao Li , Maoqiong Gong
Effective thermal management is vital for the stable operation and long-endurance flight of high-altitude platforms, but the low-pressure environment severely limits heat dissipation. To address this challenge, a novel mini-channel tube bundle heat exchanger (MCTBHE) coated with a high infrared emissivity coating was proposed. The coating, primarily composed of graphite sheets and SiO₂, exhibited a high mid-infrared emissivity (ε = 0.93). Heat dissipation performance of the proposed exchanger was experimentally evaluated in a low-pressure wind tunnel, with the pressure reduced to 5.5 kPa. The results indicated that the high infrared coating synergistically enhanced the convective and radiative heat dissipation performance of the MCTBHE. Compared with the uncoated counterpart, the coated exchanger achieved a 7.8% higher heat transfer coefficient and a 4% improvement in overall thermohydraulic performance, despite a 10.5% increase in pressure drop. Notably, under low-pressure conditions, its heat transfer coefficient was 2.6 times that of conventional designs reported in the literature while maintaining comparable resistance. This study contributes to the experimental understanding of MCTBHEs under low-pressure conditions and demonstrates the potential of coating-based approaches for improving thermal management in high-altitude platforms.
{"title":"Convection-radiation synergistically enhanced mini-channel heat exchanger via high infrared emissivity coating for high-altitude low-pressure environments","authors":"Shen Gao , Yue Ren , Yanxing Zhao , Jiayu Zhang , Yunxiao Wang , Kun Wang , Yong Li , Jiangtao Li , Maoqiong Gong","doi":"10.1016/j.applthermaleng.2026.129716","DOIUrl":"10.1016/j.applthermaleng.2026.129716","url":null,"abstract":"<div><div>Effective thermal management is vital for the stable operation and long-endurance flight of high-altitude platforms, but the low-pressure environment severely limits heat dissipation. To address this challenge, a novel mini-channel tube bundle heat exchanger (MCTBHE) coated with a high infrared emissivity coating was proposed. The coating, primarily composed of graphite sheets and SiO₂, exhibited a high mid-infrared emissivity (ε = 0.93). Heat dissipation performance of the proposed exchanger was experimentally evaluated in a low-pressure wind tunnel, with the pressure reduced to 5.5 kPa. The results indicated that the high infrared coating synergistically enhanced the convective and radiative heat dissipation performance of the MCTBHE. Compared with the uncoated counterpart, the coated exchanger achieved a 7.8% higher heat transfer coefficient and a 4% improvement in overall thermohydraulic performance, despite a 10.5% increase in pressure drop. Notably, under low-pressure conditions, its heat transfer coefficient was 2.6 times that of conventional designs reported in the literature while maintaining comparable resistance. This study contributes to the experimental understanding of MCTBHEs under low-pressure conditions and demonstrates the potential of coating-based approaches for improving thermal management in high-altitude platforms.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129716"},"PeriodicalIF":6.9,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145969005","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 : 2026-01-10DOI: 10.1016/j.applthermaleng.2026.129750
Long Zhang, Tianze Yu, Jian Zhang, Hua Zhou
The effects of flame holding chamber on the flame dynamics are numerically investigated at 100% and 50% loads in a hydrogen industrial burner under the framework of large eddy simulation and non-adiabatic flamelet generated manifold model. For combustion characteristics, the flame holding chamber is beneficial for maintaining consistency in the flow field under different loads and can form a high-temperature corner recirculation zone to promote mixing and ignition. At 50% load, the temperature in the corner recirculation zone surrounded by the flame holding chamber and swirling shear layer is about 100 K higher than other areas in the calculation domain. Chemical eigenvalue analysis shows that unstable combustion is mainly concentrated in the shear layer, with the dominant species being H, and the dominant elementary reactions being R10 () and R11 (). For combustion instability, removing the flame holding chamber can effectively alleviate pressure fluctuations and weaken combustion instability. At 100% load, the pressure fluctuation range decreases by 34%, and the FFT amplitude decreases by 80%. Singular spectrum analysis further indicates that removing the flame stabilization chamber significantly suppresses pressure fluctuations in the dominant SSA modes. The above results provide guidance for the on-site application of hydrogen industrial burners. For the scenario of long-term rated load operation (chemical furnace, metallurgical heating furnace, etc.), the application of flame holding chamber can be omitted, thereby mitigating the combustion instability. For operation scenarios requiring frequent load adjustment (civil heating furnace, drying furnace, etc.), the application of flame holding chamber should be considered to enhance the thermal intensity and flame stability in the combustion chamber during load switching.
{"title":"Numerical investigation of the effects of flame holding geometry on the flame dynamics in a hydrogen industrial burner","authors":"Long Zhang, Tianze Yu, Jian Zhang, Hua Zhou","doi":"10.1016/j.applthermaleng.2026.129750","DOIUrl":"10.1016/j.applthermaleng.2026.129750","url":null,"abstract":"<div><div>The effects of flame holding chamber on the flame dynamics are numerically investigated at 100% and 50% loads in a hydrogen industrial burner under the framework of large eddy simulation and non-adiabatic flamelet generated manifold model. For combustion characteristics, the flame holding chamber is beneficial for maintaining consistency in the flow field under different loads and can form a high-temperature corner recirculation zone to promote mixing and ignition. At 50% load, the temperature in the corner recirculation zone surrounded by the flame holding chamber and swirling shear layer is about 100 K higher than other areas in the calculation domain. Chemical eigenvalue analysis shows that unstable combustion is mainly concentrated in the shear layer, with the dominant species being H, and the dominant elementary reactions being R10 (<span><math><mi>H</mi><msub><mi>O</mi><mn>2</mn></msub><mo>+</mo><mi>H</mi><mo>⇔</mo><msub><mi>H</mi><mn>2</mn></msub><mo>+</mo><msub><mi>O</mi><mn>2</mn></msub></math></span>) and R11 (<span><math><mi>H</mi><msub><mi>O</mi><mn>2</mn></msub><mo>+</mo><mi>H</mi><mo>⇔</mo><mi>OH</mi><mo>+</mo><mi>OH</mi></math></span>). For combustion instability, removing the flame holding chamber can effectively alleviate pressure fluctuations and weaken combustion instability. At 100% load, the pressure fluctuation range decreases by 34%, and the FFT amplitude decreases by 80%. Singular spectrum analysis further indicates that removing the flame stabilization chamber significantly suppresses pressure fluctuations in the dominant SSA modes. The above results provide guidance for the on-site application of hydrogen industrial burners. For the scenario of long-term rated load operation (chemical furnace, metallurgical heating furnace, etc.), the application of flame holding chamber can be omitted, thereby mitigating the combustion instability. For operation scenarios requiring frequent load adjustment (civil heating furnace, drying furnace, etc.), the application of flame holding chamber should be considered to enhance the thermal intensity and flame stability in the combustion chamber during load switching.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129750"},"PeriodicalIF":6.9,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145969137","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 : 2026-01-10DOI: 10.1016/j.applthermaleng.2026.129774
Ying Wang , Yutong Yang , Yuxin Zhang , Jiayi Han , Jiaji Cheng , Yapeng Wang , Shaoxiang Li
This study proposes the incorporation of vanadium dioxide (VO2) nanorods with high thermal conductivity, flame retardancy, and thermally induced phase change properties into the shell layer of microcapsules, targeting the issues of poor thermal conductivity, flammability, and limited energy storage in practical applications of organic phase change microcapsules. Based on this, a modified phase change material microcapsule (V-MPCM) containing capric acid@PMMA doped with VO2 nanorods was prepared through in-situ polymerization, establishing a channel-shell-core structure. Data indicate excellent thermal stability of V-MPCM. To develop functional coatings, V-MPCM was incorporated into an epoxy resin (EP) matrix, yielding V-MPCM/EP composite coatings. Compared to existing studies, this work achieves a core breakthrough by integrating three functions—heat storage, flame retardancy, and intelligent photothermal regulation—overcoming the single-function limitation of traditional phase change materials. Results demonstrate the coating's excellent temperature regulation capability, with stable performance maintained after 100 solidification-melting cycles. Compared to pure EP, the V-MPCM/EP coating reduces peak heat release rate and total heat release rate by 12% and 24.9%, respectively. Simultaneously, it exhibits infrared reflection functionality above 68 °C, with light reflectance increased by 61%, effectively blocking solar radiation transmission into building interiors. This research provides a viable approach for developing highly efficient, energy-saving, and reliable functional coatings for buildings.
{"title":"Preparation of VO2 nanorod-modified phase change microcapsules for enhancing building's fire safety and energy management","authors":"Ying Wang , Yutong Yang , Yuxin Zhang , Jiayi Han , Jiaji Cheng , Yapeng Wang , Shaoxiang Li","doi":"10.1016/j.applthermaleng.2026.129774","DOIUrl":"10.1016/j.applthermaleng.2026.129774","url":null,"abstract":"<div><div>This study proposes the incorporation of vanadium dioxide (VO<sub>2</sub>) nanorods with high thermal conductivity, flame retardancy, and thermally induced phase change properties into the shell layer of microcapsules, targeting the issues of poor thermal conductivity, flammability, and limited energy storage in practical applications of organic phase change microcapsules. Based on this, a modified phase change material microcapsule (V-MPCM) containing capric acid@PMMA doped with VO<sub>2</sub> nanorods was prepared through in-situ polymerization, establishing a channel-shell-core structure. Data indicate excellent thermal stability of V-MPCM. To develop functional coatings, V-MPCM was incorporated into an epoxy resin (EP) matrix, yielding V-MPCM/EP composite coatings. Compared to existing studies, this work achieves a core breakthrough by integrating three functions—heat storage, flame retardancy, and intelligent photothermal regulation—overcoming the single-function limitation of traditional phase change materials. Results demonstrate the coating's excellent temperature regulation capability, with stable performance maintained after 100 solidification-melting cycles. Compared to pure EP, the V-MPCM/EP coating reduces peak heat release rate and total heat release rate by 12% and 24.9%, respectively. Simultaneously, it exhibits infrared reflection functionality above 68 °C, with light reflectance increased by 61%, effectively blocking solar radiation transmission into building interiors. This research provides a viable approach for developing highly efficient, energy-saving, and reliable functional coatings for buildings.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 129774"},"PeriodicalIF":6.9,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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