Article
Energy & Fuels
Pooja Kumari, Arnab Atta
Summary: This study investigates the droplet breakup dynamics in a branched microdevice and analyzes the influence of controlling factors on droplet breakup behavior using a computational model. The homogeneous pressure field inside the droplet is found to be the main reason for non-breakup in widely asymmetric configurations. Different breakup regimes are identified for other branching configurations, and a regime map is formulated. Furthermore, it is observed that the configuration with fi = 0.8 is more susceptible to droplet breakup.
CHEMICAL ENGINEERING AND PROCESSING-PROCESS INTENSIFICATION
(2022)
Article
Energy & Fuels
Yaquan Ai, Han Wu, Vladimir Markov, Jianhui Zhao, Xiangrong Li
Summary: Supercritical transition of fuel spray in diesel engines, especially supercharged ones, has been widely studied. However, its significant impact on fuel-air mixing under relevant conditions is still uncertain and needs careful evaluation.
Article
Thermodynamics
Siyu Xie, Yunpeng Fu, Ping Yi, Tie Li, Run Chen
Summary: The transitional behavior of multi-component sprays under ECN Spray-A conditions has been investigated using numerical methods in this study. The development and implementation of robust thermodynamic equilibrium solvers and multi-component droplet evaporation models in OpenFOAM have led to new insights. The results indicate that dilute sprays are more prone to transitioning to the supercritical mixing regime, while dense sprays experience a decrease in trans-critical possibility before the end of injection due to the cooling effect of extensive evaporation. Additionally, it was found that multi-component diesel sprays are more likely to transition to the supercritical regime than n-dodecane sprays due to their low mixture critical temperature and evaporation rate.
APPLIED THERMAL ENGINEERING
(2022)
Article
Nuclear Science & Technology
Xinsheng Xu, Fengrong Qiu, Ming Ding, Zehua Guo
Summary: This paper presents a numerical model based on the Volume of Fluid (VOF) to Discrete Particle Method (DPM) to analyze the physical processes of the interaction between melt jet and coolant in the event of a nuclear reactor core melting accident. The influence of coolant phase change on jet breakup length, degree of fragmentation, and particle diameter of melt debris is analyzed under different conditions. The simulation results are compared with empirical formulas, and a good agreement is achieved. This study provides a feasible numerical scheme for the analysis of melt jet entering the lower head coolant under accident conditions.
PROGRESS IN NUCLEAR ENERGY
(2023)
Article
Energy & Fuels
Ping Yi, Tie Li, Yunpeng Fu, Siyu Xie
Summary: The study focuses on the micro-explosion of blended ethanol-diesel droplets under diesel engine-like conditions, using a model to predict the bubble generation, growth, and explosion process. It is found that the heat transfer rate and superheat limit are predominant factors under low pressures, while the competition among evaporation rate, heating rate, transcritical transition, and bubble growth rate determines the micro-explosion under higher pressures.
Article
Energy & Fuels
Heng Wu, Fangxi Xie, Yongqiang Han
Summary: The study revealed that the cetane number of diesel fuel has a significant impact on diesel engine performance, with lower CN values resulting in higher emissions. Additionally, load changes have a more significant impact on particulate matter emissions.
Article
Engineering, Environmental
Juan Pablo Valdes, Lyes Kahouadji, Fuyue Liang, Seungwon Shin, Jalel Chergui, Damir Juric, Omar K. Matar
Summary: The internal dynamics of static mixers handling liquid-liquid flows have been comprehensively explored over the past decade. The effect of the inlet configuration and its relationship with the performance of the mixer in terms of droplet size distribution has been investigated. The study provides new insight into droplet deformation and breakage in SMX mixers for industrially-relevant scenarios using three-dimensional numerical simulations.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Energy & Fuels
Shiquan Feng, Shenglong Zhang, Jidong Shi
Summary: In this work, a 3D model was constructed to simulate the collision behavior of fuel droplets in a diesel engine. The impacts of the radius of influence (ROI) and adaptive collision mesh (ACM) models were analyzed, and relevant parameters were modified. It was found that the ROI model affected the average Sauter mean diameter (SMD) of the diesel droplets, while the ACM model had a larger impact on computational fluid dynamics calculation time. The efficiency of the ACM model was higher than that of the ROI model for simulations with more parcels.
Article
Thermodynamics
Ri Zhang, Yumiao Wang, Yong Liu, Jifu Yin
Summary: This study investigates the impact of droplet breakup and coalescence processes on droplet size distribution in annular flow. The influence of these processes is reflected in four factors: breakup-induced droplet birth, breakup-induced droplet death, coalescence-induced droplet birth, and coalescence-induced droplet death. These four effects collectively shape the probability density distribution of droplet size after reaching a dynamic equilibrium. A numerical procedure is developed to calculate the droplet size distribution and characteristic droplet sizes using microscopic mechanisms of droplet breakup and coalescence, and the predictions are validated against experimental data.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Green & Sustainable Science & Technology
Alexandru Cernat, Constantin Pana, Niculae Negurescu, Gheorghe Lazaroiu, Cristian Nutu
Summary: The study analyzed the effects of hydrogen addition on processes like vaporization and combustion in a diesel engine, using a dual-fueled diesel engine for experimentation.
Article
Engineering, Aerospace
Y. Zhu, X. Sun, V. Sethi, P. Gauthier, S. Guo, R. Bai, D. Yan
Summary: The study utilized commercial CFD software to simulate the flow and breakup characteristics of a liquid jet injected into gaseous crossflow, validating the numerical method and applying it to real engine conditions, showing good accuracy in predicting jet trajectory and breakup mode.
AERONAUTICAL JOURNAL
(2021)
Article
Thermodynamics
Junhao Yan, Suya Gao, Weihua Zhao, Timothy H. Lee
Summary: With economic and population growth, human activities in high-altitude regions are expanding rapidly. This study investigated the combustion and emission characteristics of a common-rail diesel engine fueled with diesel, butanol-diesel, and hexanol-diesel mixtures under low intake pressure conditions. The results showed that reducing intake pressure affects combustion and emission characteristics, and adding alcohol fuel can improve emission performance.
ENERGY CONVERSION AND MANAGEMENT
(2021)
Article
Energy & Fuels
Saravanan Chidambaram Ganapathy, Thiruvenkatachari Seshadri, Sasikala Jayaraman, Vallinayagam Raman, Vikneswaran Malaiperumal, Manoj Babu Arondoss, Femilda Josephin Joseph Shobana Bai, Edwin Geo Varuvel
Summary: This study investigates the feasibility of third-generation biodiesel derived from Azolla microphylla algae by studying its droplet combustion behavior and diesel engine characteristics. The experimental results demonstrate that the physical properties of biodiesel affect its combustion characteristics, but the presence of microexplosion and droplet ejection can enhance the combustion process. Furthermore, increasing the fuel injection pressure improves the engine performance.
ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS
(2022)
Article
Engineering, Chemical
Lingzhen Kong, Jiaqing Chen, Tian Lan, Huan Sun, Kuisheng Wang
Summary: This study analyzed the primary breakup process of liquid jet column, droplet size and velocity distribution, as well as the hydrodynamic characteristics of gas flow in a tubular gas-liquid atomization mixer. The results showed that the gas flow rate is the main influencing parameter for droplet size and distribution uniformity in atomization.
CHINESE JOURNAL OF CHEMICAL ENGINEERING
(2021)
Article
Mechanics
Sepehr Mousavi, Majid Siavashi, Mehran Bagheri
Summary: Jet breakup and droplet formation in different regimes are studied using three Newtonian and three shear-thinning non-Newtonian fluids. Results show that in periodic dripping and dripping faucet regimes, viscosity and non-Newtonian rheology of shear-thinning fluids do not affect jet breakup properties. However, in the jetting regime, increasing viscosity significantly increases jet breakup length and leads to a lower regime transition at lower Weber numbers.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2023)
Article
Energy & Fuels
Renos Rotas, Petros Iliadis, Nikos Nikolopoulos, Ananias Tomboulides, Elias Kosmatopoulos
Summary: Research on combined cooling heating power (trigeneration) systems with high renewable energy source contributions has increased rapidly, aligned with the European Union legislation. This study examines the operation of a trigeneration system in Greece and proposes design and control measures to optimize renewable energy generation. Simulation and validation results show significant improvements in solar and renewable energy contributions.
Article
Energy & Fuels
Adamantios G. Papatsounis, Pantelis N. Botsaris, Konstantinos A. Lymperopoulos, Renos Rotas, Zafeiria Kanellia, Petros Iliadis, Nikos Nikolopoulos
Summary: As the climate crisis intensifies, there is increasing research attention on refrigeration systems, specifically solar cooling. This study examines the performance of a large-scale solar-driven cooling system and finds that combined heat generation (solar and biomass) has significant advantages over using biomass or solar energy alone. Additionally, the economic indicators of an absorption chiller are more appealing than those of an electric chiller, with a significantly reduced payback period.
ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS
(2022)
Article
Energy & Fuels
Vasilis Apostolopoulos, Ioannis Mamounakis, Andreas Seitaridis, Nikolas Tagkoulis, Dimitrios-Sotirios Kourkoumpas, Petros Iliadis, Komninos Angelakoglou, Nikolaos Nikolopoulos
Summary: Building stock retrofitting is crucial for achieving sustainable goals in the building sector. This paper introduces a developed online tool called VERIFY, which performs dynamic life cycle analysis and global warming impact assessments for building renovation. The tool analyzes temporal profiles of energy consumption and temperature changes, and can exchange data with other energy simulation engines. The paper also evaluates the impact of energy retrofitting measures for a residential building in Athens, Greece, resulting in significant reductions in primary energy needs and CO2eq emissions.
Article
Energy & Fuels
Renos Rotas, Maria Fotopoulou, Panagiotis Drosatos, Dimitrios Rakopoulos, Nikos Nikolopoulos
Summary: This study assesses the annual performance improvement of two actual building spaces retrofitted with Adaptive Dynamic Building Envelopes (ADBEs) and evaluates their potential to contribute to the electricity and heating load of the spaces. The results demonstrate that the ADBE system can significantly benefit the energy consumption of the buildings in Cardiff and Grevena.
Review
Computer Science, Information Systems
David Cervero, Maria Fotopoulou, Jesus Munoz-Cruzado, Dimitrios Rakopoulos, Fotis Stergiopoulos, Nikos Nikolopoulos, Spyros Voutetakis, Jose Francisco Sanz
Summary: The paper provides a practical review of the solid state transformer (SST), which is considered to be the dominant solution for the changing architecture of electricity networks. It presents the main functionalities and possible applications of SST, including smart grids, data centres, railways, and offshore wind farms. The analysis of SST prototypes and future trends and challenges in wider implementation of SST technology in the electrical grid are also discussed.
Article
Energy & Fuels
Charalampos Papadopoulos, Athanasios Bachoumis, Niki Skopetou, Costas Mylonas, Nikolaos Tagkoulis, Petros Iliadis, Ioannis Mamounakis, Nikolaos Nikolopoulos
Summary: This paper presents an integrated methodology for decision making in smart grid investments, assessing the investment plans of stakeholders in local energy communities. The methodology utilizes specialized tools and evaluates different smart grid investment scenarios from a multi-dimensional perspective, highlighting the most sustainable and profitable solution.
Article
Energy & Fuels
Christos Papalexis, Dionisis Stefanitsis, Myrto Zeneli, Nikolaos Nikolopoulos, Panteleimon Tzouganakis
Summary: This paper presents a proof of concept for a novel parallel-flow solid-solid heat exchanger, called Double L-Valve, consisting of two L-Valves with concentric vertical tubes. The heat exchanger is designed for the Carbonate Looping process as a CO2 capture technology. The study includes experimental analysis on a small scale and proposes a scaled-up hydrodynamic model for industrial application.
Article
Energy & Fuels
Panagiotis Drosatos, Grigorios Itskos, Nikolaos Nikolopoulos
Summary: This study focuses on optimizing the design of an electric heater for pre-heating molten salt in a supercritical CO2-molten-salt loop. Computational fluid dynamics simulations are used to identify potential issues and propose modifications to eliminate hot spots and thermal stratification. The results show that a homogeneous distribution of heat flux density and turbulent flow can prevent the development of hot spots and thermal stratification. This study contributes to the optimization of molten-salt electric heater operation and the development of next-generation molten-salt-supercritical-CO2 concentrating solar power plants.
Article
Energy & Fuels
Georgios Kanellis, Myrto Zeneli, Nikolaos Nikolopoulos, Carina Hofmann, Jochen Stroehle, Sotirios Karellas, Jukka Konttinen
Summary: This study focuses on the transient three-dimensional CFD simulation of the novel bubbling-bed calciner for calcium looping pilot plant. The study accurately models the granular flow using the state-of-the-art Eulerian-Eulerian approach and considers the drag coefficient and calcination kinetics. The study also takes into account the heat transfer mechanisms from the heat pipes to the bubbling bed, verifying the simulation results against experimental data. The study provides insights into the effect of hydrodynamics on heat transfer and indicates that fluidization velocity has a mild impact on the total heat flux.
Article
Green & Sustainable Science & Technology
Angeliki Kitsopoulou, Antonis Zacharis, Nikolaos Ziozas, Evangelos Bellos, Petros Iliadis, Ioannis Lampropoulos, Eleni Chatzigeorgiou, Komninos Angelakoglou, Nikolaos Nikolopoulos
Summary: This paper investigates different heating configurations utilizing renewable thermal sources in conjunction with a heat pump-based system, aiming to determine the optimal configuration in terms of efficiency. Through dynamic energy simulations, it is demonstrated that renewable thermally driven heat pumps are more efficient than conventional air-source ones. The most effective and economical design is found to be the dual-source system, while the ground-source configuration is the most expensive.
Article
Construction & Building Technology
Komninos Angelakoglou, Eleni Chatzigeorgiou, Ioannis Lampropoulos, Paraskevi Giourka, Georgios Martinopoulos, Nikolaos Nikolopoulos
Summary: This study proposes a four-step methodology to identify suitable key performance indicators (KPIs) for assessing the sustainability performance of buildings transitioning into zero-carbon, resource-efficient, and resilient structures. The methodology involves developing a KPI repository, expanding it with literature information, refining it based on predefined criteria and stakeholder feedback, and developing KPI cards for coordination of data gathering. The implementation of this methodology resulted in a final repository of 31 KPIs.
Article
Chemistry, Physical
Christos Papalexis, Dimitrios Rakopoulos, Nikolaos Nikolopoulos, Alessandro Della Rocca, Guido Jochler, Oriana Tassa, Christos Kalligeros, Panteleimon Tzouganakis, Vasilios Spitas
Summary: This work focuses on developing creep and stress relaxation models for Inconel 625 and Stainless Steel 310 materials used in additive manufacturing. The study evaluates the operational lifespan of an industrial-scale additively manufactured recuperator. Tensile testing, FEA modeling, and analytical models are employed to determine material parameters, predict creep response, and assess the service life. The results show that Inconel 625 has higher resistance to creep and lower thermal stresses, resulting in a significantly longer service life compared to Stainless Steel 310.
Article
Engineering, Chemical
P. Stamatopoulos, D. Stefanitsis, M. Zeneli, N. Nikolopoulos
Summary: This study presents an Artificial Neural Network EMMS (ANN-EMMS) drag scheme specifically developed for fluidized bed reactors in chemical looping combustion. The ANN-EMMS, along with three other drag models, is tested in CFD simulations for a pilot scale FB air reactor. The results show that the ANN-EMMS provides the closest fit to experimental data for pressure profiles in the reactor and accurately predicts ilmenite conversion rates.
CHEMICAL ENGINEERING SCIENCE
(2023)
Proceedings Paper
Computer Science, Artificial Intelligence
Andreas Seitaridis, Ioannis Mamounakis, Nikolas Tagkoulis, Petros Iliadis, Evangelos Bellos, Christos Papalexis, Vasileios Sougakis, Nikos Nikolopoulos
Summary: This study presents a building renovation assessment platform that enables rapid and accurate consideration of multiple retrofit scenarios. The platform integrates specialized tools for lifecycle and energetic calculations and showcases significant reductions in CO2 emissions and primary energy consumption. The economic viability of the retrofit solutions is also demonstrated.
ARTIFICIAL INTELLIGENCE APPLICATIONS AND INNOVATIONS. AIAI 2022 IFIP WG 12.5 INTERNATIONAL WORKSHOPS
(2022)
Article
Thermodynamics
Navid Freidoonimehr, Azadeh Jafari, Maziar Arjomandi
Summary: In this study, a high-fidelity flow visualisation technique is used to investigate the resemblance between a turbulent boundary layer generated by different tripping devices in a lab environment and a naturally developed canonical turbulent boundary layer. The study finds that the blockage created by trips is the main factor affecting the turbulence statistics at a certain downstream distance.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2024)
Article
Thermodynamics
Yuning Wang, Alberto Solera-Rico, Carlos Sanmiguel Vila, Ricardo Vinuesa
Summary: This study proposes a method that combines 6-VAEs for modal decomposition and transformer neural networks for temporal-dynamics prediction in the latent space to develop reduced-order models (ROMs) for turbulent flows. The method achieves high reconstruction accuracy and accurate prediction of temporal dynamics.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2024)
Article
Thermodynamics
L. Laguarda, S. Hickel, F. F. J. Schrijer, B. W. van Oudheusden
Summary: Wall-resolved large-eddy simulations were used to investigate the Reynolds number effects in supersonic turbulent boundary layers at Mach 2.0. The study covered a wide range of friction Reynolds numbers and identified trends in various statistics and scaling laws. The size and topology of turbulent structures in the boundary layer were examined, with a focus on the outer-layer motions at high Reynolds numbers. The study also assessed the influence of outer-layer structures on near-wall turbulence and the sensitivity of uniform momentum regions to compressibility.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2024)
Article
Thermodynamics
A. Doehring, T. Kaller, S. J. Schmidt, N. A. Adams
Summary: In this study, well-resolved large-eddy simulations were used to investigate turbulent duct flows with a square cross section. The influence of a modified wall shear stress on the secondary flow was analyzed by artificially modifying the wall shear stress at one of the four walls. The results showed that the modification led to an asymmetrical distribution of the secondary flow source terms, affecting the momentum distribution. Furthermore, the anisotropy of the Reynolds stress tensor, which induces the secondary flow vortices, was significantly affected by the wall shear stress modulation.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2024)
