Applied Thermal Engineering最新文献_第4页

Dynamic characteristics analysis of supercritical CO2 closed Brayton power generation system for hypersonic vehicles

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-22 DOI: 10.1016/j.applthermaleng.2025.126016

Lei Lang , Fangyan Jiang , Kunlin Cheng , Zhijie Liu , Song Wang , Chaolei Dang , Jiang Qin , Hongyan Huang , Xin Zhang

Supercritical CO₂ closed Brayton cycle (SCO₂CBC) has great application potential in the field of airborne power generation (APG) for hypersonic vehicles due to its high power-to-weight ratio and high thermal efficiency. Owing to the complex thermophysical properties of SCO₂ in CBC and considering the unique limited cold source environment on hypersonic vehicles, the dynamic cycle law of the SCO₂CBC APG system remains unknown. In this context, this paper constructs the dynamic model of the SCO₂CBC APG system for hypersonic vehicles and validates the key components and systems. On this basis, the main dynamic process and control effect in the cycle process are simulated and analyzed. Finally, the dynamic operating characteristics and the coupling influence law among the main components are determined through sensitivity analysis. The results demonstrate that the dynamic response of the system to the decrease in the power of the wall cooling channel is noticeably slower than that to the increase in the power. Furthermore, the system is more sensitive to the flow of cooling fuel than to temperature of cooling fuel. The designed SCO₂ dynamic regulation module can effectively adjust the fluctuation range of compressor inlet pressure in the load reduction process, and ensure the efficient and stable operation of the cycle, but the control range of the pressure threshold should not be too low. Among all the system components, the recuperator is the most sensitive to the change in the power of the wall cooling channel, while the compressor is the most sensitive to the dynamic response of cooling fuel flow and temperature disturbance. The above conclusions can provide necessary theoretical support for the performance evaluation, dynamic regulation, and variable condition design of the APG system of hypersonic vehicles.

{"title":"Dynamic characteristics analysis of supercritical CO2 closed Brayton power generation system for hypersonic vehicles","authors":"Lei Lang , Fangyan Jiang , Kunlin Cheng , Zhijie Liu , Song Wang , Chaolei Dang , Jiang Qin , Hongyan Huang , Xin Zhang","doi":"10.1016/j.applthermaleng.2025.126016","DOIUrl":"10.1016/j.applthermaleng.2025.126016","url":null,"abstract":"<div><div>Supercritical CO<sub>2</sub> closed Brayton cycle (SCO<sub>2</sub>CBC) has great application potential in the field of airborne power generation (APG) for hypersonic vehicles due to its high power-to-weight ratio and high thermal efficiency. Owing to the complex thermophysical properties of SCO<sub>2</sub> in CBC and considering the unique limited cold source environment on hypersonic vehicles, the dynamic cycle law of the SCO<sub>2</sub>CBC APG system remains unknown. In this context, this paper constructs the dynamic model of the SCO<sub>2</sub>CBC APG system for hypersonic vehicles and validates the key components and systems. On this basis, the main dynamic process and control effect in the cycle process are simulated and analyzed. Finally, the dynamic operating characteristics and the coupling influence law among the main components are determined through sensitivity analysis. The results demonstrate that the dynamic response of the system to the decrease in the power of the wall cooling channel is noticeably slower than that to the increase in the power. Furthermore, the system is more sensitive to the flow of cooling fuel than to temperature of cooling fuel. The designed SCO<sub>2</sub> dynamic regulation module can effectively adjust the fluctuation range of compressor inlet pressure in the load reduction process, and ensure the efficient and stable operation of the cycle, but the control range of the pressure threshold should not be too low. Among all the system components, the recuperator is the most sensitive to the change in the power of the wall cooling channel, while the compressor is the most sensitive to the dynamic response of cooling fuel flow and temperature disturbance. The above conclusions can provide necessary theoretical support for the performance evaluation, dynamic regulation, and variable condition design of the APG system of hypersonic vehicles.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126016"},"PeriodicalIF":6.1,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480396","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}

引用次数: 0

Functional support structure-based high thermal performance L-shaped ultra-thin vapor chamber design and evaluation

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-22 DOI: 10.1016/j.applthermaleng.2025.126013

Shubin Yin , Bonian Zhou , Qin Shui , Wei Zhao , Yong Tang , Wei Ji , Wei Yuan , Shiwei Zhang

Ultra-thin vapor chambers are widely used in various applications due to their high thermal conductivity. However, their performance is often limited by structural challenges, especially when heat and cold sources are not on the same plane. The 3D molding process typically leads to significant cover collapse in ultra-thin designs, increasing vapor resistance, reducing heat transfer efficiency, and potentially causing vapor chamber failure. This paper introduces an innovative L-shaped ultra-thin vapor chamber with integrated functional support structures. These strategically placed support structures effectively reduce vapor resistance caused by cover collapse. Comprehensive thermal performance tests show that the proposed method achieves exceptional results, with a maximum thermal conductivity of 8233.82 W/m·K and a maximum power limit of 40 W. These improvements represent a 333.97 % increase in thermal conductivity and a 100 % increase in power limit compared to conventional designs, marking a significant advancement in the thermal performance of L-shaped ultra-thin vapor chambers.

{"title":"Functional support structure-based high thermal performance L-shaped ultra-thin vapor chamber design and evaluation","authors":"Shubin Yin , Bonian Zhou , Qin Shui , Wei Zhao , Yong Tang , Wei Ji , Wei Yuan , Shiwei Zhang","doi":"10.1016/j.applthermaleng.2025.126013","DOIUrl":"10.1016/j.applthermaleng.2025.126013","url":null,"abstract":"<div><div>Ultra-thin vapor chambers are widely used in various applications due to their high thermal conductivity. However, their performance is often limited by structural challenges, especially when heat and cold sources are not on the same plane. The 3D molding process typically leads to significant cover collapse in ultra-thin designs, increasing vapor resistance, reducing heat transfer efficiency, and potentially causing vapor chamber failure. This paper introduces an innovative L-shaped ultra-thin vapor chamber with integrated functional support structures. These strategically placed support structures effectively reduce vapor resistance caused by cover collapse. Comprehensive thermal performance tests show that the proposed method achieves exceptional results, with a maximum thermal conductivity of 8233.82 W/m·K and a maximum power limit of 40 W. These improvements represent a 333.97 % increase in thermal conductivity and a 100 % increase in power limit compared to conventional designs, marking a significant advancement in the thermal performance of L-shaped ultra-thin vapor chambers.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126013"},"PeriodicalIF":6.1,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480447","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}

引用次数: 0

An efficient assessment method for the thermal environment of a row-based cooling data center

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126020

Ligang Wang, Yating Wang, Xuelian Bai, Tong Wu, Yuhong Ma, Yewei Jin, Hang Jiang

A suitable thermal environment is essential for the operation of IT equipment in the data center. Thermal environment monitoring methods in data centers are divided into large-scale manual and long-term stationary monitoring. However, long-term stationary monitoring will not effectively capture the changes in the thermal environment within a data center, and large-scale monitoring will result in enormous sensor arrangement costs. Especially for row-based cooling systems, the short air supply paths result in uneven airflow and temperature distribution in the channel, and sensors are needed to capture this information accurately. This study is based on field experiments and numerical simulations, by changing the rack power density, air supply temperature, and air supply flow rate to analyze flow field characteristics. Locations prone to generated hot and cold spots and where airflow mutations are proposed. Then, the correlation between different points and the supply heat index (SHI) was analyzed, and the key monitor point locations were screened. The results show that hot spots in row-based cooling systems are often located in the upper part of racks where in the row terminal and the 2 ∼ 3 racks adjacent to coolers, with the 1.8 m height being the most severe. Cold spots often occur in the height range of 0.7 ∼ 1.5 m in the middle and terminal of the row. The numbers of the new evaluation model’s sensors for the different modules in the data center have only 9 and 4; the R² is 0.824 and 0.819, respectively, and the root mean square error (RMSE) is only 0.012 and 0.019. This method is highly accurate and can be used as a simplified method for large-scale sensor placement and as an alternative to fixed monitoring in data centers.

{"title":"An efficient assessment method for the thermal environment of a row-based cooling data center","authors":"Ligang Wang, Yating Wang, Xuelian Bai, Tong Wu, Yuhong Ma, Yewei Jin, Hang Jiang","doi":"10.1016/j.applthermaleng.2025.126020","DOIUrl":"10.1016/j.applthermaleng.2025.126020","url":null,"abstract":"<div><div>A suitable thermal environment is essential for the operation of IT equipment in the data center. Thermal environment monitoring methods in data centers are divided into large-scale manual and long-term stationary monitoring. However, long-term stationary monitoring will not effectively capture the changes in the thermal environment within a data center, and large-scale monitoring will result in enormous sensor arrangement costs. Especially for row-based cooling systems, the short air supply paths result in uneven airflow and temperature distribution in the channel, and sensors are needed to capture this information accurately. This study is based on field experiments and numerical simulations, by changing the rack power density, air supply temperature, and air supply flow rate to analyze flow field characteristics. Locations prone to generated hot and cold spots and where airflow mutations are proposed. Then, the correlation between different points and the supply heat index (SHI) was analyzed, and the key monitor point locations were screened. The results show that hot spots in row-based cooling systems are often located in the upper part of racks where in the row terminal and the 2 ∼ 3 racks adjacent to coolers, with the 1.8 m height being the most severe. Cold spots often occur in the height range of 0.7 ∼ 1.5 m in the middle and terminal of the row. The numbers of the new evaluation model’s sensors for the different modules in the data center have only 9 and 4; the R<sup>2</sup> is 0.824 and 0.819, respectively, and the root mean square error (RMSE) is only 0.012 and 0.019. This method is highly accurate and can be used as a simplified method for large-scale sensor placement and as an alternative to fixed monitoring in data centers.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126020"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471561","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}

引用次数: 0

Experimental analysis of a solar heating system with seasonal storage operated in first year

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126033

Xiaoxia Li , lifeng Jin , Guobing Yuan , Zhifeng Wang , Jinping Li , Xiao Guo , Jing Zhao

Seasonal thermal energy storage technology has attracted widespread attention due to its ability to successfully solve the intermittent and seasonal fluctuations of solar energy, as well as the seasonal mismatch between solar energy and heating loads. Due to the significant differences in climatic conditions and heating characteristics between China and European countries, there are also significant differences in the operational characteristics of seasonal heat storage systems in China, with relatively few relevant cases. This paper presents experimental investigations on a solar heating system with seasonal thermal energy storage built in North China. The focuses of the investigation are performance assessment on the system during the first year and the dynamic operating characteristics of the main components. The experimental results showed that the charging efficiency of the seasonal thermal energy storage can reach about 72.0 % in heat storage season. The maximum daily average heat collection per aperture area of the concentrated solar thermal system can reach 2.5 kWh/m²/d in October with the highest solar radiation and running days. The solar fraction of the system reached 41.9 % in the first year. This experimental study serves as a reference for future research on solar heating system with STES, including system optimization design and control.

{"title":"Experimental analysis of a solar heating system with seasonal storage operated in first year","authors":"Xiaoxia Li , lifeng Jin , Guobing Yuan , Zhifeng Wang , Jinping Li , Xiao Guo , Jing Zhao","doi":"10.1016/j.applthermaleng.2025.126033","DOIUrl":"10.1016/j.applthermaleng.2025.126033","url":null,"abstract":"<div><div>Seasonal thermal energy storage technology has attracted widespread attention due to its ability to successfully solve the intermittent and seasonal fluctuations of solar energy, as well as the seasonal mismatch between solar energy and heating loads. Due to the significant differences in climatic conditions and heating characteristics between China and European countries, there are also significant differences in the operational characteristics of seasonal heat storage systems in China, with relatively few relevant cases. This paper presents experimental investigations on a solar heating system with seasonal thermal energy storage built in North China. The focuses of the investigation are performance assessment on the system during the first year and the dynamic operating characteristics of the main components. The experimental results showed that the charging efficiency of the seasonal thermal energy storage can reach about 72.0 % in heat storage season. The maximum daily average heat collection per aperture area of the concentrated solar thermal system can reach 2.5 kWh/m<sup>2</sup>/d in October with the highest solar radiation and running days. The solar fraction of the system reached 41.9 % in the first year. This experimental study serves as a reference for future research on solar heating system with STES, including system optimization design and control.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126033"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488807","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}

引用次数: 0

A comparative investigation on the energy flow of pure battery electric vehicle under different driving conditions 不同驾驶条件下纯电池电动汽车能量流的比较研究

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126035

Renhua Feng , Zhanye Hua , Jing Yu , Zhichao Zhao , Yong Dan , Huikai Zhai , Xing Shu

The battery electric vehicle (BEV) shows great potential in energy security guarantee and harmful emissions reduction resulting from road traffic increasing. The energy consumption characteristics and operation status of key components under different driving conditions have great impacts on the performance of EVs. However, studies on its variations under different driving conditions over the entire driving distance are limited. In this study, the BEV energy flow characteristics, energy loss, working conditions, and efficiencies of key components under the New European Driving Cycle (NEDC), Worldwide Harmonized Light-duty Test Cycle (WLTC), China Light-duty Vehicle Test Cycle (CLTC), and a constant speed of 120 km/h were comparatively investigated using a chassis dynamometer. The test results revealed that the power consumption rate at 120 km/h was much higher than those under other driving cycle conditions. The increased ratios of the power consumption rate under 120 km/h over NEDC, WLTC, and CLTC were 27.1 %, 16.5 %, and 26.3 %, respectively. However, the energy utilization of the BEV under 120 km/h is much higher than that under other conditions, owing to the relatively high efficiency of the working points and the lack of brake energy consumption. The proportions of motor and motor control unit (MCU) losses under NEDC, WLTC, CLTC, and 120 km/h were 28.8 %, 27.5 %, 32.3 %, and 9.1 %, respectively. The power battery losses under NEDC, WLTC, CLTC, and 120 km/h were 5.4 %, 4 %, 4.8 %, and 1.3 %, respectively. The working efficiencies of the direct current (DC)/ DC and front and rear electric drive assemblies under the WLTC, NEDC, and CLTC conditions were less than 80 %. This study thoroughly demonstrates how driving conditions influence energy flow distribution and the operational state of critical components in BEVs. It provides a significant reference and foundation for the future optimization of BEV performance and energy consumption.

{"title":"A comparative investigation on the energy flow of pure battery electric vehicle under different driving conditions","authors":"Renhua Feng , Zhanye Hua , Jing Yu , Zhichao Zhao , Yong Dan , Huikai Zhai , Xing Shu","doi":"10.1016/j.applthermaleng.2025.126035","DOIUrl":"10.1016/j.applthermaleng.2025.126035","url":null,"abstract":"<div><div>The battery electric vehicle (BEV) shows great potential in energy security guarantee and harmful emissions reduction resulting from road traffic increasing. The energy consumption characteristics and operation status of key components under different driving conditions have great impacts on the performance of EVs. However, studies on its variations under different driving conditions over the entire driving distance are limited. In this study, the BEV energy flow characteristics, energy loss, working conditions, and efficiencies of key components under the New European Driving Cycle (NEDC), Worldwide Harmonized Light-duty Test Cycle (WLTC), China Light-duty Vehicle Test Cycle (CLTC), and a constant speed of 120 km/h were comparatively investigated using a chassis dynamometer. The test results revealed that the power consumption rate at 120 km/h was much higher than those under other driving cycle conditions. The increased ratios of the power consumption rate under 120 km/h over NEDC, WLTC, and CLTC were 27.1 %, 16.5 %, and 26.3 %, respectively. However, the energy utilization of the BEV under 120 km/h is much higher than that under other conditions, owing to the relatively high efficiency of the working points and the lack of brake energy consumption. The proportions of motor and motor control unit (MCU) losses under NEDC, WLTC, CLTC, and 120 km/h were 28.8 %, 27.5 %, 32.3 %, and 9.1 %, respectively. The power battery losses under NEDC, WLTC, CLTC, and 120 km/h were 5.4 %, 4 %, 4.8 %, and 1.3 %, respectively. The working efficiencies of the direct current (DC)/ DC and front and rear electric drive assemblies under the WLTC, NEDC, and CLTC conditions were less than 80 %. This study thoroughly demonstrates how driving conditions influence energy flow distribution and the operational state of critical components in BEVs. It provides a significant reference and foundation for the future optimization of BEV performance and energy consumption.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126035"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471458","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}

引用次数: 0

Effect of wetting methods of the pseudopotential lattice Boltzmann model on boiling phenomena

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126037

Hoongyo Oh , HangJin Jo

The pseudopotential lattice Boltzmann method (LBM) is a promising numerical approach for studying boiling phenomena due to its ability to model bubble nucleation and interfacial dynamics. While several wetting methods have been proposed within the pseudopotential LBM framework, these methods were primarily designed for isothermal multiphase phenomena, limiting their applicability to boiling scenarios that involve complex thermal gradients and dynamic interactions. This study introduces a novel pseudopotential-based wetting method explicitly tailored for boiling phenomena, addressing the limitations of existing approaches. The proposed method is validated against experimental and molecular dynamics (MD) results, demonstrating superior accuracy in reproducing key boiling characteristics, such as onset of nucleate boiling (ONB) temperature trends as a function of contact angle and initial bubble nucleation configurations. Furthermore, the method reduces spurious currents in isothermal cases while providing more accurate predictions of bubble behaviors on hydrophilic surfaces. By bridging the gap between isothermal and non-isothermal wetting methods, this work offers new insights into the relationship between wetting behavior and boiling dynamics, advancing the understanding and simulation of boiling phenomena.

{"title":"Effect of wetting methods of the pseudopotential lattice Boltzmann model on boiling phenomena","authors":"Hoongyo Oh , HangJin Jo","doi":"10.1016/j.applthermaleng.2025.126037","DOIUrl":"10.1016/j.applthermaleng.2025.126037","url":null,"abstract":"<div><div>The pseudopotential lattice Boltzmann method (LBM) is a promising numerical approach for studying boiling phenomena due to its ability to model bubble nucleation and interfacial dynamics. While several wetting methods have been proposed within the pseudopotential LBM framework, these methods were primarily designed for isothermal multiphase phenomena, limiting their applicability to boiling scenarios that involve complex thermal gradients and dynamic interactions. This study introduces a novel pseudopotential-based wetting method explicitly tailored for boiling phenomena, addressing the limitations of existing approaches. The proposed method is validated against experimental and molecular dynamics (MD) results, demonstrating superior accuracy in reproducing key boiling characteristics, such as onset of nucleate boiling (ONB) temperature trends as a function of contact angle and initial bubble nucleation configurations. Furthermore, the method reduces spurious currents in isothermal cases while providing more accurate predictions of bubble behaviors on hydrophilic surfaces. By bridging the gap between isothermal and non-isothermal wetting methods, this work offers new insights into the relationship between wetting behavior and boiling dynamics, advancing the understanding and simulation of boiling phenomena.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126037"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480395","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}

引用次数: 0

Experimental investigation on the phase change liquid cooling characteristics in the offset grooved microchannel heat sink

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126032

Yifan Li , Congzhe Zhu , Guodong Xia , Bin Yang

Improving chip integration and computing power leads to serious local overheating and high energy consumption in data centers. An innovative heat sink with offset triangular grooves is introduced to solve heat dissipation issue and improve energy efficiency of the cooling system. The flow boiling properties in the new configuration are examined by visualization experiment for a flow rate of 3 ∼ 15 ml/min and heat flux of 4.58 ∼ 100.66 W/cm². The influence of groove arrangement on the flow evolution, boiling curve, heat transfer rate, pump power, coefficient of performance, and temperature features is explored in detail. The new findings include that: compared to the rectangular microchannel, the offset grooves induce boiling with a 16.8 ℃ lower temperature and 10.52 times higher heat transport efficiency, attributing to the increased nucleation sites and enhanced liquid film vaporization. For low heat flux, the heat transport rate of offset grooves is 2.87 times larger than the symmetrical one because of the efficient steam removal. For high heat flux, the symmetrical grooves present superior thermal performance due to stronger flow disturbance. Moreover, the pump power for the offset grooves is dropped by 71.47 % and 14.23 % compared to the smooth one and symmetrical counterpart, respectively. The temperature stability and uniformity of the offset grooves are also better than those of other heat sinks. The effect of groove arrangement on the flow boiling features is revealed thoroughly, and the optimal configuration under different operating conditions is obtained. The innovative configuration achieves heat dissipation enhancement while reducing pump power with a significantly improved coefficient of performance. In addition, the interaction between flow evolution and heat transfer is elucidated by bubble dynamics analysis. The new design has a better application prospect for chip-scale cooling in data centers because of the improved boiling stability, increased heat transport efficiency, reduced pump power, and favorable temperature performance.

{"title":"Experimental investigation on the phase change liquid cooling characteristics in the offset grooved microchannel heat sink","authors":"Yifan Li , Congzhe Zhu , Guodong Xia , Bin Yang","doi":"10.1016/j.applthermaleng.2025.126032","DOIUrl":"10.1016/j.applthermaleng.2025.126032","url":null,"abstract":"<div><div>Improving chip integration and computing power leads to serious local overheating and high energy consumption in data centers. An innovative heat sink with offset triangular grooves is introduced to solve heat dissipation issue and improve energy efficiency of the cooling system. The flow boiling properties in the new configuration are examined by visualization experiment for a flow rate of 3 ∼ 15 ml/min and heat flux of 4.58 ∼ 100.66 W/cm<sup>2</sup>. The influence of groove arrangement on the flow evolution, boiling curve, heat transfer rate, pump power, coefficient of performance, and temperature features is explored in detail. The new findings include that: compared to the rectangular microchannel, the offset grooves induce boiling with a 16.8 ℃ lower temperature and 10.52 times higher heat transport efficiency, attributing to the increased nucleation sites and enhanced liquid film vaporization. For low heat flux, the heat transport rate of offset grooves is 2.87 times larger than the symmetrical one because of the efficient steam removal. For high heat flux, the symmetrical grooves present superior thermal performance due to stronger flow disturbance. Moreover, the pump power for the offset grooves is dropped by 71.47 % and 14.23 % compared to the smooth one and symmetrical counterpart, respectively. The temperature stability and uniformity of the offset grooves are also better than those of other heat sinks. The effect of groove arrangement on the flow boiling features is revealed thoroughly, and the optimal configuration under different operating conditions is obtained. The innovative configuration achieves heat dissipation enhancement while reducing pump power with a significantly improved coefficient of performance. In addition, the interaction between flow evolution and heat transfer is elucidated by bubble dynamics analysis. The new design has a better application prospect for chip-scale cooling in data centers because of the improved boiling stability, increased heat transport efficiency, reduced pump power, and favorable temperature performance.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126032"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474313","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}

引用次数: 0

Enhancement effects of variable gradient channel on output performance of fuel cells

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126015

Yuxi Zhu , Tao Jiang , Chaoling Han , Bo Xu , Qiang Ma , Zhenqian Chen

The gas channel design of proton exchange membrane fuel cell (PEMFC) has a significant impact on the transport of the oxygen and water, which indirectly affects the performance of the PEMFC. In this paper, the gradient gas channel is studied first, and based on the optimal structure, two different variable gradient design schemes are proposed. The results show that the output performance of PEMFC can be improved by adopting the gradient channel design only at the cathode. When the height of the cathode channel is gradually reduced from 1 mm to 0.1 mm, the net power density is 3.88 % higher than that of the traditional straight channel at 0.3 V. Only by moving the end position of height change to the inlet further improves the output performance. When the end position is 18 mm away from the inlet, the maximum peak net power density is 0.597 W/cm², which is 5.68 % higher than the traditional straight channel. By establishing the evaluation index of fluctuation, it is revealed that the performance improvement in the variable gradient channel can be attributed to the improvement of the oxygen concentration and the uniformity in latter part of the channel while keeping the water concentration in the cathode channel almost unchanged. Finally, the dimensionless correlation between net power density and outlet height, end position and voltage under low voltage is established to guide the design of cathode channel.

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引用次数: 0

Lithography-free thermal camouflage device with efficient thermal management for ultrahigh-temperature objects

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126031

Mingze Li , Xiqiao Huang , Biyuan Wu , Xiaohu Wu

Infrared detectors make use of atmospheric transmission windows, typically in the 3–5 μm and 8–14 μm ranges, to identify objects by capturing the thermal radiation they emit, thereby posing a threat to the survival of military assets like aircraft. For high-temperature objects, minimizing emissivity in the 3–5 μm band is more important for effective infrared stealth. Additionally, radiative cooling utilizing a non-atmospheric window in the 5–8 μm range can efficiently lower the temperature of hot objects. In this study, we employ cost-effective molybdenum (Mo) in combination with germanium (Ge) dielectric to achieve selective emission in the infrared spectrum. Using the Finite Element Method (FEM), the average emissivity in the 3–5 μm band is calculated to be 0.29, while in the 5–8 μm band, the emissivity reaches 0.86. We also conduct infrared thermal imaging simulations, confirming its effectiveness for mid-infrared (MIR) stealth under both high and low-temperature conditions, as well as its radiative cooling capability. In addition, the film we propose has potential for application in high-temperature environments compared to previous studies, with a simple structure that is easy to fabricate. Its emissivity in the 5–8 μm band is significantly better than that of previous works, presenting highly promising application opportunities.

{"title":"Lithography-free thermal camouflage device with efficient thermal management for ultrahigh-temperature objects","authors":"Mingze Li , Xiqiao Huang , Biyuan Wu , Xiaohu Wu","doi":"10.1016/j.applthermaleng.2025.126031","DOIUrl":"10.1016/j.applthermaleng.2025.126031","url":null,"abstract":"<div><div>Infrared detectors make use of atmospheric transmission windows, typically in the 3–5 μm and 8–14 μm ranges, to identify objects by capturing the thermal radiation they emit, thereby posing a threat to the survival of military assets like aircraft. For high-temperature objects, minimizing emissivity in the 3–5 μm band is more important for effective infrared stealth. Additionally, radiative cooling utilizing a non-atmospheric window in the 5–8 μm range can efficiently lower the temperature of hot objects. In this study, we employ cost-effective molybdenum (Mo) in combination with germanium (Ge) dielectric to achieve selective emission in the infrared spectrum. Using the Finite Element Method (FEM), the average emissivity in the 3–5 μm band is calculated to be 0.29, while in the 5–8 μm band, the emissivity reaches 0.86. We also conduct infrared thermal imaging simulations, confirming its effectiveness for mid-infrared (MIR) stealth under both high and low-temperature conditions, as well as its radiative cooling capability. In addition, the film we propose has potential for application in high-temperature environments compared to previous studies, with a simple structure that is easy to fabricate. Its emissivity in the 5–8 μm band is significantly better than that of previous works, presenting highly promising application opportunities.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126031"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480397","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}

引用次数: 0

Energy and exergy performance investigation of a transcritical CO2 vapor ejector-based refrigeration system for marine provision plants

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-21 DOI: 10.1016/j.applthermaleng.2025.126036

Evangelos Syngounas , Dimitrios Tsimpoukis , Evangelos Bellos , Maria K. Koukou , Christos Tzivanidis , Michail Gr. Vrachopoulos

Marine refrigeration has a high energy share in a vessel’s performance which can lead to up to 19 % of its total power consumption. Traditional cooling systems employing refrigerants of high GWP are subject of continuous imposed restrictions, leading to the need for adoption of more efficient and sustainable alternatives such as CO₂ refrigeration applications. This study investigates a novel transcritical CO₂ vapor ejector-based refrigeration system delivering the refrigeration needs of marine provision plants. The examined topology is analyzed in terms of energy efficiency, and it is compared with a conventional marine refrigeration system using R407F as the working media. Additionally, the advanced exergy analysis approach is employed to specify and quantify the irreversibilities minimization potential for improving the performance of the system examined. The thermodynamic simulation analysis is conducted using validated numerical models that are developed in MATLAB using the CoolProp library. The system is parametrically investigated for different sea water temperatures ranging from 5 to 32 °C. The results show that the proposed configuration has a maximum COP improvement of 13.2 % for the sea water temperature of 26 °C in comparison to the baseline direct expansion system using R407F. The highest exergy destruction ratios are calculated for the components of the gas cooler, the vapor ejector and the constant pressure valve, with values of 31.3 %, 22.6 % and 17.2 % respectively. Finally, for the examined sea water temperature of 32 °C, 33.6 % of the total exergy destruction is avoidable showing a significant amelioration potential. The latter figure splits further to 16.4 % endogenous-avoidable and the rest 17.2 % to exogenous-avoidable exergy destruction, verifying the potential for extra optimization of the system in the future.

{"title":"Energy and exergy performance investigation of a transcritical CO2 vapor ejector-based refrigeration system for marine provision plants","authors":"Evangelos Syngounas , Dimitrios Tsimpoukis , Evangelos Bellos , Maria K. Koukou , Christos Tzivanidis , Michail Gr. Vrachopoulos","doi":"10.1016/j.applthermaleng.2025.126036","DOIUrl":"10.1016/j.applthermaleng.2025.126036","url":null,"abstract":"<div><div>Marine refrigeration has a high energy share in a vessel’s performance which can lead to up to 19 % of its total power consumption. Traditional cooling systems employing refrigerants of high GWP are subject of continuous imposed restrictions, leading to the need for adoption of more efficient and sustainable alternatives such as CO<sub>2</sub> refrigeration applications. This study investigates a novel transcritical CO<sub>2</sub> vapor ejector-based refrigeration system delivering the refrigeration needs of marine provision plants. The examined topology is analyzed in terms of energy efficiency, and it is compared with a conventional marine refrigeration system using R407F as the working media. Additionally, the advanced exergy analysis approach is employed to specify and quantify the irreversibilities minimization potential for improving the performance of the system examined. The thermodynamic simulation analysis is conducted using validated numerical models that are developed in MATLAB using the CoolProp library. The system is parametrically investigated for different sea water temperatures ranging from 5 to 32 °C. The results show that the proposed configuration has a maximum COP improvement of 13.2 % for the sea water temperature of 26 °C in comparison to the baseline direct expansion system using R407F. The highest exergy destruction ratios are calculated for the components of the gas cooler, the vapor ejector and the constant pressure valve, with values of 31.3 %, 22.6 % and 17.2 % respectively. Finally, for the examined sea water temperature of 32 °C, 33.6 % of the total exergy destruction is avoidable showing a significant amelioration potential. The latter figure splits further to 16.4 % endogenous-avoidable and the rest 17.2 % to exogenous-avoidable exergy destruction, verifying the potential for extra optimization of the system in the future.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126036"},"PeriodicalIF":6.1,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143508804","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}

引用次数: 0