Applied Thermal Engineering最新文献_第7页

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

Cooling performance and energy efficiency optimization of H-type mani-fold counter-flow mini-channel for electric vehicle high-power motor controller

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.2025.126014

Shuai Feng , Jun Chen , Jie Song , Chenguang Lai , Junxiong Zeng

This study introduces a new H-Type fractal mani-fold counter-flow mini-channel to tackle the growing thermal issues in high-power motor controller. The optimal geometrical parameters and hydro-thermal performance are obtained by multi-objective optimization and conjugate heat transfer simulation. The results show that the mini-channel depth and width play an important role in the pressure drop, exhibiting a sensitivity exceeding 0.95, although the width of the mini-channel and the third-class manifold are the primary factors influencing the maximum temperature and temperature difference, respectively. Relatively large values for the main geometrical parameters are obtained in the optimal case after optimization procedure. Differing from the conventional pin–fin structure, the advanced mani-fold structure attains twice the heat transfer coefficient and cuts down the junction-coolant’s thermal resistance by 11.4 %, along with a less pressure decrease, attributed to shorter flow path and higher impinging local velocity. These strengths effectively mitigate the local high gradient temperature downstream, lowering the maximum temperature and the temperature variance by 5.3 ℃ and 6.1 ℃, respectively, at a flow rate of 8 L/min. Moreover, there is a 55.6 % increase in the efficiency of cooling energy, indicating the substantial potential for efficient cooling of high-power motor controller.

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引用次数: 0

Parametric analysis and multi-objective optimization of the ammonia/diesel dual-fuel engine for efficient and cleaner combustion

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.2025.126048

Jing Li , Xiaorong Deng , Siyu Liu , Yicheng Yu , Lifeng Li , Rui Liu , Xinyi Zhou

This study aims to conduct a parametric analysis and optimize the combustion and emissions of the ammonia/diesel dual fuel (ADDF) engine. To achieve this, a reliable computational model was first constructed and validated against experimental data. Subsequently, three parameters, namely the ammonia energy fraction (f_NH3), start of injection (SOI) timing, and injection pressure (P_inj), were varied over wide ranges to perform the parametric and interaction analysis. A novel application of the dynamic equivalence ratio-temperature map technique was performed to provide deeper insights into pollutant formation mechanisms. Pearson correlation coefficient analysis was conducted to reveal the linear correlation between input and output parameters of the engine. The optimization of the ADDF engine was then achieved by integrating a surrogate model with the NSGA-II algorithm. The results indicate that the f_NH3 shows the greatest influence on CO₂ emission, primarily due to the replacement of diesel with ammonia. Adjusting P_inj and SOI timing can achieve the combustion mode with higher premixed combustion fraction, which consequently reduces CO and N₂O emissions but increases CO₂ and NOx emissions. It also reveals that the effects of the three parameters on the combustion and emissions characteristics are, in descending order, SOI timing, f_NH3, and P_inj. Finally, the optimized case is identified with a f_NH3 of 0.64, a P_inj of 460 bar for diesel, and an SOI timing of −11.2 °CA ATDC, which improves the indicated thermal efficiency from 42.81 % to 44.64 % and reduces the greenhouse gases by 34.5 %.

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引用次数: 0

Numerical investigation on helium pressurization behavior of cryogenic propellant in microgravity

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.125926

Songyuan Guo , Zan Jiang , Jianqiang Li , Pengli Xu , Rui Zhuan , Mingkun Xiao , Qingtai Cao , Jianfu Zhao , Guang Yang , Jingyi Wu

In deep space exploration, the pressurization of cryogenic propellant in microgravity is an essential technique of propellant transfer on orbit. In this study, a numerical model is newly developed based on an open source computational fluid dynamics (CFD) code OpenFOAM to address the helium pressurization of cryogenic fluids in microgravity. The model incorporates phase change model, species transfer model, and interface reconstruction to predict the interface, temperature and concentration distributions. In the microgravity pressurization, weak buoyancy-driven convection prevents the formation of temperature and species stratification in the ullage. The smaller vorticity during microgravity pressurization results in reduced wall heat flux compared to normal gravity. The contact line of the solid–liquid interface reaches a maximum height of 122.5 mm, which leads to evaporation dominating the microgravity pressurization process. Fluctuations of gradually increasing amplitude at the interface result in localized gas stagnation, which reduces heat flux at the interface. This reduction in heat transfer from the gas phase subsequently leads to an increase in the pressurization rate to peak value. As a result, the combined effects of interface evaporation and the reduced heat flux at both the interface and inner wall lead to a higher pressurization rate under microgravity conditions compared to normal gravity. Specifically, the average pressurization rate in microgravity is approximately two times greater than in normal gravity. The findings of this study are crucial for enhancing the understanding and optimization of microgravity pressurization processes, offering valuable insights for future cryogenic propellant transfer systems in space exploration.

{"title":"Numerical investigation on helium pressurization behavior of cryogenic propellant in microgravity","authors":"Songyuan Guo , Zan Jiang , Jianqiang Li , Pengli Xu , Rui Zhuan , Mingkun Xiao , Qingtai Cao , Jianfu Zhao , Guang Yang , Jingyi Wu","doi":"10.1016/j.applthermaleng.2025.125926","DOIUrl":"10.1016/j.applthermaleng.2025.125926","url":null,"abstract":"<div><div>In deep space exploration, the pressurization of cryogenic propellant in microgravity is an essential technique of propellant transfer on orbit. In this study, a numerical model is newly developed based on an open source computational fluid dynamics (CFD) code OpenFOAM to address the helium pressurization of cryogenic fluids in microgravity. The model incorporates phase change model, species transfer model, and interface reconstruction to predict the interface, temperature and concentration distributions. In the microgravity pressurization, weak buoyancy-driven convection prevents the formation of temperature and species stratification in the ullage. The smaller vorticity during microgravity pressurization results in reduced wall heat flux compared to normal gravity. The contact line of the solid–liquid interface reaches a maximum height of 122.5 mm, which leads to evaporation dominating the microgravity pressurization process. Fluctuations of gradually increasing amplitude at the interface result in localized gas stagnation, which reduces heat flux at the interface. This reduction in heat transfer from the gas phase subsequently leads to an increase in the pressurization rate to peak value. As a result, the combined effects of interface evaporation and the reduced heat flux at both the interface and inner wall lead to a higher pressurization rate under microgravity conditions compared to normal gravity. Specifically, the average pressurization rate in microgravity is approximately two times greater than in normal gravity. The findings of this study are crucial for enhancing the understanding and optimization of microgravity pressurization processes, offering valuable insights for future cryogenic propellant transfer systems in space exploration.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125926"},"PeriodicalIF":6.1,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471459","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

Examining performance of microchannel cold plate heat sink from its three parts along coolant flow direction and new structure designs based on the new considerations

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.125963

Yu-Ting Li , Shu-Qi Jin , Xiao-Jun Hu , Zhan-Jun Wang , Zhi-Yang Li , Li Chen , Wen-Quan Tao

The microchannel cold plate heat sink is a very compact heat exchanger with higher ratios of heat transfer area to volume and is widely used in the field of active cooling of electronic devices with high heat flux. A variety of structural forms have been proposed and a huge amount of studies, both experimental and numerical, have been conducted. It can be broadly divided into single-layer structure and double-layer structure, of which the single-layer structure is more widely used. This article first discusses the geometric structure classification method of the single-layer microchannel cold plate heat sink. Along the cooling medium flow direction of the cold plate, there are three indispensable subsequent parts: inlet/outlet, manifold, and microchannel. It is because of the differences in the three parts, a variety of cold plates are formed. A classification method according to the three major parts is proposed. Summarizes of the existing forms of each part have been made and their major flow and heat transfer characteristics have been commented. Taking the three parts as three variables many levels are selected. By using the orthogonal experiment design of the Taguchi method, 26 new structural designs of the microchannel cold plate heat sink are provided. Numerical simulations of the heat transfer and flow resistance for the 26 newly designed cold plates are conducted and performance comparisons between them are provided. TOPSIS method is used to evaluate the comprehensive performance of different designs. Experiment validation for numerical results is conducted for No.20 cold plate. Finally, the cold plate design is further improved to increase the heat flux to 266.60 W/cm², with the ratio of q/Δp being 14.08 W/cm⁻²·kPa⁻¹, superior to most existing similar cold plate.

{"title":"Examining performance of microchannel cold plate heat sink from its three parts along coolant flow direction and new structure designs based on the new considerations","authors":"Yu-Ting Li , Shu-Qi Jin , Xiao-Jun Hu , Zhan-Jun Wang , Zhi-Yang Li , Li Chen , Wen-Quan Tao","doi":"10.1016/j.applthermaleng.2025.125963","DOIUrl":"10.1016/j.applthermaleng.2025.125963","url":null,"abstract":"<div><div>The microchannel cold plate heat sink is a very compact heat exchanger with higher ratios of heat transfer area to volume and is widely used in the field of active cooling of electronic devices with high heat flux. A variety of structural forms have been proposed and a huge amount of studies, both experimental and numerical, have been conducted. It can be broadly divided into single-layer structure and double-layer structure, of which the single-layer structure is more widely used. This article first discusses the geometric structure classification method of the single-layer microchannel cold plate heat sink. Along the cooling medium flow direction of the cold plate, there are three indispensable subsequent parts: inlet/outlet, manifold, and microchannel. It is because of the differences in the three parts, a variety of cold plates are formed. A classification method according to the three major parts is proposed. Summarizes of the existing forms of each part have been made and their major flow and heat transfer characteristics have been commented. Taking the three parts as three variables many levels are selected. By using the orthogonal experiment design of the Taguchi method, 26 new structural designs of the microchannel cold plate heat sink are provided. Numerical simulations of the heat transfer and flow resistance for the 26 newly designed cold plates are conducted and performance comparisons between them are provided. TOPSIS method is used to evaluate the comprehensive performance of different designs. Experiment validation for numerical results is conducted for No.20 cold plate. Finally, the cold plate design is further improved to increase the heat flux to 266.60 W/cm<sup>2</sup>, with the ratio of <em>q</em>/<em>Δp</em> being 14.08 W/cm<sup>−2</sup>·kPa<sup>−1</sup>, superior to most existing similar cold plate.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 125963"},"PeriodicalIF":6.1,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480400","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

Coupled heat and mass transfer analysis for indoor air quality and thermal comfort in naturally ventilated offices

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.126019

Zhaopeng Huang, Qiong Li, Yiyuan He, Xiang Ding, Yunli Dong, Wenfeng Gao

Multiple discrete heat and pollution sources have a significant impact on the thermal comfort and indoor environment of naturally ventilated offices. Based on the heat-mass coupling mechanism, Computational Fluid Dynamics (CFD) numerical simulation combined with measurements were used to evaluate the influencing factors such as equipment load, inlet air temperature and ventilation strategy. Furthermore, key indicators such as air diffusion performance index (ADPI), air exchange efficiency (AEE) and pollutant removal rate (PRR) were quantified to analyze the thermodynamic coupling relationship between indoor airflow, temperature field and pollutant concentration field. The results show that from the perspective of heat transfer, when the indoor temperature is significantly higher than the outdoor temperature (ΔT = 4 °C), buoyancy-driven natural convection dominates the flow, enhancing air exchange while causing uneven temperature distribution that can reduce thermal comfort. Under strong buoyancy, pollutants such as CO₂ rise with the warm air, leading to clear stratification in the upper part of the room. In contrast, a slight negative temperature difference (ΔT = –1.6 °C) causes cold air to sink, which suppresses natural convection. This results in localized heat accumulation, air stagnation, and the buildup of pollutants near the floor. From a mass transfer perspective, the heat output from equipment primarily affects the temperature field and has minimal impact on airflow velocity. Global sensitivity analysis (GSA) identifies the ΔT as the primary factor influencing thermal comfort (PMV), followed by CO₂ concentration. Moreover, the combined effect of door and window openings (θ_w, θ_d) contributes up to 68 % of the PRR, emphasizing the importance of balanced ventilation to maintain effective diffusion. The research results provide a scientific basis for optimizing thermal comfort and pollutant control in natural ventilation environments.

{"title":"Coupled heat and mass transfer analysis for indoor air quality and thermal comfort in naturally ventilated offices","authors":"Zhaopeng Huang, Qiong Li, Yiyuan He, Xiang Ding, Yunli Dong, Wenfeng Gao","doi":"10.1016/j.applthermaleng.2025.126019","DOIUrl":"10.1016/j.applthermaleng.2025.126019","url":null,"abstract":"<div><div>Multiple discrete heat and pollution sources have a significant impact on the thermal comfort and indoor environment of naturally ventilated offices. Based on the heat-mass coupling mechanism, Computational Fluid Dynamics (CFD) numerical simulation combined with measurements were used to evaluate the influencing factors such as equipment load, inlet air temperature and ventilation strategy. Furthermore, key indicators such as air diffusion performance index (ADPI), air exchange efficiency (AEE) and pollutant removal rate (PRR) were quantified to analyze the thermodynamic coupling relationship between indoor airflow, temperature field and pollutant concentration field. The results show that from the perspective of heat transfer, when the indoor temperature is significantly higher than the outdoor temperature (<em>ΔT</em> = 4 °C), buoyancy-driven natural convection dominates the flow, enhancing air exchange while causing uneven temperature distribution that can reduce thermal comfort. Under strong buoyancy, pollutants such as CO<sub>2</sub> rise with the warm air, leading to clear stratification in the upper part of the room. In contrast, a slight negative temperature difference (<em>ΔT</em> = –1.6 °C) causes cold air to sink, which suppresses natural convection. This results in localized heat accumulation, air stagnation, and the buildup of pollutants near the floor. From a mass transfer perspective, the heat output from equipment primarily affects the temperature field and has minimal impact on airflow velocity. Global sensitivity analysis (GSA) identifies the <em>ΔT</em> as the primary factor influencing thermal comfort (PMV), followed by CO<sub>2</sub> concentration. Moreover, the combined effect of door and window openings (<em>θ<sub>w</sub>, θ<sub>d</sub></em>) contributes up to 68 % of the PRR, emphasizing the importance of balanced ventilation to maintain effective diffusion. The research results provide a scientific basis for optimizing thermal comfort and pollutant control in natural ventilation environments.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126019"},"PeriodicalIF":6.1,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471562","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 study of flow boiling cooling in a novel variable density pin–fin device

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.126023

Jaume Camarasa, Montse Vilarrubí, Manel Ibáñez, Pol Rosell, David Beberide, Jérôme Barrau

Flow boiling is an effective cooling technique for microelectronic systems. However, it presents flow instability issues, most of them associated with critical heat flux situations. In recent years, decreasing variable density microstructured heatsinks have been successfully tested, proving that with a suitable pathway design, the flow boiling instabilities can be mitigated. However, increasing variable density design remains largely unexplored, despite obtaining promising results in single-phase applications. The present work is an experimental study that analyzes the flow boiling performance of a novel increasing density pin–fin array with jet impingement technology. Working with DI water at atmospheric pressure, for an inlet temperature of 75 °C (inlet subcooling of 30 K), 3 flow rates (100–150–200 ml/min) were performed under heat fluxes up to 55 W/cm². Focusing on the cooling device design, thermofluidic studies were carried out, supported by high-speed flow visualization. The results demonstrated that this unique cooling device reduces bubble blockage while enhancing bubble breakage and departure. In terms of flow patterns, bubbly, plug, slug and annular flow were observed. The main heat transfer mechanisms detected were single-phase convection, saturated boiling, nucleated boiling and film evaporation. The highest heat transfer coefficient (h_th) was obtained for the 200 ml/min test and had a value of 9323 W/°C·m². The maximum critical heat flux (CHF) achieved was 58.11 W/cm² for the 200 ml/min test. A flow boiling performance evaluation was carried out using the dimensionless Boiling utilization (Bu) number. Compared to existing literature, this novel cooling device emerges as one promising solution.

{"title":"Experimental study of flow boiling cooling in a novel variable density pin–fin device","authors":"Jaume Camarasa, Montse Vilarrubí, Manel Ibáñez, Pol Rosell, David Beberide, Jérôme Barrau","doi":"10.1016/j.applthermaleng.2025.126023","DOIUrl":"10.1016/j.applthermaleng.2025.126023","url":null,"abstract":"<div><div>Flow boiling is an effective cooling technique for microelectronic systems. However, it presents flow instability issues, most of them associated with critical heat flux situations. In recent years, decreasing variable density microstructured heatsinks have been successfully tested, proving that with a suitable pathway design, the flow boiling instabilities can be mitigated. However, increasing variable density design remains largely unexplored, despite obtaining promising results in single-phase applications. The present work is an experimental study that analyzes the flow boiling performance of a novel increasing density pin–fin array with jet impingement technology. Working with DI water at atmospheric pressure, for an inlet temperature of 75 °C (inlet subcooling of 30 K), 3 flow rates (100–150–200 ml/min) were performed under heat fluxes up to 55 W/cm<sup>2</sup>. Focusing on the cooling device design, thermofluidic studies were carried out, supported by high-speed flow visualization. The results demonstrated that this unique cooling device reduces bubble blockage while enhancing bubble breakage and departure. In terms of flow patterns, bubbly, plug, slug and annular flow were observed. The main heat transfer mechanisms detected were single-phase convection, saturated boiling, nucleated boiling and film evaporation. The highest heat transfer coefficient (h<sub>th</sub>) was obtained for the 200 ml/min test and had a value of 9323 W/°C·m<sup>2</sup>. The maximum critical heat flux (CHF) achieved was 58.11 W/cm<sup>2</sup> for the 200 ml/min test. A flow boiling performance evaluation was carried out using the dimensionless Boiling utilization (Bu) number. Compared to existing literature, this novel cooling device emerges as one promising solution.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126023"},"PeriodicalIF":6.1,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474257","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

Enhancing ultra-low-temperature heat pump performance for high-speed trains using mechanism-based model

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.126021

Che Wang , Qihang Wu , Jie Zhang , Zibo Zhao , Hongyan Shi , Jianhua Wu

Heat pumps are a promising technique for providing energy-efficient thermal comfort for passengers in high-speed trains, especially in cold winters of northern China. This study investigates the heating capacity and other performance characteristics of an economizer vapor-injection heat pump system, particularly under ultra-low-temperature conditions. A theoretical analysis of the EVI cycle is conducted, comparing ideal and detailed compressors to highlight differences in the variation trends of COP and heating capacity. Subsequently, a mechanism-based model incorporating a detailed scroll compressor and heat exchangers is developed and validated against experimental data. A 40 kW R410A heat pump operating under rated heating conditions is analyzed, and five experimental results with varying injection pressures (ranging from 0.55 MPa to 1.05 MPa) are used to validate the simulation under ultra-low-temperature conditions. The experiment results indicate that vapor injection significantly boosts the heating capacity by 9.8–24.1 % and improves the coefficient of performance (COP) by 0.7–21.6 %. The performance trends of various models emphasize the importance of accounting for injection port geometry and heat transfer within the economizer during simulation. Under ultra-low-temperature conditions, the optimal injection pressure is identified to be approximately 0.95 MPa, resulting in two-phase injection. Furthermore, an updated injection port design featuring an involute geometry is proposed, yielding a 4.6 % increase in maximum heating capacity.

{"title":"Enhancing ultra-low-temperature heat pump performance for high-speed trains using mechanism-based model","authors":"Che Wang , Qihang Wu , Jie Zhang , Zibo Zhao , Hongyan Shi , Jianhua Wu","doi":"10.1016/j.applthermaleng.2025.126021","DOIUrl":"10.1016/j.applthermaleng.2025.126021","url":null,"abstract":"<div><div>Heat pumps are a promising technique for providing energy-efficient thermal comfort for passengers in high-speed trains, especially in cold winters of northern China. This study investigates the heating capacity and other performance characteristics of an economizer vapor-injection heat pump system, particularly under ultra-low-temperature conditions. A theoretical analysis of the EVI cycle is conducted, comparing ideal and detailed compressors to highlight differences in the variation trends of COP and heating capacity. Subsequently, a mechanism-based model incorporating a detailed scroll compressor and heat exchangers is developed and validated against experimental data. A 40 kW R410A heat pump operating under rated heating conditions is analyzed, and five experimental results with varying injection pressures (ranging from 0.55 MPa to 1.05 MPa) are used to validate the simulation under ultra-low-temperature conditions. The experiment results indicate that vapor injection significantly boosts the heating capacity by 9.8–24.1 % and improves the coefficient of performance (COP) by 0.7–21.6 %. The performance trends of various models emphasize the importance of accounting for injection port geometry and heat transfer within the economizer during simulation. Under ultra-low-temperature conditions, the optimal injection pressure is identified to be approximately 0.95 MPa, resulting in two-phase injection. Furthermore, an updated injection port design featuring an involute geometry is proposed, yielding a 4.6 % increase in maximum heating capacity.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126021"},"PeriodicalIF":6.1,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474314","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

Numerical investigation on flow and heat transfer characteristics of various special-shaped narrow channels at high Reynolds number

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.126012

Ruizhi Hao , Tao Lu , Qi Lu , Jian Deng

This paper introduces three innovative special-shaped narrow channels: the transverse sinusoidal wavy channel, the longitudinal sinusoidal wavy channel, and the scale-roughened channel. These channels are designed for the heat transfer enhancement (HTC) of the heat transfer components within nuclear industry under high Reynolds number conditions. Numerical simulations using ANSYS Fluent 2023R2 are conducted to investigate the thermal–hydraulic characteristics of these channels for turbulent water flow, incorporating three-dimensional conjugate heat transfer. The simulations are performed at different mass fluxes (G = 500 kg/m²s and 3000 kg/m²s, corresponding to Reynolds numbers of 22638 and 135827, respectively). The results are compared with and validated against the classic Dittus-Boelter correlation and the conventional friction correlations proposed by Blasius and MacAdams. It has been demonstrated that, compared to the rectangular channel, these three proposed channels can effectively reduce the temperatures of solid regions (external claddings and exothermic cores) only under low mass fluxes. Furthermore, at mass fluxes of 3000 kg/m²s and 500 kg/m²s, the longitudinal sinusoidal wavy channel exhibits average Nusselt numbers significantly higher than those of the rectangular channel, by 24.76 % and 51.24 %, respectively. Although the scale-roughened channel also demonstrates higher average Nusselt numbers (exceeding those of the rectangular channel by 39.90 % and 42.94 % at the same mass fluxes), its Darcy friction factors are significantly greater (4.95 times and 9.6 times greater than those of the rectangular channel). This substantial increase in friction factors significantly diminishes its overall performance. Therefore, the longitudinal sinusoidal wavy channel has been identified as the optimal design due to its ability to enhance comprehensive performance across a wide range of mass fluxes and will be employed in subsequent numerical simulations of multiphase flow.

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引用次数: 0

Semi-empirical study based on numerical analysis for analyzing LP-EGR condensation phenomenon in the gasoline engine of a hybrid electric vehicle

IF 6.1 2区工程技术 Q2 ENERGY & FUELS

Applied Thermal Engineering

Pub Date : 2025-02-20 DOI: 10.1016/j.applthermaleng.2025.126022

Kangmin Ju , Hanul Song , Youngkwon Kim , Jungsoo Park

This study focuses on condensation phenomena within a critical component, the low-pressure exhaust gas recirculation (LP-EGR) cooler. By combining experimental and computational techniques, we aimed to understand and predict condensation behavior under various operating conditions. A dynamometer test was conducted to identify the condensation issue and its location. Computational Fluid Dynamics (CFD) analysis was employed to visualize flow patterns and temperature distributions within the cooler. Coolant temperature was selected as the primary variable influencing condensation. Our findings revealed an inverse relationship between the LP-EGR rate and the amount of condensation. A lower LP-EGR rate led to increased condensation. At 2000 rpm and an EGR rate of 4.7 %, approximately 16.4 g of condensation was observed. Furthermore, CFD simulations predicted that at a coolant temperature of −17 °C, condensation could reach up to 55 g. Tube 4 in the cooler was identified as the most susceptible area due to prolonged residence time of low-temperature flow. Based on these results, we recommend implementing a flexible LP-EGR rate strategy to mitigate condensation issues, especially under cold operating conditions. This approach can help optimize engine performance and reduce emissions while minimizing the negative impacts of condensation.

{"title":"Semi-empirical study based on numerical analysis for analyzing LP-EGR condensation phenomenon in the gasoline engine of a hybrid electric vehicle","authors":"Kangmin Ju , Hanul Song , Youngkwon Kim , Jungsoo Park","doi":"10.1016/j.applthermaleng.2025.126022","DOIUrl":"10.1016/j.applthermaleng.2025.126022","url":null,"abstract":"<div><div>This study focuses on condensation phenomena within a critical component, the low-pressure exhaust gas recirculation (LP-EGR) cooler. By combining experimental and computational techniques, we aimed to understand and predict condensation behavior under various operating conditions. A dynamometer test was conducted to identify the condensation issue and its location. Computational Fluid Dynamics (CFD) analysis was employed to visualize flow patterns and temperature distributions within the cooler. Coolant temperature was selected as the primary variable influencing condensation. Our findings revealed an inverse relationship between the LP-EGR rate and the amount of condensation. A lower LP-EGR rate led to increased condensation. At 2000 rpm and an EGR rate of 4.7 %, approximately 16.4 g of condensation was observed. Furthermore, CFD simulations predicted that at a coolant temperature of −17 °C, condensation could reach up to 55 g. Tube 4 in the cooler was identified as the most susceptible area due to prolonged residence time of low-temperature flow. Based on these results, we recommend implementing a flexible LP-EGR rate strategy to mitigate condensation issues, especially under cold operating conditions. This approach can help optimize engine performance and reduce emissions while minimizing the negative impacts of condensation.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"269 ","pages":"Article 126022"},"PeriodicalIF":6.1,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143508806","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