Pub Date : 2026-01-31DOI: 10.1016/j.applthermaleng.2026.129977
Enchun Xing , Xuelian Sun , Hongyan Wei , Zhi Zhang , Huaqiang Zhong , Jinghui Cai
To meet the pressing need for lightweight and efficient cryogenic cooling in space-based long-wave infrared detection, this study addresses the performance degradation of the cold finger in 60 K pulse tube cryocoolers (PTCs) under high-frequency operation for system mass reduction. Using a combined approach of numerical simulation and experimental validation, the geometry of the regenerator—a key component of the cold finger—and its graded stainless-steel wire-mesh packing strategy were systematically optimized, while the influence of operating parameters on cryocooler performance was analyzed. An integrated high-frequency prototype was subsequently developed.Experimental results demonstrate that with an input power of 250 W, a charging pressure of 6 MPa, and an operating frequency of 100 Hz, the 4.4 kg cryocooler achieves a no-load temperature of 29.75 K and delivers a cooling capacity of 9.76 W at 60 K, corresponding to a relative Carnot efficiency of 15.6%. When the input power is increased to 300 W, the system provides 3.8 W of cooling capacity at 40 K and 11.5 W at 60 K.The study further reveals the shift in the optimal operating frequency across different temperature zones and confirms the coupled governing mechanism of system efficiency, which is jointly determined by compressor efficiency and cold-finger efficiency.
{"title":"Development and optimization of a 100 Hz lightweight pulse tube cryocooler achieving 9.76 W at 60 K for space applications","authors":"Enchun Xing , Xuelian Sun , Hongyan Wei , Zhi Zhang , Huaqiang Zhong , Jinghui Cai","doi":"10.1016/j.applthermaleng.2026.129977","DOIUrl":"10.1016/j.applthermaleng.2026.129977","url":null,"abstract":"<div><div>To meet the pressing need for lightweight and efficient cryogenic cooling in space-based long-wave infrared detection, this study addresses the performance degradation of the cold finger in 60 K pulse tube cryocoolers (PTCs) under high-frequency operation for system mass reduction. Using a combined approach of numerical simulation and experimental validation, the geometry of the regenerator—a key component of the cold finger—and its graded stainless-steel wire-mesh packing strategy were systematically optimized, while the influence of operating parameters on cryocooler performance was analyzed. An integrated high-frequency prototype was subsequently developed.Experimental results demonstrate that with an input power of 250 W, a charging pressure of 6 MPa, and an operating frequency of 100 Hz, the 4.4 kg cryocooler achieves a no-load temperature of 29.75 K and delivers a cooling capacity of 9.76 W at 60 K, corresponding to a relative Carnot efficiency of 15.6%. When the input power is increased to 300 W, the system provides 3.8 W of cooling capacity at 40 K and 11.5 W at 60 K.The study further reveals the shift in the optimal operating frequency across different temperature zones and confirms the coupled governing mechanism of system efficiency, which is jointly determined by compressor efficiency and cold-finger efficiency.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 129977"},"PeriodicalIF":6.9,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096133","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}
The high energy density of diesel fuel (MJ/kg) makes it difficult to replace it entirely with alternative fuels for transportation and power generation. Hence, in order to enhance diesel fuel saving and reduce environmental pollution by waste to energy conversion, this paper deals with the generation of producer gas by coconut shell gasification and utilization in CI engine for power generation and emission mitigation. Despite significant progress, challenges still exist in conducting experimental pilot-scale studies and in optimizing the operating parameters of the integrated gasification–engine system for enhanced fuel savings and emission control. Accordingly, this study employs the experimental investigation of in situ Gasifier-Engine performance, especially the adoption of down draft air gasification and variable compression ratio (CR) engine. By integrating, the novelty is to identify the performance trends with operating parameter that lead to enhance replacement of diesel fuel and optimize the engine power and exhaust emission. Accordingly, the experiments were carried out on 50kWe(thermal)-pilot-scale downdraft gasifier with VCR engine under different loads, CR, and fuel injection pressure (FIP) for the assessment of performance characteristic. In experiments, maximum 63.81% diesel savings was obtained. Emission levels were notably low, with minimum values of 0.06 vol% CO, 12 ppm HC, 1.3 vol% CO₂, and 10 ppm NOₓ. Since, the trade-off performance nature has been observed with parametric variation, so, RSM was employed to optimize engine performance and emissions. The optimal operating conditions identified were a CR of 16, BP of 2.97 kW and FIP of 220 bars. Under these conditions, the predicted optimal outcomes included 56.13% diesel savings, 16.19% BTE, 0.075 vol% CO, 23.9 ppm HC, 2.65 vol% CO₂ and 30.3 ppm NOₓ. These results demonstrate the effectiveness of integrating coconut biomass gasification with CI engine technology and utilization of RSM tool for optimizing system performance in pilot scale.
{"title":"Experimental and RSM-based optimization of CI engine performance using coconut shell gasified producer gas blend","authors":"Pushpendu Kasaudhan, Jeewan Vachan Tirkey, Lawalesh Kumar Prajapati, Akash Giri, Priyaranjan Jena","doi":"10.1016/j.applthermaleng.2026.129909","DOIUrl":"10.1016/j.applthermaleng.2026.129909","url":null,"abstract":"<div><div>The high energy density of diesel fuel (MJ/kg) makes it difficult to replace it entirely with alternative fuels for transportation and power generation. Hence, in order to enhance diesel fuel saving and reduce environmental pollution by waste to energy conversion, this paper deals with the generation of producer gas by coconut shell gasification and utilization in CI engine for power generation and emission mitigation. Despite significant progress, challenges still exist in conducting experimental pilot-scale studies and in optimizing the operating parameters of the integrated gasification–engine system for enhanced fuel savings and emission control. Accordingly, this study employs the experimental investigation of in situ Gasifier-Engine performance, especially the adoption of down draft air gasification and variable compression ratio (CR) engine. By integrating, the novelty is to identify the performance trends with operating parameter that lead to enhance replacement of diesel fuel and optimize the engine power and exhaust emission. Accordingly, the experiments were carried out on 50kWe(thermal)-pilot-scale downdraft gasifier with VCR engine under different loads, CR, and fuel injection pressure (FIP) for the assessment of performance characteristic. In experiments, maximum 63.81% diesel savings was obtained. Emission levels were notably low, with minimum values of 0.06 vol% CO, 12 ppm HC, 1.3 vol% CO₂, and 10 ppm NOₓ. Since, the trade-off performance nature has been observed with parametric variation, so, RSM was employed to optimize engine performance and emissions. The optimal operating conditions identified were a CR of 16, BP of 2.97 kW and FIP of 220 bars. Under these conditions, the predicted optimal outcomes included 56.13% diesel savings, 16.19% BTE, 0.075 vol% CO, 23.9 ppm HC, 2.65 vol% CO₂ and 30.3 ppm NOₓ. These results demonstrate the effectiveness of integrating coconut biomass gasification with CI engine technology and utilization of RSM tool for optimizing system performance in pilot scale.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 129909"},"PeriodicalIF":6.9,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096138","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 : 2026-01-30DOI: 10.1016/j.applthermaleng.2026.129920
Mehdi Aliehyaei , Vincenzo Bianco , Mattia De Rosa
With the increasing energy density of batteries in electric vehicles (EVs), the design of battery thermal management systems with high energy performance and reduced economic and environmental costs has become a critical challenge. However, most previous studies have focused mainly on energy or exergy analyses, while comprehensive frameworks simultaneously incorporating economic and environmental aspects remain limited. In this study, a novel integrated thermal management system is developed to simultaneously control the temperature of the battery pack, cabin, and electric motor. The system is evaluated using a comprehensive five-dimensional (5E) framework, including energy, exergy, economic, exergo-economic, and exergo-environmental analyses. A detailed thermodynamic model of the proposed system is developed and validated against experimental data, showing deviations below 6% for key performance indicators. Under baseline operating conditions, the system achieves a coefficient of performance (COP) of 3.81, while the overall exergy efficiency is 5.5%, revealing a significant gap between energy quantity and energy quality. Exergy destruction analysis indicates that the evaporator and condenser are the dominant sources of irreversibility, with the condenser accounting for approximately 80% of the total capital cost. The specific cooling cost is estimated as 0.055 US$/kWh. Parametric analyses demonstrate that optimal thermodynamic and economic performance is obtained at mid-range battery state of charge (SOC 0.65–0.75). A comparative assessment of alternative refrigerants (R152a, R1234yf, and R513A) shows that R152a provides the highest COP ( 4.0), whereas R1234yf offers superior environmental performance due to its ultra-low global warming potential. The results highlight the effectiveness of the proposed 5E framework in identifying dominant inefficiencies and trade-offs, and provide practical guidance for the thermodynamic design, refrigerant selection, and sustainable optimization of next-generation EV thermal management systems.
{"title":"Comprehensive energy, exergo-economic, and exergo-environmental (5E) assessment of a novel electric vehicle battery cooling system layout","authors":"Mehdi Aliehyaei , Vincenzo Bianco , Mattia De Rosa","doi":"10.1016/j.applthermaleng.2026.129920","DOIUrl":"10.1016/j.applthermaleng.2026.129920","url":null,"abstract":"<div><div>With the increasing energy density of batteries in electric vehicles (EVs), the design of battery thermal management systems with high energy performance and reduced economic and environmental costs has become a critical challenge. However, most previous studies have focused mainly on energy or exergy analyses, while comprehensive frameworks simultaneously incorporating economic and environmental aspects remain limited. In this study, a novel integrated thermal management system is developed to simultaneously control the temperature of the battery pack, cabin, and electric motor. The system is evaluated using a comprehensive five-dimensional (5E) framework, including energy, exergy, economic, exergo-economic, and exergo-environmental analyses. A detailed thermodynamic model of the proposed system is developed and validated against experimental data, showing deviations below 6% for key performance indicators. Under baseline operating conditions, the system achieves a coefficient of performance (COP) of 3.81, while the overall exergy efficiency is 5.5%, revealing a significant gap between energy quantity and energy quality. Exergy destruction analysis indicates that the evaporator and condenser are the dominant sources of irreversibility, with the condenser accounting for approximately 80% of the total capital cost. The specific cooling cost is estimated as 0.055 US$/kWh. Parametric analyses demonstrate that optimal thermodynamic and economic performance is obtained at mid-range battery state of charge (SOC <span><math><mo>≈</mo></math></span> 0.65–0.75). A comparative assessment of alternative refrigerants (R152a, R1234yf, and R513A) shows that R152a provides the highest COP (<span><math><mo>≈</mo></math></span> 4.0), whereas R1234yf offers superior environmental performance due to its ultra-low global warming potential. The results highlight the effectiveness of the proposed 5E framework in identifying dominant inefficiencies and trade-offs, and provide practical guidance for the thermodynamic design, refrigerant selection, and sustainable optimization of next-generation EV thermal management systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 129920"},"PeriodicalIF":6.9,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096194","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 : 2026-01-30DOI: 10.1016/j.applthermaleng.2026.130023
K. Santhosh , Jayashish Kumar Pandey , B.E. Naveena , H.M. Shankara Murthy , B.M. Praveenkumara , R. Thirumaleswara Naik , N.R. Banapurmath , Solomon Jenoris Muthiya
Reducing carbon emissions from diesel engines has increased interest in oxygenated biofuels that offer cleaner combustion without engine modifications. Among higher alcohols, n-pentanol offers a promising combination of high oxygen content, renewable origin, and favorable combustion properties. This study experimentally demonstrates an additive-free strategy for operating a 40% n-pentanol/diesel blend (D60P40) in a common-rail direct injection diesel engine through the synergistic integration of advanced injection timing (15° BTDC) and exhaust gas recirculation (10% and 20%) across 20–80% engine loads. Advancing injection timing to 15° BTDC improved combustion, with an 8.85% increase in peak cylinder pressure and 15.19% higher heat release rate compared to diesel. Brake thermal efficiency (BTE) of D60P40 at this timing was only 2.36% lower than diesel, while retarded timing (9° BTDC) reduced BTE by 15.7%. EGR at 20% reduced NOx by 15.15%, but increased HC and CO due to thermal quenching. However, the inherent oxygen in pentanol helped limit these increases. The synergy of advanced injection timing with moderate EGR resolved the NOx–CO/HC trade-off, maintaining combustion efficiency while reducing emissions. These findings demonstrate a viable, retrofitting-free pathway for diesel engine decarbonization using oxygenated fuel blends, supporting global efforts toward cleaner and sustainable transport energy systems.
{"title":"Impact of injection timing and EGR on the combustion characteristics and emission behavior of DI diesel engines fueled with renewable alcohol based oxygenated blends","authors":"K. Santhosh , Jayashish Kumar Pandey , B.E. Naveena , H.M. Shankara Murthy , B.M. Praveenkumara , R. Thirumaleswara Naik , N.R. Banapurmath , Solomon Jenoris Muthiya","doi":"10.1016/j.applthermaleng.2026.130023","DOIUrl":"10.1016/j.applthermaleng.2026.130023","url":null,"abstract":"<div><div>Reducing carbon emissions from diesel engines has increased interest in oxygenated biofuels that offer cleaner combustion without engine modifications. Among higher alcohols, n-pentanol offers a promising combination of high oxygen content, renewable origin, and favorable combustion properties. This study experimentally demonstrates an additive-free strategy for operating a 40% n-pentanol/diesel blend (D60P40) in a common-rail direct injection diesel engine through the synergistic integration of advanced injection timing (15° BTDC) and exhaust gas recirculation (10% and 20%) across 20–80% engine loads. Advancing injection timing to 15° BTDC improved combustion, with an 8.85% increase in peak cylinder pressure and 15.19% higher heat release rate compared to diesel. Brake thermal efficiency (BTE) of D60P40 at this timing was only 2.36% lower than diesel, while retarded timing (9° BTDC) reduced BTE by 15.7%. EGR at 20% reduced NOx by 15.15%, but increased HC and CO due to thermal quenching. However, the inherent oxygen in pentanol helped limit these increases. The synergy of advanced injection timing with moderate EGR resolved the NOx–CO/HC trade-off, maintaining combustion efficiency while reducing emissions. These findings demonstrate a viable, retrofitting-free pathway for diesel engine decarbonization using oxygenated fuel blends, supporting global efforts toward cleaner and sustainable transport energy systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130023"},"PeriodicalIF":6.9,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096124","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 : 2026-01-30DOI: 10.1016/j.applthermaleng.2026.130059
Xuesong Li , Mingli Cui , Jinhong Fu , Guodong Wang , Bowei Yao , Hongchang Xu , Mohamed Almanzalawy
Substituting conventional fuels with clean fuels such as methanol, ethanol, or butanol has the potential to achieve carbon neutrality goals. This study systematically investigates the effects of alcohol fuels on the combustion and emissions of gasoline under low pressure of 60 kPa and rich conditions of 1.25, representing cold-start relevant environments. Methanol was tested at different volume concentrations of 25%, 50%, and 75% with gasoline, while ethanol and butanol were compared to methanol at a 50% concentration. Experiments were conducted in a constant volume combustion chamber under sub-cooled conditions at a temperature of 30 °C and under flash boiling conditions at a superheat index of 0.3. Alcohols with shorter carbon chains or lower concentrations of methanol increased the flame propagation speed by 14.5% with 50% of methanol. Fourier transform infrared spectroscopy (FTIR) analysis showed reductions in unburned hydrocarbons, mono-aromatic compounds, and nitrogen oxide emissions by 38.6%, 56.1%, and 7.7%, respectively, although formaldehyde formation was increased by 200%. An inflection point was observed at M25 for all emissions. Soot morphology and nanostructure analysis revealed that soot formation is suppressed and oxidation is increased. Spray morphology indicated that flash boiling improved atomization, while flame images confirmed that flash boiling accelerated flame propagation, particularly with shorter alcohols or lower percentages. Flash boiling enhanced carbon oxidation by reducing unburned hydrocarbons and monocyclic aromatic compounds, with a corresponding increase in carbon oxide formation, indicating improved combustion in terms of oxidation completeness. Furthermore, flash boiling suppressed the formation of fuel-rich zones, thereby reducing soot generation from all blends (with a 51.3% reduction in the size of the soot aggregates), even under rich combustion conditions. This work establishes a unified framework linking fuel molecular structure and flash-boiling atomization to combustion behavior and soot formation in alcohol-fueled systems.
{"title":"Effect of alcohol type and blending ratio on sub-cooled and flash boiling combustion of gasoline-alcohol fuels","authors":"Xuesong Li , Mingli Cui , Jinhong Fu , Guodong Wang , Bowei Yao , Hongchang Xu , Mohamed Almanzalawy","doi":"10.1016/j.applthermaleng.2026.130059","DOIUrl":"10.1016/j.applthermaleng.2026.130059","url":null,"abstract":"<div><div>Substituting conventional fuels with clean fuels such as methanol, ethanol, or butanol has the potential to achieve carbon neutrality goals. This study systematically investigates the effects of alcohol fuels on the combustion and emissions of gasoline under low pressure of 60 kPa and rich conditions of 1.25, representing cold-start relevant environments. Methanol was tested at different volume concentrations of 25%, 50%, and 75% with gasoline, while ethanol and butanol were compared to methanol at a 50% concentration. Experiments were conducted in a constant volume combustion chamber under sub-cooled conditions at a temperature of 30 °C and under flash boiling conditions at a superheat index of 0.3. Alcohols with shorter carbon chains or lower concentrations of methanol increased the flame propagation speed by 14.5% with 50% of methanol. Fourier transform infrared spectroscopy (FTIR) analysis showed reductions in unburned hydrocarbons, mono-aromatic compounds, and nitrogen oxide emissions by 38.6%, 56.1%, and 7.7%, respectively, although formaldehyde formation was increased by 200%. An inflection point was observed at M25 for all emissions. Soot morphology and nanostructure analysis revealed that soot formation is suppressed and oxidation is increased. Spray morphology indicated that flash boiling improved atomization, while flame images confirmed that flash boiling accelerated flame propagation, particularly with shorter alcohols or lower percentages. Flash boiling enhanced carbon oxidation by reducing unburned hydrocarbons and monocyclic aromatic compounds, with a corresponding increase in carbon oxide formation, indicating improved combustion in terms of oxidation completeness. Furthermore, flash boiling suppressed the formation of fuel-rich zones, thereby reducing soot generation from all blends (with a 51.3% reduction in the size of the soot aggregates), even under rich combustion conditions. This work establishes a unified framework linking fuel molecular structure and flash-boiling atomization to combustion behavior and soot formation in alcohol-fueled systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130059"},"PeriodicalIF":6.9,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096136","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 : 2026-01-30DOI: 10.1016/j.applthermaleng.2026.129979
Haobo Jia , Jingmin Zhang , Zhen Pan , Wenhui Song , Shuaiqi Liang
Motivated by the catastrophic hazards associated with leaks from buried hydrogen pipelines, this work systematically investigates the dynamics of leakage and thermal evolution using numerical simulation. Results reveal a high-pressure zone above the leak hole and gradual horizontal pressure attenuation. The velocity field exhibits a mushroom-like structure under subsonic flow. Hydrogen diffusion is buoyancy-dominated, forming concentric horizontal concentration profiles and reaching the atmosphere vertically within thousands of seconds, while diffusion delays occur below the pipeline due to soil barriers. Pipeline pressure and leak diameter synergistically enhance Joule-Thomson cooling and the injection of cold gas; their interaction with low porosity leads to an exponential expansion of the low-temperature zone. Soil temperature affects only initial conditions; leakage direction and burial depth show minimal impact. A validated steady-state temperature model (Eq. 10) achieved R2 = 0.99 (error < 3%) across 13 cases. A novel localization method based on temperature gradient fitting (Eq. 11) achieved a 0.1% error with R2 = 0.95. Key risk factors include pressure, leak diameter, and porosity. The models provide critical risk assessment tools, with future work integrating multi-physics and machine learning for broader applicability.
{"title":"Investigation on thermal behavior during leakage from subsurface hydrogen pipelines","authors":"Haobo Jia , Jingmin Zhang , Zhen Pan , Wenhui Song , Shuaiqi Liang","doi":"10.1016/j.applthermaleng.2026.129979","DOIUrl":"10.1016/j.applthermaleng.2026.129979","url":null,"abstract":"<div><div>Motivated by the catastrophic hazards associated with leaks from buried hydrogen pipelines, this work systematically investigates the dynamics of leakage and thermal evolution using numerical simulation. Results reveal a high-pressure zone above the leak hole and gradual horizontal pressure attenuation. The velocity field exhibits a mushroom-like structure under subsonic flow. Hydrogen diffusion is buoyancy-dominated, forming concentric horizontal concentration profiles and reaching the atmosphere vertically within thousands of seconds, while diffusion delays occur below the pipeline due to soil barriers. Pipeline pressure and leak diameter synergistically enhance Joule-Thomson cooling and the injection of cold gas; their interaction with low porosity leads to an exponential expansion of the low-temperature zone. Soil temperature affects only initial conditions; leakage direction and burial depth show minimal impact. A validated steady-state temperature model (Eq. <span><span>10</span></span>) achieved R<sup>2</sup> = 0.99 (error < 3%) across 13 cases. A novel localization method based on temperature gradient fitting (Eq. <span><span>11</span></span>) achieved a 0.1% error with R<sup>2</sup> = 0.95. Key risk factors include pressure, leak diameter, and porosity. The models provide critical risk assessment tools, with future work integrating multi-physics and machine learning for broader applicability.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 129979"},"PeriodicalIF":6.9,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096148","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 : 2026-01-29DOI: 10.1016/j.applthermaleng.2026.130038
Liu Junrong , Liu Wenqiang , Wu Xingru , Zhang Yaping
To address the challenge of aligning seasonal heat supply with demand, this study delves into four distinct operational modes: (I) deep recharge – shallow production; (II) shallow recharge - deep production; (III) simultaneous deep and shallow recharge - shallow production; and (IV) simultaneous deep and shallow recharge - deep production.By examining these four operational modes, we investigate how recharge intensity and temperature impact heat production efficiency and thermal imbalance within coupled deep and shallow geothermal reservoirs. Our findings reveal that, across all four modes, a combination of high recharge temperature and low recharge intensity effectively mitigates the decrease in formation temperature. Higher recharge temperature reduces thermal drawdown by decreasing the fluid–rock temperature contrast, while lower recharge intensity limits advective heat depletion. Notably, when CO2 serves as the circulating fluid, the rate and extent of formation temperature decline are less pronounced compared to when water is used. This enhanced thermal retention indicates that CO₂ is a favorable working-fluid option for long-term heat extraction under moderate thermal loads.
{"title":"Numerical simulation of heat transfer phenomena and influencing factors between deep and shallow geothermal reservoirs","authors":"Liu Junrong , Liu Wenqiang , Wu Xingru , Zhang Yaping","doi":"10.1016/j.applthermaleng.2026.130038","DOIUrl":"10.1016/j.applthermaleng.2026.130038","url":null,"abstract":"<div><div>To address the challenge of aligning seasonal heat supply with demand, this study delves into four distinct operational modes: (I) deep recharge – shallow production; (II) shallow recharge - deep production; (III) simultaneous deep and shallow recharge - shallow production; and (IV) simultaneous deep and shallow recharge - deep production.By examining these four operational modes, we investigate how recharge intensity and temperature impact heat production efficiency and thermal imbalance within coupled deep and shallow geothermal reservoirs. Our findings reveal that, across all four modes, a combination of high recharge temperature and low recharge intensity effectively mitigates the decrease in formation temperature. Higher recharge temperature reduces thermal drawdown by decreasing the fluid–rock temperature contrast, while lower recharge intensity limits advective heat depletion. Notably, when CO<sub>2</sub> serves as the circulating fluid, the rate and extent of formation temperature decline are less pronounced compared to when water is used. This enhanced thermal retention indicates that CO₂ is a favorable working-fluid option for long-term heat extraction under moderate thermal loads.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130038"},"PeriodicalIF":6.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096131","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 : 2026-01-29DOI: 10.1016/j.applthermaleng.2026.130035
Zong-bao Li , Yue Yu , Li Jia , Ya-wen Wu , Peng Cheng , Zhen Zhang , Zi-kuo Li , Chu-hao Fan , Xue-mao Guo
Premixed low-nitrogen heating boilers face challenges such as suboptimal thermal efficiency, tube rupture risks, and difficulties in high-temperature experimental analysis. To address these issues, this study employs an innovative approach by integrating a porous media model for the metal fiber burner and finned tubes, enabling efficient three-dimensional numerical simulation of an asymmetric four-pass heat exchanger. Simulations across a range of excess air coefficients (α = 1.1–1.6) reveal that α = 1.3 represents the optimal condition, achieving a thermal efficiency of 94.6%, NOX emissions of only 5.95 mg/m3, and a stable finned-tube wall temperature of approximately 570 K. To further overcome problems of uneven burner flames, inefficient waste heat utilization, and poor flue gas exhaust, a comprehensive structural optimization strategy is proposed and validated. This includes a 4-zone perforated plate design for balanced fuel distribution, the integration of a gas-water heat exchanger for waste heat recovery, and the replacement of the single flue gas outlet with dual 120 mm outlets. These modifications collectively increase the boiler thermal efficiency to 97.1%, reduce the flue gas exhaust temperature from 365.3 K to 357.8 K, alleviate local high temperatures, and significantly improve flue gas flow uniformity. This work provides a validated framework for the performance enhancement and engineering application of efficient, low-emission heating boilers.
{"title":"Thermal characteristic analysis and performance optimization of a novel heating boiler based on a porous media model","authors":"Zong-bao Li , Yue Yu , Li Jia , Ya-wen Wu , Peng Cheng , Zhen Zhang , Zi-kuo Li , Chu-hao Fan , Xue-mao Guo","doi":"10.1016/j.applthermaleng.2026.130035","DOIUrl":"10.1016/j.applthermaleng.2026.130035","url":null,"abstract":"<div><div>Premixed low-nitrogen heating boilers face challenges such as suboptimal thermal efficiency, tube rupture risks, and difficulties in high-temperature experimental analysis. To address these issues, this study employs an innovative approach by integrating a porous media model for the metal fiber burner and finned tubes, enabling efficient three-dimensional numerical simulation of an asymmetric four-pass heat exchanger. Simulations across a range of excess air coefficients (<em>α</em> = 1.1–1.6) reveal that <em>α</em> = 1.3 represents the optimal condition, achieving a thermal efficiency of 94.6%, NO<sub>X</sub> emissions of only 5.95 mg/m<sup>3</sup>, and a stable finned-tube wall temperature of approximately 570 K. To further overcome problems of uneven burner flames, inefficient waste heat utilization, and poor flue gas exhaust, a comprehensive structural optimization strategy is proposed and validated. This includes a 4-zone perforated plate design for balanced fuel distribution, the integration of a gas-water heat exchanger for waste heat recovery, and the replacement of the single flue gas outlet with dual 120 mm outlets. These modifications collectively increase the boiler thermal efficiency to 97.1%, reduce the flue gas exhaust temperature from 365.3 K to 357.8 K, alleviate local high temperatures, and significantly improve flue gas flow uniformity. This work provides a validated framework for the performance enhancement and engineering application of efficient, low-emission heating boilers.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"289 ","pages":"Article 130035"},"PeriodicalIF":6.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074825","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 : 2026-01-29DOI: 10.1016/j.applthermaleng.2026.130018
S.K. Gugulothu , Praveen Barmavatu
This study presents a coupled Computational Fluid Dynamics (CFD)–Machine Learning Algorithm (MLA) framework to optimize the thermo-hydraulic performance of a triangular duct solar air heater (SAH) with rounded corners and artificial roughness elements. A CFD-generated dataset of 60 cases was used to train and evaluate six supervised regression models—Linear Regression (LR), k-Nearest Neighbor (KNN), Random Forest (RF), Stochastic Gradient Descent Regressor (SGDR), Multilayer Perceptron (MLP), and Decision Tree (DT)—based on Nusselt number (Nu) and friction factor (f). Among these, DT achieved the highest accuracy for Nu prediction (R2 = 0.9988 for training and 0.9967 for testing), while LR performed best for f (R2 = 0.8924 for training and 0.9273 for testing). GridSearchCV-based hyperparameter tuning further improved model robustness, enabling predictions closely aligned with CFD results. Subsequent optimization using Design Expert confirmed negligible deviation between MLA-based and CFD-based optimal inputs, validating the surrogate modelling approach. The optimal configuration z'/e = 10, Rc ≈ 0.335, and Re ≈ 21,000—yielded enhanced heat transfer with manageable frictional penalties. These findings highlight the ability of ML to replicate CFD outcomes at a fraction of the computational cost, providing a scalable and efficient strategy for rapid design and optimization of solar thermal systems.
{"title":"Multi-objective optimization of thermo-hydraulic performance in triangular duct solar air heaters using machine learning models","authors":"S.K. Gugulothu , Praveen Barmavatu","doi":"10.1016/j.applthermaleng.2026.130018","DOIUrl":"10.1016/j.applthermaleng.2026.130018","url":null,"abstract":"<div><div>This study presents a coupled Computational Fluid Dynamics (CFD)–Machine Learning Algorithm (MLA) framework to optimize the thermo-hydraulic performance of a triangular duct solar air heater (SAH) with rounded corners and artificial roughness elements. A CFD-generated dataset of 60 cases was used to train and evaluate six supervised regression models—Linear Regression (LR), k-Nearest Neighbor (KNN), Random Forest (RF), Stochastic Gradient Descent Regressor (SGDR), Multilayer Perceptron (MLP), and Decision Tree (DT)—based on Nusselt number (Nu) and friction factor (f). Among these, DT achieved the highest accuracy for Nu prediction (R<sup>2</sup> = 0.9988 for training and 0.9967 for testing), while LR performed best for f (R<sup>2</sup> = 0.8924 for training and 0.9273 for testing). GridSearchCV-based hyperparameter tuning further improved model robustness, enabling predictions closely aligned with CFD results. Subsequent optimization using Design Expert confirmed negligible deviation between MLA-based and CFD-based optimal inputs, validating the surrogate modelling approach. The optimal configuration z'/e = 10, Rc ≈ 0.335, and Re ≈ 21,000—yielded enhanced heat transfer with manageable frictional penalties. These findings highlight the ability of ML to replicate CFD outcomes at a fraction of the computational cost, providing a scalable and efficient strategy for rapid design and optimization of solar thermal systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 130018"},"PeriodicalIF":6.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096153","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 : 2026-01-29DOI: 10.1016/j.applthermaleng.2026.129910
Simon Bagnis , Bertrand Baudouy , Steffen Krämer , Clément Lorin , Hugo Reymond
Through a series of experimental sessions, we have characterized pool boiling heat transfer in liquid helium (LHe) around saturation (4.2 K) under reduced gravity conditions ranging from 0.02g to 1g using magnetic forces. The magnetic forces were generated using a 30 T resistive magnet. First, the experimental results confirm and strengthen previous measurements regarding the critical heat flux dependency with respect to reduced gravity. Secondly and more importantly, they provide Nukiyama’s curves for liquid helium at 4.2 K and 1 bar at various reduced gravity levels (0.02g, 0.25g, 0.5g, 1g). Measurements of both nucleate and film boiling regimes are studied and compared with considerations of their theoretically predicted gravity-dependent evolution. The measurements do not show significant degradation of the heat transfer coefficient under reduced gravity only the critical heat flux seems to be drastically impacted by the gravity level.
{"title":"Influence of reduced gravity on liquid helium pool boiling heat transfer","authors":"Simon Bagnis , Bertrand Baudouy , Steffen Krämer , Clément Lorin , Hugo Reymond","doi":"10.1016/j.applthermaleng.2026.129910","DOIUrl":"10.1016/j.applthermaleng.2026.129910","url":null,"abstract":"<div><div>Through a series of experimental sessions, we have characterized pool boiling heat transfer in liquid helium (LHe) around saturation (4.2 K) under reduced gravity conditions ranging from 0.02g to 1g using magnetic forces. The magnetic forces were generated using a 30 T resistive magnet. First, the experimental results confirm and strengthen previous measurements regarding the critical heat flux dependency with respect to reduced gravity. Secondly and more importantly, they provide Nukiyama’s curves for liquid helium at 4.2 K and 1 bar at various reduced gravity levels (<span><math><mo>≈</mo></math></span>0.02g, <span><math><mo>≈</mo></math></span>0.25g, <span><math><mo>≈</mo></math></span>0.5g, 1g). Measurements of both nucleate and film boiling regimes are studied and compared with considerations of their theoretically predicted gravity-dependent evolution. The measurements do not show significant degradation of the heat transfer coefficient under reduced gravity only the critical heat flux seems to be drastically impacted by the gravity level.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"290 ","pages":"Article 129910"},"PeriodicalIF":6.9,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096195","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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