Pub Date : 2024-11-22DOI: 10.1016/j.applthermaleng.2024.124873
Raffaele De Rosa , Marco Bernagozzi , Anastasios Georgoulas , Luca Romagnuolo , Emma Frosina , Adolfo Senatore
This paper presents the development and application of an optimization algorithm for determining the geometric parameters of an extruded Liquid Cold Plate (LCP) with internally finned channels. The entire workflow operates within a fully open-source environment, offering a comprehensive and accessible solution for optimizing LCP geometric parameters for efficient thermal management in railway power electronics as well as other industrial applications. In particular, the aim is to minimize the maximum temperature and the temperature gradient at the interface between the LCP and an electronic device for electric trains that dissipates heat. The algorithm explores a defined range of geometric parameters and automatically generates combinations and performs Computational Fluid Dynamics (CFD) simulations, using the open-source C++ toolbox OpenFOAM. Implemented in a bash script, the algorithm not only automates the simulation process but also provides a geometry of the LCP that is easy to manufacture and cost-effective. The correct value of parameters, such as the distance between the fins bottom surface and the channel base (gap), along with others, has shown a significant impact, leading to a reduction in both the maximum interface temperature (8 K) and the temperature gradient (25 K/m) within the system.
{"title":"An Open-Source algorithm for automatic geometrical optimization of extruded liquid cold plates for enhanced thermal management in railway electronics","authors":"Raffaele De Rosa , Marco Bernagozzi , Anastasios Georgoulas , Luca Romagnuolo , Emma Frosina , Adolfo Senatore","doi":"10.1016/j.applthermaleng.2024.124873","DOIUrl":"10.1016/j.applthermaleng.2024.124873","url":null,"abstract":"<div><div>This paper presents the development and application of an optimization algorithm for determining the geometric parameters of an extruded Liquid Cold Plate (LCP) with internally finned channels. The entire workflow operates within a fully open-source environment, offering a comprehensive and accessible solution for optimizing LCP geometric parameters for efficient thermal management in railway power electronics as well as other industrial applications. In particular, the aim is to minimize the maximum temperature and the temperature gradient at the interface between the LCP and an electronic device for electric trains that dissipates heat. The algorithm explores a defined range of geometric parameters and automatically generates combinations and performs Computational Fluid Dynamics (CFD) simulations, using the open-source C++ toolbox OpenFOAM. Implemented in a bash script, the algorithm not only automates the simulation process but also provides a geometry of the LCP that is easy to manufacture and cost-effective. The correct value of parameters, such as the distance between the fins bottom surface and the channel base (gap), along with others, has shown a significant impact, leading to a reduction in both the maximum interface temperature (8<!--> <!-->K) and the temperature gradient (25<!--> <!-->K/m) within the system.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 124873"},"PeriodicalIF":6.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743842","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}
Pub Date : 2024-11-22DOI: 10.1016/j.applthermaleng.2024.124953
Zhihang Lin , Pingfa Feng , Jianfu Zhang
Roll grinders are essential in high-precision roll manufacturing. However, lubricant temperature fluctuations decrease the precision of grinders. The complicated dynamic heat transfer within the closed-loop cooling systems of roll grinders poses significant challenges to accurately modeling their thermal states. This study proposed a novel model based on circulation differential equations for the thermofluid temperatures in roll grinders. Based on thermodynamic principles, differential equations of each component within the closed-loop cooling system were derived. To improve model accuracy, a thermal resistance approach was utilized, and the thermal interaction between lubricant and hydrodynamic bearings under different speeds and the heat convection between hydraulic hoses and air are considered. To validate the proposed model, a series of experiments across a range of spindle speeds were carried out. The results showed the model could achieve prediction accuracy less than 5.27%. Subsequently, the influence of system design parameters on cooling performance was analyzed. The proposed temperature model better comprehends the thermodynamic interaction within closed-loop cooling systems featuring hydrodynamic bearings. The limitations and potential application in other industrial areas were discussed.
{"title":"A thermofluid temperature modeling, prediction of closed-loop cooling system of roll grinder based on circulation differential equations","authors":"Zhihang Lin , Pingfa Feng , Jianfu Zhang","doi":"10.1016/j.applthermaleng.2024.124953","DOIUrl":"10.1016/j.applthermaleng.2024.124953","url":null,"abstract":"<div><div>Roll grinders are essential in high-precision roll manufacturing. However, lubricant temperature fluctuations decrease the precision of grinders. The complicated dynamic heat transfer within the closed-loop cooling systems of roll grinders poses significant challenges to accurately modeling their thermal states. This study proposed a novel model based on circulation differential equations for the thermofluid temperatures in roll grinders. Based on thermodynamic principles, differential equations of each component within the closed-loop cooling system were derived. To improve model accuracy, a thermal resistance approach was utilized, and the thermal interaction between lubricant and hydrodynamic bearings under different speeds and the heat convection between hydraulic hoses and air are considered. To validate the proposed model, a series of experiments across a range of spindle speeds were carried out. The results showed the model could achieve prediction accuracy less than 5.27%. Subsequently, the influence of system design parameters on cooling performance was analyzed. The proposed temperature model better comprehends the thermodynamic interaction within closed-loop cooling systems featuring hydrodynamic bearings. The limitations and potential application in other industrial areas were discussed.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 124953"},"PeriodicalIF":6.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722418","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}
Pub Date : 2024-11-22DOI: 10.1016/j.applthermaleng.2024.125049
Shengchun Liu , Shentong Guo , Haiwang Sun , Zhiming Xu , Xueqiang Li , Xinyue Wang
Single-phase immersion cooling system (SPICS) has become one of the important ways to solve the energy challenge in data centers (DCs). However, limited attention has been paid to comprehensively evaluate the energy efficiency, economic viability, and pollution emission for such system. To bridge this knowledge gap, the TRNSYS model is established and validated by experimental data. Then, the performance is analyzed in ten typical cities, representing different climates, by using dry cooler (DRC) and cooling tower (CT) in SPICS, which is compared to the traditional air-based cooling system (ACS). Results show that, compared to ACS, SPICS-DRC and SPICS-CT could save the energy consumption by 62.9 %-80.0 % and 75.4 %-77.6 %, respectively. There is also an obvious difference by using SPICS-DRC and SPICS-CT in different climates. For example, the difference of energy consumption could be as high as 27 MW·h in Riyadh, which belongs to tropical desert climate. Life cycle cost (LCC) of ACS is 1.52–3.94 times higher than that of SPICS, in which the future cost ranges from 38.2 % to 97.3 % of LCC and it comes from the different ambient parameters, electricity prices, carbon prices, and carbon emission factors. Compared to ACS, SPICS can reduce CO2 emissions by 63 % to 80 % in different cities where the carbon emission factor shows the obvious impact.
{"title":"Evaluation of energy, economic, and pollution emission for single-phase immersion cooling data center with different economizers","authors":"Shengchun Liu , Shentong Guo , Haiwang Sun , Zhiming Xu , Xueqiang Li , Xinyue Wang","doi":"10.1016/j.applthermaleng.2024.125049","DOIUrl":"10.1016/j.applthermaleng.2024.125049","url":null,"abstract":"<div><div>Single-phase immersion cooling system (SPICS) has become one of the important ways to solve the energy challenge in data centers (DCs). However, limited attention has been paid to comprehensively evaluate the energy efficiency, economic viability, and pollution emission for such system. To bridge this knowledge gap, the TRNSYS model is established and validated by experimental data. Then, the performance is analyzed in ten typical cities, representing different climates, by using dry cooler (DRC) and cooling tower (CT) in SPICS, which is compared to the traditional air-based cooling system (ACS). Results show that, compared to ACS, SPICS-DRC and SPICS-CT could save the energy consumption by 62.9 %-80.0 % and 75.4 %-77.6 %, respectively. There is also an obvious difference by using SPICS-DRC and SPICS-CT in different climates. For example, the difference of energy consumption could be as high as 27 MW·h in Riyadh, which belongs to tropical desert climate. Life cycle cost (LCC) of ACS is 1.52–3.94 times higher than that of SPICS, in which the future cost ranges from 38.2 % to 97.3 % of LCC and it comes from the different ambient parameters, electricity prices, carbon prices, and carbon emission factors. Compared to ACS, SPICS can reduce CO<sub>2</sub> emissions by 63 % to 80 % in different cities where the carbon emission factor shows the obvious impact.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 125049"},"PeriodicalIF":6.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743655","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 : 2024-11-22DOI: 10.1016/j.applthermaleng.2024.125030
Luqiang Li , Qinghuang Huang , Peiyong Wang
When a thermocouple is used to measure the temperature of a gas flow, the reading is the junction temperature. The junction temperature, resulting from the energy balance of the conduction with wires, the convective and radiative heat transfer with incoming gas, and the radiative heat transfer with surroundings, is not equal to the gas temperature. The energy conservation of the junction can be used for the correction to obtain the gas temperature. However, when the gas velocity is unknown, two thermocouples of different sizes should be used to get two different readings; the gas velocity and temperature can be obtained simultaneously by analyzing the energy conservation of the two thermocouples. The principle of the velocity-temperature correction method with double thermocouples is stated first. Then the experimental data of two S type thermocouples with spherical junctions measuring the standard flames with known velocity, composition and temperature (1642–1994 K) are used for the correction, and the gas velocity and temperature are obtained. Compared with the real gas data, the relative errors of the corrected velocity and temperature are less than 4.6 % and 1.1 %, respectively. The correction method is also used for the measurement of the standard flames with two S type butt-welded thermocouples; compared with the real gas data (1281–1998 K), the relative errors of the corrected velocity and temperature are less than 6.4 % and 1.7 %, respectively. The effects of the estimation errors in gas composition, junction diameter, and thermocouple emissivity and the number and distribution of velocity-temperature combinations on the correction accuracy are also investigated, showing that the above factors have almost no effect on the temperature correction accuracy and the velocity correction accuracy depends on most of them.
{"title":"An application of velocity-temperature correction method with double thermocouples in measuring standard flames","authors":"Luqiang Li , Qinghuang Huang , Peiyong Wang","doi":"10.1016/j.applthermaleng.2024.125030","DOIUrl":"10.1016/j.applthermaleng.2024.125030","url":null,"abstract":"<div><div>When a thermocouple is used to measure the temperature of a gas flow, the reading is the junction temperature. The junction temperature, resulting from the energy balance of the conduction with wires, the convective and radiative heat transfer with incoming gas, and the radiative heat transfer with surroundings, is not equal to the gas temperature. The energy conservation of the junction can be used for the correction to obtain the gas temperature. However, when the gas velocity is unknown, two thermocouples of different sizes should be used to get two different readings; the gas velocity and temperature can be obtained simultaneously by analyzing the energy conservation of the two thermocouples. The principle of the velocity-temperature correction method with double thermocouples is stated first. Then the experimental data of two S type thermocouples with spherical junctions measuring the standard flames with known velocity, composition and temperature (1642–1994 K) are used for the correction, and the gas velocity and temperature are obtained. Compared with the real gas data, the relative errors of the corrected velocity and temperature are less than 4.6 % and 1.1 %, respectively. The correction method is also used for the measurement of the standard flames with two S type butt-welded thermocouples; compared with the real gas data (1281–1998 K), the relative errors of the corrected velocity and temperature are less than 6.4 % and 1.7 %, respectively. The effects of the estimation errors in gas composition, junction diameter, and thermocouple emissivity and the number and distribution of velocity-temperature combinations on the correction accuracy are also investigated, showing that the above factors have almost no effect on the temperature correction accuracy and the velocity correction accuracy depends on most of them.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 125030"},"PeriodicalIF":6.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743743","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 : 2024-11-22DOI: 10.1016/j.applthermaleng.2024.125052
Xueyang Wang , Dong Li , Fanbin Meng , Yangyang Wu , Ruitong Yang , Meng Gao , Changyu Liu
Solar collectors are significantly influenced by weather conditions, leading to a mismatch between thermal energy production and demand. To mitigate this issue, U-tube solar collectors integrated with phase change material (PCM) were investigated to store excess solar energy and regulate the temperature of collectors. This study investigates the effects of fin spacing and fin length on the heat transfer performance of these collectors under various conditions. Additionally, the impact of different collector tube lengths was analyzed. The results show that adding fins in solar collectors enhances temperature distribution uniformity and accelerates the PCM melting process. And the addition of fins to the U-tube produces faster temperature increase and significant improvement of temperature uniformity. In configurations featuring with fin length 20 mm and fin spacing 30 mm, the average PCM temperature decreased by 9.4 % and the liquid fraction decreased by 10.2 %, compared with non-finned. Smaller fin spacing or longer fins can improve heat transfer efficiency, and reduce PCM temperatures and liquid fractions. The 2L configuration exhibited optimal performance with an average PCM temperature of 330 K and a liquid fraction of 0.60 and achieved a significant reduction in time to reach 318 K by 47.9 % when compared to the L configuration.
{"title":"Structure optimization of U-tube solar collector integrated with phase change materials","authors":"Xueyang Wang , Dong Li , Fanbin Meng , Yangyang Wu , Ruitong Yang , Meng Gao , Changyu Liu","doi":"10.1016/j.applthermaleng.2024.125052","DOIUrl":"10.1016/j.applthermaleng.2024.125052","url":null,"abstract":"<div><div>Solar collectors are significantly influenced by weather conditions, leading to a mismatch between thermal energy production and demand. To mitigate this issue, U-tube solar collectors integrated with phase change material (PCM) were investigated to store excess solar energy and regulate the temperature of collectors. This study investigates the effects of fin spacing and fin length on the heat transfer performance of these collectors under various conditions. Additionally, the impact of different collector tube lengths was analyzed. The results show that adding fins in solar collectors enhances temperature distribution uniformity and accelerates the PCM melting process. And the addition of fins to the U-tube produces faster temperature increase and significant improvement of temperature uniformity. In configurations featuring with fin length 20 mm and fin spacing 30 mm, the average PCM temperature decreased by 9.4 % and the liquid fraction decreased by 10.2 %, compared with non-finned. Smaller fin spacing or longer fins can improve heat transfer efficiency, and reduce PCM temperatures and liquid fractions. The 2L configuration exhibited optimal performance with an average PCM temperature of 330 K and a liquid fraction of 0.60 and achieved a significant reduction in time to reach 318 K by 47.9 % when compared to the L configuration.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 125052"},"PeriodicalIF":6.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743848","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 : 2024-11-21DOI: 10.1016/j.applthermaleng.2024.125018
Qi Liu , Zijian Zhao , Zhe Lin , Haifeng Wang , Yunchao Yuan
The material property of bipolar plates is extremely vital for thermal and energy management in power performance improvement of a proton exchange membrane fuel cell. The aim of this work is to reveal the influence of the material properties of bipolar plates on power performances of proton exchange membrane fuel cell stacks from detailed internal flow, electricity, heat and mass distribution characteristics. The power performances of large-scale proton exchange membrane fuel cell stacks consisted by two kinds of bipolar plates (the metal and the graphite bipolar plates) were evaluated experimentally. A three-dimensional coupled numerical simulation model for a stack cell was established and experimentally verified to reveal internal current density, heat and mass and potential distribution characteristics during electrochemical reaction by considering the material properties of bipolar plates. It was found that the power performance of the proton exchange membrane fuel cell stack consisted by the graphite bipolar plates was better than that of the metal bipolar plates. Cross-sectional distribution characteristics of the temperature, current density, ohmic heat source, hydrogen, oxygen and potential at corresponding interfaces for two kinds of bipolar plates were comparatively discussed. The mechanism of the superior power performance in the case of the graphite bipolar plates was revealed by a better distribution uniformity of the interfacial temperature and a lower contact resistance. The heat transfer entropy generation and the gases consumption in electrochemical reaction for different material properties of bipolar plates were assessed to compare the energy conversion degree.
{"title":"Influence of material properties of bipolar plates on power performances of proton exchange membrane fuel cell stacks","authors":"Qi Liu , Zijian Zhao , Zhe Lin , Haifeng Wang , Yunchao Yuan","doi":"10.1016/j.applthermaleng.2024.125018","DOIUrl":"10.1016/j.applthermaleng.2024.125018","url":null,"abstract":"<div><div>The material property of bipolar plates is extremely vital for thermal and energy management in power performance improvement of a proton exchange membrane fuel cell. The aim of this work is to reveal the influence of the material properties of bipolar plates on power performances of proton exchange membrane fuel cell stacks from detailed internal flow, electricity, heat and mass distribution characteristics. The power performances of large-scale proton exchange membrane fuel cell stacks consisted by two kinds of bipolar plates (the metal and the graphite bipolar plates) were evaluated experimentally. A three-dimensional coupled numerical simulation model for a stack cell was established and experimentally verified to reveal internal current density, heat and mass and potential distribution characteristics during electrochemical reaction by considering the material properties of bipolar plates. It was found that the power performance of the proton exchange membrane fuel cell stack consisted by the graphite bipolar plates was better than that of the metal bipolar plates. Cross-sectional distribution characteristics of the temperature, current density, ohmic heat source, hydrogen, oxygen and potential at corresponding interfaces for two kinds of bipolar plates were comparatively discussed. The mechanism of the superior power performance in the case of the graphite bipolar plates was revealed by a better distribution uniformity of the interfacial temperature and a lower contact resistance. The heat transfer entropy generation and the gases consumption in electrochemical reaction for different material properties of bipolar plates were assessed to compare the energy conversion degree.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 125018"},"PeriodicalIF":6.1,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142697436","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 : 2024-11-21DOI: 10.1016/j.applthermaleng.2024.124989
Ruquan You , Runzhou Liu , Haiwang Li
This study investigates the couple effects of internal and external cooling on double-wall laminate cooling (DWLC) structure with novel impingement jet, pin-fins, and slot hole. The distribution of film cooling effectiveness (FCE) and heat transfer coefficient (HTC) were measured using transient liquid crystal (TLC) and pressure sensitive paint (PSP) methods. In order to improve the accuracy of TLC method, a thermal inertia correction method based on radial basis function neural network (RBFNN) was proposed. It was found that the pin-fins would significantly affect the external film cooling characteristics. There is a counter-rotating vortex pair at the downstream of the pin-fins inside the coolant film. This leads to a higher FCE at the downstream region of pin-fins and a lower FCE at the region between the pin-fins. The internal heat transfer is minimally influenced by slot height and inclination angle. Increasing filling ratio greatly reduces the area-averaged FCE and changes the flow field at slot outlet. The DWLC structure in this study shows excellent cooling performance and is currently mainly used in the field of aero-engines. However, it can also be applied to the cooling design of gas turbines, electronics, and other fields after scaling the size. Additionally, the improved TLC experimental method can be widely used in heat transfer measurement in the aforementioned research fields.
{"title":"Experimental study of the couple effects of internal and external cooling on double-wall laminate structure with novel slot and pin-fins","authors":"Ruquan You , Runzhou Liu , Haiwang Li","doi":"10.1016/j.applthermaleng.2024.124989","DOIUrl":"10.1016/j.applthermaleng.2024.124989","url":null,"abstract":"<div><div>This study investigates the couple effects of internal and external cooling on double-wall laminate cooling (DWLC) structure with novel impingement jet, pin-fins, and slot hole. The distribution of film cooling effectiveness (FCE) and heat transfer coefficient (HTC) were measured using transient liquid crystal (TLC) and pressure sensitive paint (PSP) methods. In order to improve the accuracy of TLC method, a thermal inertia correction method based on radial basis function neural network (RBFNN) was proposed. It was found that the pin-fins would significantly affect the external film cooling characteristics. There is a counter-rotating vortex pair at the downstream of the pin-fins inside the coolant film. This leads to a higher FCE at the downstream region of pin-fins and a lower FCE at the region between the pin-fins. The internal heat transfer is minimally influenced by slot height and inclination angle. Increasing filling ratio greatly reduces the area-averaged FCE and changes the flow field at slot outlet. The DWLC structure in this study shows excellent cooling performance and is currently mainly used in the field of aero-engines. However, it can also be applied to the cooling design of gas turbines, electronics, and other fields after scaling the size. Additionally, the improved TLC experimental method can be widely used in heat transfer measurement in the aforementioned research fields.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 124989"},"PeriodicalIF":6.1,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142697264","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 : 2024-11-21DOI: 10.1016/j.applthermaleng.2024.125021
Meilin Liu , Tiannian Zhou , Yangpeng Liu , Baohui Chen , Liangxuan Ouyang , Pan Long , Xishi Wang
Realistic fire disaster scenarios always refer to multiple fires burning at adjacent positions at the same time (MF), leading to a higher risk compared with a single fire (SF). That is, fire suppression in realistic fire disasters differs from existing fire suppression studies focusing on a single flame. It is worthy to extend the fire suppression study to multiple fires. This study investigates the thermodynamic characteristics of applying the water mist on the double flames through FDS (Fire Dynamic Simulator v. 6.9.1). The fire suppression mechanism is discussed from two aspects (the cooling effect and the dynamic effect). The cooling effect of the water mist on the double flames is revealed based on the onset time of cooling. The droplet distribution is considered the main factor in the cooling effect of the water mist on the double flames (DF). The dynamic effect dominates in the two effects of the water mist. It is found that the interaction effect between double flames significantly improves the difficulty of penetrating the combustion area. This study can provide numerical data support and theoretical reference for water mist fire suppression systems applied in realistic scenarios.
真实的火灾灾难场景总是指相邻位置同时有多处着火（MF），与单处着火（SF）相比风险更高。也就是说，现实火灾灾难中的灭火不同于现有的针对单个火焰的灭火研究。将灭火研究扩展到多重火灾是很有价值的。本研究通过 FDS（Fire Dynamic Simulator v. 6.9.1）研究了在双火焰上喷洒水雾的热力学特性。从两个方面（冷却效应和动态效应）讨论了灭火机制。水雾对双层火焰的冷却效果是基于冷却开始时间来揭示的。水滴分布被认为是水雾对双重火焰（DF）产生冷却效果的主要因素。动态效应在水雾的两种效应中占主导地位。研究发现，双层火焰之间的相互作用效应大大提高了穿透燃烧区域的难度。该研究可为水雾灭火系统在实际场景中的应用提供数值数据支持和理论参考。
{"title":"Thermodynamic characterization on the suppression process of water mist under the interaction effect between two buoyant non-premixed flames","authors":"Meilin Liu , Tiannian Zhou , Yangpeng Liu , Baohui Chen , Liangxuan Ouyang , Pan Long , Xishi Wang","doi":"10.1016/j.applthermaleng.2024.125021","DOIUrl":"10.1016/j.applthermaleng.2024.125021","url":null,"abstract":"<div><div>Realistic fire disaster scenarios always refer to multiple fires burning at adjacent positions at the same time (MF), leading to a higher risk compared with a single fire (SF). That is, fire suppression in realistic fire disasters differs from existing fire suppression studies focusing on a single flame. It is worthy to extend the fire suppression study to multiple fires. This study investigates the thermodynamic characteristics of applying the water mist on the double flames through FDS (Fire Dynamic Simulator v. 6.9.1). The fire suppression mechanism is discussed from two aspects (the cooling effect and the dynamic effect). The cooling effect of the water mist on the double flames is revealed based on the onset time of cooling. The droplet distribution is considered the main factor in the cooling effect of the water mist on the double flames (DF). The dynamic effect dominates in the two effects of the water mist. It is found that the interaction effect between double flames significantly improves the difficulty of penetrating the combustion area. This study can provide numerical data support and theoretical reference for water mist fire suppression systems applied in realistic scenarios.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"260 ","pages":"Article 125021"},"PeriodicalIF":6.1,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142697441","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 : 2024-11-20DOI: 10.1016/j.applthermaleng.2024.124966
Hongyan Wang , Peiyang Li , Ye Chen , Yaohua Zhao , Jibang Tian , Chong Li , Zhenhua Quan
A double L-shaped heat pipe sink that uses a micro heat pipe array is proposed for heat dissipation and temperature uniformity in high-power electronics chip cooling for the first time in this work. The radiator is composed of two L-shaped micro heat pipe arrays filled with copper foam wick (the composite wick structure) and aluminum flat fins, which can reduce the temperature of hotspots of electronics effectively and has good inclination adaptability. Through experiments, the heat transfer performance is studied under different copper foam filling lengths, liquid filling rates, and inclination angles. Then, a numerical simulation of the effect of different fin parameters on the radiator is conducted using Icepak. The composite wick structure effectively enhances the heat transfer capability of the radiator. Results show that the average thermal resistance of the micro heat pipe array with a composite wick structure is 0.258 K/W, indicating a 23 % reduction compared with that of a single wick structure double L shape heat pipe sink. The double L shape heat pipe sink solves the phenomenon of chip temperature jump caused by the hotspots of high heat flux. The average temperature of the chip surface can be controlled below 62 ℃ when the localized heat flux is 200 W/cm2. Simulation results show that optimization of the fin structure can stabilize the temperature of the 214 W chip at 70.1 ℃, which is reduced by 8.7 % than before optimization.
本研究首次提出了一种使用微型热管阵列的双 L 型热管散热器，用于大功率电子芯片冷却中的散热和温度均匀性。该散热器由两个L型微热管阵列组成，阵列内填充有泡沫铜灯芯（复合灯芯结构）和铝制扁平散热片，能有效降低电子器件热点温度，并具有良好的倾角适应性。通过实验，研究了不同泡沫铜填充长度、液体填充率和倾斜角度下的传热性能。然后，使用 Icepak 对不同翅片参数对散热器的影响进行了数值模拟。复合芯结构有效地提高了散热器的传热能力。结果表明，采用复合灯芯结构的微型热管阵列的平均热阻为 0.258 K/W，与单灯芯结构的双 L 形热管散热器相比降低了 23%。双 L 型热管散热器解决了高热流热点导致的芯片温度跃变现象。当局部热通量为 200 W/cm2 时，芯片表面的平均温度可控制在 62 ℃ 以下。仿真结果表明，优化鳍片结构可将 214 W 芯片的温度稳定在 70.1 ℃，比优化前降低了 8.7%。
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Pub Date : 2024-11-20DOI: 10.1016/j.applthermaleng.2024.124961
Wai Hong Lai, Jack Nihill, Petros Lappas, Mladenko Kajtaz, Aliakbar Akbarzadeh, Abhijit Date
Over the last decade due to rapid global population growth and industrialisation of developing economies, the demand for freshwater and energy is rising, placing significant stress on these vital resources. Seawater desalination has been widely used as a solution to water scarcity, but it is energy intensive. At the same time, low and medium-grade heat sources are readily available, and has potential to supplement mainstream renewable energy sources, such as solar and wind due to their intermittent nature. Despite the availability of low and medium grade heat, its utilization remains limited due to thermodynamic inefficiencies and economic feasibility. Considering this, researchers have focused their efforts to develop more sustainable energy and water production technologies. While the broad aim of this paper it to investigate the sustainable water desalination and power generation technologies, the paper focuses on examining their integration to improve energy resource utilisation through combined desalination and power generation systems. A comprehensive review and comparative analysis of technologies, including Rankine cycle-based power generation, membrane-based processes, and hybrid systems, in conjunction with desalination techniques like reverse osmosis, membrane distillation, and multiple-effect distillation is conducted. Power generation from low grade thermal energy sources is inherently inefficient due to the thermodynamics limitations and hence not many pilot/commercial applications have been realised over the years. Similarly, thermal desalination with low grade thermal energy sources has low recovery due to limitations maximum stages. Furthermore, both these systems need comparatively large heat exchangers due to low temperature differentials, make the systems expensive leading to high cost per unit of power and water. The paper compares different configurations of combined desalination power generation systems available in the literature. The literature shows that under the same input parameters, a combined systems operating on trilateral flash cycle will produce 2.7 time more freshwater production compared to other configurations, while a Rankine cycle based combined system will provide 45.2 % more power. Literature shows the potential of membrane based combined desalination and power generation, but the currently reported power densities for such systems of 0.3 to 0.6 W/m2 is not viable and must be increase the power density must increase by at least one order of magnitude to be net positive producer of power. The paper provides several suggestions/directions for future work.
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