Archives of Thermodynamics最新文献_第10页

Boundary effects on electrothermal convection in a dielectric fluid layer 介电流体层中电热对流的边界效应

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Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2019.128287

M. Ravisha

{"title":"Boundary effects on electrothermal convection in a dielectric fluid layer","authors":"M. Ravisha","doi":"10.24425/ather.2019.128287","DOIUrl":"https://doi.org/10.24425/ather.2019.128287","url":null,"abstract":"The instability characteristics of a dielectric fluid layer heated from below under the influence of a uniform vertical alternating current (AC) electric field is analyzed for different types of electric potential (constant electric potential/ electric current), velocity (rigid/free) and temperature boundary conditions (constant temperature/heat flux or a mixed condition at the upper boundary). The resulting eigenvalue problem is solved numerically using the shooting method for various boundary conditions and the solution is also found in a simple closed form when the perturbation heat flux is zero at the boundaries. The possibility of a more precise control of electrothermal convection (ETC) through various boundary conditions is emphasized. The effect of increasing AC electric Rayleigh number is to hasten while that of Biot number is to delay the onset of ETC. The system is more stable for rigid-rigid boundaries when compared to rigid-free and least stable for free-free boundaries. The change of electric potential boundary condition at the upper boundary from constant electric potential to constant electric current is found to instill more stability on the system. ∗Corresponding Author. Email: ravishmamatha@gmail.com 4 M. Ravisha, K.R. Raghunatha, A.L. Mamatha and I.S. Shivakumara Besides, increase in the AC electric Rayleigh number and the Biot number is to reduce the size of convection cells.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46489509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Numerical investigation and sensitivity analysis of entropy generation of Al2O3/H2O nanofluid in turbulent regime using response surface methodology 响应面法研究Al2O3/H2O纳米流体在湍流状态下的熵产生及其灵敏度分析

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2020.133625

引用次数: 1

Reduction of carbon footprint from spark ignition power facilities by the dual approach 通过双重方法减少火花点火电力设施的碳足迹

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Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2021.137559

K. Janusz-Szymańska, K. Grzywnowicz, G. Wiciak, L. Remiorz

{"title":"Reduction of carbon footprint from spark ignition power facilities by the dual approach","authors":"K. Janusz-Szymańska, K. Grzywnowicz, G. Wiciak, L. Remiorz","doi":"10.24425/ather.2021.137559","DOIUrl":"https://doi.org/10.24425/ather.2021.137559","url":null,"abstract":"Power generation units, suitable for individual users and small scale applications, are mainly based on spark ignition engines. In recently performed research, reductions of emissions coming from such units, especially considering carbon dioxide emissions, are deemed as the issue of particular importance. One of solutions, postponed to reduce impact of spark ignition engine-based units on the natural environment, is transition from fossil fuels into renewable gaseous fuels, as products of organic digestion. Nonetheless, development of new solutions is required to prevent further carbon dioxide emissions. The paper presents a novel dual approach developed to reduce carbon dioxide emissions from stationary power units, basing on spark ignition engine. The discussed approach includes both reduction in carbon content in the fuel, which is realized by its enrichment with hydrogen produced using the solar energy-supported electrolysis process, as well as application of post-combustion carbon dioxide separation. Results of the performed analysis suggest proﬁtability of transition from fossil into the hydrogen-enriched fuel mixture, with signiﬁcant rise in operational parameters of the system following increase in the hydrogen content. Nevertheless, utilization of the carbon dioxide separation leads to vital soar in internal energy demand, causing vital loss in operational and economical parameters of the analyzed system.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":"28 10","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41265082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Simplified exergy analysis of ship heating systems with different heat carriers and with the recovery of waste heat 具有不同热载体和废热回收的船舶供暖系统的简化火用分析

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2019.130002

W. Zeńczak

{"title":"Simplified exergy analysis of ship heating systems with different heat carriers and with the recovery of waste heat","authors":"W. Zeńczak","doi":"10.24425/ather.2019.130002","DOIUrl":"https://doi.org/10.24425/ather.2019.130002","url":null,"abstract":"The application of waste heat from exhaust gas of ship’s main engines has become widely practiced as early as in the 1930s. Thus the increase of ship’s overall eﬃciency was improved. Nowadays all newly built ships of the 400 gross tonnage and above must have speciﬁed energy eﬃciency design index, which is a measure for CO 2 emissions of the ship and its impact on the environment. Therefore, the design of waste heat recovery systems requires special attention. The use of these systems is one of the basic ways to reduce CO 2 emissions and to improve the ship’s energy eﬃciency. The paper describes the ship’s heating systems designed for the use of waste heat contained in the exhaust gas of self-ignition engines, in which the heat carriers are respectively water vapor, water or thermal oil. Selected results of comparative exergy analysis of simpliﬁed steam, water and oil heating systems have been presented. The results indicate that the oil heating system is comparable to the water system in terms of internal exergy losses. However, larger losses of exergy occur in the case of a steam system. In the steam system, a signiﬁcant loss is caused by the need to cool the condensate to avoid cavitation in boiler feed pumps. This loss can in many cases cause the negative heat balance of ship during sea voyage while using only the exhaust gas boilers.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41335758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Uncommon turbine architectures for distributed power generation – development of a small velocity compounded radial re-entry turbine 用于分布式发电的罕见涡轮机结构——小速度复合径向再入涡轮机的开发

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2020.135862

Andreas Weiß, Philipp Streit, T. Popp, P. Shoemaker, T. Hildebrandt

{"title":"Uncommon turbine architectures for distributed power generation – development of a small velocity compounded radial re-entry turbine","authors":"Andreas Weiß, Philipp Streit, T. Popp, P. Shoemaker, T. Hildebrandt","doi":"10.24425/ather.2020.135862","DOIUrl":"https://doi.org/10.24425/ather.2020.135862","url":null,"abstract":"The energy industry is undergoing a major upheaval. In Germany, for example, the large nuclear and coal-fired power plants in the gigawatt scale are planned to be shut down in the forthcoming years. Electricity is to be generated in many small units in a decentralized, renewable and environmentally friendly manner. The large 1000 MW multistage axial steam turbines used to this date are no longer suitable for these tasks. For this reason, the authors examine turbine architectures that are known per se but have fallen into oblivion due to their inferior efficiency and upcoming electric drives about 100 year ago. However, these uncommon turbine concepts could be suitable for small to micro scale distributed power plants using thermodynamic cycles, which use for example geothermal wells or waste heat from industry to generate electricity close to the consumers. Thus, the ∗Corresponding Author. Email: a.weiss@oth-aw.de 236 A.P. Weiss et al. paper describes and discusses the concept of a velocity-compounded single wheel re-entry cantilever turbine in comparison with other turbine concepts, especially other velocity-compounded turbines like the Curtis-type. Furthermore, the authors describe the design considerations, which led to a specific design of a 5 kW air turbine demonstrator, which was later manufactured and investigated. Finally, first numerical as well as experimental results are presented, compared and critically discussed with regards to the originally defined design approach.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42164644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Exergy based analysis of solar air heater duct with W-shaped rib roughness on the absorber plate 基于火用能的吸收板W形肋粗糙太阳能空气加热器风道分析

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ATHER.2019.130006

S. S. Patel, A. Lanjewar

引用次数: 4

Experimental investigation of gravity-assisted wickless heat pipes (thermosyphons) at low heat inputs for solar application 用于太阳能应用的重力辅助无芯热管（热虹吸管）在低热输入下的实验研究

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ATHER.2020.133632

H. N. S. Al-Joboory

{"title":"Experimental investigation of gravity-assisted wickless heat pipes (thermosyphons) at low heat inputs for solar application","authors":"H. N. S. Al-Joboory","doi":"10.24425/ATHER.2020.133632","DOIUrl":"https://doi.org/10.24425/ATHER.2020.133632","url":null,"abstract":"The performance of ten wickless heat pipes without adiabatic sections is investigated experimentally at low heat inputs 120 to 2000 W/m 2 for use in solar water heaters. Three heat pipe diameter groups were tested, namely 16, 22, and 28.5 mm. Each group had evaporator lengths of 1150, 1300, and 1550 mm, respectively, with an extra evaporator length of 1800 mm added to the second group. The condenser section length of all heat pipes was 200 mm. Ethanol, methanol, and acetone were utilized as working ﬂuids, at inventory of 25%, 50%, 70%, and 90% by evaporator volume respectively. The 22 mm diameter pipes were tested at inclination angles 30 ◦ , 45 ◦ , and 60 ◦ . Other diameter groups were tested at 45 ◦ only. Experiments revealed increased surface temperatures and heat transfer coeﬃcients with increased pipe diameter and evaporator length, and that increased working ﬂuid inventory caused pronounced reduction in evaporator surface temperature accompanied by improved heat transfer coeﬃcient to reach maximum values at 50% inventory for the selected ﬂuids. Violent noisy shocks were observed with 70% and 90% inventories with the tested heat pipes and the selected working ﬂuids with heat ﬂux inputs from 320–1900 W/m 2 . These shocks signiﬁcantly aﬀected the heat pipes heat transfer capability and operation stability. Experiments revealed a 45 ◦ and 50% optimum inclination angle of ﬁll charge ratio respectively, and that wickless heat pipes can be satisfactorily used in solar applications. The eﬀect of evaporator length and heat pipe diameter on the performance was included in data correlations.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42738096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Digital twins application in control systems for distributed generation of heat and electric energy 数字孪生在分布式热电发电控制系统中的应用

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2021.137555

M. Sultanov, E. Arakelyan, I. Boldyrev, V. Lunenko, P. D. Menshikov

{"title":"Digital twins application in control systems for distributed generation of heat and electric energy","authors":"M. Sultanov, E. Arakelyan, I. Boldyrev, V. Lunenko, P. D. Menshikov","doi":"10.24425/ather.2021.137555","DOIUrl":"https://doi.org/10.24425/ather.2021.137555","url":null,"abstract":"By the emergence of distributed energy resources, with their associated communication and control complexities, there is a need for an eﬃcient platform that can digest all the incoming data and ensure the reliable operation of the power system, which can be achieved by using digital twins. The paper discusses the advantages of using digital twins in the development of control systems and operation of distributed heat and electric power generation facilities. The possibilities of using the digital doubles for increasing the eﬃciency of the considered objects is presented as the example of optimizing the conﬁguration of a control system of solar collectors in the presence of heat losses in pipelines of the external circuit. Further, the total balance consumed and generated electric and heat energy are presented. Examples of algorithms for protecting equipment to improve security are given, and the possibilities of improving the reliability of distributed power systems are considered. The system use of the digital twins provides the possibility of developing and debugging control algorithms, which increase the eﬃciency, reliability and safety of control objects, including distributed thermal and electrical power generation complexes.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45956673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Neuro-genetic optimization of ribbed heat exchanger using entropy augmentation generation number 基于熵增生成数的肋式换热器神经遗传优化

IF 0.9

Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ather.2020.133627

P. K. Konchada

引用次数: 1

Design and computational fluid dynamics analysis of the last stage of innovative gas-steam turbine 新型燃气轮机末级的设计与计算流体动力学分析

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Archives of Thermodynamics Pub Date : 2023-07-20 DOI: 10.24425/ATHER.2021.XXXXXX

S. Głuch, P. Ziółkowski, Ł. Witanowski, J. Badur

{"title":"Design and computational fluid dynamics analysis of the last stage of innovative gas-steam turbine","authors":"S. Głuch, P. Ziółkowski, Ł. Witanowski, J. Badur","doi":"10.24425/ATHER.2021.XXXXXX","DOIUrl":"https://doi.org/10.24425/ATHER.2021.XXXXXX","url":null,"abstract":"Research regarding blade design and analysis of flow has been\u0000attracting interest for over a century. Meanwhile new concepts and design\u0000approaches were created and improved. Advancements in information technologies\u0000allowed to introduce computational fluid dynamics and computational\u0000flow mechanics. Currently a combination of mentioned methods is\u0000used for the design of turbine blades. These methods enabled us to improve\u0000flow efficiency and strength of turbine blades. This paper relates to\u0000a new type turbine which is in the phase of theoretical analysis, because the\u0000working fluid is a mixture of steam and gas generated in a wet combustion\u0000chamber. The main aim of this paper is to design and analyze the flow characteristics\u0000of the last stage of gas-steam turbine. When creating the spatial\u0000model, the atlas of profiles of reaction turbine steps was used. Results of\u0000computational fluid dynamics simulations of twisting of the last stage are\u0000presented. Blades geometry and the computational mesh are also presented.\u0000Velocity vectors, for selected dividing sections that the velocity along the\u0000pitch diameter varies greatly. The blade has the shape of its cross-section\u0000similar to action type blades near the root and to reaction type blades near\u0000the tip. Velocity fields and pressure fields show the flow characteristics of\u0000the last stage of gas-steam turbine. The net efficiency of the cycle is equal\u0000to 52.61%.","PeriodicalId":45257,"journal":{"name":"Archives of Thermodynamics","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43537624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4