Pub Date : 2025-12-05DOI: 10.1016/j.ijheatmasstransfer.2025.128219
Ngoc Van Trinh , Hoang Hiep Le , Ngoc Dat Nguyen , Jongbin Woo , Sangseok Yu
As a promising CO2 capture, utilization, and storage technique, plant-level cryogenic CO2 separation is utilized to capture CO2 emitted in the combustion of fossil fuel. Vortex tubes can effectively resolve the difficulties related to cryogenic carbon capture with low energy consumption. In this study, the performance of a vortex tube in terms of energy and species separation was evaluated via parametric analysis. Different configurations of the nozzle generator, main tube, and divergence angle were compared and analyzed to find the optimal design for tuning the CO2 concentration at the cold outlet. The performance of the vortex tube varied directly with the magnitude of the tangential and swirling velocity. Therefore, decreasing the diameter of the induction nozzle and divergence angle at the hot outlet had the most significant effect on the performance of the vortex system. Additionally, the orifice diameter regulated the pressure drop at the cold outlet, and had a moderate effect on CO2 separation. The main tube serves as the central element enabling energy separation via controlled vortex dynamics, and was also evaluated in this study. Increasing the cyclone angle to 10° led to a significant increase in the species separation.
{"title":"Sensitivity analysis of vortex-tube design variables for evaluation of CO2 separation performance","authors":"Ngoc Van Trinh , Hoang Hiep Le , Ngoc Dat Nguyen , Jongbin Woo , Sangseok Yu","doi":"10.1016/j.ijheatmasstransfer.2025.128219","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128219","url":null,"abstract":"<div><div>As a promising CO<sub>2</sub> capture, utilization, and storage technique, plant-level cryogenic CO<sub>2</sub> separation is utilized to capture CO<sub>2</sub> emitted in the combustion of fossil fuel. Vortex tubes can effectively resolve the difficulties related to cryogenic carbon capture with low energy consumption. In this study, the performance of a vortex tube in terms of energy and species separation was evaluated via parametric analysis. Different configurations of the nozzle generator, main tube, and divergence angle were compared and analyzed to find the optimal design for tuning the CO<sub>2</sub> concentration at the cold outlet. The performance of the vortex tube varied directly with the magnitude of the tangential and swirling velocity. Therefore, decreasing the diameter of the induction nozzle and divergence angle at the hot outlet had the most significant effect on the performance of the vortex system. Additionally, the orifice diameter regulated the pressure drop at the cold outlet, and had a moderate effect on CO<sub>2</sub> separation. The main tube serves as the central element enabling energy separation via controlled vortex dynamics, and was also evaluated in this study. Increasing the cyclone angle to 10° led to a significant increase in the species separation.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128219"},"PeriodicalIF":5.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683091","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 : 2025-12-05DOI: 10.1016/j.ijheatmasstransfer.2025.128134
Jana Rogiers , Ilya T’Jollyn , Jasper Nonneman , Michel De Paepe
Flow boiling, or forced convection boiling, is a highly efficient heat transfer method that combines forced convection with nucleate boiling, achieving high heat transfer rates at low temperature differences. Its advantages include uniform temperature distribution and compact system designs. It is widely used in nuclear reactor cooling, electronic thermal management, solar power systems, and power plant heat exchangers. Effective application demands understanding of the heat transfer efficiency and critical heat flux (CHF), which are closely tied to boiling phenomena.
Research often focuses on constant, uniform heat flux conditions, which do not reflect real-world applications featuring spatial and temporal heat flux variations. This review examines non-uniform heat flux cases - categorized as single-heater configurations, in-line, in-plane, and circumferential variations – and their relevance to specific applications. Time-varying heat fluxes are explored through step changes, pulses, and periodic oscillations, discussing the influence of flux magnitude, duration, and inlet conditions.
Findings underscore the difficulty of direct (quantitative) comparison across studies due to application-specific conditions and diverse methodologies. Recommendations for designing non-uniform systems and understanding system responses to time-varying flux are presented, emphasizing the critical role of flow regimes. Flow regimes significantly impact boiling behaviour, heat transfer performance, and CHF. Therefore, future research should prioritize studying these influences under varied spatial and temporal heat flux conditions. This will enable the design of more reliable and efficient systems, and bridge gaps in understanding the interplay between flow regimes and system performance. Furthermore, expanding experimental and numerical datasets will aid in validating results and refining predictive models.
{"title":"Flow boiling under non-uniform or time-varying heat flux conditions: a review","authors":"Jana Rogiers , Ilya T’Jollyn , Jasper Nonneman , Michel De Paepe","doi":"10.1016/j.ijheatmasstransfer.2025.128134","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128134","url":null,"abstract":"<div><div>Flow boiling, or forced convection boiling, is a highly efficient heat transfer method that combines forced convection with nucleate boiling, achieving high heat transfer rates at low temperature differences. Its advantages include uniform temperature distribution and compact system designs. It is widely used in nuclear reactor cooling, electronic thermal management, solar power systems, and power plant heat exchangers. Effective application demands understanding of the heat transfer efficiency and critical heat flux (CHF), which are closely tied to boiling phenomena.</div><div>Research often focuses on constant, uniform heat flux conditions, which do not reflect real-world applications featuring spatial and temporal heat flux variations. This review examines non-uniform heat flux cases - categorized as single-heater configurations, in-line, in-plane, and circumferential variations – and their relevance to specific applications. Time-varying heat fluxes are explored through step changes, pulses, and periodic oscillations, discussing the influence of flux magnitude, duration, and inlet conditions.</div><div>Findings underscore the difficulty of direct (quantitative) comparison across studies due to application-specific conditions and diverse methodologies. Recommendations for designing non-uniform systems and understanding system responses to time-varying flux are presented, emphasizing the critical role of flow regimes. Flow regimes significantly impact boiling behaviour, heat transfer performance, and CHF. Therefore, future research should prioritize studying these influences under varied spatial and temporal heat flux conditions. This will enable the design of more reliable and efficient systems, and bridge gaps in understanding the interplay between flow regimes and system performance. Furthermore, expanding experimental and numerical datasets will aid in validating results and refining predictive models.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128134"},"PeriodicalIF":5.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683088","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}
Preventing microscale ice accretion on critical surfaces is essential for enhancing the reliability of aerospace equipment, power transmission systems, and precision instruments. In this study, aiming to construct an ice-free zone at the submillimeter scale, we focus on the dynamics of the vapor diffusion layer above microstructured surfaces. The effects of key geometrical parameters — including array height, spacing (pitch) ratio, and structural inclination angle — on mass transfer and vapor diffusion are systematically investigated. By decoupling the vapor condensation and icing process into two distinct stages: the nucleation competition preceding icing and the hygroscopic ice transformation following icing, the vapor flux aggregation mechanism at preferential nucleation sites and the mechanism sustaining the steady-state ice-free region are elucidated separately. Dimensionless regional vapor flux ratios are introduced to quantify the driving force of ice hygroscopicity and the ability to maintain the steady-state ice-free region. Numerical simulations reveal that, under fixed environmental conditions, the pitch ratio and height are the dominant influencing factors: reducing the pitch ratio to 2 increases the proportion of vapor flux concentrated at the structure tops to 45%, while increasing the height primarily enhances the sidewalls’ vapor flux trapping capability. Comparison between 2D and 3D models demonstrates that, for identical geometries, the array arrangement form also significantly impacts vapor flux aggregation and concentration field distribution; corresponding correction coefficients for the 3D model relative to the 2D model are provided. Furthermore, a phase diagram of frost coverage is developed, revealing that a 10% increase in ambient humidity leads to a substantial rise in frost coverage and an exponential decay of the critical pitch ratio with increasing humidity. This study elucidates the synergistic regulation of microstructure geometry optimization and environmental parameters, providing a theoretical basis for the design of anti-icing surface engineering.
{"title":"Effects of geometric features on the diffusion and heat transfer behavior of vapor on a passive anti-frosting surfaces","authors":"Yusong Tian, Chunyu Li, Guang Yang, Mingkun Xiao, Aifeng Cai, Jingyi Wu","doi":"10.1016/j.ijheatmasstransfer.2025.128233","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128233","url":null,"abstract":"<div><div>Preventing microscale ice accretion on critical surfaces is essential for enhancing the reliability of aerospace equipment, power transmission systems, and precision instruments. In this study, aiming to construct an ice-free zone at the submillimeter scale, we focus on the dynamics of the vapor diffusion layer above microstructured surfaces. The effects of key geometrical parameters — including array height, spacing (pitch) ratio, and structural inclination angle — on mass transfer and vapor diffusion are systematically investigated. By decoupling the vapor condensation and icing process into two distinct stages: the nucleation competition preceding icing and the hygroscopic ice transformation following icing, the vapor flux aggregation mechanism at preferential nucleation sites and the mechanism sustaining the steady-state ice-free region are elucidated separately. Dimensionless regional vapor flux ratios are introduced to quantify the driving force of ice hygroscopicity and the ability to maintain the steady-state ice-free region. Numerical simulations reveal that, under fixed environmental conditions, the pitch ratio and height are the dominant influencing factors: reducing the pitch ratio to 2 increases the proportion of vapor flux concentrated at the structure tops to 45%, while increasing the height primarily enhances the sidewalls’ vapor flux trapping capability. Comparison between 2D and 3D models demonstrates that, for identical geometries, the array arrangement form also significantly impacts vapor flux aggregation and concentration field distribution; corresponding correction coefficients for the 3D model relative to the 2D model are provided. Furthermore, a phase diagram of frost coverage is developed, revealing that a 10% increase in ambient humidity leads to a substantial rise in frost coverage and an exponential decay of the critical pitch ratio with increasing humidity. This study elucidates the synergistic regulation of microstructure geometry optimization and environmental parameters, providing a theoretical basis for the design of anti-icing surface engineering.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128233"},"PeriodicalIF":5.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683140","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 : 2025-12-04DOI: 10.1016/j.ijheatmasstransfer.2025.128210
Shichun Wang , Haiyu Fu , Leping Zhou , Xiaoze Du
Understanding ice nucleation under nanoconfinement is critical for cryopreservation and materials science, yet the coupled effects of pressure and temperature gradients remain poorly quantified. This study employs molecular dynamics simulations with a coarse-grained mW water model to dissect nucleation kinetics across pressures (1 ∼ 540 atm) and temperature gradients (0 ∼ 20 K). By implementing a piston-based pressure control method validated for confined systems and establishing a temperature gradient model via Langevin thermostats, we resolve pressure-induced nucleation barrier elevation (ΔG* increases by 6 % at 540 atm vs. 1 atm) driven by interfacial energy γ and suppressed attachment rates (f decreases exponentially with pressure). Temperature gradients exceeding 4.6 × 10⁸ K/m shift nucleation from homogeneous to heterogeneous modes (probability drops from >60 % to <20 % at ΔT= 20 K) due to thermal non-uniformity and adsorption-layer restructuring. Critically, a corrected nucleation theory incorporating local temperature fluctuations around nuclei is developed, reducing prediction errors to < 9 %. These insights enable precise control of ice microstructures in phase-change applications under extreme conditions.
{"title":"Nanoconfinement effects on ice nucleation: Pressure-dependent barrier modulation and temperature gradient-driven regime transition","authors":"Shichun Wang , Haiyu Fu , Leping Zhou , Xiaoze Du","doi":"10.1016/j.ijheatmasstransfer.2025.128210","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128210","url":null,"abstract":"<div><div>Understanding ice nucleation under nanoconfinement is critical for cryopreservation and materials science, yet the coupled effects of pressure and temperature gradients remain poorly quantified. This study employs molecular dynamics simulations with a coarse-grained mW water model to dissect nucleation kinetics across pressures (1 ∼ 540 atm) and temperature gradients (0 ∼ 20 K). By implementing a piston-based pressure control method validated for confined systems and establishing a temperature gradient model via Langevin thermostats, we resolve pressure-induced nucleation barrier elevation (Δ<em>G</em>* increases by 6 % at 540 atm vs. 1 atm) driven by interfacial energy <em>γ</em> and suppressed attachment rates (<em>f</em> decreases exponentially with pressure). Temperature gradients exceeding 4.6 × 10⁸ K/m shift nucleation from homogeneous to heterogeneous modes (probability drops from >60 % to <20 % at Δ<em>T</em> <em>=</em> 20 K) due to thermal non-uniformity and adsorption-layer restructuring. Critically, a corrected nucleation theory incorporating local temperature fluctuations around nuclei is developed, reducing prediction errors to < 9 %. These insights enable precise control of ice microstructures in phase-change applications under extreme conditions.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128210"},"PeriodicalIF":5.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683094","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 : 2025-12-04DOI: 10.1016/j.ijheatmasstransfer.2025.128193
Bei Hu , Baisheng Nie , Chao Ma , Hongwei Yan , Xianfeng Liu , Xiaotong Wang , Yushu Zhang
Hydraulic technology is one of the most important methodologies for improving coal structure in low-permeability coal seams. However, the injection of moisture will produce water locking effect, competitive adsorption effect, and change the properties of coal body, resulting in a complex impact on the gas migration in coal. In this study, the low temperature nitrogen adsorption (LTNA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and contact angle measurement were conducted to clarify the main controlling factors of wettability of soft coal sample containing moisture. Then, the gas desorption experiments under different water injection conditions were carried out to analyze the desorption characteristics of gas in soft coal under the presence of moisture. The results show that the pore size distribution of soft coal in different mining areas is similar, with the characteristics of relatively developed micropores and mesopores. According to the gas desorption difference of soft coal before and after water injection, the soft coal can be divided into three categories, namely completely inhibition type, semi-inhibition type and promotion type. The pore connectivity dominates gas desorption behavior when there is no water participation, while the pore size and wettability dominate gas desorption behavior when water invades coal body. However, for coal samples with good wettability and high oxygen-containing functional groups (OCFG), H2O preferentially forms hydrogen bonds with OCFG on the surface of coal pores to displace gas, which has a promoting effect on gas desorption. The water locking dominated by water phase plugging and desorption enhancement induced by water displacement have a competitive control effect on gas desorption in coal containing moisture. This research provides theoretical guidance for hydraulic enhanced coalbed methane extraction engineering.
{"title":"Experimental study on the influence mechanism of water injection on gas desorption in soft coal","authors":"Bei Hu , Baisheng Nie , Chao Ma , Hongwei Yan , Xianfeng Liu , Xiaotong Wang , Yushu Zhang","doi":"10.1016/j.ijheatmasstransfer.2025.128193","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128193","url":null,"abstract":"<div><div>Hydraulic technology is one of the most important methodologies for improving coal structure in low-permeability coal seams. However, the injection of moisture will produce water locking effect, competitive adsorption effect, and change the properties of coal body, resulting in a complex impact on the gas migration in coal. In this study, the low temperature nitrogen adsorption (LTNA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and contact angle measurement were conducted to clarify the main controlling factors of wettability of soft coal sample containing moisture. Then, the gas desorption experiments under different water injection conditions were carried out to analyze the desorption characteristics of gas in soft coal under the presence of moisture. The results show that the pore size distribution of soft coal in different mining areas is similar, with the characteristics of relatively developed micropores and mesopores. According to the gas desorption difference of soft coal before and after water injection, the soft coal can be divided into three categories, namely completely inhibition type, semi-inhibition type and promotion type. The pore connectivity dominates gas desorption behavior when there is no water participation, while the pore size and wettability dominate gas desorption behavior when water invades coal body. However, for coal samples with good wettability and high oxygen-containing functional groups (OCFG), H<sub>2</sub>O preferentially forms hydrogen bonds with OCFG on the surface of coal pores to displace gas, which has a promoting effect on gas desorption. The water locking dominated by water phase plugging and desorption enhancement induced by water displacement have a competitive control effect on gas desorption in coal containing moisture. This research provides theoretical guidance for hydraulic enhanced coalbed methane extraction engineering.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128193"},"PeriodicalIF":5.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683096","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 : 2025-12-04DOI: 10.1016/j.ijheatmasstransfer.2025.128175
Doron Sahray , Robert A. Stavins , Vivek S. Garimella , Elad Koronio , William P. King , Nenad Miljkovic , Gennady Ziskind
This study focuses on a basic configuration in which Close-Contact Melting (CCM) takes place, namely, a vertical cylindrical block of a Phase-Change Material (PCM), melting under its own weight on a heated horizontal surface while surrounded by air. The initial purpose is to demonstrate that the widely used enthalpy–porosity approach fails to address even this simple configuration properly, and to suggest practical ways to overcome this major drawback. Accordingly, to capture the dynamics of CCM and its inherent features without distortions, a numerical approach is developed that incorporates an additional source term directly into the momentum equation. The suggested method allows gravity to act selectively on the solid phase, enabling it to descend as a rigid body without deformation. Consequently, the model overcomes the damping limitations of the conventional mushy-zone parameter of the enthalpy–porosity approach, facilitating a realistic simulation of heat transfer, phase change, and liquid motion in the thin layer between the heated surface and solid PCM. The method is validated against experimental data and with several benchmark experimental datasets from the literature concerning in-depth CCM studies. The results demonstrate excellent agreement in solid descent, melting front evolution, and liquid layer behavior. In addition, a parametric study is performed to quantify the influence of sample geometry and applied heat flux on the melting rate, pressure distribution, and liquid layer thickness. On the theoretical side, it is argued that the problem in question is similar to the classical squeezing flow configuration, and some insights gained there are applicable in the current study. Thus, this research refines the enthalpy–porosity method and establishes a robust simulation framework for analyzing CCM. These outcomes provide a foundation for future studies of similar processes in thermal energy storage and thermal management solutions that involve PCMs, where extended surfaces and external loading may be used to further enhance the PCM thermal performance.
{"title":"Close-contact melting of a cylindrical phase change material block on a heated surface","authors":"Doron Sahray , Robert A. Stavins , Vivek S. Garimella , Elad Koronio , William P. King , Nenad Miljkovic , Gennady Ziskind","doi":"10.1016/j.ijheatmasstransfer.2025.128175","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128175","url":null,"abstract":"<div><div>This study focuses on a basic configuration in which Close-Contact Melting (CCM) takes place, namely, a vertical cylindrical block of a Phase-Change Material (PCM), melting under its own weight on a heated horizontal surface while surrounded by air. The initial purpose is to demonstrate that the widely used enthalpy–porosity approach fails to address even this simple configuration properly, and to suggest practical ways to overcome this major drawback. Accordingly, to capture the dynamics of CCM and its inherent features without distortions, a numerical approach is developed that incorporates an additional source term directly into the momentum equation. The suggested method allows gravity to act selectively on the solid phase, enabling it to descend as a rigid body without deformation. Consequently, the model overcomes the damping limitations of the conventional mushy-zone parameter of the enthalpy–porosity approach, facilitating a realistic simulation of heat transfer, phase change, and liquid motion in the thin layer between the heated surface and solid PCM. The method is validated against experimental data and with several benchmark experimental datasets from the literature concerning in-depth CCM studies. The results demonstrate excellent agreement in solid descent, melting front evolution, and liquid layer behavior. In addition, a parametric study is performed to quantify the influence of sample geometry and applied heat flux on the melting rate, pressure distribution, and liquid layer thickness. On the theoretical side, it is argued that the problem in question is similar to the classical squeezing flow configuration, and some insights gained there are applicable in the current study. Thus, this research refines the enthalpy–porosity method and establishes a robust simulation framework for analyzing CCM. These outcomes provide a foundation for future studies of similar processes in thermal energy storage and thermal management solutions that involve PCMs, where extended surfaces and external loading may be used to further enhance the PCM thermal performance.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128175"},"PeriodicalIF":5.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683105","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 : 2025-12-04DOI: 10.1016/j.ijheatmasstransfer.2025.128209
Tianhao Yuan , Xuan Zhang , Haiyang Liu , Chengbin Zhang
Efficient temperature control of compact electronic devices that intermittently emit short bursts of high heat flux presents a significant challenge. This paper proposes a promising and effective solution by the implementation of a pumped two-phase loop (PTL) system integrated with a latent heat storage (LHS) unit. A simulation study is conducted to examine the dynamic thermal response of the pumped two-phase loop during a thermal shock of 10 kW class, with a focus on the effects of varying heat loads, LHS unit configurations, and mass flow rates on system performance. The results indicate that the integration of an LHS unit into a PTL system significantly mitigates temperature and pressure fluctuations in response to transient high heat fluxes and reduces peak evaporator wall temperatures. The LHS configuration in which the phase change material (PCM) is stored inside the metal tube while the working fluid flows externally demonstrates superior heat transfer performance. The pumped two-phase loop consumes less power while maintaining efficient cooling performance when the dryness of the working fluid at the evaporator outlet is adjusted between 0.32 and 0.43.
{"title":"Efficient thermal regulation using pumped two-phase flow","authors":"Tianhao Yuan , Xuan Zhang , Haiyang Liu , Chengbin Zhang","doi":"10.1016/j.ijheatmasstransfer.2025.128209","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128209","url":null,"abstract":"<div><div>Efficient temperature control of compact electronic devices that intermittently emit short bursts of high heat flux presents a significant challenge. This paper proposes a promising and effective solution by the implementation of a pumped two-phase loop (PTL) system integrated with a latent heat storage (LHS) unit. A simulation study is conducted to examine the dynamic thermal response of the pumped two-phase loop during a thermal shock of 10 kW class, with a focus on the effects of varying heat loads, LHS unit configurations, and mass flow rates on system performance. The results indicate that the integration of an LHS unit into a PTL system significantly mitigates temperature and pressure fluctuations in response to transient high heat fluxes and reduces peak evaporator wall temperatures. The LHS configuration in which the phase change material (PCM) is stored inside the metal tube while the working fluid flows externally demonstrates superior heat transfer performance. The pumped two-phase loop consumes less power while maintaining efficient cooling performance when the dryness of the working fluid at the evaporator outlet is adjusted between 0.32 and 0.43.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128209"},"PeriodicalIF":5.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683141","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 : 2025-12-04DOI: 10.1016/j.ijheatmasstransfer.2025.128192
Ruofeng Cao, Yongle Sun, Wojciech Suder, Xin Chen, Zhiyong Li, Stewart Williams
Induction preheating of filler wire is an emerging auxiliary process that allows precise control of wire temperature before melting by a main energy source in directed energy deposition (DED). This can enhance deposition rate and reduce defects. The induction heating mechanism for DED applications needs to be understood for establishing a robust process window that integrates coil design and key process parameters. This study investigates the evolution of electromagnetic and thermal fields during induction heating of a stainless-steel filler wire moving through a helical coil. A coupled electromagnetic-thermal model of a moving wire was developed to determine the magnetic flux, eddy current, temperature, and energy transfer efficiency. The wire temperatures predicted by the multiphysics model are consistent with experimental measurements under diverse conditions, with an error of less than 7 % after the heating reaches a steady state. The typical energy transfer efficiency for a wire diameter of 1.6 mm ranges in 3 %-9 %, which can be significantly enhanced through increasing the wire diameter and reducing the radial distance to the coil. The model enables a deeper understanding of the electromagnetic-thermal mechanisms governing both the transient and steady-state temperature distributions in the wire. In the steady state, the peak temperature is located immediately outside the exit end of the coil, and the temperature gradient across the wire diameter is marginal. A sensitivity analysis to identify dominant parameters was also carried out, showing that the wire feed speed (up to 150 mm/s), coil current (up to 700 A) and frequency (up to 500 kHz) are most influential. This study demonstrates an effective modelling approach to induction heating of moving wire, and it also provides critical insights for designing and optimising the induction coil and process for preheating filler wires in additive manufacturing and other similar processes (e.g. welding and cladding).
{"title":"Modelling and analysis of induction preheating of moving filler wire for directed energy deposition","authors":"Ruofeng Cao, Yongle Sun, Wojciech Suder, Xin Chen, Zhiyong Li, Stewart Williams","doi":"10.1016/j.ijheatmasstransfer.2025.128192","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128192","url":null,"abstract":"<div><div>Induction preheating of filler wire is an emerging auxiliary process that allows precise control of wire temperature before melting by a main energy source in directed energy deposition (DED). This can enhance deposition rate and reduce defects. The induction heating mechanism for DED applications needs to be understood for establishing a robust process window that integrates coil design and key process parameters. This study investigates the evolution of electromagnetic and thermal fields during induction heating of a stainless-steel filler wire moving through a helical coil. A coupled electromagnetic-thermal model of a moving wire was developed to determine the magnetic flux, eddy current, temperature, and energy transfer efficiency. The wire temperatures predicted by the multiphysics model are consistent with experimental measurements under diverse conditions, with an error of less than 7 % after the heating reaches a steady state. The typical energy transfer efficiency for a wire diameter of 1.6 mm ranges in 3 %-9 %, which can be significantly enhanced through increasing the wire diameter and reducing the radial distance to the coil. The model enables a deeper understanding of the electromagnetic-thermal mechanisms governing both the transient and steady-state temperature distributions in the wire. In the steady state, the peak temperature is located immediately outside the exit end of the coil, and the temperature gradient across the wire diameter is marginal. A sensitivity analysis to identify dominant parameters was also carried out, showing that the wire feed speed (up to 150 mm/s), coil current (up to 700 A) and frequency (up to 500 kHz) are most influential. This study demonstrates an effective modelling approach to induction heating of moving wire, and it also provides critical insights for designing and optimising the induction coil and process for preheating filler wires in additive manufacturing and other similar processes (e.g. welding and cladding).</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128192"},"PeriodicalIF":5.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683095","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 : 2025-12-04DOI: 10.1016/j.ijheatmasstransfer.2025.128199
Wanling Hu , Changcong Jiang , Yong Guan , Xiuxiu Zhang , Jianyu Hao , Chengxu Wang , Juanli Ma
Greenhouses in high-altitude regions often encounter challenges of low temperature and excessive humidity. These result from structural and climatic constraints, leading to high energy consumption for dehumidification. Conventional finned-tube heat exchangers (FTHXs), as core components of refrigeration and dehumidification systems, suffer from inefficient heat transfer and condensate retention, which exacerbate operational losses. To address these limitations, this study proposes a novel finned-tube heat exchanger with superhydrophilic-superhydrophobic dot array (FTHX-SSDA) and introduces a heat and mass transfer enhancement factor (JFhm). A numerical heat transfer model was developed, and computational fluid dynamics (CFD) simulations were conducted to analyze the thermal and hydraulic performance of the FTHX-SSDA under low-temperature, high-humidity conditions. The results demonstrate that, compared to a finned-tube heat exchanger with hydrophilic-surface (FTHX-HS), the FTHX-SSDA exhibits superior performance. Average enhancements include 31.89 % in the heat transfer factor (jh), 21.37 % in the mass transfer factor (jm), and a 1.19 % reduction in the friction factor (f). The JFhm consistently exceeds unity, confirming the excellent thermal efficiency of the FTHX-SSDA. Furthermore, both jh and jm decrease with increasing air-side Reynolds number. However, higher inlet air temperature elevated relative humidity, or lower tube wall temperature improve heat and mass transfer performance. The fitted performance correlation equations for the FTHX-SSDA’s air-side performance under low-temperature, high-humidity conditions were derived. The average errors were 0.6 % (jh), 0.24 % (jm), and 0.1 % (f), indicating high predictive accuracy. These results provide valuable technical insights and serve as a reference for improving and optimizing dehumidification systems in greenhouse settings.
{"title":"Improvement of heat-mass transfer performance of finned tube heat exchangers via superhydrophilic-superhydrophobic dot arrays for dehumidification in greenhouse environment","authors":"Wanling Hu , Changcong Jiang , Yong Guan , Xiuxiu Zhang , Jianyu Hao , Chengxu Wang , Juanli Ma","doi":"10.1016/j.ijheatmasstransfer.2025.128199","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128199","url":null,"abstract":"<div><div>Greenhouses in high-altitude regions often encounter challenges of low temperature and excessive humidity. These result from structural and climatic constraints, leading to high energy consumption for dehumidification. Conventional finned-tube heat exchangers (FTHXs), as core components of refrigeration and dehumidification systems, suffer from inefficient heat transfer and condensate retention, which exacerbate operational losses. To address these limitations, this study proposes a novel finned-tube heat exchanger with superhydrophilic-superhydrophobic dot array (FTHX-SSDA) and introduces a heat and mass transfer enhancement factor (<em>JF</em><sub>hm</sub>). A numerical heat transfer model was developed, and computational fluid dynamics (CFD) simulations were conducted to analyze the thermal and hydraulic performance of the FTHX-SSDA under low-temperature, high-humidity conditions. The results demonstrate that, compared to a finned-tube heat exchanger with hydrophilic-surface (FTHX-HS), the FTHX-SSDA exhibits superior performance. Average enhancements include 31.89 % in the heat transfer factor (<em>j</em><sub>h</sub>), 21.37 % in the mass transfer factor (<em>j</em><sub>m</sub>), and a 1.19 % reduction in the friction factor (<em>f</em>). The <em>JF</em><sub>hm</sub> consistently exceeds unity, confirming the excellent thermal efficiency of the FTHX-SSDA. Furthermore, both <em>j</em><sub>h</sub> and <em>j</em><sub>m</sub> decrease with increasing air-side Reynolds number. However, higher inlet air temperature elevated relative humidity, or lower tube wall temperature improve heat and mass transfer performance. The fitted performance correlation equations for the FTHX-SSDA’s air-side performance under low-temperature, high-humidity conditions were derived. The average errors were 0.6 % (<em>j</em><sub>h</sub>), 0.24 % (<em>j</em><sub>m</sub>), and 0.1 % (<em>f</em>), indicating high predictive accuracy. These results provide valuable technical insights and serve as a reference for improving and optimizing dehumidification systems in greenhouse settings.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128199"},"PeriodicalIF":5.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682987","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}
Based on the core flow theory and boundary layer theory, this study proposes a novel heat transfer enhancement element for tubular heat exchangers: a twisted tape fabricated from open-cell copper foam. Experimental investigations were conducted to analyze the heat transfer characteristics, resistance characteristics, and overall thermal-hydraulic performance of tubes equipped with these copper foam twisted tapes under turbulent flow conditions. Empirical correlations for the Nusselt number (Nu) and friction factor (f) were established. An experimental platform was designed and constructed, and its validity was confirmed through a benchmark case study. The platform was subsequently employed to simulate the performance of the proposed copper foam twisted tape inserts. Results indicate that, compared to solid thick twisted tapes, the copper foam twisted tapes significantly enhance the Nusselt number and the heat transfer effect, albeit with an associated increase in the pressure drop resistance coefficient. The experimental findings show good agreement with established empirical correlations within acceptable error margins. Furthermore, leveraging the experimental data and existing empirical formulas, this paper introduces a new mathematical model tailored for calculating the performance of the specific copper foam twisted tapes studied herein. This work presents, for the first time, a relevant computational mathematical model for tubular heat exchangers incorporating copper foam twisted tape inserts, offering a new design paradigm for such enhanced structures.
{"title":"Experimental research on heat transfer enhancement and pressure drop in tube fitted with foam copper on the shape of twisted tape","authors":"Jin Xin , Zhou Zibo , Yin Hongyi , Yu Xueqian , Wu Yujuan","doi":"10.1016/j.ijheatmasstransfer.2025.128194","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128194","url":null,"abstract":"<div><div>Based on the core flow theory and boundary layer theory, this study proposes a novel heat transfer enhancement element for tubular heat exchangers: a twisted tape fabricated from open-cell copper foam. Experimental investigations were conducted to analyze the heat transfer characteristics, resistance characteristics, and overall thermal-hydraulic performance of tubes equipped with these copper foam twisted tapes under turbulent flow conditions. Empirical correlations for the Nusselt number (<em>Nu</em>) and friction factor (<em>f</em>) were established. An experimental platform was designed and constructed, and its validity was confirmed through a benchmark case study. The platform was subsequently employed to simulate the performance of the proposed copper foam twisted tape inserts. Results indicate that, compared to solid thick twisted tapes, the copper foam twisted tapes significantly enhance the Nusselt number and the heat transfer effect, albeit with an associated increase in the pressure drop resistance coefficient. The experimental findings show good agreement with established empirical correlations within acceptable error margins. Furthermore, leveraging the experimental data and existing empirical formulas, this paper introduces a new mathematical model tailored for calculating the performance of the specific copper foam twisted tapes studied herein. This work presents, for the first time, a relevant computational mathematical model for tubular heat exchangers incorporating copper foam twisted tape inserts, offering a new design paradigm for such enhanced structures.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"257 ","pages":"Article 128194"},"PeriodicalIF":5.8,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683144","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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