Pub Date : 2024-11-13DOI: 10.1016/j.applthermaleng.2024.124925
Shuoshuo Li , Xinxin Liu , Yu Zeng , Gang Li , Xiaohui Pan , Liang Liu , Pengfei Li , Youzhou Jiao , Chao He
To suppress heat transfer deterioration (HTD) in supercritical CO2 Rankine cycle, the flow and heat transfer characteristics of supercritical CO2 in elliptical dimple tubes (ET) are numerically investigated by the Shear-Stress Transport k-ω model in Fluent software. The ET based on a smooth tube with length of 2000 mm and diameter of 9 mm. The operating conditions consist of pressure 8 MPa, mass flux 100–700 kg/(m2∙s), and heat flux 70–300 kW/m2. The results indicate that dimples can prevent sharp decrease in radial density near-wall where HTD originally occurs, which mitigates buoyancy effect and improves heat transfer performance. Compared to staggered dimple, inline elliptical dimple tubes exhibit a better heat transfer. Reducing space (p = 10–30 mm) and increasing rows (n = 3–6) of dimples can further improve the effectiveness. At mass flux 300 kg/(m2∙s) and heat flux 70 kW/m2, the performance evaluation criterion (PEC) increases by 42.7 % and 34.7 % respectively, while the maximum buoyancy value (Bumax) decreases by 52.2 % and 28.7 % respectively. Additionally, the Bumax is highly influenced by ac, which represents the product of dimple width and depth. The optimal ET has a PEC of 2.45 and Bumax of 6.42 × 10-5, begin to be affected by buoyancy effect at Bu ≥ 2 × 10-5 and recovers heat transfer at Bu ≥ 2 × 10-4. A new heat transfer correlation is developed and over 95 % of data falls in a 30 % accuracy.
{"title":"Numerical study of dimpled structures on heat transfer deterioration mitigation with supercritical CO2 heated in vertical tube","authors":"Shuoshuo Li , Xinxin Liu , Yu Zeng , Gang Li , Xiaohui Pan , Liang Liu , Pengfei Li , Youzhou Jiao , Chao He","doi":"10.1016/j.applthermaleng.2024.124925","DOIUrl":"10.1016/j.applthermaleng.2024.124925","url":null,"abstract":"<div><div>To suppress heat transfer deterioration (HTD) in supercritical CO<sub>2</sub> Rankine cycle, the flow and heat transfer characteristics of supercritical CO<sub>2</sub> in elliptical dimple tubes (ET) are numerically investigated by the Shear-Stress Transport <em>k</em>-<em>ω</em> model in Fluent software. The ET based on a smooth tube with length of 2000 mm and diameter of 9 mm. The operating conditions consist of pressure 8 MPa, mass flux 100–700 kg/(m<sup>2</sup>∙s), and heat flux 70–300 kW/m<sup>2</sup>. The results indicate that dimples can prevent sharp decrease in radial density near-wall where HTD originally occurs, which mitigates buoyancy effect and improves heat transfer performance. Compared to staggered dimple, inline elliptical dimple tubes exhibit a better heat transfer. Reducing space (<em>p</em> = 10–30 mm) and increasing rows (<em>n</em> = 3–6) of dimples can further improve the effectiveness. At mass flux 300 kg/(m<sup>2</sup>∙s) and heat flux 70 kW/m<sup>2</sup>, the performance evaluation criterion (<em>PEC</em>) increases by 42.7 % and 34.7 % respectively, while the maximum buoyancy value (<em>Bu</em><sub>max</sub>) decreases by 52.2 % and 28.7 % respectively. Additionally, the <em>Bu</em><sub>max</sub> is highly influenced by <em>ac</em>, which represents the product of dimple width and depth. The optimal ET has a <em>PEC</em> of 2.45 and <em>Bu</em><sub>max</sub> of 6.42 × 10<sup>-5</sup>, begin to be affected by buoyancy effect at <em>Bu</em> ≥ 2 × 10<sup>-5</sup> and recovers heat transfer at <em>Bu</em> ≥ 2 × 10<sup>-4</sup>. A new heat transfer correlation is developed and over 95 % of data falls in a 30 % accuracy.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124925"},"PeriodicalIF":6.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657840","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 : 2024-11-13DOI: 10.1016/j.applthermaleng.2024.124881
M. Muneeshwaran , Hao-Yu Lin , Cheng-Min Yang , Kashif Nawaz , Chi-Chuan Wang
Horizontal falling film evaporators are widely utilized in desalination industries to increase fresh water supply. However, universal correlations for seawater falling film evaporation under varied operational and geometrical conditions are simply unavailable in open literature. Thus, this study aims to develop such a universal correlation for both plain and enhanced tubes. The detailed heat transfer mechanisms are reviewed, and rational parameters are incorporated to develop the universal correlation. A dataset of 994 data points from 9 sources covering a wide range of conditions was compiled. These conditions include Reynolds numbers from 10 to 7235, heat fluxes from 7.7 to 208 kW/m−2, saturation temperatures from 278 to 401 K, salinities from 0 to 60 gsalt kg−1water, tube diameters from 15.8 to 50.8 mm, and liquid feeder height to diameter ratios from 1 to 2.25. Upon analysis, it was found that most of the recommended existing correlations exhibited poor predictive accuracy, as evidenced by larger MADs. The developed correlation in this study demonstrated the best predictive accuracy for the entire dataset, yielding a MAD of 16.8 % and an R2 of 0.82. Furthermore, the performance of the new correlation was individually assessed across a broader spectrum of operational and design conditions, reflecting the individual conditions’ influences with an overall MAD of 20 %.
{"title":"Universal correlation for falling film evaporation heat transfer coefficients of water and seawater","authors":"M. Muneeshwaran , Hao-Yu Lin , Cheng-Min Yang , Kashif Nawaz , Chi-Chuan Wang","doi":"10.1016/j.applthermaleng.2024.124881","DOIUrl":"10.1016/j.applthermaleng.2024.124881","url":null,"abstract":"<div><div>Horizontal falling film evaporators are widely utilized in desalination industries to increase fresh water supply. However, universal correlations for seawater falling film evaporation under varied operational and geometrical conditions are simply unavailable in open literature. Thus, this study aims to develop such a universal correlation for both plain and enhanced tubes. The detailed heat transfer mechanisms are reviewed, and rational parameters are incorporated to develop the universal correlation. A dataset of 994 data points from 9 sources covering a wide range of conditions was compiled. These conditions include Reynolds numbers from 10 to 7235, heat fluxes from 7.7 to 208 kW/m<sup>−2</sup>, saturation temperatures from 278 to 401 K, salinities from 0 to 60 g<sub>salt</sub> kg<sup>−1</sup><sub>water</sub>, tube diameters from 15.8 to 50.8 mm, and liquid feeder height to diameter ratios from 1 to 2.25. Upon analysis, it was found that most of the recommended existing correlations exhibited poor predictive accuracy, as evidenced by larger MADs. The developed correlation in this study demonstrated the best predictive accuracy for the entire dataset, yielding a MAD of 16.8 % and an R<sup>2</sup> of 0.82. Furthermore, the performance of the new correlation was individually assessed across a broader spectrum of operational and design conditions, reflecting the individual conditions’ influences with an overall MAD of 20 %.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124881"},"PeriodicalIF":6.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658190","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 : 2024-11-13DOI: 10.1016/j.applthermaleng.2024.124862
Yanfang Yu , Wen Sun , Huibo Meng , Puyu Zhang , Dadian Wang , Jinyu Guo
Hydrothermal pretreatment is an efficient process to convert microalgae slurry into biodiesel. The conversion efficiency largely depends on the heat transfer performance of microalgae slurry in various mixers. Compared with previous studies on laminar heat transfer performance of microalgae slurry in horizontal empty tubes, this study numerically investigates the turbulent heat transfer performance of microalgae slurry in vertical Lightnin static mixer and Kenics static mixer with different aspect ratios. The generalized Reynolds number is in the range of 530–5850. The effects of inlet velocity and mass fraction for microalgae slurry on the enhanced heat transfer performance of static mixers are evaluated. Results indicate the Performance evaluation criteria of Kenics static mixers with the aspect ratios of 1, 1.5, and 2 are higher than those of Lightnin static mixers by 9.32–17.81 %, 10.38–20.51 %, and 3.19–14.95 %, respectively. The empirical correlations of microalgae slurry for Nusselt number and Fanning friction coefficient are proposed. Additionally, the entropy generations of Kenics static mixer are higher than that of Lightnin static mixer by 21.34–27.37 %, 10.80–20.57 %, and 12.31–20.46 %, when the aspect ratios are 1, 1.5, and 2, respectively. Therefore, the Lightnin static mixer is recommended when the enhanced heat transfer performance is mainly considered. Additionally, 5 wt% microalgae slurry is recommended for hydrothermal pretreatment.
{"title":"Enhancing turbulent hydrothermal pretreatment of non-Newtonian microalgae slurry utilizing static mixers with secondary flow generators","authors":"Yanfang Yu , Wen Sun , Huibo Meng , Puyu Zhang , Dadian Wang , Jinyu Guo","doi":"10.1016/j.applthermaleng.2024.124862","DOIUrl":"10.1016/j.applthermaleng.2024.124862","url":null,"abstract":"<div><div>Hydrothermal pretreatment is an efficient process to convert microalgae slurry into biodiesel. The conversion efficiency largely depends on the heat transfer performance of microalgae slurry in various mixers. Compared with previous studies on laminar heat transfer performance of microalgae slurry in horizontal empty tubes, this study numerically investigates the turbulent heat transfer performance of microalgae slurry in vertical Lightnin static mixer and Kenics static mixer with different aspect ratios. The generalized Reynolds number is in the range of 530–5850. The effects of inlet velocity and mass fraction for microalgae slurry on the enhanced heat transfer performance of static mixers are evaluated. Results indicate the Performance evaluation criteria of Kenics static mixers with the aspect ratios of 1, 1.5, and 2 are higher than those of Lightnin static mixers by 9.32–17.81 %, 10.38–20.51 %, and 3.19–14.95 %, respectively. The empirical correlations of microalgae slurry for Nusselt number and Fanning friction coefficient are proposed. Additionally, the entropy generations of Kenics static mixer are higher than that of Lightnin static mixer by 21.34–27.37 %, 10.80–20.57 %, and 12.31–20.46 %, when the aspect ratios are 1, 1.5, and 2, respectively. Therefore, the Lightnin static mixer is recommended when the enhanced heat transfer performance is mainly considered. Additionally, 5 wt% microalgae slurry is recommended for hydrothermal pretreatment.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124862"},"PeriodicalIF":6.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658197","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 : 2024-11-13DOI: 10.1016/j.applthermaleng.2024.124860
Chen Chen, Ming Liu, Chaoyang Wang, Junjie Yan
In order to facilitate the increasing penetration of grid-connected renewable power, coal-fired power plants should operate more and more flexibly. Most of the-state-of-the-art control strategies, which are mainly based on the idea of direct energy balance, cannot perform well when coal-fired power plants change load with high load cycling ramp rate. To enhance the operational flexibility of coal-fired power plants, the control idea of the direct exergy balance is proposed in this study, which directly characterizes the work capacity balance between the boiler and the steam turbine. The new control strategy of direct exergy balance emphasizes the feedback of the deviation between the turbine exergy demand signal and the boiler exergy signal. Dynamic models of a reference power plant were developed and validated, and performances of control strategies based on direct energy balance and direct exergy balance were evaluated and compared. In the 50 %–75 % load cycling process of the reference power plant, the control strategy of direct exergy balance demonstrated markedly improvements in the load cycling ramp rate (29.2 % relatively), the load cycling comprehensive index Kp (39.4 %), and reduction in the maximum deviations (28.2 %), overshoots (59.8 %), and cumulative deviations (28.7 %) of the key thermal parameters. In conclusion, the control strategy of direct exergy balance significantly strengthens the control performance during rapid load cycling processes and attains a notable enhancement in operational flexibility and a slight improvement in energy efficiency of coal-fired power plant.
{"title":"A new control strategy of direct exergy balance for coal-fired power plants: Fundamentals and performance evaluation","authors":"Chen Chen, Ming Liu, Chaoyang Wang, Junjie Yan","doi":"10.1016/j.applthermaleng.2024.124860","DOIUrl":"10.1016/j.applthermaleng.2024.124860","url":null,"abstract":"<div><div>In order to facilitate the increasing penetration of grid-connected renewable power, coal-fired power plants should operate more and more flexibly. Most of the-state-of-the-art control strategies, which are mainly based on the idea of direct energy balance, cannot perform well when coal-fired power plants change load with high load cycling ramp rate. To enhance the operational flexibility of coal-fired power plants, the control idea of the direct exergy balance is proposed in this study, which directly characterizes the work capacity balance between the boiler and the steam turbine. The new control strategy of direct exergy balance emphasizes the feedback of the deviation between the turbine exergy demand signal and the boiler exergy signal. Dynamic models of a reference power plant were developed and validated, and performances of control strategies based on direct energy balance and direct exergy balance were evaluated and compared. In the 50 %–75 % load cycling process of the reference power plant, the control strategy of direct exergy balance demonstrated markedly improvements in the load cycling ramp rate (29.2 % relatively), the load cycling comprehensive index <em>K</em><sub>p</sub> (39.4 %), and reduction in the maximum deviations (28.2 %), overshoots (59.8 %), and cumulative deviations (28.7 %) of the key thermal parameters. In conclusion, the control strategy of direct exergy balance significantly strengthens the control performance during rapid load cycling processes and attains a notable enhancement in operational flexibility and a slight improvement in energy efficiency of coal-fired power plant.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124860"},"PeriodicalIF":6.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657782","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}
With the application of hydrogen in marine engines, greenhouse gas emissions can be effectively reduced. However, abnormal combustion restricts the development of hydrogen engines. Lubricating oil is considered the main factor responsible for the onset of abnormal combustion modes. The pre-ignition that occurred in hydrogen engines may have some different characteristics, due to lower ignition energy and higher burning rate of hydrogen. To understand the characteristics of the pre-ignition induced by lubricating oil, experimental research was carried out based on a rapid compression machine (RCM). The pre-ignition is usually accompanied by an engine knock. Both the increase of temperature and pressure intensifies the occurrence tendency of pre-ignition for hydrogen engines. In particular, when the temperature is increased by 70 K, the oil droplet (0.1 mm) ignition delay is shortened by about 70 % and the flame diffusion speed is increased by about 40 %. The reduction of air-to-fuel equivalence ratio (λ) promotes the occurrence of pre-ignition accompanied by varying degrees of engine knock. To avoid knocking associated with pre-ignition, an air-to-fuel equivalence ratio in the range of 2.5 to 3.0 is appropriate while maintaining thermal efficiency. Compared with methane, the effect on the physical ignition delay of oil droplets is significantly greater, whereas the effect on the chemical ignition delay is less pronounced.
{"title":"Investigation of the hydrogen pre-ignition induced by the auto-ignition of lubricating oil droplets","authors":"Zixin Wang, Meijia Song, Huazhi Zhao, Yao Lu, Zhen Gong, Liyan Feng","doi":"10.1016/j.applthermaleng.2024.124927","DOIUrl":"10.1016/j.applthermaleng.2024.124927","url":null,"abstract":"<div><div>With the application of hydrogen in marine engines, greenhouse gas emissions can be effectively reduced. However, abnormal combustion restricts the development of hydrogen engines. Lubricating oil is considered the main factor responsible for the onset of abnormal combustion modes. The pre-ignition that occurred in hydrogen engines may have some different characteristics, due to lower ignition energy and higher burning rate of hydrogen. To understand the characteristics of the pre-ignition induced by lubricating oil, experimental research was carried out based on a rapid compression machine (RCM). The pre-ignition is usually accompanied by an engine knock. Both the increase of temperature and pressure intensifies the occurrence tendency of pre-ignition for hydrogen engines. In particular, when the temperature is increased by 70 K, the oil droplet (0.1 mm) ignition delay is shortened by about 70 % and the flame diffusion speed is increased by about 40 %. The reduction of air-to-fuel equivalence ratio (λ) promotes the occurrence of pre-ignition accompanied by varying degrees of engine knock. To avoid knocking associated with pre-ignition, an air-to-fuel equivalence ratio in the range of 2.5 to 3.0 is appropriate while maintaining thermal efficiency. Compared with methane, the effect on the physical ignition delay of oil droplets is significantly greater, whereas the effect on the chemical ignition delay is less pronounced.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124927"},"PeriodicalIF":6.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657779","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 investigates the thermal performance and temperature uniformity of a hybrid battery thermal management system (BTMS) that integrates phase change material (PCM), metal foam, and minichannels. Computational fluid dynamics is used to model the PCM melting process and heat transfer between all components. The primary goal of the work is to investigate BTMS architectures which can enhance thermal uniformity and prevent critical temperature rise in a high-voltage battery pack under fast discharging and real-world driving cycle. Four BTMS designs are compared. The design that integrates PCM, metal foam, and counterflow minichannels is shown to have the best performance. At low pumping power (coolant Reynolds number Re = 10), this design reduces the peak battery temperature by 11.5 K compared to a design employing pure PCM only. This configuration also ensures a temperature difference of less than 5 K among individual battery cells, addressing thermal safety considerations and extending battery lifespan. Further analysis revealed that the inclusion of metal foam delays PCM melting, enhances both system and battery thermal uniformity, and offers a higher performance-to-weight ratio compared to designs without metal foam. Although wavy-shaped minichannels offer minimal temperature improvement (0.3 K) over straight minichannels, their higher cost and increased pumping power requirements do not justify their practicality. Under both fast discharging and real driving conditions, the first design with pure PCM provides uniform heat distribution within batteries but fails to maintain the maximum battery temperature within the optimal range. Overall, this study highlights the effectiveness of the proposed hybrid BTMS design in providing uniform temperature distribution and maintaining the maximum battery temperature within the optimal range under harsh environmental conditions, fast discharging, and the Urban Dynamometer Driving Schedule (UDDS) drive cycle.
{"title":"Thermal uniformity analysis of a hybrid battery pack using integrated phase change material, metal foam, and counterflow minichannels","authors":"Hasan Najafi Khaboshan , Kumaran Kadirgama , Devarajan Ramasamy , Virendra Talele , Peng Zhao , Harsh Tyagi , Nenad Miljkovic","doi":"10.1016/j.applthermaleng.2024.124910","DOIUrl":"10.1016/j.applthermaleng.2024.124910","url":null,"abstract":"<div><div>This study investigates the thermal performance and temperature uniformity of a hybrid battery thermal management system (BTMS) that integrates phase change material (PCM), metal foam, and minichannels. Computational fluid dynamics is used to model the PCM melting process and heat transfer between all components. The primary goal of the work is to investigate BTMS architectures which can enhance thermal uniformity and prevent critical temperature rise in a high-voltage battery pack under fast discharging and real-world driving cycle. Four BTMS designs are compared. The design that integrates PCM, metal foam, and counterflow minichannels is shown to have the best performance. At low pumping power (coolant Reynolds number <em>Re</em> = 10), this design reduces the peak battery temperature by 11.5 K compared to a design employing pure PCM only. This configuration also ensures a temperature difference of less than 5 K among individual battery cells, addressing thermal safety considerations and extending battery lifespan. Further analysis revealed that the inclusion of metal foam delays PCM melting, enhances both system and battery thermal uniformity, and offers a higher performance-to-weight ratio compared to designs without metal foam. Although wavy-shaped minichannels offer minimal temperature improvement (0.3 K) over straight minichannels, their higher cost and increased pumping power requirements do not justify their practicality. Under both fast discharging and real driving conditions, the first design with pure PCM provides uniform heat distribution within batteries but fails to maintain the maximum battery temperature within the optimal range. Overall, this study highlights the effectiveness of the proposed hybrid BTMS design in providing uniform temperature distribution and maintaining the maximum battery temperature within the optimal range under harsh environmental conditions, fast discharging, and the Urban Dynamometer Driving Schedule (UDDS) drive cycle.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124910"},"PeriodicalIF":6.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658192","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 : 2024-11-12DOI: 10.1016/j.applthermaleng.2024.124911
Zhengyang Dong, Kai Liu, Hanrui Qiu, Mingjun Wang, Wenxi Tian, G.H. Su
Significant coupling effects exist among system components in nuclear pressure vessel. Due to the complex geometric structures, the nuclear industry primarily relies on system codes or sub-channel methods for core safety analysis. However, these methods suffer from low model accuracy and insufficient coupling capabilities. Additionally, the differences in model scales impede direct coupling analysis with the CFD calculations of the plenum system. To address these issues, this paper proposes a multi −scale coupling calculation method for the entire pressure vessel: For the plenum system, detailed CFD modeling is employed, while the core calculations are conducted using CorTAF, a high-resolution core Multiphysics-coupling analysis method developed by our team. A cross-resolution coupling model is utilized to integrate the two, achieving cross-resolution coupling simulations for the entire pressure vessel, encompassing both the plenum and core system. The above method was applied to the coupling calculations of a typical pressurized water reactor’s lower plenum and core, revealing detailed thermal–hydraulic phenomena under precise core flow inlet distribution conditions. The lateral flow at the core inlet exceeds 1 m/s, with the maximum and minimum fluid velocities in the subchannels deviating by up to 70 % from the average velocity of 2.42 m/s. The flow distribution only begins to stabilize after a height of 1.2 m in the core. The paper also includes inlet asymmetric flow reduction calculations. Overall, the method enables multi-scale and multi-physics coupling calculations, which provide significant reference value for improving the accuracy of current core safety analyses.
{"title":"Preliminary Implementation of High-Resolution Multi-Scale coupling calculations for the entire pressure vessel based on OpenFOAM","authors":"Zhengyang Dong, Kai Liu, Hanrui Qiu, Mingjun Wang, Wenxi Tian, G.H. Su","doi":"10.1016/j.applthermaleng.2024.124911","DOIUrl":"10.1016/j.applthermaleng.2024.124911","url":null,"abstract":"<div><div>Significant coupling effects exist among system components in nuclear pressure vessel. Due to the complex geometric structures, the nuclear industry primarily relies on system codes or sub-channel methods for core safety analysis. However, these methods suffer from low model accuracy and insufficient coupling capabilities. Additionally, the differences in model scales impede direct coupling analysis with the CFD calculations of the plenum system. To address these issues, this paper proposes a multi −scale coupling calculation method for the entire pressure vessel: For the plenum system, detailed CFD modeling is employed, while the core calculations are conducted using CorTAF, a high-resolution core Multiphysics-coupling analysis method developed by our team. A cross-resolution coupling model is utilized to integrate the two, achieving cross-resolution coupling simulations for the entire pressure vessel, encompassing both the plenum and core system. The above method was applied to the coupling calculations of a typical pressurized water reactor’s lower plenum and core, revealing detailed thermal–hydraulic phenomena under precise core flow inlet distribution conditions. The lateral flow at the core inlet exceeds 1 m/s, with the maximum and minimum fluid velocities in the subchannels deviating by up to 70 % from the average velocity of 2.42 m/s. The flow distribution only begins to stabilize after a height of 1.2 m in the core. The paper also includes inlet asymmetric flow reduction calculations. Overall, the method enables multi-scale and multi-physics coupling calculations, which provide significant reference value for improving the accuracy of current core safety analyses.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124911"},"PeriodicalIF":6.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657549","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 hot-end components of gas turbines necessitate efficient cooling strategies to enhance performance and durability. This research focuses on how the Coriolis force affects the purge flow’s cooling effectiveness on the turbine endwall. Utilizing both experimental and numerical methods, the study examines various rotational speeds and Mach numbers to understand the Coriolis force’s impact on aerodynamic losses and cooling effectiveness. This study’s methodological innovations are demonstrated in the following aspects: The implementation of a deflector plate within the rim seal ensures that the circumferential velocity of the purge flow relative to the rotor remains constant at any cascade speed, thereby guaranteeing that the focus of this research is on the “Coriolis effect” rather than the “rotational effect.” The development of a dual-coordinate analysis method allows for a clear presentation of the mechanism by which the Coriolis force influences the vortex’s motion characteristics. Increasing the rotational speed of the cascade enhances the adiabatic cooling effectiveness of the endwall. Similarly, increasing the Mach number of both the main flow and the purge flow under the same blowing ratio also enhances the endwall’s adiabatic cooling effectiveness. This study demonstrates that the underlying mechanisms of these effects are essentially the same, as both alter the Coriolis forces acting on the fluid. Coriolis forces expand the pressure leg of the horseshoe vortex and the passage vortex while reducing the suction leg of the horseshoe vortex. Given that vortex cores are low-pressure regions, the purge flow is entrained into the cores of the pressure leg of the horseshoe vortex and the passage vortex. The increase in rotational speed and Mach number results in greater Coriolis forces, inducing a movement away from the vortex core that expels the denser cooling air from the core. The conclusions of this study can provide insights for the design of gas turbines. Furthermore, the research methodology employed here can serve as a reference for studies on the interaction between purge flow and main flow.
{"title":"Effects of Coriolis force on the aero-thermal performance of stator-rotor purge flow","authors":"Hongyu Gao , Yutian Wang , Renjie Xu , Wanfu Zhang , Jing Ren","doi":"10.1016/j.applthermaleng.2024.124907","DOIUrl":"10.1016/j.applthermaleng.2024.124907","url":null,"abstract":"<div><div>The hot-end components of gas turbines necessitate efficient cooling strategies to enhance performance and durability. This research focuses on how the Coriolis force affects the purge flow’s cooling effectiveness on the turbine endwall. Utilizing both experimental and numerical methods, the study examines various rotational speeds and Mach numbers to understand the Coriolis force’s impact on aerodynamic losses and cooling effectiveness. This study’s methodological innovations are demonstrated in the following aspects: The implementation of a deflector plate within the rim seal ensures that the circumferential velocity of the purge flow relative to the rotor remains constant at any cascade speed, thereby guaranteeing that the focus of this research is on the “Coriolis effect” rather than the “rotational effect.” The development of a dual-coordinate analysis method allows for a clear presentation of the mechanism by which the Coriolis force influences the vortex’s motion characteristics. Increasing the rotational speed of the cascade enhances the adiabatic cooling effectiveness of the endwall. Similarly, increasing the Mach number of both the main flow and the purge flow under the same blowing ratio also enhances the endwall’s adiabatic cooling effectiveness. This study demonstrates that the underlying mechanisms of these effects are essentially the same, as both alter the Coriolis forces acting on the fluid. Coriolis forces expand the pressure leg of the horseshoe vortex and the passage vortex while reducing the suction leg of the horseshoe vortex. Given that vortex cores are low-pressure regions, the purge flow is entrained into the cores of the pressure leg of the horseshoe vortex and the passage vortex. The increase in rotational speed and Mach number results in greater Coriolis forces, inducing a movement away from the vortex core that expels the denser cooling air from the core. The conclusions of this study can provide insights for the design of gas turbines. Furthermore, the research methodology employed here can serve as a reference for studies on the interaction between purge flow and main flow.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124907"},"PeriodicalIF":6.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658189","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 : 2024-11-12DOI: 10.1016/j.applthermaleng.2024.124780
Jiuxuan Xiang , Aikun Tang , Yuting Pan , Yi Jin , Tao Cai
Phase change cold storage refrigerators are a core of low-carbon development in cold chain logistics. This study is dedicated to optimizing the performance of phase-change cold storage refrigerators for the refrigerated transport of fruits and vegetables. Firstly, a high-performance inorganic phase change material was developed. By selecting a ratio of 2 wt% Carboxymethyl cellulose and 0.25 wt% Fumed Silica to solve the defects of supercooling and phase separation of this material, Subsequently, an experimental platform was built based on this material to test the charging and cooling characteristics of the phase change module. It was found that the opening of the expansion valve, the compressor’s speed, and the condenser fan’s speed were positively correlated to the charging and cooling efficiencies. Still, the effects of the first two on the system performance coefficient had optimal value points. However, there is an optimum point for the impact of the first two on the system performance coefficient. The optimized system coefficient of performance is increased to 1.62, and the charging time is reduced by 47.6 %, which is a good balance between energy efficiency and transport efficiency. In addition, it was found that the radial thermal resistance of the evaporator tubes in the charging module was more significant than the axial direction, and a new type of finned tube was designed to enhance the heat transfer, which resulted in a further reduction of 29 percent in the charge time.
{"title":"Development of inorganic phase change material and cold charging performance analysis based on cold storage refrigerator","authors":"Jiuxuan Xiang , Aikun Tang , Yuting Pan , Yi Jin , Tao Cai","doi":"10.1016/j.applthermaleng.2024.124780","DOIUrl":"10.1016/j.applthermaleng.2024.124780","url":null,"abstract":"<div><div>Phase change cold storage refrigerators are a core of low-carbon development in cold chain logistics. This study is dedicated to optimizing the performance of phase-change cold storage refrigerators for the refrigerated transport of fruits and vegetables. Firstly, a high-performance inorganic phase change material was developed. By selecting a ratio of 2 wt% Carboxymethyl cellulose and 0.25 wt% Fumed Silica to solve the defects of supercooling and phase separation of this material, Subsequently, an experimental platform was built based on this material to test the charging and cooling characteristics of the phase change module. It was found that the opening of the expansion valve, the compressor’s speed, and the condenser fan’s speed were positively correlated to the charging and cooling efficiencies. Still, the effects of the first two on the system performance coefficient had optimal value points. However, there is an optimum point for the impact of the first two on the system performance coefficient. The optimized system coefficient of performance is increased to 1.62, and the charging time is reduced by 47.6 %, which is a good balance between energy efficiency and transport efficiency. In addition, it was found that the radial thermal resistance of the evaporator tubes in the charging module was more significant than the axial direction, and a new type of finned tube was designed to enhance the heat transfer, which resulted in a further reduction of 29 percent in the charge time.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124780"},"PeriodicalIF":6.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657651","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 : 2024-11-12DOI: 10.1016/j.applthermaleng.2024.124917
S. Schroderus , J. Havelka , A. Kouch , K. Illikainen , S. Alitalo , F. Fedorik
Climate change, energy efficiency, and carbon footprint objectives pose significant challenges to the hygrothermal performance of building structures in climates with extreme temperature variations. To meet long term sustainability targets, buildings designed for a lifespan of up to 100 years must exhibit resilience not only to current climate conditions but also to projected future scenarios. This study evaluated the hygrothermal performance of a hybrid log-concrete multi-storey building, combining the structural strength of concrete with the sustainable, moisture-regulating properties of wood, to address energy efficiency and moisture control challenges in subarctic climates. Onsite measurements were validated using numerical simulations to assess hygrothermal performance of log wall structure under climate change scenarios. Results showed minimal mould growth risk under present conditions, while future climate projections (RCP8.5 for 2080) indicated a maximum mould index of 1.32 near the exterior log surface. These findings highlight the resilience of log-based structures in cold climates and underscore the need for proactive moisture management under warmer, more humid future scenarios. Stable ideal indoor temperatures (averaging 21.56 °C to 22.09 °C) and effective moisture control (with a maximum average moisture excess of 0.89 g/m3) over the measurement period further demonstrate the suitability of hybrid log-concrete buildings for energy-efficient, moisture-regulating construction in cold climates. The study recommends surface treatments that allow vapour diffusion while preserving wood’s hygroscopic qualities to enhance durability in changing climates.
{"title":"Hygrothermal performance of hybrid multi-storey buildings under future climate scenarios","authors":"S. Schroderus , J. Havelka , A. Kouch , K. Illikainen , S. Alitalo , F. Fedorik","doi":"10.1016/j.applthermaleng.2024.124917","DOIUrl":"10.1016/j.applthermaleng.2024.124917","url":null,"abstract":"<div><div>Climate change, energy efficiency, and carbon footprint objectives pose significant challenges to the hygrothermal performance of building structures in climates with extreme temperature variations. To meet long term sustainability targets, buildings designed for a lifespan of up to 100 years must exhibit resilience not only to current climate conditions but also to projected future scenarios. This study evaluated the hygrothermal performance of a hybrid log-concrete multi-storey building, combining the structural strength of concrete with the sustainable, moisture-regulating properties of wood, to address energy efficiency and moisture control challenges in subarctic climates. Onsite measurements were validated using numerical simulations to assess hygrothermal performance of log wall structure under climate change scenarios. Results showed minimal mould growth risk under present conditions, while future climate projections (RCP8.5 for 2080) indicated a maximum mould index of 1.32 near the exterior log surface. These findings highlight the resilience of log-based structures in cold climates and underscore the need for proactive moisture management under warmer, more humid future scenarios. Stable ideal indoor temperatures (averaging 21.56 °C to 22.09 °C) and effective moisture control (with a maximum average moisture excess of 0.89 g/m<sup>3</sup>) over the measurement period further demonstrate the suitability of hybrid log-concrete buildings for energy-efficient, moisture-regulating construction in cold climates. The study recommends surface treatments that allow vapour diffusion while preserving wood’s hygroscopic qualities to enhance durability in changing climates.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124917"},"PeriodicalIF":6.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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