Pub Date : 2024-11-04DOI: 10.1016/j.applthermaleng.2024.124809
Weiwu Ma , Yifan Xu , Shams Forruque Ahmed , Jiangzirui Xu , Gang Liu
The successful development of Enhanced Geothermal Systems relies on constructing high-quality fracture networks. However, the mechanism of hydrothermal evolution in geothermal reservoirs with artificial fracture networks remains poorly understood. This study aims to elucidate the mechanism of hydrothermal evolution in fractured reservoirs to optimize geothermal energy extraction. Novel metrics, namely reservoir heating efficiency and reservoir flow efficiency, were introduced to assess performance. The study comparatively investigated six fracture structures and evaluated their impact on system production. Key findings reveal that fluid flow in multiple horizontal wells fractures reservoirs efficiently, with heat effectively extracted from the edges of the Stimulated Reservoir Volume. Enhanced reservoir heating efficiency and optimized flow efficiency were achieved due to improved heat exchange and fluid diversion. Optimal hydrothermal evolution was realized with a reservoir heating efficiency of 0.2022 and a reservoir flow efficiency of 0.2398, using a configuration of a 0° rotation angle, 30 kg/s injection mass flow, 60 °C injection temperature, 3.12 mm hydraulic fracture aperture, and 200 m production well spacing. These findings provide valuable insights into reservoir design and production strategies for Enhanced Geothermal System.
{"title":"Hydrothermal evolution analysis and performance optimization in multi-well fractured reservoirs for enhanced geothermal systems","authors":"Weiwu Ma , Yifan Xu , Shams Forruque Ahmed , Jiangzirui Xu , Gang Liu","doi":"10.1016/j.applthermaleng.2024.124809","DOIUrl":"10.1016/j.applthermaleng.2024.124809","url":null,"abstract":"<div><div>The successful development of Enhanced Geothermal Systems relies on constructing high-quality fracture networks. However, the mechanism of hydrothermal evolution in geothermal reservoirs with artificial fracture networks remains poorly understood. This study aims to elucidate the mechanism of hydrothermal evolution in fractured reservoirs to optimize geothermal energy extraction. Novel metrics, namely reservoir heating efficiency and reservoir flow efficiency, were introduced to assess performance. The study comparatively investigated six fracture structures and evaluated their impact on system production. Key findings reveal that fluid flow in multiple horizontal wells fractures reservoirs efficiently, with heat effectively extracted from the edges of the Stimulated Reservoir Volume. Enhanced reservoir heating efficiency and optimized flow efficiency were achieved due to improved heat exchange and fluid diversion. Optimal hydrothermal evolution was realized with a reservoir heating efficiency of 0.2022 and a reservoir flow efficiency of 0.2398, using a configuration of a 0° rotation angle, 30 kg/s injection mass flow, 60 °C injection temperature, 3.12 mm hydraulic fracture aperture, and 200 m production well spacing. These findings provide valuable insights into reservoir design and production strategies for Enhanced Geothermal System.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124809"},"PeriodicalIF":6.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659952","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 : 2024-11-04DOI: 10.1016/j.applthermaleng.2024.124811
Weijie Yan , Tianjiao Li , Xiaoyu Xing , Xuebin Wang , Dong Liu
The temperature of the rotating turbine blades of a turbojet engine must be known to assess the combustion state and improve turbine blade quality. Obtaining online temperature measurements of high-speed rotating turbine blades in high-temperature gas flow remains challenging. A multispectral radiation thermometry method without emissivity assumption is proposed to measure the temperature of high-speed rotating turbine blades of a micro turbojet engine. The relative radiative intensity is calculated by accounting for smooth changes in the wavelength using the moving narrowband method to determine the influence of emissivity on multispectral radiation thermometry results. The method’s performance in measuring the surface temperature of high-speed rotating objects is tested. The wavelength range of 970 nm to 1700 nm is selected because the radiation from gases is weaker in comparison to the radiation emitted by solid surfaces within this band. The spectral radiation of the turbine blade surface is measured at three rotational speeds: 38,000 r/min, 48,000 r/min, and 58,000 r/min. The results show that, unlike thermocouples that measure the temperature of the hot gas flow near the blade, multispectral radiation thermometry provides the average surface temperature with high consistency (with a deviation smaller than 50 K). Multispectral radiation thermometry can be applied to measure the surface temperature and emissivity of high-speed rotating objects, such as the blades of turbojet engines.
{"title":"Experimental study on surface temperature and emissivity of rotating turbine blades of a micro turbojet engine","authors":"Weijie Yan , Tianjiao Li , Xiaoyu Xing , Xuebin Wang , Dong Liu","doi":"10.1016/j.applthermaleng.2024.124811","DOIUrl":"10.1016/j.applthermaleng.2024.124811","url":null,"abstract":"<div><div>The temperature of the rotating turbine blades of a turbojet engine must be known to assess the combustion state and improve turbine blade quality. Obtaining online temperature measurements of high-speed rotating turbine blades in high-temperature gas flow remains challenging. A multispectral radiation thermometry method without emissivity assumption is proposed to measure the temperature of high-speed rotating turbine blades of a micro turbojet engine. The relative radiative intensity is calculated by accounting for smooth changes in the wavelength using the moving narrowband method to determine the influence of emissivity on multispectral radiation thermometry results. The method’s performance in measuring the surface temperature of high-speed rotating objects is tested. The wavelength range of 970 nm to 1700 nm is selected because the radiation from gases is weaker in comparison to the radiation emitted by solid surfaces within this band. The spectral radiation of the turbine blade surface is measured at three rotational speeds: 38,000 r/min, 48,000 r/min, and 58,000 r/min. The results show that, unlike thermocouples that measure the temperature of the hot gas flow near the blade, multispectral radiation thermometry provides the average surface temperature with high consistency (with a deviation smaller than 50 K). Multispectral radiation thermometry can be applied to measure the surface temperature and emissivity of high-speed rotating objects, such as the blades of turbojet engines.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124811"},"PeriodicalIF":6.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657722","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}
Thermal radiation is a large contributor to the total heat transfer of combustion systems so that it cannot be neglected, with the improvement of gas temperature and infrared stealth requirements. This paper deeply investigated the convective parameters in film cooling with thermal radiation through theoretical analysis and numerical simulation. A method to obtain the convective driving temperature under radiation was proposed and demonstrated. Research found that the film cooling effectiveness with radiation should be expressed by the mixing temperature rather than the adiabatic wall temperature. Although heat transfer and mass transfer under radiation cannot be theoretically analogized due to the radiant source term in the energy equation, the concentration cooling effectiveness without and with radiation remains approximately the same. The numerical results indicate that although conjugate coupling plays a crucial role in determining convective and radiative heat fluxes, the coupling of radiation and convective parameters is very weak. Radiation has little influence on the film cooling effectiveness (η) and the convective heat transfer coefficient (hf). Convective parameters can be decoupled from radiation with negligible loss of accuracy. This allows the non-radiation convective parameters η and hf to be directly used for calculating the convective heat flux under radiation, with relative deviations of less than 5%.
热辐射对燃烧系统的总传热贡献很大，因此随着气体温度的提高和红外隐身要求的提高，热辐射的作用不容忽视。本文通过理论分析和数值模拟，深入研究了热辐射薄膜冷却中的对流参数。提出并论证了辐射下对流驱动温度的求取方法。研究发现，辐射下的薄膜冷却效果应该用混合温度而不是绝热壁温来表示。虽然由于能量方程中的辐射源项，辐射条件下的传热和传质无法从理论上进行类比，但无辐射和有辐射时的浓度冷却效果大致相同。数值结果表明，虽然共轭耦合在决定对流和辐射热通量方面起着关键作用，但辐射和对流参数的耦合非常弱。辐射对薄膜冷却效果（η）和对流传热系数（hf）的影响很小。对流参数可以与辐射解耦，精度损失可以忽略不计。这使得非辐射对流参数 η 和 hf 可以直接用于计算辐射下的对流热通量，相对偏差小于 5%。
{"title":"Convective heat transfer parameters in the film cooling with thermal radiation","authors":"Fei-fei Cao, Cun-liang Liu, Xian-long Meng, Zhi-peng Xu","doi":"10.1016/j.applthermaleng.2024.124802","DOIUrl":"10.1016/j.applthermaleng.2024.124802","url":null,"abstract":"<div><div>Thermal radiation is a large contributor to the total heat transfer of combustion systems so that it cannot be neglected, with the improvement of gas temperature and infrared stealth requirements. This paper deeply investigated the convective parameters in film cooling with thermal radiation through theoretical analysis and numerical simulation. A method to obtain the convective driving temperature under radiation was proposed and demonstrated. Research found that the film cooling effectiveness with radiation should be expressed by the mixing temperature rather than the adiabatic wall temperature. Although heat transfer and mass transfer under radiation cannot be theoretically analogized due to the radiant source term in the energy equation, the concentration cooling effectiveness without and with radiation remains approximately the same. The numerical results indicate that although conjugate coupling plays a crucial role in determining convective and radiative heat fluxes, the coupling of radiation and convective parameters is very weak. Radiation has little influence on the film cooling effectiveness (<em>η</em>) and the convective heat transfer coefficient (<em>h</em><sub>f</sub>). Convective parameters can be decoupled from radiation with negligible loss of accuracy. This allows the non-radiation convective parameters <em>η</em> and <em>h</em><sub>f</sub> to be directly used for calculating the convective heat flux under radiation, with relative deviations of less than 5%.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124802"},"PeriodicalIF":6.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659958","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 : 2024-11-04DOI: 10.1016/j.applthermaleng.2024.124814
Chandan Nashine , Manmohan Pandey , Kamlesh K. Baraya
To expand the knowledge of miniature loop heat pipes under different conditions, i.e., vacuum and ambient, it is essential to study the start-up and transient characteristics of the device. Transient experiments were performed on a cylindrical evaporator miniature loop heat pipe at different heat loads from 5 W to 148 W and sink temperatures from −10 °C to 35 °C. The device was tested under ambient and vacuum conditions to better understand the transients under different loading conditions. Temperature oscillations were observed at the condenser outlet for all heat loads at lower sink temperatures and for a limited range of heat loads at higher sink temperatures. Experiments were also performed to study the hysteresis during heating and cooling cycles under different sink temperatures. Thermal hysteresis was observed in the device under lower sink temperature (0 °C). Start-up studies were conducted for different heat loads and sink temperatures, in which temperature oscillations were observed for specific ranges of heat loads. Overshoot, oscillating, and smooth startups were observed under different operating conditions. With increase in the heat load, the startup time was found to decrease initially and then increase for higher heat loads. The condenser outlet temperature showed large oscillations of about 2.5 °C amplitude and 80 s period for a 40 W heat load. The device can start at a low heat load of 4.8 W for the sink temperature of 10 °C. The trends observed in this work are similar to those reported in the literature.
为了扩展微型环形热管在真空和环境等不同条件下的知识，必须研究设备的启动和瞬态特性。我们在圆柱形蒸发器微型环路热管上进行了瞬态实验，热负荷从 5 W 到 148 W 不等，散热器温度从 -10 °C 到 35 °C 不等。在环境和真空条件下对该装置进行了测试，以更好地了解不同负载条件下的瞬态。在散热器温度较低时，所有热负荷下冷凝器出口处都出现了温度振荡，在散热器温度较高时，有限范围内的热负荷下也出现了温度振荡。实验还研究了不同散热器温度下加热和冷却循环过程中的滞后现象。在较低的散热器温度（0 °C）下，器件出现了热滞后现象。针对不同的热负荷和水槽温度进行了启动研究，在特定的热负荷范围内观察到了温度振荡。在不同的工作条件下，观察到过冲、振荡和平稳启动。随着热负荷的增加，启动时间开始缩短，热负荷越高，启动时间越长。在热负荷为 40 W 时，冷凝器出口温度出现振幅约为 2.5 °C、周期为 80 s 的大幅振荡。在散热器温度为 10 °C、热负荷为 4.8 W 的情况下，设备可以在较低的热负荷下启动。这项工作中观察到的趋势与文献报道的趋势相似。
{"title":"Experimental studies on the transient characteristics and start-up behaviour of a miniature loop heat pipe","authors":"Chandan Nashine , Manmohan Pandey , Kamlesh K. Baraya","doi":"10.1016/j.applthermaleng.2024.124814","DOIUrl":"10.1016/j.applthermaleng.2024.124814","url":null,"abstract":"<div><div>To expand the knowledge of miniature loop heat pipes under different conditions, i.e., vacuum and ambient, it is essential to study the start-up and transient characteristics of the device. Transient experiments were performed on a cylindrical evaporator miniature loop heat pipe at different heat loads from 5 W to 148 W and sink temperatures from −10 °C to 35 °C. The device was tested under ambient and vacuum conditions to better understand the transients under different loading conditions. Temperature oscillations were observed at the condenser outlet for all heat loads at lower sink temperatures and for a limited range of heat loads at higher sink temperatures. Experiments were also performed to study the hysteresis during heating and cooling cycles under different sink temperatures. Thermal hysteresis was observed in the device under lower sink temperature (0 °C). Start-up studies were conducted for different heat loads and sink temperatures, in which temperature oscillations were observed for specific ranges of heat loads. Overshoot, oscillating, and smooth startups were observed under different operating conditions. With increase in the heat load, the startup time was found to decrease initially and then increase for higher heat loads. The condenser outlet temperature showed large oscillations of about 2.5 °C amplitude and 80 s period for a 40 W heat load. The device can start at a low heat load of 4.8 W for the sink temperature of 10 °C. The trends observed in this work are similar to those reported in the literature.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124814"},"PeriodicalIF":6.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657720","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 : 2024-11-04DOI: 10.1016/j.applthermaleng.2024.124754
Xulong Cai, Qiao Deng, Kai Xu, Xuan Zhong, Minghe Yang
As environmental and economic issues exacerbated by traditional fossil fuels intensify, Dry Hot Rock geothermal energy has garnered significant attention due to its immense potential. Current research predominantly focuses on the heat extraction effectiveness in complex fractures within Enhanced Geothermal Systems, with relatively less emphasis on fluid behavior between large fractures. This study employs finite element software to establish a multi-horizontal well model in a low permeability reservoir (5 × 10-17 m2), analyzing the impact of different spatial configurations of two fractures on fluid flow, heat transfer, and heat extraction efficiency. The results indicate that fractures are the primary channels for fluid flow in low permeability reservoirs. Optimal heat extraction occurs when fractures are parallel, spaced 100 m apart, and perpendicular to the horizontal well, with significant threshold effects of fracture spacing and angle on temperature distribution. The highest heat extraction is achieved at a 37° intersection angle of fractures at the production well. Over a 60-year production period, reservoir extraction degrees for parallel or intersecting fractures range from 8 % to 15 %, while that for fracture communication between injection and production well horizontal segments is only 1.91 % to 3.01 %. Under the optimal injection scenario, cumulative 60-year heat production for parallel, intersecting, and communicating fractures is 2.13 × 1018J, 2.20 × 1018J, and 2.22 × 1018J, respectively, with the best heat extraction efficiency when fractures communicate. Additionally, under constant flow rate and inlet temperature, outlet temperature and system thermal power show near-linear declines, while reservoir extraction degree rises linearly. This study provides crucial theoretical support and practical guidance for the efficient extraction of geothermal energy.
{"title":"Impact of dual-fracture location on heat extraction from Enhanced geothermal system in low-permeability reservoirs","authors":"Xulong Cai, Qiao Deng, Kai Xu, Xuan Zhong, Minghe Yang","doi":"10.1016/j.applthermaleng.2024.124754","DOIUrl":"10.1016/j.applthermaleng.2024.124754","url":null,"abstract":"<div><div>As environmental and economic issues exacerbated by traditional fossil fuels intensify, Dry Hot Rock geothermal energy has garnered significant attention due to its immense potential. Current research predominantly focuses on the heat extraction effectiveness in complex fractures within Enhanced Geothermal Systems, with relatively less emphasis on fluid behavior between large fractures. This study employs finite element software to establish a multi-horizontal well model in a low permeability reservoir (5 × 10<sup>-</sup><sup>17</sup> m<sup>2</sup>), analyzing the impact of different spatial configurations of two fractures on fluid flow, heat transfer, and heat extraction efficiency. The results indicate that fractures are the primary channels for fluid flow in low permeability reservoirs. Optimal heat extraction occurs when fractures are parallel, spaced 100 m apart, and perpendicular to the horizontal well, with significant threshold effects of fracture spacing and angle on temperature distribution. The highest heat extraction is achieved at a 37° intersection angle of fractures at the production well. Over a 60-year production period, reservoir extraction degrees for parallel or intersecting fractures range from 8 % to 15 %, while that for fracture communication between injection and production well horizontal segments is only 1.91 % to 3.01 %. Under the optimal injection scenario, cumulative 60-year heat production for parallel, intersecting, and communicating fractures is 2.13 × 10<sup>18</sup>J, 2.20 × 10<sup>18</sup>J, and 2.22 × 10<sup>18</sup>J, respectively, with the best heat extraction efficiency when fractures communicate. Additionally, under constant flow rate and inlet temperature, outlet temperature and system thermal power show near-linear declines, while reservoir extraction degree rises linearly. This study provides crucial theoretical support and practical guidance for the efficient extraction of geothermal energy.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"259 ","pages":"Article 124754"},"PeriodicalIF":6.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657553","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 : 2024-11-04DOI: 10.1016/j.applthermaleng.2024.124749
Xingliang Ji, Qianyu Yang, Xinyue Huang, Daining Wei, Tao Wang, Baomin Sun
This article analyses the effects of sludge moisture content and blending ratio on combustion characteristics, furnace temperature distribution and NOx release during co-firing with coal in a 660 MW tangentially fired boiler using CFD. When the sludge water content increases from 10 % to 30 %, the water in the fuel is rapidly released during the initial combustion process and absorbs the reaction heat, resulting in a 2.8 % decrease in the temperature of the main combustion zone and a gradual decrease in the heat flux density, while the presence of water leads to the intensification of the incomplete combustion, resulting in the increase of the NOx conversion rate. With the increase of sludge blending ratio from 5 % to 25 % and the increase of water, the combustion temperature in the main combustion zone decreased by 4.0 %, and the heat flow density decreased significantly in the whole furnace and MBR area, by 6.43 % and 12.78 %, respectively. However, the nitrogen content present in the sludge is much higher than that of coal, and the fuel-based NOx produced by the combustion process increased dramatically, which led to the boiler exit NOx increasing by 35.4 %. Reasonable selection of sludge blending ratio and water content is a key issue to be considered for boiler co-combustion.
{"title":"Combustion characteristics and NOx release of sludge combustion with coal in a 660 MW boiler","authors":"Xingliang Ji, Qianyu Yang, Xinyue Huang, Daining Wei, Tao Wang, Baomin Sun","doi":"10.1016/j.applthermaleng.2024.124749","DOIUrl":"10.1016/j.applthermaleng.2024.124749","url":null,"abstract":"<div><div>This article analyses the effects of sludge moisture content and blending ratio on combustion characteristics, furnace temperature distribution and NOx release during co-firing with coal in a 660 MW tangentially fired boiler using CFD. When the sludge water content increases from 10 % to 30 %, the water in the fuel is rapidly released during the initial combustion process and absorbs the reaction heat, resulting in a 2.8 % decrease in the temperature of the main combustion zone and a gradual decrease in the heat flux density, while the presence of water leads to the intensification of the incomplete combustion, resulting in the increase of the NOx conversion rate. With the increase of sludge blending ratio from 5 % to 25 % and the increase of water, the combustion temperature in the main combustion zone decreased by 4.0 %, and the heat flow density decreased significantly in the whole furnace and MBR area, by 6.43 % and 12.78 %, respectively. However, the nitrogen content present in the sludge is much higher than that of coal, and the fuel-based NOx produced by the combustion process increased dramatically, which led to the boiler exit NOx increasing by 35.4 %. Reasonable selection of sludge blending ratio and water content is a key issue to be considered for boiler co-combustion.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124749"},"PeriodicalIF":6.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659950","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 : 2024-11-03DOI: 10.1016/j.applthermaleng.2024.124777
C.X. He , Q.L. Yue , S.B. Wan , Z.X. Guo , J. Sun , T.S. Zhao
Ensuring the thermal safety of lithium-ion batteries requires efficient and reliable thermal management systems. However, the non-uniform heat generation of lithium-ion batteries results in uneven temperature distribution, which complicates the comprehension of the flow pattern design and operating parameter optimization in liquid-based battery thermal management, especially under extreme conditions. This study evaluates the thermal management performance of four classic liquid cooling plate designs for pouch batteries by considering their non-uniform heat generation through the electrochemical-thermal coupled model. Through experiment and numerical simulation, the optimal flow pattern is identified. Subsequently, the capability of the thermal management system, utilizing the best flow design, is further assessed under varying operating conditions. The results indicate that while a higher flow rate marginally enhances cooling, the coolant inlet temperature exerts a more substantial impact on the cooling performance. In addition, the recommended parameter settings for cell-level liquid cooling systems are outlined under extreme conditions. With a 5 C discharge rate and an initial temperature of 35 °C, the recommended coolant temperature range and coolant flow rate range are 20–30 °C and 60–100 mL min−1, respectively. As a typical example of computer-aided engineering, this study reveals the impact of battery non-uniform heat generation on battery temperature performance and provides a critical reference for the optimization of liquid-based battery thermal management systems.
确保锂离子电池的热安全需要高效可靠的热管理系统。然而，锂离子电池的非均匀发热会导致温度分布不均，这使得液基电池热管理中的流型设计和运行参数优化变得复杂，尤其是在极端条件下。本研究通过电化学-热学耦合模型，考虑了袋式电池的非均匀发热，评估了四种经典液冷板设计的热管理性能。通过实验和数值模拟，确定了最佳流动模式。随后，利用最佳流动设计，进一步评估了热管理系统在不同工作条件下的能力。结果表明，虽然较高的流速能略微提高冷却效果，但冷却剂入口温度对冷却性能的影响更大。此外，还概述了在极端条件下电池级液体冷却系统的建议参数设置。在放电速率为 5 C、初始温度为 35 °C 的条件下，推荐的冷却液温度范围和冷却液流速范围分别为 20-30 °C 和 60-100 mL/min-1。作为计算机辅助工程的典型实例，本研究揭示了电池非均匀发热对电池温度性能的影响，为优化液态电池热管理系统提供了重要参考。
{"title":"Experimental and numerical investigations of liquid cooling plates for pouch lithium-ion batteries considering non-uniform heat generation","authors":"C.X. He , Q.L. Yue , S.B. Wan , Z.X. Guo , J. Sun , T.S. Zhao","doi":"10.1016/j.applthermaleng.2024.124777","DOIUrl":"10.1016/j.applthermaleng.2024.124777","url":null,"abstract":"<div><div>Ensuring the thermal safety of lithium-ion batteries requires efficient and reliable thermal management systems. However, the non-uniform heat generation of lithium-ion batteries results in uneven temperature distribution, which complicates the comprehension of the flow pattern design and operating parameter optimization in liquid-based battery thermal management, especially under extreme conditions. This study evaluates the thermal management performance of four classic liquid cooling plate designs for pouch batteries by considering their non-uniform heat generation through the electrochemical-thermal coupled model. Through experiment and numerical simulation, the optimal flow pattern is identified. Subsequently, the capability of the thermal management system, utilizing the best flow design, is further assessed under varying operating conditions. The results indicate that while a higher flow rate marginally enhances cooling, the coolant inlet temperature exerts a more substantial impact on the cooling performance. In addition, the recommended parameter settings for cell-level liquid cooling systems are outlined under extreme conditions. With a 5 C discharge rate and an initial temperature of 35 °C, the recommended coolant temperature range and coolant flow rate range are 20–30 °C and 60–100 mL min<sup>−1</sup>, respectively. As a typical example of computer-aided engineering, this study reveals the impact of battery non-uniform heat generation on battery temperature performance and provides a critical reference for the optimization of liquid-based battery thermal management systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124777"},"PeriodicalIF":6.1,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660060","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}
Due to the urgent need for heat dissipation of high heat flux devices in many engineering applications to maintain high performance and stable operation, flow boiling in micro/mini-channel heat sinks is an enabling and promising approach to tackling high heat flux cooling issues in emerging cutting-edge technology. Various enhancement techniques for flow boiling in micro/mini-channels have been investigated in recent years. These mainly include various surface modifications, enhanced channel structures and composite enhancement techniques. These techniques are able to improve flow boiling heat transfer coefficient (HTC), critical heat transfer (CHF) and mitigate two phase flow instabilities. The composite enhancement techniques take the advantage of each individual technique for flow boiling to achieve more efficient heat transfer and stable flow. However, there are challenges to optimizing these techniques and understanding the very complex mechanisms involved in these emerging techniques. This paper presents a comprehensive review of the studies of various enhancement techniques for flow boiling and mechanisms in micro/mini-channels having hydraulic diameter of 0.1–3 mm over the past five years. First, the criteria for distinction of micro/mini-channels and classification of flow boiling enhancement techniques are discussed. Then, studies of flow boiling enhancement techniques using surface modification techniques and enhanced structures are critically reviewed. Next, the effects of surface modification techniques and enhanced structures on flow boiling heat transfer, CHF, two phase flow patterns, two phase flow instability and mechanisms in micro/mini-channels are discussed and analyzed. Other enhancement techniques such as using surfactants to enhance flow boiling is also mentioned. Finally, future research needs have been identified and recommended according to the comprehensive review and deep analysis. Systematic research on the physical mechanisms underlying the composite heat transfer enhancement techniques is urgently needed. Optimization design of micro/mini-channel flow boiling heat transfer enhancement techniques is a big challenge and should be focused on in future. In order to understand the mechanisms, the bubble dynamics, bubble nucleation and flow patterns of flow boiling in the composite enhancement techniques in micro/mini-channels should be systematically investigated to understand the mechanisms and optimizing the enhancement techniques. Effort should be made to develop prediction methods for flow boiling heat transfer and CHF in the long run.
{"title":"Comprehensive review of enhancement techniques and mechanisms for flow boiling in micro/mini-channels","authors":"Huiqing Shang , Guodong Xia , Lixin Cheng , Shanshan Miao","doi":"10.1016/j.applthermaleng.2024.124783","DOIUrl":"10.1016/j.applthermaleng.2024.124783","url":null,"abstract":"<div><div>Due to the urgent need for heat dissipation of high heat flux devices in many engineering applications to maintain high performance and stable operation, flow boiling in micro/mini-channel heat sinks is an enabling and promising approach to tackling high heat flux cooling issues in emerging cutting-edge technology. Various enhancement techniques for flow boiling in micro/mini-channels have been investigated in recent years. These mainly include various surface modifications, enhanced channel structures and composite enhancement techniques. These techniques are able to improve flow boiling heat transfer coefficient (HTC), critical heat transfer (CHF) and mitigate two phase flow instabilities. The composite enhancement techniques take the advantage of each individual technique for flow boiling to achieve more efficient heat transfer and stable flow. However, there are challenges to optimizing these techniques and understanding the very complex mechanisms involved in these emerging techniques. This paper presents a comprehensive review of the studies of various enhancement techniques for flow boiling and mechanisms in micro/mini-channels having hydraulic diameter of 0.1–3 mm over the past five years. First, the criteria for distinction of micro/mini-channels and classification of flow boiling enhancement techniques are discussed. Then, studies of flow boiling enhancement techniques using surface modification techniques and enhanced structures are critically reviewed. Next, the effects of surface modification techniques and enhanced structures on flow boiling heat transfer, CHF, two phase flow patterns, two phase flow instability and mechanisms in micro/mini-channels are discussed and analyzed. Other enhancement techniques such as using surfactants to enhance flow boiling is also mentioned. Finally, future research needs have been identified and recommended according to the comprehensive review and deep analysis. Systematic research on the physical mechanisms underlying the composite heat transfer enhancement techniques is urgently needed. Optimization design of micro/mini-channel flow boiling heat transfer enhancement techniques is a big challenge and should be focused on in future. In order to understand the mechanisms, the bubble dynamics, bubble nucleation and flow patterns of flow boiling in the composite enhancement techniques in micro/mini-channels should be systematically investigated to understand the mechanisms and optimizing the enhancement techniques. Effort should be made to develop prediction methods for flow boiling heat transfer and CHF in the long run.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124783"},"PeriodicalIF":6.1,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659921","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}
Effective management of cooling tower systems requires thorough water quality control. While traditional chemical water treatment methods are currently the most prominent strategy, they are costly and may yield limited results when relied upon as the sole approach. Cross-flow microsand filtration systems offer an interesting alternative with the added benefit of potentially increasing evaporative cooling efficiency, thus saving energy. The focus of the study was to evaluate the effect of these filtration systems on cooling tower operation. A comprehensive data-driven analysis over two cooling seasons evaluated the energetic performance of a system equipped with and without an operating filter using continuous monitoring and statistical modeling. For similar environmental conditions, the coefficient of performance was on average 18% higher and was higher 63% of the time when the filter was operating, indicating superior heat transfer efficiency and significant energy savings. It was also 41% higher during periods of high cooling demand. Consequently, the filter and the system work more efficiently at high wet-bulb temperature and thermal load. Machine learning modeling suggested that operating the filter year-round could save between 5% and 13% of the energy bill, primarily during the cooling season. Continuous filter operation is essential as it mitigates biofouling, underscoring its long-term significance, even during periods of lower thermal loads. The results of this study are significant for sustainability, public health and hold broader implications for cooling tower management. Integrating filtration systems into cooling tower management therefore fosters sustainable practices by decreasing energy consumption and biofouling. This study presents a novel approach by demonstrating, for the first time, the significant impact of continuous cross-flow microsand filtration on cooling tower efficiency, both in terms of energy savings and biofouling mitigation.
{"title":"Data-driven cooling tower optimization: A comprehensive analysis of energy savings using microsand filtration","authors":"Xavier Lefebvre , Vaishali Ashok , Dominique Claveau-Mallet , Etienne Robert , Emilie Bedard","doi":"10.1016/j.applthermaleng.2024.124736","DOIUrl":"10.1016/j.applthermaleng.2024.124736","url":null,"abstract":"<div><div>Effective management of cooling tower systems requires thorough water quality control. While traditional chemical water treatment methods are currently the most prominent strategy, they are costly and may yield limited results when relied upon as the sole approach. Cross-flow microsand filtration systems offer an interesting alternative with the added benefit of potentially increasing evaporative cooling efficiency, thus saving energy. The focus of the study was to evaluate the effect of these filtration systems on cooling tower operation. A comprehensive data-driven analysis over two cooling seasons evaluated the energetic performance of a system equipped with and without an operating filter using continuous monitoring and statistical modeling. For similar environmental conditions, the coefficient of performance was on average 18% higher and was higher 63% of the time when the filter was operating, indicating superior heat transfer efficiency and significant energy savings. It was also 41% higher during periods of high cooling demand. Consequently, the filter and the system work more efficiently at high wet-bulb temperature and thermal load. Machine learning modeling suggested that operating the filter year-round could save between 5% and 13% of the energy bill, primarily during the cooling season. Continuous filter operation is essential as it mitigates biofouling, underscoring its long-term significance, even during periods of lower thermal loads. The results of this study are significant for sustainability, public health and hold broader implications for cooling tower management. Integrating filtration systems into cooling tower management therefore fosters sustainable practices by decreasing energy consumption and biofouling. This study presents a novel approach by demonstrating, for the first time, the significant impact of continuous cross-flow microsand filtration on cooling tower efficiency, both in terms of energy savings and biofouling mitigation.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124736"},"PeriodicalIF":6.1,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659946","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}
Due to low-carbon transformation of heating sources in northern China, the combination of the solar heating system (SHS) and the air source heat pump (ASHP) has attracted widespread attention due to their significant low-carbon and energy-saving characteristics. Nevertheless, different outdoor meteorological parameters simultaneously affect both the SHS and the ASHP. The heat supply of the SHS is primarily influenced by solar radiation intensity, and the efficiency of the ASHP is mainly constrained by outdoor temperature. The dual uncertainty and volatility of the output capacities of these two heat sources pose significant challenges to their coordinated control. Previous research has primarily focused on traditional rule-based control (RBC) and feedback control, prioritizing the utilization of solar energy while employing ASHP to compensate for heating deficiencies. However, these methods ignore the variations in ASHP efficiency due to fluctuations in outdoor temperature, leading to low whole-system operating efficiency and limiting the flexibility and responsiveness of the control. In this paper, a model predictive control strategy of global optimal dispatch for a combined solar and ASHP (SASHP) heating system is proposed, which focuses on the flexibility and adaptability of dual heat source dispatch under different external conditions. A Temporal Convolutional Network (TCN) was used to establish a solar radiation intensity and load prediction model. A solar heat production prediction was realized by combining the mechanism model based on solar radiation intensity prediction; a two-step room temperature prediction model was established by introducing new input parameters in the load prediction. This strategy achieves globally optimal dynamic planning of the heat supply and duration of the SHS and ASHP systems by considering solar radiation, outdoor temperature, room temperature, and energy consumption, ensuring the efficient and stable operation of the system. Compared to RBC, experimental results indicated that under conditions of sufficient solar energy, the heating proportion of the SHS increased by 31.1 %, the average COP of the ASHP improved by 8.7 %, the energy-saving rate was 14.6 %, and the room temperature control was also more effective; whole-season simulation results showed an average energy-saving rate of 8.35 %.
{"title":"A model predictive control strategy of global optimal dispatch for a combined solar and air source heat pump heating system","authors":"Jing Zhao , Yawen Li , Yabing Qin , Dehan Liu , Xia Wu , Xinyu Zhang , Xiangping Cheng , Yanyuan Wu","doi":"10.1016/j.applthermaleng.2024.124778","DOIUrl":"10.1016/j.applthermaleng.2024.124778","url":null,"abstract":"<div><div>Due to low-carbon transformation of heating sources in northern China, the combination of the solar heating system (SHS) and the air source heat pump (ASHP) has attracted widespread attention due to their significant low-carbon and energy-saving characteristics. Nevertheless, different outdoor meteorological parameters simultaneously affect both the SHS and the ASHP. The heat supply of the SHS is primarily influenced by solar radiation intensity, and the efficiency of the ASHP is mainly constrained by outdoor temperature. The dual uncertainty and volatility of the output capacities of these two heat sources pose significant challenges to their coordinated control. Previous research has primarily focused on traditional rule-based control (RBC) and feedback control, prioritizing the utilization of solar energy while employing ASHP to compensate for heating deficiencies. However, these methods ignore the variations in ASHP efficiency due to fluctuations in outdoor temperature, leading to low whole-system operating efficiency and limiting the flexibility and responsiveness of the control. In this paper, a model predictive control strategy of global optimal dispatch for a combined solar and ASHP (SASHP) heating system is proposed, which focuses on the flexibility and adaptability of dual heat source dispatch under different external conditions. A Temporal Convolutional Network (TCN) was used to establish a solar radiation intensity and load prediction model. A solar heat production prediction was realized by combining the mechanism model based on solar radiation intensity prediction; a two-step room temperature prediction model was established by introducing new input parameters in the load prediction. This strategy achieves globally optimal dynamic planning of the heat supply and duration of the SHS and ASHP systems by considering solar radiation, outdoor temperature, room temperature, and energy consumption, ensuring the efficient and stable operation of the system. Compared to RBC, experimental results indicated that under conditions of sufficient solar energy, the heating proportion of the SHS increased by 31.1 %, the average COP of the ASHP improved by 8.7 %, the energy-saving rate was 14.6 %, and the room temperature control was also more effective; whole-season simulation results showed an average energy-saving rate of 8.35 %.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"258 ","pages":"Article 124778"},"PeriodicalIF":6.1,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号