bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical study on the mixed convection with nanofluids in vertical channel asymmetrically heated
Authors: Barbato Maria , Buonomo Bernardo , Manca Oronzio , Sarli Gianluca 
Published: December 2023

Abstract
Mixed convection heat transfer in cavities is of great interest in many industrial applications, such as the development of crystals, the thermal control of electronic components, the nuclear reactors and various manufacturing processes. Components are generally located on the wall of a channel, that can be also tilted and their thermal control is carried out by the fluid flow. They can be schematized as thermal sources on vertical boards and the heat flux is removed by natural or mixed convection. As to the mixed convection, the interaction between the buoyancy forces and the external flow plays a significant role in the thermal design of systems. When natural convection is not strong enough to remove heat flux, mixed convection is adoptedIn particular, mixed convection due to moving surfaces is very important is these applications. Mixed convection because of buoyancy and motion of one of the channel walls has received little research attention and few guidelines are available for choosing the best performing channel configuration. Moreover, to optimize the transfer through natural convection, it is possible to modify the geometric parameters of the component, thus maximizing the convective heat transfer coefficient. If this is not possible or if one chooses to keep the geometry of the component unchanged for design choices, a possible alternative is the use of nanofluids. The properties of nanofluids exhibit a behaviour ranging between the properties of the base fluid and the properties of the nanoparticles. However, the addition of nanoparticles in the working fluid is considered to enhance the thermal behaviour of the base fluid. In this study a numerical investigation of mixed convection in nanofluids due to the interaction between a buoyancy flow and a moving plate induced flow in a vertical channel is carried out. The moving plate has a constant velocity and moves in the same direction with respect to the buoyancy force. The channel principal walls are heated with uniform heat flux. The numerical analysis is obtained by means of the commercial code Fluent. The effects of the different wall heat fluxes and moving plate velocities are investigated and results in terms of the channel wall and moving plate temperatures and Nusselt numbers are given.
Performance assessment of electro-osmotic flow of rectangular microchannels with smoothed corners
Authors: Suzzi Nicola , Lorenzini Marco 
Published: December 2023

Abstract
Microchannel heat sinks are a viable alternative to traditional thermal management systems when high fluxes over small surfaces are involved. To avoid high pressure drops especially when liquids are concerned, electro-osmotic flow, a phenomenon which is relevant at the microscales only, can be employed profitably. Joule heating, which occurs every time an electrical current is circulated through a conductor with finite electrical resistance, may hamper the application of electro-osmotic flows significantly; its effects must therefore be investigated, as should the influence of the entry length on the overall transport phenomena which occur in the microchannel, especially so since channels with uniform temperature at the walls tend to be somewhat short, to mitigate heat generation due to Joule heating. In this paper the transport phenomena occurring within a microchannel of rectangular cross-section with uniform wall temperature through which an electro-osmotic flow occurs is studied, while considering the flow fully developed hydrodynamically but thermally developing (Graetz problem). The corners are then smoothed progressively and the effect of this change in the shape of the cross-section over the non-dimensional dissipated power or temperature difference between wall and fluid is investigated using the performance evaluation criteria introduced by Webb. Correlations are suggested for the Poiseuille and Nusselt numbers for all configurations as are criteria to obtain the maximum allowable channel length, i.e. the length of the channel over which the walls start to cool the fluid, owing to Joule heating, in terms of the hydraulic diameter.
A phenomenological model for predicting the early development of the flame kernel in spark-ignition engines
Authors: Giannattasio Pietro , Pretto Marco , Betta Enrico De 
Published: December 2023

Abstract
This work presents a simple and effective phenomenological model for the prediction of the early growth of the flame kernel in SI engines, including its initiation as a result of the electrical breakdown of the fuel/air mixture between the spark plug electrodes. The present model aims to provide an improved description of the ignition-affected early phases of flame kernel development compared to the majority of models currently available in literature. In particular, these models focus on electrical energy supply and turbulence, whereas the stretch-induced kernel growth slowdown is quantified with linear models that are inconsistent with the small kernel radius. For the flame kernel initiation, this model replaces the current methods that rely on 1D heat diffusion within a plasma column with a more consistent analysis of post-breakdown conditions. Concerning the kernel growth, the present model couples the mass and energy conservation equations of a spherical kernel with the species and temperature profiles outside of it. This combination leads to a non-linear description of the flame stretch, according to which the kernel development is controlled by the Lewis-number-dependent balance between the heat gained via combustion and the heat lost via thermal diffusion. As a result, the kernel temperature differs from the adiabatic flame temperature, causing the laminar flame speed to change from its adiabatic value and ultimately affecting the overall kernel development. Kernel growth predictions are conducted for laminar flames and compared to literature data, showing a satisfactory agreement and highlighting the ability to describe the stretch-induced kernel slowdown, up to its possible extinction. A good agreement with literature data is also obtained for kernel expansions under moderately turbulent conditions, typical of internal combustion engines. The simple formulation of the present model enables swift integration into phenomenological combustion models for sparkignition engines, while simultaneously offering useful insight into the early kernel development even for CFD-based approaches.
Experimental analysis of boost limits in a hydrogen fueled PFI internal combustion engine
Authors: Frigo S , Bonini D , Regibus S De , Sguaitamatti L 
Published: December 2023

Abstract
In recent years we have witnessed a renewed interest in the use of hydrogen as a fuel for the land transportation sector, not only for the decarbonisation of the propulsion system but also, above all, as an energy vector for accumulating excess energy deriving from the use of intermittent renewable sources such as wind and photovoltaics.
The present study shows the results of an ongoing research aimed at fine-tuning ready-to-market strategies for the use of hydrogen in ICEs. Starting from a turbocharged engine fueled by natural gas and utilized on light commercial vehicles, a low-cost indirect hydrogen injection system (PFI) was implemented, combined with appropriate injection strategies and boost pressure analysis, this last assuming a fundamental aspect in recovering engine performance that inevitably deteriorates with the use of diluted mixtures.
It is found that the adoption of an air/hydrogen lambda value (λ) ≈ 2.5 allows the utilization of high boost ratios without knocking and backfire and with the possibility of reaching performance similar to the original natural gas fueled engine, with a higher efficiency (> 39 %) and with low NOx emissions (< 200 ppm).
Preliminary experimental data analysis for Digital Twin development of a large bore Dual-Fuel engine
Authors: Mondo Federico Del , Pivetta Davide , Fratti Simone , Parussini Lucia , Padoano Elio , Gallina Paolo , Taccani Rodolfo 
Published: December 2023

Abstract
In recent years, digital models, and in particular Digital Twins (DTs), have seen a growing interest due to their ability to provide support in the development of more efficient systems and processes. This study presents the preliminary steps taken to develop a DT model for a marine Large Bore Dual-Fuel engine manufactured by Wärtsilä. The correlation between dependend and independent data set variables is presented in order to map the engine behaviour and validate the DT model before becoming operational. The analyses are conducted using the engine in gas mode, operating at 85% of Load (at the nominal speed of 600rpm). This operating point represents the typical target design for constant speed applications. The engine efficiency, emissions and combustion chamber parameters are investigated by varying the air-fuel mixture pressure, timing and duration parameters. Sensitivity analysis presents a tight relation between Nitrogen Oxides and Hydrocarbons (HC) emissions by varying the Scavenging Air Pressure. The HC emission function around the nominal value of the Pilot Fuel Injection Duration reverse its trend, while In Cylinder-Pressure and Combustion Duration functions presents opposite gradients. By advancing the Pilot Fuel Injection timing is shown an increase in Engine Efficiency respect to others input parameters.
Influence of E85 on performance and efficiency of a motorcycle engine
Authors: Di Gaetano C , Volza A , Caprioli S , Scrignoli F , Rinaldini C A 
Published: December 2023

Abstract
E85 (85 vol% ethanol and 15 vol% gasoline blend) is one of the most promising sustainable fuels for SI engines, thanks to the optimum trade-off between pollutant emissions and cost of implementation, starting from a pure gasoline baseline.
From the point of view of engine performance, the most relevant differences from such a baseline are related to the heat of vaporization and to the laminar flame speed. The higher heat of vaporization helps to reduce combustion temperature, thus the risk of knocking, but it also slows down the air-mixing process; the small amount of Oxygen in the fuel molecule leads to a slightly different combustion behavior.
The goal of this study is to compare commercial gasoline (E5, 5 vol% ethanol and 95 vol% gasoline blend) and E85, by means of CFD 1D (GT-Power) and 3D (AVL-FIRE) simulations, using experimentally calibrated models. The reference engine is a single-cylinder, four-stroke, PFI motorcycle unit, with a displacement of 463 cc and a maximum power > 30 kW at 9500 rpm.
After the calibration, carried out on the E5 version, the fuel type is changed to E85 in the 1D model, in order to provide accurate Initial Conditions (ICs) and Boundary Conditions (BNDs) to the CFD-3D analysis. Then, a series of combustion simulations are carried out at maximum power operative point (9500 rpm – WOT), varying spark advance and equivalence ratios.
Results reveal that an increase of fuel flow rate and a new calibration of spark timing are needed when the engine runs on E85 to reach performances comparable to the ones obtained with E5. Simulations also show that, moving from E5 to E85, combustion efficiency can be significantly increased, with a small reduction in engine performance.
An estimation of specific emissions, provided by ECFM-3Z combustion model, show that, using E85, CO and HC emissions can be significantly reduced with a small increase of NO emissions, compared to gasoline case.
Can lubricant oil promote undesired self-ignition of the charge in hydrogen engines?
Authors: Distaso E. , Calò G. , Amirante R. , Baloch D. A. , De Palma P. , Tamburrano P. 
Published: December 2023

Abstract
Hydrogen utilization in internal combustion engines is deemed a viable solution for promoting a rapid transition towards a carbon-free mobility, especially for those hard-to-electrify applications. However, critical aspects still poorly understood remain and need to be investigated in order to accelerate the development of such a promising technology. Some of these might originate from the undesired but unavoidable participation of lubricant oil to the combustion process. The present work aims at ascertaining if the lubricant oil chemical characteristics can be at the basis of the onset of certain uncontrolled self-ignition modes of the charge. Considering a lubricant oil droplet suspended in a H2/air environment, an analytical model was developed to derive essential information about mixture composition and thermodynamic conditions that might establish where oil contamination occurs. The results were used to initialize zero-dimensional numerical simulations performed in the OpenSMOKE++ framework with the aim of highlighting charge reactivity variations induced by the presence of oil vapour in the vicinity of an oil droplet. A reduced chemical model, developed for this very purpose in a previous recent work, was employed in the simulations for emulating the reactivity properties of the H2/oil/air mixture.
Instantaneous flowrate measurements in high-pressure liquid flows
Authors: Ferrari A , Pizzo P , Rundo M , Vento O 
Published: December 2023

Abstract
A new flowmeter suitable for high-pressure flows and with a prompt dynamic response is presented. It is constituted by two pressure transducers installed on the monitored high-pressure pipe at a fixed distance one from the other, together with a low-pressure flowmeter that provides a time-averaged flowrate. The measurement algorithm consists of an ordinary differential equation obtained by combining the mass conservation partial differential equation and the momentum balance one applied to the considered piece of pipe comprised between the two pressure transducers. Due to the absence of a master instrument that can be employed as reference to verify the consistency of the measured flowrate, the flowmeter accuracy has been demonstrated by means of numerical models of various hydraulic components, rigorously validated through pressure measurements. The flow ripple of gear pumps has been measured, as well as the flowrate entering a Common Rail injector. For all these cases, the measured flowrate and the one obtained by means of the numerical model are in very good agreement, leading to a robust validation of the presented measurement device.
Acoustic tomography for velocity estimation in high temperature flows
Authors: Ferrari Lorenzo , Sugaroni Antonio 
Published: December 2023

Abstract
Accurately measuring the temperature of a gas flow is essential for monitoring purposes in many energy conversion applications. Typically, this is achieved using either contact measurement techniques, like thermocouple sensors, or radiation-based methods, like optic pyrometry. In harsh conditions, contact measurement techniques are prone to degradation due to the high oxidizing and high-temperature environment, thus reducing sensor lifespan. Radiation-based methods, on the other hand, rely on expensive and highly non-linear transduction systems. Acoustic pyrometry is attracting an increasing interest as it allows the estimation of the temperature distribution in a section by computing the time of flight of acoustic waves. If two measurement sections, at different axial positions, are considered, the same theoretical approach can be adapted to also compute the velocity map of the flow (acoustic tomography). However, the complexity of the mathematical problem to be solved for such a calculation needs a careful analysis. In this study, starting from a known temperature and velocity profile, a reconstruction algorithm was developed and tuned with a particular focus on velocity estimation. Relevant guidelines for a proper application of this measurement technique were also derived.
Cooling Potential Evaluation of a Ground Heat Exchanger in a Tropical Climate: A Case Study of an Office Building
Authors: Austin Miguel Chen , Sánchez David , Bernal Ana 
Published: December 2023

Abstract
The main implications of the hot-humid climate characteristics stipulate the need for cooling indoor environments. Ground thermal characteristics can be exploited in the search for sustainable ways to cool the indoor environment. Thus, this work aims to assess the cooling potential of the ground thermal characteristics through a vertical ground heat exchanger (VGHE) in a tropical climate such as Panama City via dynamic simulation. This potential is evaluated in a two-stories office building complying with Panama’s building regulation requirements, where a VGHE system is designed to cover the cooling needs. Since underground temperature data are unavailable, parametric and sensitivity analyses are carried out. For sizing the VGHE, a vertical ground system is chosen since this allows a better configuration in the installation for a building with large cooling demands and eliminates the need for large amounts of land. A difference of 33.52% (4481.4 kWh) in the electricity consumption for cooling was obtained compared to a conventional air conditioning system, which translates into a 770.80$ saving (0.172$/kWh). These results confirm that the system studied for air conditioning is feasible since it could provide positive results in thermal comfort and energy savings for the user.
A battery-to-electrolyzer pathway for energy management in a hybrid battery/hydrogen microgrid
Authors: Ahmad Athar , Iamarino Mario , D’Angola Antonio 
Published: December 2023

Abstract
A RES-based microgrid with two simultaneous storage options - battery and hydrogen - is considered. While the battery pack serves as a short-term storage solution, the hydrogen-cycle (consisting of an electrolyzer, a hydrogen pressurized tank and a fuel cell stack) provides for a long-term (seasonal) storage in order to improve the system resilience and to allow off-grid operation for longer time. With respect to the most classical energy management approach, where energy is transferred either from PV to battery (as the priority transfer) or from PV to electrolyzer, the novel strategy adopted in this paper also adds the possibility of a battery-to-electrolyzer energy conversion route. This route is enabled whenever the energy stored in the battery is expected to overcome the estimated short-term energy needs. The novel strategy reveals significant potential to increase the hydrogen production during the summer months, by redirecting to the electrolyzer part of the excess energy that would be otherwise curtailed or transferred to an external grid. Application of the strategy during autumn and winter time reveals on the contrary a clear worsening of the microgrid performance and should be avoided.
Hybrid diagnostic approach for the diagnosis of district heating networks
Authors: Losi E , Manservigi L , Spina P R , Venturini M , Castorino G A M 
Published: December 2023

Abstract
Decarbonization of the heating sector is a mandatory target towards climate neutrality by 2050. In this framework, District Heating Networks (DHNs) do play an important role since the heat carrier is dispatched from a heat source to end-users.
Reliability of DHNs can be affected by several faults, of which the negative consequences can be prevented by employing diagnostic methodologies to evaluate the health state of the DHN and promptly localize the fault cause.
In the literature, DHN faults are usually detected by means of physics-based and data-driven methodologies, but their drawbacks may hinder their application. Thus, this paper proposes a hybrid approach composed of two steps aimed at detecting the most common faults occurring in DHNs, i.e., water leakages as well as anomalous heat and pressure losses. First, a data-driven diagnostic methodology is employed to assess whether a fault is occurring. Then, a physics-based diagnostic approach identifies the health indices of each pipe of the DHN, the fault position, its type and magnitude. In this paper, the hybrid diagnostic approach is applied to the DHN of the campus of the University of Parma, where different faults were artificially implanted.
The diagnostic approach proves to correctly detect and identify the implanted faults, by also correctly estimating their magnitude even in the most challenging scenarios.
Potential Role of green hydrogen as an energy carrier in smart energy system communities
Authors: Mojtahed Ali , Ciancio Alessandro , Sgaramella Antonio 
Published: December 2023

Abstract
Smart energy systems refer to the use of advanced technologies and systems to optimize the generation, distribution, and consumption of energy. The main goal of such a concept is to create an intelligent energy infrastructure based mostly on sustainable solutions namely renewable generations. Notwithstanding, renewable energy resources by their nature are unprogrammable. The main challenge is to balance properly the demand and supply curve To do so, various interventions should be employed to improve the reliability of the system (namely: real-time energy consumption monitoring to optimize energy efficiency and integration of energy storage systems). The final outcome is significant energy saving as well as cost reduction and cutting carbon footprint.
Hydrogen is mostly refers to as ‘future fuel’ due to its marvellous properties. It is an energy carrier that is characterized by water and heat as byproducts of combustion. Furthermore, it can be used in a variety of applications, including transportation, power generation, and industrial processes. It can be used in fuel cells to power electric vehicles or blended directly with natural gas to reduce GHG emissions.
The current work investigates the potential role of Hydrogen inside a smart energy system on a community scale. Various contributions are defined for Hydrogen inside a community featuring power to gas, power to vehicles or blending into NG. The layout is composed of hybrid electric, thermal and cooling power generation which is integrated with storage systems. At the end of the simulation, various scenarios are compared to each other in terms of energy performance, economic indicators and environmental impacts to carry out the best suitable option.
Thermal mapping analysis of a 48V prismatic lithium-ion battery pack with active and passive cooling
Authors: Carlucci Antonio Paolo , Darvish Hossein , Laforgia Domenico 
Published: December 2023

Abstract
This experimental study investigates the thermal behavior of a 48V lithium-ion battery (LIB) pack comprising three identical modules, each containing 12 prismatic LIB cells, during five charge-discharge cycles. A homogeneous liquid cooling system is applied at the bottom of the modules to control the pack temperature when it reaches 40°C (active cooling phase). The initial two cycles represent passive cooling, where the cooling liquid remains stationary. Temperature distribution is measured and analyzed using 27 thermocouples, providing insights into temperature changes in the cells, modules, pack, and cooling system inlet/outlet. Results show that in passive cooling cycles, minimum temperature occurs at pack surfaces due to better convective heat transfer, while maximum temperature is observed in the central LIB cells. The active cooling phase alters the temperature distribution within the pack. One module is found to be more sensitive to high currents, generating more heat and releasing it faster. Additionally, the positive tab temperature is higher than the negative tab temperature within a single cell. The liquid cooling system decreases the temperature rise from 5.8°C to 3.5°C in the discharge cycles with a constant current of -237A. This study emphasizes the significance of evaluating the thermal behavior of individual modules and highlights the complexity of the LIB pack system, as well as the impact of an indirect liquid cooling system on enhancing its thermal performance.