Pub Date : 2026-01-14DOI: 10.1016/j.csite.2026.107681
Ilja Astrouski, Krystof Mraz, Jan Bohacek, Ales Horak, Erik Bartuli
{"title":"Thermal performance of automotive radiators made of plastic and stainless steel microtubes","authors":"Ilja Astrouski, Krystof Mraz, Jan Bohacek, Ales Horak, Erik Bartuli","doi":"10.1016/j.csite.2026.107681","DOIUrl":"https://doi.org/10.1016/j.csite.2026.107681","url":null,"abstract":"","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"11 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995394","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.csite.2026.107667
Samr Ul Hasnain, Salim Newaz Kazi, Mohd Nashrul Mohd Zubir, Rab Nawaz, Kaleemullah Shaikh, Wajahat Ahmed Khan, Ammar Ahmed, Imran Afgan
{"title":"Heat Transfer Enhancement for Annular Heat Exchangers Using Inclined Dimple Configurations","authors":"Samr Ul Hasnain, Salim Newaz Kazi, Mohd Nashrul Mohd Zubir, Rab Nawaz, Kaleemullah Shaikh, Wajahat Ahmed Khan, Ammar Ahmed, Imran Afgan","doi":"10.1016/j.csite.2026.107667","DOIUrl":"https://doi.org/10.1016/j.csite.2026.107667","url":null,"abstract":"","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"50 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962522","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.csite.2026.107702
Md Nadimul Akram, Zhaoxuan Liu, Biao Zhang, Wenming Li
With growing demand for energy-efficient cooling systems, compact heat exchangers have become increasingly important, yet their performance is often constrained by persistent thermal boundary layers within mini-tubes. While numerous studies have explored various insert designs to enhance heat transfer in mini-tubes, the persistence of boundary layers remains a significant challenge for achieving high-performance heat exchange. This study introduces a novel jet chamber insert that disrupts thermal boundary layers by generating sequential, wall-impinging jets from the core flow. We systematically examine how variations in jet chamber length influence flow behavior, jet dynamics, and the resulting convective heat transfer characteristics in miniature heat exchangers. Numerical and experimental analyses were conducted to investigate the influence of jet chamber length on the thermal–hydraulic performance of miniature heat exchangers. The results reveal that chamber length plays a dominant role in shaping the internal flow structure and convective heat transfer behavior. As the length increases, a larger number of jet orifices contribute to fluid ejection toward the tube walls, enhancing near-wall mixing and promoting more effective boundary-layer disruption. The mini tube equipped with a 15 mm jet chamber insert achieved a Nusselt number 6.27 times higher than that of the smooth tube at Re = 1200, with a corresponding performance evaluation criterion (PEC) of 2.16. These findings highlight the strong potential of jet chamber inserts to enhance the thermal efficiency of compact mini-tube heat exchangers for energy-efficient thermal management applications.
{"title":"Numerical and experimental study of jet chamber designs for enhancing convective heat transfer in mini-tube heat exchangers","authors":"Md Nadimul Akram, Zhaoxuan Liu, Biao Zhang, Wenming Li","doi":"10.1016/j.csite.2026.107702","DOIUrl":"10.1016/j.csite.2026.107702","url":null,"abstract":"<div><div>With growing demand for energy-efficient cooling systems, compact heat exchangers have become increasingly important, yet their performance is often constrained by persistent thermal boundary layers within mini-tubes. While numerous studies have explored various insert designs to enhance heat transfer in mini-tubes, the persistence of boundary layers remains a significant challenge for achieving high-performance heat exchange. This study introduces a novel jet chamber insert that disrupts thermal boundary layers by generating sequential, wall-impinging jets from the core flow. We systematically examine how variations in jet chamber length influence flow behavior, jet dynamics, and the resulting convective heat transfer characteristics in miniature heat exchangers. Numerical and experimental analyses were conducted to investigate the influence of jet chamber length on the thermal–hydraulic performance of miniature heat exchangers. The results reveal that chamber length plays a dominant role in shaping the internal flow structure and convective heat transfer behavior. As the length increases, a larger number of jet orifices contribute to fluid ejection toward the tube walls, enhancing near-wall mixing and promoting more effective boundary-layer disruption. The mini tube equipped with a 15 mm jet chamber insert achieved a Nusselt number 6.27 times higher than that of the smooth tube at <em>Re</em> = 1200, with a corresponding performance evaluation criterion (PEC) of 2.16. These findings highlight the strong potential of jet chamber inserts to enhance the thermal efficiency of compact mini-tube heat exchangers for energy-efficient thermal management applications.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"78 ","pages":"Article 107702"},"PeriodicalIF":6.4,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962507","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.csite.2026.107701
Xi Chen, Qianhang Jia, Shoukun Xu, Kai Zheng, Ming Peng
To enhance the safety of hydrogen-ammonia fuel utilization, this study explores the complicated relationship between hydrogen content (α(H2)) and explosion dynamics. By integrating an optimized combustion mechanism with large eddy simulation (LES) and thickened flame (TF) models, it uncovers how α(H2) can modulate flame acceleration via regulating chain-branching and nitrogen-chemistry pathways. The LES-TF approach successfully reproduces the crucial explosion parameters, including flame propagation speed, explosion overpressure development, three-dimensional flame structure and radical distribution. Quantitative analysis reveals that increasing α(H2) from 50 % to 75 % causes the reaction flux of H2 - H to surge by 110 %, while the sensitivity coefficient of the chain-propagating reaction OH + H2 ⇌ H + H2O increases by 63.2 %. The key findings indicate that increasing the hydrogen volume fraction (α(H2)) significantly enhances laminar burning velocity (LBV) by promoting the radical-driven chain branching reactions while simultaneously suppressing the influence of nitrogen chemical pathways. The flow fields in the burned zones significantly influence flame evolution and radical distributions during flame acceleration, particularly during the formation of “tulip” flames. The intricate interplay of radical mass fractions and flow fields modulates explosion behavior. This work can establish a predictive approach for H2/NH3/air explosion and provide guidelines for mitigating explosion risk in fuel storage systems.
为了提高氢氨燃料利用的安全性，本研究探讨了氢含量（α(H2)）与爆炸动力学之间的复杂关系。通过将优化的燃烧机制与大涡模拟（LES）和增厚火焰（TF）模型相结合，揭示了α(H2)如何通过调节链分支和氮化学途径调节火焰加速。LES-TF方法成功地再现了包括火焰传播速度、爆炸超压发展、三维火焰结构和径向分布在内的关键爆炸参数。定量分析表明，当α(H2)浓度从50%增加到75%时，H2 - H的反应通量增加了110%，而OH + H2 + H + H2O反应的敏感性系数增加了63.2%。结果表明，增加氢体积分数（α(H2)）可显著提高层流燃烧速度（LBV），促进自由基驱动的链支反应，同时抑制氮化学途径的影响。燃烧区流场对火焰加速过程中火焰演化和自由基分布有显著影响，特别是在“郁金香”火焰形成过程中。自由基质量分数和流场的复杂相互作用调节了爆炸行为。这项工作可以建立H2/NH3/空气爆炸的预测方法，并为降低燃料储存系统的爆炸风险提供指导。
{"title":"Prediction of explosion dynamics of H2/NH3/Air using large eddy simulation and thickened flame model","authors":"Xi Chen, Qianhang Jia, Shoukun Xu, Kai Zheng, Ming Peng","doi":"10.1016/j.csite.2026.107701","DOIUrl":"10.1016/j.csite.2026.107701","url":null,"abstract":"<div><div>To enhance the safety of hydrogen-ammonia fuel utilization, this study explores the complicated relationship between hydrogen content (α(H<sub>2</sub>)) and explosion dynamics. By integrating an optimized combustion mechanism with large eddy simulation (LES) and thickened flame (TF) models, it uncovers how α(H<sub>2</sub>) can modulate flame acceleration via regulating chain-branching and nitrogen-chemistry pathways. The LES-TF approach successfully reproduces the crucial explosion parameters, including flame propagation speed, explosion overpressure development, three-dimensional flame structure and radical distribution. Quantitative analysis reveals that increasing α(H<sub>2</sub>) from 50 % to 75 % causes the reaction flux of H<sub>2</sub> - H to surge by 110 %, while the sensitivity coefficient of the chain-propagating reaction OH + H<sub>2</sub> ⇌ H + H<sub>2</sub>O increases by 63.2 %. The key findings indicate that increasing the hydrogen volume fraction (α(H<sub>2</sub>)) significantly enhances laminar burning velocity (LBV) by promoting the radical-driven chain branching reactions while simultaneously suppressing the influence of nitrogen chemical pathways. The flow fields in the burned zones significantly influence flame evolution and radical distributions during flame acceleration, particularly during the formation of “tulip” flames. The intricate interplay of radical mass fractions and flow fields modulates explosion behavior. This work can establish a predictive approach for H<sub>2</sub>/NH<sub>3</sub>/air explosion and provide guidelines for mitigating explosion risk in fuel storage systems.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"78 ","pages":"Article 107701"},"PeriodicalIF":6.4,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962508","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.csite.2025.107511
Wenlong Tian , Lihao He , Bo Li , ZhaoYong Mao , HuanYu Ou , Bo Cheng
Permanent magnet synchronous motors (PMSMs) demonstrate significant advantages in enhancing propulsion efficiency and system compactness for unmanned underwater vehicles (UUVs), yet their operational reliability is constrained by winding insulation degradation and permanent magnet demagnetization caused by accumulated heat in sealed and narrow space,and traditional oil-cooled systems require extra cooling equipment, which can take up more space and make it difficult to fit into the tight layout of UUVs. Aiming at this challenge, an oil cooling system without extra cooling equipment utilizing oil churning effect is proposed in this paper to address the thermal management limitations of UUV propulsion systems. An electromagnetic-thermal-fluid multi-physics coupling model is established for UUV propulsion motor thermal management system. The oil ratio coefficient (ORC), the UUV's different speeds, type of cooling oil, and different motor working conditions as input parameters are used to analyzes the influence on the motor's cooling conditions. The result shows that oil cooling have excellent thermal management performance compared with natural cooling, achieving a temperature reduction of 80 K at 150 kW. The type of oil shows a relatively small impact on motor components temperature. Satisfyingly, the cooling efficiency of the oil churning system increases with the increase of UUV speed. Besides, a dimensionless power density enhancement factor is proposed firstly to evaluate the cooling system comprehensive performance. The cooling system shows the best performance at an ORC of 0.6. The power density reaches 3.067 kW/kg, which is 43 % higher than that of natural cooling. Therefore, in the design of oil cooling systems for UUV motors, the ORC is a crucial parameter for effective temperature control.
{"title":"Investigation on the influence of oil ratio coefficient on temperature rise in UUV propulsion motors","authors":"Wenlong Tian , Lihao He , Bo Li , ZhaoYong Mao , HuanYu Ou , Bo Cheng","doi":"10.1016/j.csite.2025.107511","DOIUrl":"10.1016/j.csite.2025.107511","url":null,"abstract":"<div><div>Permanent magnet synchronous motors (PMSMs) demonstrate significant advantages in enhancing propulsion efficiency and system compactness for unmanned underwater vehicles (UUVs), yet their operational reliability is constrained by winding insulation degradation and permanent magnet demagnetization caused by accumulated heat in sealed and narrow space,and traditional oil-cooled systems require extra cooling equipment, which can take up more space and make it difficult to fit into the tight layout of UUVs. Aiming at this challenge, an oil cooling system without extra cooling equipment utilizing oil churning effect is proposed in this paper to address the thermal management limitations of UUV propulsion systems. An electromagnetic-thermal-fluid multi-physics coupling model is established for UUV propulsion motor thermal management system. The oil ratio coefficient (ORC), the UUV's different speeds, type of cooling oil, and different motor working conditions as input parameters are used to analyzes the influence on the motor's cooling conditions. The result shows that oil cooling have excellent thermal management performance compared with natural cooling, achieving a temperature reduction of 80 K at 150 kW. The type of oil shows a relatively small impact on motor components temperature. Satisfyingly, the cooling efficiency of the oil churning system increases with the increase of UUV speed. Besides, a dimensionless power density enhancement factor is proposed firstly to evaluate the cooling system comprehensive performance. The cooling system shows the best performance at an ORC of 0.6. The power density reaches 3.067 kW/kg, which is 43 % higher than that of natural cooling. Therefore, in the design of oil cooling systems for UUV motors, the ORC is a crucial parameter for effective temperature control.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"78 ","pages":"Article 107511"},"PeriodicalIF":6.4,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956646","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.csite.2026.107665
Zhang Pengfei
In the context of global low-carbon transition, controlling natural gas station leakages is critically important. This study combines CFD simulations and laboratory experiments to develop a 3D multiphysics coupling model, investigating the effects of leakage velocity, season, wind direction, and speed on gas dispersion.Results show seasonal and wind conditions significantly influence dispersion: spring/summer leakages exhibit larger dispersion ranges with high-concentration zones near walls, while autumn/winter leakages remain concentrated near pipelines. Upwind conditions promote longer gas travel, whereas downwind leakage leads to ground-hugging clouds. Seasonal temperature anomalies (colder in spring/summer, warmer in autumn/winter) show a belt-shaped distribution indicative of leakage sources. Low wind speeds prolong concentration retention in upwind scenarios, while downwind conditions promote multi-directional diffusion.Experimental validation confirms model reliability, with mean relative errors below 8.5%. This study provides theoretical and practical support for dynamic risk assessment and safety management of natural gas stations.
{"title":"Numerical Simulation on Heat Transfer and Flow Characteristics in the Leakage and Diffusion Process at Gas Distribution Stations","authors":"Zhang Pengfei","doi":"10.1016/j.csite.2026.107665","DOIUrl":"https://doi.org/10.1016/j.csite.2026.107665","url":null,"abstract":"In the context of global low-carbon transition, controlling natural gas station leakages is critically important. This study combines CFD simulations and laboratory experiments to develop a 3D multiphysics coupling model, investigating the effects of leakage velocity, season, wind direction, and speed on gas dispersion.Results show seasonal and wind conditions significantly influence dispersion: spring/summer leakages exhibit larger dispersion ranges with high-concentration zones near walls, while autumn/winter leakages remain concentrated near pipelines. Upwind conditions promote longer gas travel, whereas downwind leakage leads to ground-hugging clouds. Seasonal temperature anomalies (colder in spring/summer, warmer in autumn/winter) show a belt-shaped distribution indicative of leakage sources. Low wind speeds prolong concentration retention in upwind scenarios, while downwind conditions promote multi-directional diffusion.Experimental validation confirms model reliability, with mean relative errors below 8.5%. This study provides theoretical and practical support for dynamic risk assessment and safety management of natural gas stations.","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"51 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956647","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.csite.2026.107695
Hsiang-Wen Wang , Ying-Fan Lin , Chia-Hao Chang , Bo-Tsen Wang , Hikari Fujii , Yu-Feng Forrest Lin , Kuo-Hsin Yang , Jui-Pin Tsai
Accurate estimation of subsurface thermal properties is essential for the efficient design of ground-source heat pump (GSHP) and underground thermal energy storage (UTES) systems. However, conventional analytical models for thermal response tests (TRTs), such as the infinite line-source (ILS) and infinite cylindrical-surface-source (ICSS) solutions, neglect grout heat storage, leading to systematic bias during early heating periods. This study develops an analytical composite cylindrical source (CCS) model that explicitly accounts for the volumetric heat capacity of the grout (defined generically herein to denote borehole filling materials, including silica–sand backfill). The closed-form formulation reproduces Laplace-transform finite-difference simulations within 0.1 ° and demonstrates excellent agreement with a distributed TRT conducted on a 54 m borehole. The CCS model reduces the root-mean-square error from 0.163 ° (ILS) to 0.116 °, resolves meter-scale stratification, and yields practically stable estimates of thermal conductivity and heat capacity using 48–50 h of data. A Bayesian uncertainty analysis reveals a ‘transition zone’ around 42 h, suggesting that tests should extend beyond this period to avoid false convergence, but need not extend to 72 h for engineering purposes. Sensitivity analysis indicates that grout heat capacity governs early-time temperature response, whereas ground conductivity dominates later stages. The results show that incorporating grout heat storage significantly improves TRT interpretation accuracy and allows test duration to be shortened without compromising reliability, offering a practical framework for field-scale thermal characterization in GSHP design.
{"title":"Analytical modeling of grout heat storage effects in thermal response tests: Toward faster and more reliable parameter estimation","authors":"Hsiang-Wen Wang , Ying-Fan Lin , Chia-Hao Chang , Bo-Tsen Wang , Hikari Fujii , Yu-Feng Forrest Lin , Kuo-Hsin Yang , Jui-Pin Tsai","doi":"10.1016/j.csite.2026.107695","DOIUrl":"10.1016/j.csite.2026.107695","url":null,"abstract":"<div><div>Accurate estimation of subsurface thermal properties is essential for the efficient design of ground-source heat pump (GSHP) and underground thermal energy storage (UTES) systems. However, conventional analytical models for thermal response tests (TRTs), such as the infinite line-source (ILS) and infinite cylindrical-surface-source (ICSS) solutions, neglect grout heat storage, leading to systematic bias during early heating periods. This study develops an analytical composite cylindrical source (CCS) model that explicitly accounts for the volumetric heat capacity of the grout (defined generically herein to denote borehole filling materials, including silica–sand backfill). The closed-form formulation reproduces Laplace-transform finite-difference simulations within 0.1 °<span><math><mi>C</mi></math></span> and demonstrates excellent agreement with a distributed TRT conducted on a 54 m borehole. The CCS model reduces the root-mean-square error from 0.163 °<span><math><mi>C</mi></math></span> (ILS) to 0.116 °<span><math><mi>C</mi></math></span>, resolves meter-scale stratification, and yields practically stable estimates of thermal conductivity and heat capacity using 48–50 h of data. A Bayesian uncertainty analysis reveals a ‘transition zone’ around 42 h, suggesting that tests should extend beyond this period to avoid false convergence, but need not extend to 72 h for engineering purposes. Sensitivity analysis indicates that grout heat capacity governs early-time temperature response, whereas ground conductivity dominates later stages. The results show that incorporating grout heat storage significantly improves TRT interpretation accuracy and allows test duration to be shortened without compromising reliability, offering a practical framework for field-scale thermal characterization in GSHP design.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"78 ","pages":"Article 107695"},"PeriodicalIF":6.4,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956688","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.csite.2026.107670
Ying Yin , Yunxin Zhu , Dexin Zhang , Yan Li , Liang Gong
High integration of high-performance chips has led to considerable heat generation, making efficient and stable heat dissipation within the chips extremely important. In this paper, a novel microchannel structure based on the Tesla valve is proposed to dissipate the heat generated by the high heat flux density in the chips. The numerical simulations are then performed using the standard k-ε turbulence model to explore how the number of valve stages, valve core shapes, structural parameters, and arrangements affect the flow and heat transfer performance of the microchannel. The results show that the microchannel with 12 valve stages exhibits the best performance. Compared to the rectangular fin (RF) type microchannel, the heat transfer performance in Tesla valve microchannels can be significantly enhanced, where the increased performance evaluation criterion (PEC) for reverse flow is superior to that for forward flow. The optimal shape of the Tesla valve core is an ellipse, whose PEC can be increased by up to 20.23 % compared with the RF microchannel. More importantly, the increasing arrangement of the valve structure along the flow direction can optimally balance flow resistance and heat transfer, resulting in enhanced overall performance. These results can provide new insights into efficient heat dissipation in electronic devices.
{"title":"A comprehensive analysis of flow and heat transfer performance in a novel Tesla valve microchannel","authors":"Ying Yin , Yunxin Zhu , Dexin Zhang , Yan Li , Liang Gong","doi":"10.1016/j.csite.2026.107670","DOIUrl":"10.1016/j.csite.2026.107670","url":null,"abstract":"<div><div>High integration of high-performance chips has led to considerable heat generation, making efficient and stable heat dissipation within the chips extremely important. In this paper, a novel microchannel structure based on the Tesla valve is proposed to dissipate the heat generated by the high heat flux density in the chips. The numerical simulations are then performed using the standard <em>k-ε</em> turbulence model to explore how the number of valve stages, valve core shapes, structural parameters, and arrangements affect the flow and heat transfer performance of the microchannel. The results show that the microchannel with 12 valve stages exhibits the best performance. Compared to the rectangular fin (RF) type microchannel, the heat transfer performance in Tesla valve microchannels can be significantly enhanced, where the increased performance evaluation criterion (<em>PEC</em>) for reverse flow is superior to that for forward flow. The optimal shape of the Tesla valve core is an ellipse, whose <em>PEC</em> can be increased by up to 20.23 % compared with the RF microchannel. More importantly, the increasing arrangement of the valve structure along the flow direction can optimally balance flow resistance and heat transfer, resulting in enhanced overall performance. These results can provide new insights into efficient heat dissipation in electronic devices.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"78 ","pages":"Article 107670"},"PeriodicalIF":6.4,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, a pumpless gravity-driven Organic Rankine Cycle (PORC) system was developed and experimentally tested for low-temperature heat recovery applications. The system utilized a modified scroll expander, originally designed for automotive air conditioning, and operated entirely via natural circulation, without a mechanical pump. The effects of refrigerant charge, heat source temperature, and resistive electrical load were investigated to evaluate system behavior and power generation efficiency. Results revealed that stable operation was achieved with a refrigerant charge between 2.1–2.3 kg, heat-source temperatures of 40–60 °C, and a system height of 2.8–3.1 m. The maximum work output of the expander reached 18.44 W, while electrical power output peaked at 0.80 W under optimal conditions. The scroll expander isentropic efficiency ranged from 30 to 86 %. A positive, approximately linear correlation was observed between system height and work output within the tested range. Although theoretical and experimental efficiencies diverged significantly—highlighting mechanical and electrical losses—the study confirmed the technical feasibility of pumpless ORC systems. Although the output is modest, it is comparable to other small-scale ORC systems operating at similar source temperatures, demonstrating comparable efficiency without a mechanical pump. These findings support the application of gravity-driven ORC systems for power production in space-constrained and off-grid environments using low-grade thermal energy sources.
{"title":"Experimental investigation on low temperature heat source with a pumpless gravity-driven closed loop thermosyphon organic Rankine cycle","authors":"Samittisak Plaikaew, Thanit Swasdisevi, Jirawan Tiansuwan","doi":"10.1016/j.csite.2026.107672","DOIUrl":"10.1016/j.csite.2026.107672","url":null,"abstract":"<div><div>In this study, a pumpless gravity-driven Organic Rankine Cycle (PORC) system was developed and experimentally tested for low-temperature heat recovery applications. The system utilized a modified scroll expander, originally designed for automotive air conditioning, and operated entirely via natural circulation, without a mechanical pump. The effects of refrigerant charge, heat source temperature, and resistive electrical load were investigated to evaluate system behavior and power generation efficiency. Results revealed that stable operation was achieved with a refrigerant charge between 2.1–2.3 kg, heat-source temperatures of 40–60 °C, and a system height of 2.8–3.1 m. The maximum work output of the expander reached 18.44 W, while electrical power output peaked at 0.80 W under optimal conditions. The scroll expander isentropic efficiency ranged from 30 to 86 %. A positive, approximately linear correlation was observed between system height and work output within the tested range. Although theoretical and experimental efficiencies diverged significantly—highlighting mechanical and electrical losses—the study confirmed the technical feasibility of pumpless ORC systems. Although the output is modest, it is comparable to other small-scale ORC systems operating at similar source temperatures, demonstrating comparable efficiency without a mechanical pump. These findings support the application of gravity-driven ORC systems for power production in space-constrained and off-grid environments using low-grade thermal energy sources.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"78 ","pages":"Article 107672"},"PeriodicalIF":6.4,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956689","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}
This study innovatively couples ultrasonic active control technology with the structural characteristics of spiral-wound tube heat exchangers, proposing a novel multi-physical field synergistic approach for heat transfer enhancement. A tube bundle-acoustic field interaction experimental system was established to study the effects of the intensity (133,333 W/m2, 233,333 W/m2, 333,333 W/m2) and frequency (21 kHz, 25 kHz, 28 kHz) of ultrasonic waves, the installation position of transducers (inlet-only, outlet-only, simultaneous inlet-outlet), as well as the influence of installing different numbers of transducers (1–4) under different working conditions on the comprehensive heat exchange drag reduction capacity of the tube bundle were studied. The results demonstrate that ultrasonic technology provides dual enhancements: heat transfer intensification and drag reduction. The experimental results demonstrate an inverse correlation between ultrasonic frequency and enhancement magnitude. When subjected to 21 kHz excitation, the Nusselt number exhibits a 33.8% enhancement while the friction factor shows a 13.66% reduction compared to baseline conditions. This synergistic effect yields 40.86% improvement in thermal-hydraulic performance. When transducers are installed at both the inlet and outlet, optimal heat transfer performance is achieved. Compared to conditions without ultrasound, the Nusselt number increases by 72%. Comparing the installation of different numbers of transducers at the inlet of the heat exchange tube, the optimal heat transfer enhancement effect was achieved when three ultrasonic transducers were installed. The Nusselt number increased by up to 88%, and the Performance Evaluation Coefficient (PEC) reached its maximum value of 3.36.
本研究创新性地将超声主动控制技术与螺旋缠绕管换热器的结构特点结合起来，提出了一种新的多物理场协同强化换热方法。管bundle-acoustic交互建立了实验系统研究领域的影响强度(133333 W / m2, 233333 W / m2, 333333 W / m2)和频率(21 kHz, 25 kHz, 28千赫)的超声波传感器的安装位置(inlet-only outlet-only,同时进出),并研究了不同工况下安装不同数量换能器（1-4个）对管束综合换热减阻能力的影响。结果表明，超声技术提供了双重增强：传热强化和阻力减少。实验结果表明，超声频率与增强幅度呈负相关。当受到21 kHz激励时，与基线条件相比，努塞尔数增加了33.8%，而摩擦系数减少了13.66%。这种协同效应使热工性能提高了40.86%。当换能器安装在入口和出口时，可以实现最佳的传热性能。与没有超声的情况相比，努塞尔数增加了72%。对比换热管进口安装不同数量换能器的效果，安装3个换能器的换热效果最佳。Nusselt数增加了88%，性能评价系数（PEC）达到最大值3.36。
{"title":"Synergistic Heat Transfer Enhancement and Drag Reduction in Spiral Wound Tubes via Ultrasonic Excitation","authors":"Zhao Chen, Fengjun Wang, Mingbao Zhang, Zhijian Wang, Chulin Yu","doi":"10.1016/j.csite.2026.107675","DOIUrl":"https://doi.org/10.1016/j.csite.2026.107675","url":null,"abstract":"This study innovatively couples ultrasonic active control technology with the structural characteristics of spiral-wound tube heat exchangers, proposing a novel multi-physical field synergistic approach for heat transfer enhancement. A tube bundle-acoustic field interaction experimental system was established to study the effects of the intensity (133,333 W/m<ce:sup loc=\"post\">2</ce:sup>, 233,333 W/m<ce:sup loc=\"post\">2</ce:sup>, 333,333 W/m<ce:sup loc=\"post\">2</ce:sup>) and frequency (21 kHz, 25 kHz, 28 kHz) of ultrasonic waves, the installation position of transducers (inlet-only, outlet-only, simultaneous inlet-outlet), as well as the influence of installing different numbers of transducers (1–4) under different working conditions on the comprehensive heat exchange drag reduction capacity of the tube bundle were studied. The results demonstrate that ultrasonic technology provides dual enhancements: heat transfer intensification and drag reduction. The experimental results demonstrate an inverse correlation between ultrasonic frequency and enhancement magnitude. When subjected to 21 kHz excitation, the Nusselt number exhibits a 33.8% enhancement while the friction factor shows a 13.66% reduction compared to baseline conditions. This synergistic effect yields 40.86% improvement in thermal-hydraulic performance. When transducers are installed at both the inlet and outlet, optimal heat transfer performance is achieved. Compared to conditions without ultrasound, the Nusselt number increases by 72%. Comparing the installation of different numbers of transducers at the inlet of the heat exchange tube, the optimal heat transfer enhancement effect was achieved when three ultrasonic transducers were installed. The Nusselt number increased by up to 88%, and the Performance Evaluation Coefficient (PEC) reached its maximum value of 3.36.","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"15 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956684","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号