Pub Date : 2026-01-15DOI: 10.1016/j.ijheatmasstransfer.2026.128376
Gianpiero Colonna , Louis Walpot , Davide Ninni , Francesco Bonelli , Giuseppe Pascazio , Lucia Daniela Pietanza , Annarita Laricchiuta
The paper presents a multi-temperature model for H2/He mixture derived from the state-to-state kinetics. Electronically excited states have been included in the model as separate pseudo-species. The theoretical approach on the reduction of a state-specific model to multi-temperature kinetic is described in detail in the Supplementary Material, reporting also analytical fits. The model has been verified against state-to-state calculations in 0D approximation, demonstrating a good degree of accuracy. The verification has also been performed investigating the hypersonic flow past a two-dimensional capsule entering in Uranus atmosphere.
{"title":"Multi-temperature model from state-specific data for Hydrogen/Helium mixture in high-enthalpy flows","authors":"Gianpiero Colonna , Louis Walpot , Davide Ninni , Francesco Bonelli , Giuseppe Pascazio , Lucia Daniela Pietanza , Annarita Laricchiuta","doi":"10.1016/j.ijheatmasstransfer.2026.128376","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128376","url":null,"abstract":"<div><div>The paper presents a multi-temperature model for H<sub>2</sub>/He mixture derived from the state-to-state kinetics. Electronically excited states have been included in the model as separate pseudo-species. The theoretical approach on the reduction of a state-specific model to multi-temperature kinetic is described in detail in the <em>Supplementary Material</em>, reporting also analytical fits. The model has been verified against state-to-state calculations in 0D approximation, demonstrating a good degree of accuracy. The verification has also been performed investigating the hypersonic flow past a two-dimensional capsule entering in Uranus atmosphere.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128376"},"PeriodicalIF":5.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974553","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}
Particle-reinforced composites (PRCs) are widely used in electronic thermal management, energy conversion, and thermal protection. Yet, most models for predicting their effective thermal conductivity (ETC) assume uniformly dispersed, non-interacting spherical particles, overlooking the heat transfer enhancement facilitated by the presence of dimer particles (formed by two overlapping spheres). In this work, a three-dimensional composite structure containing both spherical monomers and dimer particles is established to systematically investigate the effects of the overlap ratio between the two spheres forming a dimer, the volume fraction of dimer particles, and their alignment angle on the ETC of PRCs. Numerical results show that when λp/λm >>1 and a moderate overlap ratio (γ≈0.2), dimer particles significantly enhance the ETC, yielding improvements of 12.67% at a volume fraction of 10% and 22.06% at a volume fraction of 20% compared to the configuration with only spherical monomers. The orientation of dimer particles plays a decisive role in governing the ETC. At a particle volume fraction of 10%, full alignment parallel to imposed temperature gradient increases the ETC by 26.72% relative to the random orientation, whereas perpendicular alignment results in an 13.24% decrease. Based on these findings, a geometry-dependent shape factor A is introduced into the Lewis-Nielsen model, enabling accurate prediction of composites reinforced by dimer particles with errors within 2.7%. This model is further extended to mixed configurations containing both dimer particles and spherical monomers via a “two-step homogenization” approach. This study quantitatively reveals the interplay between dimer particles and macroscopic heat conduction, and provides a directly applicable theoretical tool for the structural design and performance optimization of PRCs.
{"title":"Modeling of the effective thermal conductivity of composites containing spherical monomers and dimer particles","authors":"Chuan-Yong Zhu , Jia Wei , Xiao-Dong Wu , Liang Gong","doi":"10.1016/j.ijheatmasstransfer.2026.128380","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128380","url":null,"abstract":"<div><div>Particle-reinforced composites (PRCs) are widely used in electronic thermal management, energy conversion, and thermal protection. Yet, most models for predicting their effective thermal conductivity (ETC) assume uniformly dispersed, non-interacting spherical particles, overlooking the heat transfer enhancement facilitated by the presence of dimer particles (formed by two overlapping spheres). In this work, a three-dimensional composite structure containing both spherical monomers and dimer particles is established to systematically investigate the effects of the overlap ratio between the two spheres forming a dimer, the volume fraction of dimer particles, and their alignment angle on the ETC of PRCs. Numerical results show that when <em>λ</em><sub>p</sub>/<em>λ</em><sub>m</sub> >>1 and a moderate overlap ratio (<em>γ</em>≈0.2), dimer particles significantly enhance the ETC, yielding improvements of 12.67% at a volume fraction of 10% and 22.06% at a volume fraction of 20% compared to the configuration with only spherical monomers. The orientation of dimer particles plays a decisive role in governing the ETC. At a particle volume fraction of 10%, full alignment parallel to imposed temperature gradient increases the ETC by 26.72% relative to the random orientation, whereas perpendicular alignment results in an 13.24% decrease. Based on these findings, a geometry-dependent shape factor <em>A</em> is introduced into the Lewis-Nielsen model, enabling accurate prediction of composites reinforced by dimer particles with errors within 2.7%. This model is further extended to mixed configurations containing both dimer particles and spherical monomers via a “two-step homogenization” approach. This study quantitatively reveals the interplay between dimer particles and macroscopic heat conduction, and provides a directly applicable theoretical tool for the structural design and performance optimization of PRCs.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128380"},"PeriodicalIF":5.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974552","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 : 2026-01-15DOI: 10.1016/j.ijheatmasstransfer.2026.128365
Junbo Jung , Yongsik Ham , Jaehyun Lim , Junyong Seo , Siwon Yoon , Bong Jae Lee , Joong Bae Kim
Passive daytime radiative cooling (PDRC) offers a sustainable solution for reducing space cooling energy demand. However, achieving high cooling performance alongside scalability and durability remains a key challenge in PDRC. In this study, we propose a scalable and durable dual-layer radiative cooling paint (DRCP), composed of a bottom PDMS/TiO2 layer and a top PDMS/Al2O3 layer, fabricated using a spray-coating method. The particle size and layer thickness were determined via Monte Carlo simulations based on Mie scattering theory to maximize solar reflectance across the entire solar spectrum. The fabricated DRCP achieved a solar-weighted reflectance of 91.7% and an average emissivity of 95.9%, resulting in a peak subambient cooling temperature of 3.2 °C under 1060 W/m solar irradiance. Thermal durability was confirmed through 40 thermal cycles and a 30-day outdoor exposure test; over 99.7% of the initial solar-weighted reflectance was restored after water rinsing. EnergyPlus simulations demonstrated annual cooling energy savings of up to 44.6 GJ in hot desert climates. These findings highlight the potential of DRCP as a scalable, durable, and energy-efficient PDRC solution for real-world applications.
{"title":"Scalable and durable dual-layer radiative cooling paint using a spray-coating method","authors":"Junbo Jung , Yongsik Ham , Jaehyun Lim , Junyong Seo , Siwon Yoon , Bong Jae Lee , Joong Bae Kim","doi":"10.1016/j.ijheatmasstransfer.2026.128365","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128365","url":null,"abstract":"<div><div>Passive daytime radiative cooling (PDRC) offers a sustainable solution for reducing space cooling energy demand. However, achieving high cooling performance alongside scalability and durability remains a key challenge in PDRC. In this study, we propose a scalable and durable dual-layer radiative cooling paint (DRCP), composed of a bottom PDMS/TiO<sub>2</sub> layer and a top PDMS/Al<sub>2</sub>O<sub>3</sub> layer, fabricated using a spray-coating method. The particle size and layer thickness were determined via Monte Carlo simulations based on Mie scattering theory to maximize solar reflectance across the entire solar spectrum. The fabricated DRCP achieved a solar-weighted reflectance of 91.7% and an average emissivity of 95.9%, resulting in a peak subambient cooling temperature of <span><math><mo>−</mo></math></span>3.2 °C under 1060 W/m<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span> solar irradiance. Thermal durability was confirmed through 40 thermal cycles and a 30-day outdoor exposure test; over 99.7% of the initial solar-weighted reflectance was restored after water rinsing. EnergyPlus simulations demonstrated annual cooling energy savings of up to 44.6 GJ in hot desert climates. These findings highlight the potential of DRCP as a scalable, durable, and energy-efficient PDRC solution for real-world applications.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128365"},"PeriodicalIF":5.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974550","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 : 2026-01-15DOI: 10.1016/j.ijheatmasstransfer.2026.128383
Jimin Fang , Jiaqi Zou , Wei Chen , Xiaoqiang Sun , Daming Zhang
Most nonreciprocal thermal emitters operate in the mid-infrared wavelengths. To meet the requirements of solar cell applications, it is extremely desirable for nonreciprocal behavior to occur within the main solar wavelength range. In this paper, a nonreciprocal thermal emitter composed of (Si/SiO2)6/InAs/GaAs/Al is suggested. At the magnetic field strength of 0.2 T and optical wavelength of 802.866 nm, the absorptivity and emissivity are 99.98 % and 4.26 %, respectively. The nonreciprocity exceeds 95.23 %. The electric field distributions prove the nonreciprocity in the magnetophotonic crystal originates from the excitation of asymmetric Tamm plasmons. As the defect layer thickness increases, the nonreciprocity gradually decrease and shift slightly toward longer wavelengths. As the incident angles increases from 25° to 30°, the absorptivity, emissivity, and nonreciprocity shift toward shorter wavelengths. The coupled-mode theory further reveals the physical mechanism. By the mode competition between the Tamm plasmons and the Fabry-Pérot cavity mode, the magnitude modulation of nonreciprocity surpasses 92 %. The nonreciprocal thermal emitter operates in the main solar wavelength range is promising for energy harvesting and solar cell applications.
{"title":"Nonreciprocal thermal emitter operating in main solar wavelength range with 0.2 T magnetic fields","authors":"Jimin Fang , Jiaqi Zou , Wei Chen , Xiaoqiang Sun , Daming Zhang","doi":"10.1016/j.ijheatmasstransfer.2026.128383","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128383","url":null,"abstract":"<div><div>Most nonreciprocal thermal emitters operate in the mid-infrared wavelengths. To meet the requirements of solar cell applications, it is extremely desirable for nonreciprocal behavior to occur within the main solar wavelength range. In this paper, a nonreciprocal thermal emitter composed of (Si/SiO<sub>2</sub>)<sup>6</sup>/InAs/GaAs/Al is suggested. At the magnetic field strength of 0.2 T and optical wavelength of 802.866 nm, the absorptivity and emissivity are 99.98 % and 4.26 %, respectively. The nonreciprocity exceeds 95.23 %. The electric field distributions prove the nonreciprocity in the magnetophotonic crystal originates from the excitation of asymmetric Tamm plasmons. As the defect layer thickness increases, the nonreciprocity gradually decrease and shift slightly toward longer wavelengths. As the incident angles increases from 25° to 30°, the absorptivity, emissivity, and nonreciprocity shift toward shorter wavelengths. The coupled-mode theory further reveals the physical mechanism. By the mode competition between the Tamm plasmons and the Fabry-Pérot cavity mode, the magnitude modulation of nonreciprocity surpasses 92 %. The nonreciprocal thermal emitter operates in the main solar wavelength range is promising for energy harvesting and solar cell applications.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128383"},"PeriodicalIF":5.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974554","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 : 2026-01-14DOI: 10.1016/j.ijheatmasstransfer.2026.128373
Yadong Xiao , Yan Liu , Xiang Li , Tingan Zhang , Kun Wang
A novel type of high-speed swirl nozzle was biomimetically designed based on the wing profile of a frigatebird and streamlined. The wing profile of the frigatebird with scimitar-shaped protrusions is adopted as the side wall of the swirl tube. The spiral direction of the swirl tube is designed such that the protrusion side faces forward to break through the gas flow. The superior gas stability and gas-liquid mass transfer capability resulting from this biomimetic design was confirmed through a combination of experiments and numerical simulation. Due to the gas dispersion effect of the swirl holes, high-frequency unstable oscillations in the initial section of the jet are alleviated. The coalescence of microbubbles is weakened, resulting in the reduction of the jet expansion amplitude. The corresponding gas reverse impact is weakened. The superior stability can be quantitatively analyzed. Variance and Allan deviation of the jet root radius is half that of a pressure-type nozzle. The high-frequency signals of the jet root radius in the range of 100-150 Hz have been significantly reduced as determined by the Continuous Wavelet Transform. Besides, the jet half-width of the novel nozzle is 3.16 times that of a straight-tube and 1.89 times that of a pressure-type nozzle. Due to the acceleration effect, the horizontal penetration depth of the novel swirl nozzle is 2.15 to 2.37 times that of a straight-tube, and reaches 52.93 % to 73.09 % of that of a pressure-type nozzle. Numerical simulation determined that flow field velocity under the novel swirl nozzle can be improved in the double-side-blown process. The gas-liquid mass transfer capability is 1.66 times that of the straight-tube. The component diffusion capability is 1.49 times that of the straight-tube.
{"title":"Jet stability and mass transfer analysis of a novel high-speed swirl nozzle","authors":"Yadong Xiao , Yan Liu , Xiang Li , Tingan Zhang , Kun Wang","doi":"10.1016/j.ijheatmasstransfer.2026.128373","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128373","url":null,"abstract":"<div><div>A novel type of high-speed swirl nozzle was biomimetically designed based on the wing profile of a frigatebird and streamlined. The wing profile of the frigatebird with scimitar-shaped protrusions is adopted as the side wall of the swirl tube. The spiral direction of the swirl tube is designed such that the protrusion side faces forward to break through the gas flow. The superior gas stability and gas-liquid mass transfer capability resulting from this biomimetic design was confirmed through a combination of experiments and numerical simulation. Due to the gas dispersion effect of the swirl holes, high-frequency unstable oscillations in the initial section of the jet are alleviated. The coalescence of microbubbles is weakened, resulting in the reduction of the jet expansion amplitude. The corresponding gas reverse impact is weakened. The superior stability can be quantitatively analyzed. Variance and Allan deviation of the jet root radius is half that of a pressure-type nozzle. The high-frequency signals of the jet root radius in the range of 100-150 Hz have been significantly reduced as determined by the Continuous Wavelet Transform. Besides, the jet half-width of the novel nozzle is 3.16 times that of a straight-tube and 1.89 times that of a pressure-type nozzle. Due to the acceleration effect, the horizontal penetration depth of the novel swirl nozzle is 2.15 to 2.37 times that of a straight-tube, and reaches 52.93 % to 73.09 % of that of a pressure-type nozzle. Numerical simulation determined that flow field velocity under the novel swirl nozzle can be improved in the double-side-blown process. The gas-liquid mass transfer capability is 1.66 times that of the straight-tube. The component diffusion capability is 1.49 times that of the straight-tube.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128373"},"PeriodicalIF":5.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974549","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}
Spray cooling, a method that combines impingement convection and phase-change heat transfer, has become a promising technique for high-heat-flux devices due to its advantages, including high cooling capacity and low fluid consumption. However, under sub-atmospheric pressure conditions, the impact behaviour of droplets and the mechanisms of spray cooling remain unclear, limiting their application in aerospace and other fields. This study focuses on micron-sized droplets in spray cooling, observing the accelerated rebound phenomenon when impacting heated surfaces under sub-atmospheric pressure, and revealing the combined mechanisms of interfacial evaporation pressure and capillary pressure. Furthermore, this study establishes a physical model of the vapour film evolution during droplet impact and analyses the influence of environmental pressure on this process. A dimensionless number, Ev, is proposed to quantify the relative strength of the vapour film pressure compared with the liquid capillary pressure. It accurately captures the onset of interfacial depressions at the liquid–vapour interface and the associated droplet rebound during impact. Extending the analysis to spray-cooling processes under sub-atmospheric conditions, the study shows that reducing the ambient pressure alone does not necessarily enhance cooling performance. For R134a spray cooling at 8.4 kPa, the cooling capacity maximum increases by approximately 42.3 % compared with 1 atm. The proposed low-pressure spray-cooling correlation predicts the data with errors of <20 %. In addition, the increased temperature of a large surface will lead to intensified flash evaporation, and it is necessary to optimise the spray spacing and coverage area to ensure cooling efficiency.
{"title":"Investigation of the dynamic mechanisms of droplet impact and spray cooling on heated surfaces under sub-atmospheric pressure","authors":"Ruina Xu, Gaoyuan Wang, Chao Wang, Zhihao Zhang, Peixue Jiang","doi":"10.1016/j.ijheatmasstransfer.2026.128341","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128341","url":null,"abstract":"<div><div>Spray cooling, a method that combines impingement convection and phase-change heat transfer, has become a promising technique for high-heat-flux devices due to its advantages, including high cooling capacity and low fluid consumption. However, under sub-atmospheric pressure conditions, the impact behaviour of droplets and the mechanisms of spray cooling remain unclear, limiting their application in aerospace and other fields. This study focuses on micron-sized droplets in spray cooling, observing the accelerated rebound phenomenon when impacting heated surfaces under sub-atmospheric pressure, and revealing the combined mechanisms of interfacial evaporation pressure and capillary pressure. Furthermore, this study establishes a physical model of the vapour film evolution during droplet impact and analyses the influence of environmental pressure on this process. A dimensionless number, <em>Ev</em>, is proposed to quantify the relative strength of the vapour film pressure compared with the liquid capillary pressure. It accurately captures the onset of interfacial depressions at the liquid–vapour interface and the associated droplet rebound during impact. Extending the analysis to spray-cooling processes under sub-atmospheric conditions, the study shows that reducing the ambient pressure alone does not necessarily enhance cooling performance. For R134a spray cooling at 8.4 kPa, the cooling capacity maximum increases by approximately 42.3 % compared with 1 atm. The proposed low-pressure spray-cooling correlation predicts the data with errors of <20 %. In addition, the increased temperature of a large surface will lead to intensified flash evaporation, and it is necessary to optimise the spray spacing and coverage area to ensure cooling efficiency.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128341"},"PeriodicalIF":5.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974555","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 : 2026-01-13DOI: 10.1016/j.ijheatmasstransfer.2026.128368
Hristina Dragovic , Leo Pel , Daniela S. Damaceno , Ole H.H. Meyer , Å smund Ervik
Insulated pipelines located outdoors are subjected to fluctuations in ambient temperature and humidity. Weather conditions significantly contribute to humidity migrating into pipe insulation, and subsequent condensation on the cold side within the system. Corrosion under insulation (CUI) is a degradation mechanism closely related to prolonged impact of retained liquid water on the pipe metal surface beneath the insulation. However, the thermodynamic parameters that indicate condensation within mineral wool insulation remain insufficiently investigated. In this study, we present experimental work using nuclear magnetic resonance (NMR) to measure moisture content in mineral wool subjected to a temperature gradient and air with controlled relative humidity at the warm side. The results show that significant supersaturation of humid air occurs before and during condensation, and that the condensation region length increases linearly with the relative humidity of the warm air. The measured moisture content is close to the values estimated with a simple mass conservation model. These findings have important implications for monitoring temperature and relative humidity in mineral wool insulation to asses the amount of condensed liquid water in a thermal gradient, thereby improving methods for detecting corrosion under insulation.
{"title":"Condensation of supersaturated water vapor in mineral wool subjected to a temperature gradient: An NMR study","authors":"Hristina Dragovic , Leo Pel , Daniela S. Damaceno , Ole H.H. Meyer , Å smund Ervik","doi":"10.1016/j.ijheatmasstransfer.2026.128368","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128368","url":null,"abstract":"<div><div>Insulated pipelines located outdoors are subjected to fluctuations in ambient temperature and humidity. Weather conditions significantly contribute to humidity migrating into pipe insulation, and subsequent condensation on the cold side within the system. Corrosion under insulation (CUI) is a degradation mechanism closely related to prolonged impact of retained liquid water on the pipe metal surface beneath the insulation. However, the thermodynamic parameters that indicate condensation within mineral wool insulation remain insufficiently investigated. In this study, we present experimental work using nuclear magnetic resonance (NMR) to measure moisture content in mineral wool subjected to a temperature gradient and air with controlled relative humidity at the warm side. The results show that significant supersaturation of humid air occurs before and during condensation, and that the condensation region length increases linearly with the relative humidity of the warm air. The measured moisture content is close to the values estimated with a simple mass conservation model. These findings have important implications for monitoring temperature and relative humidity in mineral wool insulation to asses the amount of condensed liquid water in a thermal gradient, thereby improving methods for detecting corrosion under insulation.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128368"},"PeriodicalIF":5.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974545","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}
Traditional heat pipe design largely relies on empirical methods and trial-and-error analysis, lacking sufficient theoretical guidance for achieving optimal structural configurations. In this study, a novel thermal diode featuring an asymmetric flow-resistance vapor channel is designed using the density-based topology optimization method. To enhance structural versatility, five channel designs with varying aspect ratios are optimized. The unidirectional flow performance of the optimized structures is validated through three-dimensional fluid simulations, and their heat transfer performance is experimentally evaluated. Results show that the proposed thermal diode exhibits excellent unidirectional heat transfer characteristics. A maximum reverse-to-forward thermal resistance ratio (K) of 6.21 is achieved when the vapor channel is offset by 25 mm toward the evaporation section, with a liquid filling ratio of 25 % and a heating power of 8 W. Moreover, the thermal resistance ratio (K) increases progressively with higher heating power. This study introduces a density-based topology optimization strategy for vapor-channel design in thermal diodes and establishes an asymmetric flow-resistance architecture to realize efficient unidirectional heat transfer without complex microstructures, thereby providing a new structural design paradigm for convection-type thermal diodes.
{"title":"Design and heat transfer performances of thermal diode based on the optimal vapor channel by topology optimization","authors":"Jianhua Xiang, Linxin Long, Yongfeng Zheng, Zhipeng Chen, Jiale Huang","doi":"10.1016/j.ijheatmasstransfer.2026.128355","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128355","url":null,"abstract":"<div><div>Traditional heat pipe design largely relies on empirical methods and trial-and-error analysis, lacking sufficient theoretical guidance for achieving optimal structural configurations. In this study, a novel thermal diode featuring an asymmetric flow-resistance vapor channel is designed using the density-based topology optimization method. To enhance structural versatility, five channel designs with varying aspect ratios are optimized. The unidirectional flow performance of the optimized structures is validated through three-dimensional fluid simulations, and their heat transfer performance is experimentally evaluated. Results show that the proposed thermal diode exhibits excellent unidirectional heat transfer characteristics. A maximum reverse-to-forward thermal resistance ratio (K) of 6.21 is achieved when the vapor channel is offset by 25 mm toward the evaporation section, with a liquid filling ratio of 25 % and a heating power of 8 W. Moreover, the thermal resistance ratio (K) increases progressively with higher heating power. This study introduces a density-based topology optimization strategy for vapor-channel design in thermal diodes and establishes an asymmetric flow-resistance architecture to realize efficient unidirectional heat transfer without complex microstructures, thereby providing a new structural design paradigm for convection-type thermal diodes.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128355"},"PeriodicalIF":5.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974449","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 : 2026-01-13DOI: 10.1016/j.ijheatmasstransfer.2026.128364
Qiaoling Xiong , Lu Liu , Xuanyu Zhu , Yuping Li , Teng Wang , Xinyu Dong
The droplet boiling on flexible substrates holds significant potential for applications in spray cooling, printed electronics, and microfluidics. This study systematically investigates the boiling behavior of water droplets on polydimethylsiloxane (PDMS) substrates with varying elastic modulus and superheat, combining high-speed imaging and infrared thermometry to analyze bubble dynamics, heat transfer, and interfacial stability. Experimental results show that more flexible substrates effectively modulate bubble nucleation and growth, suppress droplet splashing and contact line depinning, and increase the critical substrate superheat for the transition from nucleate to transition boiling from 100°C for a PDMS substrate with a curing ratio of 10:1 to 140°C for a PDMS substrate with a 50:1 curing ratio. Enhanced interfacial pinning is attributed to elastic strain energy stored in the wetting ridge. During bubble collapse, substrate deformation dissipates potential energy, inhibiting shock waves and jet formation. This energy dissipation mechanism not only accelerates the decay of the pinning force but also mitigates violent flow disturbances, significantly improving droplet stability in high-temperature conditions.
{"title":"Bubble dynamics and heat transfer characteristics during boiling of water droplets on flexible PDMS substrates","authors":"Qiaoling Xiong , Lu Liu , Xuanyu Zhu , Yuping Li , Teng Wang , Xinyu Dong","doi":"10.1016/j.ijheatmasstransfer.2026.128364","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128364","url":null,"abstract":"<div><div>The droplet boiling on flexible substrates holds significant potential for applications in spray cooling, printed electronics, and microfluidics. This study systematically investigates the boiling behavior of water droplets on polydimethylsiloxane (PDMS) substrates with varying elastic modulus and superheat, combining high-speed imaging and infrared thermometry to analyze bubble dynamics, heat transfer, and interfacial stability. Experimental results show that more flexible substrates effectively modulate bubble nucleation and growth, suppress droplet splashing and contact line depinning, and increase the critical substrate superheat for the transition from nucleate to transition boiling from 100°C for a PDMS substrate with a curing ratio of 10:1 to 140°C for a PDMS substrate with a 50:1 curing ratio. Enhanced interfacial pinning is attributed to elastic strain energy stored in the wetting ridge. During bubble collapse, substrate deformation dissipates potential energy, inhibiting shock waves and jet formation. This energy dissipation mechanism not only accelerates the decay of the pinning force but also mitigates violent flow disturbances, significantly improving droplet stability in high-temperature conditions.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128364"},"PeriodicalIF":5.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974546","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 : 2026-01-13DOI: 10.1016/j.ijheatmasstransfer.2026.128326
Xueyu Tang , Weiqin Lu , Ling Jiang , Bingjun Du , Yang Zhang , Junfu Lyu , Dan Li , Xiwei Ke
This study develops a novel CFD-DEM coupled DDPM-KTGF method to investigate gas-solid reactions and mass transfer within micro-fluidized bed reactor analyzers (MFBRA). under varying operating conditions. In this approach, the CFD-DEM module captures the formation of emulsion and bubble phases while the DDPM-KTGF module simulates mass transfer effects, enabling a detailed analysis of reaction kinetics. Key findings show that reaction kinetics and mass transfer efficiency are strongly influenced by fluidization states. In the fixed-bed regime, low inlet gas velocities result in constant reaction rates due to high diffusion resistance and limited gas-solid contact. As gas velocity increases and fluidization occurs, mass transfer improves, but further increases lead to bubble coalescence, reducing reaction efficiency. Temperature analysis reveals that at moderate temperatures (700-850°C), mass transfer resistance increases due to enhanced bubble formation, while higher temperatures (850-900°C) improve molecular diffusion but thermodynamic limitations reduce conversion. Moreover, larger particles increase minimum fluidization velocity, promote bubble growth, and reduce catalytic efficiency, with a non-monotonic relationship observed between particle size and conversion rate. Meanwhile, radial mass transfer heterogeneity is non-negligible. This work provides valuable insights into optimizing operating conditions and further enhancing gas-solid catalytic processes within MFBRAs.
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