Pub Date : 2026-02-08DOI: 10.1016/j.applthermaleng.2026.130176
Amr S. Abouzied , Ali Basem , Hyder H. Abed Balla , Omar J. Alkhatib , Zainab Ali Bu sinnah , Hedi Elmonser , Dilsora Abduvalieva , Hind Albalawi , Abdulrahman M. Alansari , Ibrahim Mahariq
<div><div>The low thermal conductivity of air poses a significant challenge to the efficiency of solar air heaters, and this requires sophisticated heat transfer enhancement techniques. This study investigates the performance of a tubular solar air heater integrated with twisted tape inserts to address this limitation. A hybrid approach using 3D computational fluid dynamics combined with deep neural networks was adopted for systematic analysis of five dimensionless parameters- twisted tape length <span><math><mrow><mfenced><mrow><msub><mi>l</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, twisted tape diameter <span><math><mrow><mfenced><mrow><msub><mi>d</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, twisted tape thickness <span><math><mrow><mfenced><mrow><msub><mi>t</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, twisted tape pitch <span><math><mrow><mfenced><mrow><msub><mi>p</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, and Reynolds number. Quantitative results have shown that tape diameter increment coupled with pitch reduction are the major promoters for thermal enhancement, as an increase in <span><math><mrow><mfenced><mrow><msub><mi>d</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span> from 0.322 to 0.483 increases the Nusselt number by 30%. On the other hand, tighter pitch ratio <span><math><mrow><mfenced><mrow><msub><mi>p</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub><mspace></mspace></mrow></mfenced></mrow></math></span> has resulted in a 4.7-fold increase in friction factor at Re = 10,000. The surrogate model with the DNN showed highly accurate prediction results with an average deviation of approximately 1–2% relative to the CFD results. For the global optimization experiment with the DNN, the maximum value of the thermo-hydraulic performance factor of 1.45 was found at Re = 10,000, <span><math><mrow><mfenced><mrow><msub><mi>d</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub><mspace></mspace></mrow></mfenced></mrow></math></span> = 0.48, and <span><math><mrow><mfenced><mrow><msub><mi>p</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub><mspace></mspace></mrow></mfenced></mrow></math></span> = 2.68, making it superior to the state-of-the-art tubular swirl generators reported in the literature. The originality and creativity in the thesis lie in the conversion of a machine learning model from a prediction model to a design engine to expose the non-linear inter-relationship between the parameters. This hybrid approach involving CFD and ML not only captures the complex physical phenomenon associated with the twisted tape geometry in terms of affecting the flow and heat transfer mechanisms in an accurate manner, but it also
{"title":"Numerical simulation and machine learning modeling of tubular solar air heaters enhanced with twisted tape inserts","authors":"Amr S. Abouzied , Ali Basem , Hyder H. Abed Balla , Omar J. Alkhatib , Zainab Ali Bu sinnah , Hedi Elmonser , Dilsora Abduvalieva , Hind Albalawi , Abdulrahman M. Alansari , Ibrahim Mahariq","doi":"10.1016/j.applthermaleng.2026.130176","DOIUrl":"10.1016/j.applthermaleng.2026.130176","url":null,"abstract":"<div><div>The low thermal conductivity of air poses a significant challenge to the efficiency of solar air heaters, and this requires sophisticated heat transfer enhancement techniques. This study investigates the performance of a tubular solar air heater integrated with twisted tape inserts to address this limitation. A hybrid approach using 3D computational fluid dynamics combined with deep neural networks was adopted for systematic analysis of five dimensionless parameters- twisted tape length <span><math><mrow><mfenced><mrow><msub><mi>l</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, twisted tape diameter <span><math><mrow><mfenced><mrow><msub><mi>d</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, twisted tape thickness <span><math><mrow><mfenced><mrow><msub><mi>t</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, twisted tape pitch <span><math><mrow><mfenced><mrow><msub><mi>p</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span>, and Reynolds number. Quantitative results have shown that tape diameter increment coupled with pitch reduction are the major promoters for thermal enhancement, as an increase in <span><math><mrow><mfenced><mrow><msub><mi>d</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub></mrow></mfenced></mrow></math></span> from 0.322 to 0.483 increases the Nusselt number by 30%. On the other hand, tighter pitch ratio <span><math><mrow><mfenced><mrow><msub><mi>p</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub><mspace></mspace></mrow></mfenced></mrow></math></span> has resulted in a 4.7-fold increase in friction factor at Re = 10,000. The surrogate model with the DNN showed highly accurate prediction results with an average deviation of approximately 1–2% relative to the CFD results. For the global optimization experiment with the DNN, the maximum value of the thermo-hydraulic performance factor of 1.45 was found at Re = 10,000, <span><math><mrow><mfenced><mrow><msub><mi>d</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub><mspace></mspace></mrow></mfenced></mrow></math></span> = 0.48, and <span><math><mrow><mfenced><mrow><msub><mi>p</mi><mi>t</mi></msub><mo>/</mo><msub><mi>D</mi><mi>h</mi></msub><mspace></mspace></mrow></mfenced></mrow></math></span> = 2.68, making it superior to the state-of-the-art tubular swirl generators reported in the literature. The originality and creativity in the thesis lie in the conversion of a machine learning model from a prediction model to a design engine to expose the non-linear inter-relationship between the parameters. This hybrid approach involving CFD and ML not only captures the complex physical phenomenon associated with the twisted tape geometry in terms of affecting the flow and heat transfer mechanisms in an accurate manner, but it also","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130176"},"PeriodicalIF":6.9,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186429","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}
Understanding heat and mass transfer during microwave heating is essential for predicting evaporation, superheating, and temperature non-uniformity in liquid systems. Here, we present a systematic experimental–modeling investigation of microwave heating in water, sucrose, and NaCl solutions over a range of concentrations and input powers. Bulk and surface temperatures were monitored in real time using thermocouples and infrared pyrometry, enabling direct assessment of temperature non-uniformity. Evaporation- and superheating-induced mass loss was quantified using pixel-tracking image analysis (PTIA) and validated gravimetrically, with an average deviation of 6.91 ± 4.42%. Material property variations were minor for sucrose solutions but pronounced for NaCl solutions, which exhibited substantial increases in electrical conductivity and dielectric loss. Sub-boiling COMSOL simulations incorporating solution-dependent dielectric properties, microwave power dissipation, and natural convection reproduce nearly uniform heating in water and sucrose (ΔTuni = 0.37–0.51 °C) and pronounced surface-localized heating in NaCl solutions (ΔTuni = 4.0–4.9 °C), associated with reduced microwave penetration depth. All solutions exhibit superheating, reaching temperatures up to ∼112 °C with measurable mass loss. A simplified lumped and multi-domain heat–mass transfer model is used to interpret the transition from uniform to non-uniform heating and the associated evaporation behavior. Overall, this work provides an experimentally grounded framework for interpreting microwave heating in liquids and improving the reproducibility of microwave-assisted thermal processes.
{"title":"Experimental and modeling investigation of superheating, evaporation and non-uniform heating in microwave-heated liquids","authors":"Arreerat Jiamprasertboon , Natdanai Saipan , Pongsakorn Wattanasit , Tanachat Eknapakul","doi":"10.1016/j.applthermaleng.2026.130183","DOIUrl":"10.1016/j.applthermaleng.2026.130183","url":null,"abstract":"<div><div>Understanding heat and mass transfer during microwave heating is essential for predicting evaporation, superheating, and temperature non-uniformity in liquid systems. Here, we present a systematic experimental–modeling investigation of microwave heating in water, sucrose, and NaCl solutions over a range of concentrations and input powers. Bulk and surface temperatures were monitored in real time using thermocouples and infrared pyrometry, enabling direct assessment of temperature non-uniformity. Evaporation- and superheating-induced mass loss was quantified using pixel-tracking image analysis (PTIA) and validated gravimetrically, with an average deviation of 6.91 ± 4.42%. Material property variations were minor for sucrose solutions but pronounced for NaCl solutions, which exhibited substantial increases in electrical conductivity and dielectric loss. Sub-boiling COMSOL simulations incorporating solution-dependent dielectric properties, microwave power dissipation, and natural convection reproduce nearly uniform heating in water and sucrose (ΔT<sub>uni</sub> = 0.37–0.51 °C) and pronounced surface-localized heating in NaCl solutions (ΔT<sub>uni</sub> = 4.0–4.9 °C), associated with reduced microwave penetration depth. All solutions exhibit superheating, reaching temperatures up to ∼112 °C with measurable mass loss. A simplified lumped and multi-domain heat–mass transfer model is used to interpret the transition from uniform to non-uniform heating and the associated evaporation behavior. Overall, this work provides an experimentally grounded framework for interpreting microwave heating in liquids and improving the reproducibility of microwave-assisted thermal processes.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130183"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186496","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130175
Zheng Qiu , Shutian Liu , Quhao Li , Song Zhang , Qing Zhang
With the development of high-speed and lightweight aircraft, cooling channels must dissipate intense heat while maintaining structural integrity under severe thermo-mechanical loads. Current design methods mainly focus on thermal-hydraulic performance, often neglecting load-bearing capacity, which can lead to stress concentrations and premature failure. To overcome this limitation, this study proposes a multiphysics topology optimization framework that concurrently integrates structural stiffness, strength, thermal resistance, and flow resistance in cooling channel design. A density-based approach combines a multi-layer 2D conjugate heat transfer model with a projected 3D mechanical analysis, thus avoiding stiffness singularity in 2D channel analysis while enabling efficient evaluation of temperature, flow, compliance, and stress. Numerical examples under various design conditions demonstrate that incorporating load-bearing performance significantly alters channel layouts compared to thermal-hydraulic-only designs, eliminating stress-concentrating features. The optimized designs can increase stiffness by up to 27.41% and reduce maximum stress by 17.44%, while effectively managing thermal performance. These results validate the proposed method as a robust tool for designing cooling channels that meet combined structural-thermal-hydraulic requirements, providing an effective method to improve high-performance aerospace thermal management systems.
{"title":"Multiphysics topology optimization method for regenerative cooling channels integrating structural-thermal-hydraulic performance","authors":"Zheng Qiu , Shutian Liu , Quhao Li , Song Zhang , Qing Zhang","doi":"10.1016/j.applthermaleng.2026.130175","DOIUrl":"10.1016/j.applthermaleng.2026.130175","url":null,"abstract":"<div><div>With the development of high-speed and lightweight aircraft, cooling channels must dissipate intense heat while maintaining structural integrity under severe thermo-mechanical loads. Current design methods mainly focus on thermal-hydraulic performance, often neglecting load-bearing capacity, which can lead to stress concentrations and premature failure. To overcome this limitation, this study proposes a multiphysics topology optimization framework that concurrently integrates structural stiffness, strength, thermal resistance, and flow resistance in cooling channel design. A density-based approach combines a multi-layer 2D conjugate heat transfer model with a projected 3D mechanical analysis, thus avoiding stiffness singularity in 2D channel analysis while enabling efficient evaluation of temperature, flow, compliance, and stress. Numerical examples under various design conditions demonstrate that incorporating load-bearing performance significantly alters channel layouts compared to thermal-hydraulic-only designs, eliminating stress-concentrating features. The optimized designs can increase stiffness by up to 27.41% and reduce maximum stress by 17.44%, while effectively managing thermal performance. These results validate the proposed method as a robust tool for designing cooling channels that meet combined structural-thermal-hydraulic requirements, providing an effective method to improve high-performance aerospace thermal management systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130175"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186437","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130104
Ao Shen , Juan Zhao , Yongcai Li , Wenjie Zhang , Bojing Huang
To Verify the Improvements in the Indoor Thermal Environment and Photovoltaic Power Output Achieved by a Passive PV/T–EAHE Coupled System, a Full-Scale Test Rig Was Established in Hami, Xinjiang Uygur Autonomous Region, China. Indoor Ventilation Rate and Temperature, PV Module Surface Temperature, and Electrical Output Were Monitored under Three Operating Conditions: Open-Window Ventilation with PV Air Channel and Solar Chimney (Condition 1), the Setting of an Independent EAHE and Independent Photovoltaic Modules in the Room (Condition 2), and the PV/T–EAHE Coupling System (Condition 3). The Results Indicate that the Coupled System Yields Marked Benefits Representative Low- and High-Temperature Periods (1) during the Low-Temperature Period, Condition 3 Enhanced Daytime Ventilation and Stabilized Nighttime Indoor Temperatures, Mitigating Excessive Indoor Cooling. The Nocturnal Minimum Indoor Temperature under Condition 3 Was 2.30 °C Higher than that under Condition 1, the Daytime Maximum Indoor Temperature Reached 24.20 °C, and the Mean Ventilation Rate Increased by 35.92 m3/H. (2) during the High-Temperature Period, the Ventilation Enhancement Provided by the Passive Coupling Contributed to Indoor Cooling and Improved Photovoltaic Efficiency. Under Condition 3, the Maximum Ventilation Rate Reached 247.50 m3/H, the Peak Indoor Temperature Was 1.50 °C Lower than that under Condition 2, and Photovoltaic Conversion Efficiency Increased by Approximately 4.2%. Overall, the Findings Demonstrate that an Appropriately Designed Passive Coupling Strategy Can Achieve Synergistic Optimization of Ventilation, Cooling, and Photovoltaic Performance, with Notable Potential for Deployment in Areas with Limited Electricity Supply
{"title":"Experimental research on thermal and electric collaborative optimization of PV/T-EAHE passive coupling system","authors":"Ao Shen , Juan Zhao , Yongcai Li , Wenjie Zhang , Bojing Huang","doi":"10.1016/j.applthermaleng.2026.130104","DOIUrl":"10.1016/j.applthermaleng.2026.130104","url":null,"abstract":"<div><div>To Verify the Improvements in the Indoor Thermal Environment and Photovoltaic Power Output Achieved by a Passive PV/T–EAHE Coupled System, a Full-Scale Test Rig Was Established in Hami, Xinjiang Uygur Autonomous Region, China. Indoor Ventilation Rate and Temperature, PV Module Surface Temperature, and Electrical Output Were Monitored under Three Operating Conditions: Open-Window Ventilation with PV Air Channel and Solar Chimney (Condition 1), the Setting of an Independent EAHE and Independent Photovoltaic Modules in the Room (Condition 2), and the PV/T–EAHE Coupling System (Condition 3). The Results Indicate that the Coupled System Yields Marked Benefits Representative Low- and High-Temperature Periods (1) during the Low-Temperature Period, Condition 3 Enhanced Daytime Ventilation and Stabilized Nighttime Indoor Temperatures, Mitigating Excessive Indoor Cooling. The Nocturnal Minimum Indoor Temperature under Condition 3 Was 2.30 °C Higher than that under Condition 1, the Daytime Maximum Indoor Temperature Reached 24.20 °C, and the Mean Ventilation Rate Increased by 35.92 m<sup>3</sup>/H. (2) during the High-Temperature Period, the Ventilation Enhancement Provided by the Passive Coupling Contributed to Indoor Cooling and Improved Photovoltaic Efficiency. Under Condition 3, the Maximum Ventilation Rate Reached 247.50 m<sup>3</sup>/H, the Peak Indoor Temperature Was 1.50 °C Lower than that under Condition 2, and Photovoltaic Conversion Efficiency Increased by Approximately 4.2%. Overall, the Findings Demonstrate that an Appropriately Designed Passive Coupling Strategy Can Achieve Synergistic Optimization of Ventilation, Cooling, and Photovoltaic Performance, with Notable Potential for Deployment in Areas with Limited Electricity Supply</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"291 ","pages":"Article 130104"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187737","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130081
Pichakorn Kaewown, Niti Kammuang-lue, Ramnarong Wanison, Pradit Terdtoon, Phrut Sakulchangsatjatai
Developing a closed-loop pulsating heat pipe (CLPHP) capable of managing multiple heat sources and sinks (MHSCLPHP) is essential for complex thermal systems. Although conventional CLPHP with a single heat source and sink (1–1 CLPHP) have been extensively studied, their applicability to multiple heat sources and sinks remains limited. To address this gap, this study investigates the thermal performance of the MHSCLPHP, focusing on temperature characteristics, working fluid flow behavior, and the development of modified correlations for performance prediction. The CLPHP was constructed from copper tubes with a 2 mm inner diameter, 16 meandering turns, and a 50% filling ratio using ethanol and water as the working fluids. The evaporator and condenser sections each had a total length of 150 mm. The number of heat sources and sinks was varied from 1–1 to 5–5. The results showed that increasing the number of heat sources significantly enhanced heat transfer rates while reduced thermal resistance. Temperature oscillations became more continuous and stable, with smaller amplitudes, higher frequencies, and a one-directional flow of the working fluid was observed. The configuration with five heat sources achieved maximum heat transfer rates of 44.4 kW/m2 for water and 31.6 kW/m2 for ethanol, corresponding to increases of 46% and 44%, respectively, compared with the 1–1 CLPHP. The minimum thermal resistances were 0.018 °C/W and 0.027 °C/W, representing reductions of 43% and 39%, respectively. These findings clearly demonstrate that the thermal performance of a CLPHP can be substantially improved by designing it with multiple heat sources. Such a configuration consistently exhibited higher heat transfer rates, lower thermal resistance, and a one-directional flow of the working fluid, highlighting its potential for applications involving distributed heat generation. A modified correlation for predicting MHSCLPHP performance was developed and showed good agreement with the experimental data, with deviations within ±8.0%.
{"title":"Thermal performance enhancement of closed-loop pulsating heat pipes with multiple heat sources and sinks through the development of a modified predictive correlation","authors":"Pichakorn Kaewown, Niti Kammuang-lue, Ramnarong Wanison, Pradit Terdtoon, Phrut Sakulchangsatjatai","doi":"10.1016/j.applthermaleng.2026.130081","DOIUrl":"10.1016/j.applthermaleng.2026.130081","url":null,"abstract":"<div><div>Developing a closed-loop pulsating heat pipe (CLPHP) capable of managing multiple heat sources and sinks (MHSCLPHP) is essential for complex thermal systems. Although conventional CLPHP with a single heat source and sink (1–1 CLPHP) have been extensively studied, their applicability to multiple heat sources and sinks remains limited. To address this gap, this study investigates the thermal performance of the MHSCLPHP, focusing on temperature characteristics, working fluid flow behavior, and the development of modified correlations for performance prediction. The CLPHP was constructed from copper tubes with a 2 mm inner diameter, 16 meandering turns, and a 50% filling ratio using ethanol and water as the working fluids. The evaporator and condenser sections each had a total length of 150 mm. The number of heat sources and sinks was varied from 1–1 to 5–5. The results showed that increasing the number of heat sources significantly enhanced heat transfer rates while reduced thermal resistance. Temperature oscillations became more continuous and stable, with smaller amplitudes, higher frequencies, and a one-directional flow of the working fluid was observed. The configuration with five heat sources achieved maximum heat transfer rates of 44.4 kW/m<sup>2</sup> for water and 31.6 kW/m<sup>2</sup> for ethanol, corresponding to increases of 46% and 44%, respectively, compared with the 1–1 CLPHP. The minimum thermal resistances were 0.018 °C/W and 0.027 °C/W, representing reductions of 43% and 39%, respectively. These findings clearly demonstrate that the thermal performance of a CLPHP can be substantially improved by designing it with multiple heat sources. Such a configuration consistently exhibited higher heat transfer rates, lower thermal resistance, and a one-directional flow of the working fluid, highlighting its potential for applications involving distributed heat generation. A modified correlation for predicting MHSCLPHP performance was developed and showed good agreement with the experimental data, with deviations within ±8.0%.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"291 ","pages":"Article 130081"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187743","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130156
Muhammad Ahmad Jamil , Muhammad Ikhlaq , Muhammad Mehroz , Haseeb Yaqoob , William Worek , Muhammad Wakil Shahzad
Abstract
A notable substitute for traditional vapor compression chillers that is economical, sustainable, and energy-efficient is indirect evaporative cooling (IEC) technology. It offers several advantages like resource saving (energy, water, emissions, etc.), environmentally friendly working, and chemical-neutral operation. However, IEC systems are still in the development stage and require significant improvements in design and materials to outperform the market-dominant vapor compression chillers. This work offers a thorough experimental and computational fluid dynamics (CFD) investigation of an innovative cooling system that overcomes significant design constraints and provides improved performance. The proposed system's 150 W cooling capacity is fabricated and studied. Then, a robust model is developed to examine the impact of key input parameters, such as temperature, velocity, channel length, and airflow rate ratio. The CFD model is rigorously validated with the existing literature and the current experimental data. The experiment revealed a temperature reduction of 20.4 °C for an outside air temperature of 48 °C. The CFD analysis shows that increasing dry and wet channel velocities (1–3 m/s) slightly increased the supply temperature, indicating design constraints on cooling capacity. Meanwhile, an increase in the airflow rate ratio (AFR) lowers the supply air temperature because a higher AFR boosts evaporation in the wet channel, thereby increasing heat transfer. Furthermore, it is noted that latent heat transfer during evaporation accounts for most of the cooling, resulting in a temperature reduction of up to 20 °C in the dry channel compared to just a 3 °C (max) rise in the working air temperature.
{"title":"Experiments and CFD based design and analysis of a novel indirect evaporative cooler for future sustainability","authors":"Muhammad Ahmad Jamil , Muhammad Ikhlaq , Muhammad Mehroz , Haseeb Yaqoob , William Worek , Muhammad Wakil Shahzad","doi":"10.1016/j.applthermaleng.2026.130156","DOIUrl":"10.1016/j.applthermaleng.2026.130156","url":null,"abstract":"<div><div>Abstract</div><div>A notable substitute for traditional vapor compression chillers that is economical, sustainable, and energy-efficient is indirect evaporative cooling (IEC) technology. It offers several advantages like resource saving (energy, water, emissions, etc.), environmentally friendly working, and chemical-neutral operation. However, IEC systems are still in the development stage and require significant improvements in design and materials to outperform the market-dominant vapor compression chillers. This work offers a thorough experimental and computational fluid dynamics (CFD) investigation of an innovative cooling system that overcomes significant design constraints and provides improved performance. The proposed system's 150 W cooling capacity is fabricated and studied. Then, a robust model is developed to examine the impact of key input parameters, such as temperature, velocity, channel length, and airflow rate ratio. The CFD model is rigorously validated with the existing literature and the current experimental data. The experiment revealed a temperature reduction of 20.4 °C for an outside air temperature of 48 °C. The CFD analysis shows that increasing dry and wet channel velocities (1–3 m/s) slightly increased the supply temperature, indicating design constraints on cooling capacity. Meanwhile, an increase in the airflow rate ratio (AFR) lowers the supply air temperature because a higher AFR boosts evaporation in the wet channel, thereby increasing heat transfer. Furthermore, it is noted that latent heat transfer during evaporation accounts for most of the cooling, resulting in a temperature reduction of up to 20 °C in the dry channel compared to just a 3 °C (max) rise in the working air temperature.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130156"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186401","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130193
Basile Chaudoir, Samuel Gendebien, Vincent Lemort
Conventional single-zone heat exchanger models fail to resolve local temperature gradients, property variations, and phase transitions, while high-fidelity distributed models are often too computationally demanding to be embedded in integrated design optimization. To bridge this gap, this work presents a shell-and-tube heat exchanger sizing framework that couples a novel tube-pass-aware one-dimensional moving-boundary model with a particle swarm optimization algorithm. The modeling framework includes a user-defined discretization level, allowing a tunable balance between accuracy and computational cost. The optimization objective is the minimization of total heat exchanger mass, thereby reducing thermal inertia while lowering material use, handling requirements, and overall cost. Comparative validation against published reference cases under single-phase and two-phase operating conditions demonstrates heat exchanger mass reductions of 22 to 24%, while increasing modeling fidelity. The predictive accuracy was comparatively validated with the reference studies, with heat transfer deviations of approximately 1% and pressure-drop deviations below 10% for low discretization modeling. Achieving these improvements within a reasonable computational time, the optimization results show that the factors most strongly affecting heat exchanger mass are, in order of importance, the tube-thickness assumptions (−28 to −46%) as tubes represent 60 to 80% of the total mass, the discretization level (−10 to ＋56%), and the choice of objective function (−10%).
{"title":"An open-source moving-boundary approach for shell-and-tube heat exchanger sizing optimization","authors":"Basile Chaudoir, Samuel Gendebien, Vincent Lemort","doi":"10.1016/j.applthermaleng.2026.130193","DOIUrl":"10.1016/j.applthermaleng.2026.130193","url":null,"abstract":"<div><div>Conventional single-zone heat exchanger models fail to resolve local temperature gradients, property variations, and phase transitions, while high-fidelity distributed models are often too computationally demanding to be embedded in integrated design optimization. To bridge this gap, this work presents a shell-and-tube heat exchanger sizing framework that couples a novel tube-pass-aware one-dimensional moving-boundary model with a particle swarm optimization algorithm. The modeling framework includes a user-defined discretization level, allowing a tunable balance between accuracy and computational cost. The optimization objective is the minimization of total heat exchanger mass, thereby reducing thermal inertia while lowering material use, handling requirements, and overall cost. Comparative validation against published reference cases under single-phase and two-phase operating conditions demonstrates heat exchanger mass reductions of 22 to 24%, while increasing modeling fidelity. The predictive accuracy was comparatively validated with the reference studies, with heat transfer deviations of approximately 1% and pressure-drop deviations below 10% for low discretization modeling. Achieving these improvements within a reasonable computational time, the optimization results show that the factors most strongly affecting heat exchanger mass are, in order of importance, the tube-thickness assumptions (−28 to −46%) as tubes represent 60 to 80% of the total mass, the discretization level (−10 to ＋56%), and the choice of objective function (−10%).</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130193"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186334","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130188
Liu Yang , Yixin Yang , Tongwang Shi , Tao Tang , Mingbo Sun , Wang Han , Qinyuan Li , Rui Gu , Hongbo Wang , Dapeng Xiong , Jiajian Zhu
The supersonic combustion enhancement characteristics of a combined combustor configuration consisting of a backward-facing step and a cavity are investigated numerically in this paper. Numerical simulations are conducted using a hybrid RANS/LES method. Numerical validation is performed on an axisymmetric cavity supersonic combustor as the baseline configuration. The numerical results agree well with the experimental measurements. On this basis, this paper proposes a combined configuration of a backward-facing step and a cavity, introducing a connecting step upstream of the cavity to achieve combustion enhancement. By comparing the two configurations, it is found that the addition of the backward-facing step regulates the heat release distribution, shortens the premixing process, and lifts the boundary layer at the intersection zone of strong shock waves. In the combined configuration, the inflow decelerates under strong compression waves, resulting in extended fuel residence time, elevated vortex stretching, raised jet penetration boundary, all of which promote fuel mixing. Combustion initiates earlier in the combined configuration, with the step and its upstream region serving as key hot product zones. Premixed combustion dominates the flame combustion mode, and subsonic combustion prevails upstream of the step. The combustion efficiency is improved. Meanwhile, this improvement is accompanied by an increase in total pressure loss. In the combined configuration, the transport and fuel entrainment capabilities of large-scale vortex structures in the upstream region of the cavity are enhanced, leading to faster reaction rates in local areas. Most of the combustion occurs in the wrinkled flamelet mode and corrugated flamelet mode, with a small portion in the thin reaction zone mode.
{"title":"Combustion enhancement characteristics of backward-facing step in an axisymmetric scramjet","authors":"Liu Yang , Yixin Yang , Tongwang Shi , Tao Tang , Mingbo Sun , Wang Han , Qinyuan Li , Rui Gu , Hongbo Wang , Dapeng Xiong , Jiajian Zhu","doi":"10.1016/j.applthermaleng.2026.130188","DOIUrl":"10.1016/j.applthermaleng.2026.130188","url":null,"abstract":"<div><div>The supersonic combustion enhancement characteristics of a combined combustor configuration consisting of a backward-facing step and a cavity are investigated numerically in this paper. Numerical simulations are conducted using a hybrid RANS/LES method. Numerical validation is performed on an axisymmetric cavity supersonic combustor as the baseline configuration. The numerical results agree well with the experimental measurements. On this basis, this paper proposes a combined configuration of a backward-facing step and a cavity, introducing a connecting step upstream of the cavity to achieve combustion enhancement. By comparing the two configurations, it is found that the addition of the backward-facing step regulates the heat release distribution, shortens the premixing process, and lifts the boundary layer at the intersection zone of strong shock waves. In the combined configuration, the inflow decelerates under strong compression waves, resulting in extended fuel residence time, elevated vortex stretching, raised jet penetration boundary, all of which promote fuel mixing. Combustion initiates earlier in the combined configuration, with the step and its upstream region serving as key hot product zones. Premixed combustion dominates the flame combustion mode, and subsonic combustion prevails upstream of the step. The combustion efficiency is improved. Meanwhile, this improvement is accompanied by an increase in total pressure loss. In the combined configuration, the transport and fuel entrainment capabilities of large-scale vortex structures in the upstream region of the cavity are enhanced, leading to faster reaction rates in local areas. Most of the combustion occurs in the wrinkled flamelet mode and corrugated flamelet mode, with a small portion in the thin reaction zone mode.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"291 ","pages":"Article 130188"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146154186","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130125
Muhammad Irfan Khan , Leonard Franke , Andres Georg Rösch , Zirui Wang , Md. Mofasser Mallick , Patricia Alegría , Nerea Pascual , David Astrain , Uli Lemmer
Recently, thermoelectric generators (TEGs) have gained significant attention for directly converting geothermal energy into electricity. Due to the considerable variations in heat-source and sink geometries and boundary conditions, the design of TEGs should offer flexibility to fulfill the specific constraints. Printing technologies, such as screen printing or 3D printing, offer versatile, cost-effective manufacturing approaches for TEGs, enabling scalability and shape conformability. In this work, we present a comparative performance optimization of both printed TEGs and bulk-material-based TEGs for medium-temperature geothermal anomalies at T ∼ 170 °C. The proposed system for geothermal energy harvesting consists of a two-phase thermosyphon serving as the hot-side heat exchanger, TEGs, and an efficient heat sink based on heat pipes. We investigate the performance of both types of TEGs attached to the exterior of the thermosyphon for three heights (h = 100, 200, and 500 mm). For both bulk and printed TEGs, thermal and electrical impedance optimizations are achieved by adjusting the TEG fill factor, leg dimensions, and the cross-sectional areas of the n-type and p-type legs. Under the given boundary conditions, the higher power density at lower cost occurs at a TEG height of 100 mm for both bulk and printed-TEG devices. And in all three cases, at a higher fill factor (F ∼ 0.9), printed TEGs showed comparable power densities to bulk TEGs at lower cost. As F decreases, the printed TEGs' power densities drop more rapidly than those of their bulk counterparts. Despite lower performance at lower fill factors, printed TEGs remain promising, with lower cost per watt (€/W) thanks to lower TE material consumption and lower manufacturing cost. Lastly, the projection of the levelized cost of electricity LCOE (€/kWh) and the economic analysis for both approaches conclude our work.
{"title":"Thermoelectric generators for harvesting medium-temperature geothermal anomalies: printed vs bulk devices","authors":"Muhammad Irfan Khan , Leonard Franke , Andres Georg Rösch , Zirui Wang , Md. Mofasser Mallick , Patricia Alegría , Nerea Pascual , David Astrain , Uli Lemmer","doi":"10.1016/j.applthermaleng.2026.130125","DOIUrl":"10.1016/j.applthermaleng.2026.130125","url":null,"abstract":"<div><div>Recently, thermoelectric generators (TEGs) have gained significant attention for directly converting geothermal energy into electricity. Due to the considerable variations in heat-source and sink geometries and boundary conditions, the design of TEGs should offer flexibility to fulfill the specific constraints. Printing technologies, such as screen printing or 3D printing, offer versatile, cost-effective manufacturing approaches for TEGs, enabling scalability and shape conformability. In this work, we present a comparative performance optimization of both printed TEGs and bulk-material-based TEGs for medium-temperature geothermal anomalies at T ∼ 170 °C. The proposed system for geothermal energy harvesting consists of a two-phase thermosyphon serving as the hot-side heat exchanger, TEGs, and an efficient heat sink based on heat pipes. We investigate the performance of both types of TEGs attached to the exterior of the thermosyphon for three heights (h = 100, 200, and 500 mm). For both bulk and printed TEGs, thermal and electrical impedance optimizations are achieved by adjusting the TEG fill factor, leg dimensions, and the cross-sectional areas of the n-type and p-type legs. Under the given boundary conditions, the higher power density at lower cost occurs at a TEG height of 100 mm for both bulk and printed-TEG devices. And in all three cases, at a higher fill factor (<em>F</em> ∼ 0.9), printed TEGs showed comparable power densities to bulk TEGs at lower cost. As <em>F</em> decreases, the printed TEGs' power densities drop more rapidly than those of their bulk counterparts. Despite lower performance at lower fill factors, printed TEGs remain promising, with lower cost per watt (€/W) thanks to lower TE material consumption and lower manufacturing cost. Lastly, the projection of the levelized cost of electricity LCOE (€/kWh) and the economic analysis for both approaches conclude our work.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130125"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186343","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 : 2026-02-07DOI: 10.1016/j.applthermaleng.2026.130149
Mohamed A. Kotb , Mahmoud M. Elboghdadi , Mohamed A. Antar , Mohammad A. Abido , Atia E. Khalifa
This study presents a wind-powered multistage Vacuum Membrane Distillation (VMD) system with a water ejector for sustainable freshwater production. System performance is evaluated under two scenarios: with and without battery storage. The wind turbine, optimized using Blade Element Momentum (BEM) theory, achieves a power coefficient of 0.47 and 1.233 kW output at 4.4 m/s wind speed. Analytical models for both the turbine and VMD are validated against experimental data. With battery support, the system delivers a peak flux of 181 kg/m2·h, 60 L/day of freshwater, and a minimum unit production cost (UPC) of 9 $/m3 at 80 °C. Without batteries, daily output ranges from 22 to 93 L depending on average monthly wind speeds (3.5–5.5 m/s) in Dhahran, Saudi Arabia. UPC declines significantly with wind speed, from 58 $/m3 at 3 m/s to 2.8 $/m3 at 8.5 m/s, while specific energy consumption (710–780 kWh/m3) and Gained Output Ratio (0.89–0.98) remain stable. Wind resource mapping across Saudi cities shows UPC variations between 3 and 24 $/m3, emphasizing the importance of location. The proposed system demonstrates strong potential as an efficient, renewable-powered solution for desalination in wind-rich coastal and remote regions.
{"title":"Wind-powered multistage vacuum membrane distillation for sustainable water desalination","authors":"Mohamed A. Kotb , Mahmoud M. Elboghdadi , Mohamed A. Antar , Mohammad A. Abido , Atia E. Khalifa","doi":"10.1016/j.applthermaleng.2026.130149","DOIUrl":"10.1016/j.applthermaleng.2026.130149","url":null,"abstract":"<div><div>This study presents a wind-powered multistage Vacuum Membrane Distillation (VMD) system with a water ejector for sustainable freshwater production. System performance is evaluated under two scenarios: with and without battery storage. The wind turbine, optimized using Blade Element Momentum (BEM) theory, achieves a power coefficient of 0.47 and 1.233 kW output at 4.4 m/s wind speed. Analytical models for both the turbine and VMD are validated against experimental data. With battery support, the system delivers a peak flux of 181 kg/m<sup>2</sup>·h, 60 L/day of freshwater, and a minimum unit production cost (UPC) of 9 $/m<sup>3</sup> at 80 °C. Without batteries, daily output ranges from 22 to 93 L depending on average monthly wind speeds (3.5–5.5 m/s) in Dhahran, Saudi Arabia. UPC declines significantly with wind speed, from 58 $/m<sup>3</sup> at 3 m/s to 2.8 $/m<sup>3</sup> at 8.5 m/s, while specific energy consumption (710–780 kWh/m<sup>3</sup>) and Gained Output Ratio (0.89–0.98) remain stable. Wind resource mapping across Saudi cities shows UPC variations between 3 and 24 $/m<sup>3</sup>, emphasizing the importance of location. The proposed system demonstrates strong potential as an efficient, renewable-powered solution for desalination in wind-rich coastal and remote regions.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130149"},"PeriodicalIF":6.9,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146186432","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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