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exergy Analysis of Charge and Discharge Processes of Thermal Energy Storage System with Various Phase Change Materials:A Comprehensive Comparison

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Journal of Thermal Science 2024年第2期33卷 509-521页

作者： Mojtaba TAHERI Fathollah POURFAYAZ Roghayeh HABIBI Akbar MALEKI Department of Renewable Energies and Environment Faculty of New Sciences and TechnologiesUniversity of TehranTehran***Iran Faculty of Mechanical Engineering Shahrood University of TechnologyShahrood***Iran

Thermal energy storage(TES) is of great importance in solving the mismatch between energy production and *** this regard,choosing type of Phase Change Materials(PCMs) which are widely used to control heat in latent thermal energy storage systems,plays a vital role as a means of TES ***,this field suffers from lack of a comprehensive investigation on the impact of various PCMs in terms of *** address this issue,in this study,in addition to indicating the melting temperature and latent heat of various PCMs,the exergy destruction and exergy efficiency of each material are estimated and compared with each ***,in the present work the impact of PCMs mass and ambient temperature on the exergy efficiency is *** results proved that higher latent heat does not necessarily lead to higher exergy ***,to obtain a suitable exergy efficiency,the specific heat capacity and melting temperature of the PCMs must also be *** to the results,LiF-CaF_(2)(80.5%:19.5%,mass ratio) mixture led to better performance with satisfactory exergy efficiency(98.84%) and notably lower required mass compared to other ***,the highest and lowest exergy destruction are belonged to GR25 and LiF-CaF_(2)(80.5:19.5) mixture,respectively.

关键词： exergy analysis phase change materials thermal energy storage exergy efficiency

Study of Flow and Heat Transfer in an Ejector-Driven Swirl Anti-Icing Chamber

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Fluid Dynamics & Materials Processing 2024年第5期20卷 989-1014页

作者： Yi Tu Yuan Wu Yu Zeng Hunan University of Arts and Sciences Hunan Key Laboratory of Distributed Electric Propulsion Vehicle Control TechnologyChangde415000China Liaoning Provincial Key Laboratory of Aircraft Ice Protection AVIC Aerodynamics Research InstituteShenyang110034China School of Aeronautic Science and Engineering Beihang UniversityBeijing100191China

The formation of ice on the leading edge of aircraft engines is a serious issue,as it can have catastrophic *** Swirl Anti-Icing(SAI)system,driven by ejection,circulates hot fluid within a 360°annular chamber to heat the engine inlet lip surface and prevent *** study employs a validated Computational Fluid Dynamics(CFD)approach to study the impact of key geometric parameters of this system on flow and heat transfer characteristics within the anti-icing ***,the entropy generation rate and exergy efficiency are analyzed to assess the energy utilization in the *** research findings indicate that,within the considered flow range,reducing the nozzle specific areaφfrom 0.03061 to 0.01083 can enhance the ejection coefficient by over 60.7%.This enhancement increases the air circulating rate,thereby intensifying convective heat transfer within the SAI ***,the reduction inφalso leads to a significant increase in the required bleed air pressure and a higher entropy generation rate,indicating lower exergy *** nozzle angleθnotably affects the distribution of hot and cold spots on the lip surface of the SAI ***θfrom 0°to 20°reduces the maximum temperature difference on the anti-icing chamber surface by 60 K.

关键词： Swirl anti-icing heat transfer exergy efficiency hot and cold spot aircraft engine

Thermodynamic Analysis of Liquefied Natural Gas(LNG)Production Cycle in APCI Process

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Journal of Thermal Science 2012年第6期21卷 564-571页

作者： Shahrooz Abbasi Nezhad Bezhan Shabani Majid Soleimani Department of Mechanical Engineering Langroud BranchIslamic Azad UniversityLangroudIran

The appropriate production of liquefied natural gas(LNG)with least consuming energy and maximum efficiency is quite *** this paper,LNG production cycle by means of APCI Process has been *** equilibrium equations and exergy equilibrium equations of each equipment in the APCI cycle were *** equipments are described using rigorous thermodynamics and no significant simplification is *** some operating parameters as key parameters,influences of these parameters on coefficient of performance(COP)and exergy efficiency of the cascading cycle were *** results indicate that COP and exergy efficiency will be improved with the increasing of the inlet pressure of MR(mixed refrigerant)compressors,the decreasing of the NG and MR after precooling process,outlet pressure of turbine,inlet temperature of MR compressor and NG temperature after cooling in main cryogenic heat exchanger(MCHE).The COP and exergy efficiency of the APCI cycle will be above 2% and 40%,respectively,after optimizing the key parameters.

关键词： LNG APCI process Coefficient of performance exergy efficiency

Evaluation of convective heat transfer in a tube based on local exergy destruction rate

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Science China(Technological Sciences) 2016年第10期59卷 1494-1506页

作者： WANG JunBo LIU ZhiChun LIU Wei School of Energy and Power Engineering Huazhong University of Science and Technology

In this study, exergy efficiency is defined to evaluate convective heat transfer in a tube based on the local exergy destruction rate from the equilibrium equation of available potential. By calculating this destruction rate, the local irreversibility of convective heat transfer can be evaluated quantitatively. The exergy efficiency and distribution of local exergy destruction rate for a smooth tube, an enhanced tube into which short-width twisted tape has been inserted, and an optimized tube with exergy destruction minimization are analyzed by solving the governing equations through a finite volume method(FVM). For the smooth tube, the exergy efficiency increases with increasing Reynolds number(Re) and decreases as the heat flux increases, whereas the Nusselt number(Nu) remains constant. For the enhanced tube, the exergy efficiency increases with increasing Reynolds number and increases as the short-width rate(w) increases. An analysis of the distribution of the local exergy destruction rate for a smooth tube shows that exergy destruction in the annular region between the core flow and tube wall is the highest. Furthermore, the exergy destruction for the enhanced and optimized tubes is reduced compared with that of the smooth tube. When the Reynolds number varies from 500 to 1750, the exergy efficiencies for the smooth, enhanced, and optimized tubes are in the ranges 0.367–0.485, 0.705–0.857, and 0.885–0.906, respectively. The results show that exergy efficiency is an effective evaluation criterion for convective heat transfer and the distribution of the local exergy destruction rate reveals the distribution of local irreversible loss. Disturbance in the core flow can reduce exergy destruction, and improve the exergy efficiency as well as heat transfer rate. Besides, optimization with exergy destruction minimization can provide effective guidance to improve the technology of heat transfer enhancement.

关键词： convective heat transfer available potential exergy destruction rate exergy efficiency

Simulation and experiments on cooling and power system driven a solid sorption combined by the exhaust waste heat

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Frontiers in Energy 2017年第4期11卷 516-526页

作者： Peng GAO Liwei WANG Ruzhu WANG Yang YU Institute of Refrigeration and Cryogenics Shanghai Jiao Tong University Shanghai 200240 China

A solid sorption combined cooling and power system driven by exhaust waste heat is proposed, which consists of a MnCl2 sorption bed, a CaCl2 sorption bed, an evaporator, a condenser, an expansion valve, and a scroll expander, and ammonia is chosen as the working fluid. First, the theoretical model of the system is established, and the partitioning calculation method is proposed for sorption beds. Next, the experimental system is estab- lished, and experimental results show that the refrigerating capacity at the refrigerating temperature of-10℃ and the resorption time of 30 min is 1.95 kW, and the shaft power is 109.2 W. The system can provide approximately 60% of the power for the evaporator fan and the condenser fan. Finally, the performance of the system is compared with that of the solid sorption refrigeration system. The refrigerating capacity of two systems is almost the same at the same operational condition. Therefore, the power generation process does not influence the refrigeration process. The exergy efficiency of the two systems is 0.076 and 0.047, respectively. The feasibility of the system is determined, which proves that this system is especially suitable for the exhaust waste heat recovery.

关键词： solid sorption exhaust waste heat combinedcooling and power system exergy efficiency

Numerical Simulation of Nanofluid-Based Parallel Cooling Photovoltaic Thermal Collectors

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Journal of Thermal Science 2023年第4期32卷 1644-1656页

作者： WANG Jiangjiang QIN Yanbo HUO Shuojie XIE Kangzhen LI Yiming Hebei Key Laboratory of Low Carbon and High efficiency Power Generation Technology North China Electric Power UniversityBaoding071003China

A novel hybrid cogeneration system based on a parallel-cooled photovoltaic/thermal(PV/T)module is presented in this *** temperature of the parallel-cooled PV/T module is more uniform due to the parallel cooling fluid of air mixed with water or nanofluids(SiO2,CuO,Ag,and Al_(2)O_(3)).The results show that the overall temperature of the PV cell in the parallel-cooled module is about 2 K lower than that in the single-cooled module,with a 9.01%improvement in thermal efficiency and a 0.09%enhancement in electrical *** PV/T module with nanofluid shows a significant improvement in thermal and electrical *** thermal and electrical efficiencies of the parallel-cooled PV/T module consisting of Al_(2)O_(3)nanofluid and air are 89.21%and 9.84%,*** with the non-nanofluid parallel cooling scheme,the cooling method consisting of 1 wt%,3 wt%,or 5 wt%Al_(2)O_(3)and air,the thermal efficiency of PV/T was improved by 5.47%,5.30%,and 3.93%,respectively with the solar radiation of 800 W/m^(2)and the flow rate of 0.10 m/s,while the electrical efficiency was improved by 0.026%,0.027%,and 0.034%,*** addition,when the solar radiation is 1000 W/m^(2)with a flow rate of 0.025 m/s,the air-water parallel cooling PV/T module achieves a maximum exergy efficiency of 11.74%.

关键词： PV/T parallel cooling exergy efficiency nanofluid numerical simulation

End-use energy utilization efficiency of Nigerian residential sector

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Frontiers in Energy 2014年第3期8卷 322-334页

作者： Fidelis I. ABAM Bethrand N. NWANKWOJIKE Ekwe B. EKWE Olayinka S. OHUNAKIN Department of Mechanical Engineering Micheal Okpara University of Agriculture Umudike 02155 Nigeria Department of Mechanical Engineering Covenant University Ogun State 11001 Nigeria

In this paper, the end-use efficiencies of the different energy carriers and the overall energy efficiency in the Nigerian residential sector （NRS） were estimated using energy and exergy analysis. The energy and exergy flows were considered from 2006 to 2011. The overall energy efficiency ranges from 19.15% in 2006 to 20.19% in 2011 with a mean of （19.96±0.23）% while the overall exergy efficiency ranges from 4.34% in 2006 to 4.40% in 2011 with a mean of （4.31±0.059）%. The energy and exergy efficiency margin was 15.58% with a marginal improvement of 0.07% and 0.02%, respectively when compared with previous results. The contribution of the energy carriers to the total energy and exergy inputs were 1.45% and 1.43% for electricity, 1.95% and 3% for fossil fuel and 96.6% and 95.57% for bio-fuel. The result shows that approximately 65% of the residence use wood and biomass for domestic cooking and heating, and only a fraction of the residence have access to electricity. LPG was found to be the most efficient while kerosene, charcoal, wood and other biomass the least in this order. Electricity utilization exergy efficiency is affected by vapor-compression air conditioning application apart from low potential energy applications. In addition, this paper has suggested alternatives in the end-use application and has demonstrated the relevance of exergy analysis in enhancing sustainable energy policies and management and improved integration techniques.

关键词： end-use energy exergy efficiency residentialsector Nigeria

Optimization Study on Regenerative Organic Rankine Cycle(ORC) with Heat Source of Low-Grade Steam

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Energy Engineering 2022年第6期119卷 2569-2584页

作者： Zhao Wang Su Yan Mingfeng Zhu Wen Zhu Han Zhang Xiang Gou Research Center CNOOC Energy Conservation&Environmental Protection Service Co.Ltd.Tianjin300457China School of Energy and Environmental Engineering Hebei University of TechnologyTianjin300401China

Aiming at improving the performance of Organic Rankine Cycle(ORC)system with low-grade steam as heat source,this work studied and optimized the main operating parameters of the ORC *** effects of evapo-ration temperature,superheat degree,condensation temperature and regenerator pinch temperature difference on the system performance were *** optimization for the operating parameters is based on the indicators of specific net power output,waste heat pollution,cycle exergy efficiency,and total UA value(the product of overall heat transfer coefficient and heat transfer area of heat exchanger).The results show that the increase of the evaporation temperature and the superheat degree,and the decrease of the condensation temperature and regenerator pinch temperature difference can improve general system performance but lead to weaker economic *** optimal evaporation temperature,superheat degree,condensation temperature and regenerator pinch temperature difference are determined as 139℃,4°C,36°C and 8°C,respectively,reaching net power output of 114.73 kW,exergy efficiency of 37.10%.Besides,it is indicated that the regenerative ORC system can reach 13.6%additional net power output compared to the ORC system without the regenerator.

关键词： Low-grade steam optimization regenerative ORC exergy efficiency

A separate-type autothermal CH_(4) dry reforming system with exergy recuperation

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Carbon Resources Conversion 2022年第4期5卷 310-319页

作者： Zhongkai Zhao Yohanes Andre Situmorang Ping An Jingxuan Yang Xiaogang Hao Jenny Rizkiana Abuliti Abudula Guoqing Guan School of Chemistry and Chemical Engineering Taiyuan University of TechnologyTaiyuan 030024China Graduate School of Science and Technology Hirosaki University1-BunkyochoHirosaki 036-8560Japan Equipment Department Chengda Engineering Corporation of ChinaChengdu 610041China Energy Conversion Engineering Laboratory Institute of Regional Innovation(IRI)Hirosaki University3-BunkyochoHirosaki 036-856Japan Department of Chemical Engineering Institut Teknologi BandungGanesha 10Bandung 40132Indonesia Key Laboratory of Resources Chemicals and Materials(Shenyang University of Chemical Technology) Ministry of EducationShenyang 110142China

Currently,CO_(2) conversion and utilization have become a key to mitigate the global *** this study,a novel separate-type autothermal dry reforming of methane(S-ATDRM)system is proposed and simulated,in which the methane dry reforming combined with methane partial oxidation is performed in a circulating fluidized bed with exergy recuperation to eliminate the negative effect of the products of CH_(4) partial oxidation on the DRM reaction and further improve the CO_(2) conversion *** results demonstrate that this S-ATDRM system can achieve an exergy efficiency of 84.7%,and about 1055.7 kW of exergy can be recuperated from the process for crude syngas cooling and reapplied for pre-heating of feedstocks of CO_(2),O2 and CH_(4).It is found that the largest exergy destruction in this system occurs in the partial oxidation reactor,which occupies ca.45.6%of the whole exergy *** with the conventional ATDRM system,although the exergy of S-ATDRM system is decreased by approximately 0.3%,the CO_(2) conversion is substantially increased by about 11.3%.

关键词： Carbon dioxide Autothermal dry reforming Circulating fluidized bed exergy efficiency exergy recuperation