bluuebunny/crossref_metadata_2025 huggingface dataset:
Fibroblast growth factor 8b (FGF-8b) enhances myogenesis and inhibits adipogenesis in rotator cuff muscle cell populations in vitro
Authors: Otsuka Takayoshi , Kan Ho-Man , Mengsteab Paulos Y. , Tyson Breajah , Laurencin Cato T.
Published: December 2023

Fatty expansion is one of the features of muscle degeneration due to muscle injuries, and its presence interferes with muscle regeneration. Specifically, poor clinical outcomes have been linked to fatty expansion in rotator cuff tears and repairs. Our group recently found that fibroblast growth factor 8b (FGF-8b) inhibits adipogenic differentiation and promotes myofiber formation of mesenchymal stem cells in vitro. This led us to hypothesize that FGF-8b could similarly control the fate of muscle-specific cell populations derived from rotator cuff muscle involved in muscle repair following rotator cuff injury. In this study, we isolate fibro-adipogenic progenitor cells (FAPs) and satellite stem cells (SCs) from rat rotator cuff muscle tissue and analyzed the effects of FGF-8b supplementation. Utilizing a cell plating protocol, we successfully isolate FAPs-rich fibroblasts (FIBs) and SCs-rich muscle progenitor cells (MPCs). Subsequently, we demonstrate that FIB adipogenic differentiation can be inhibited by FGF-8b, while MPC myogenic differentiation can be enhanced by FGF-8b. We further demonstrate that phosphorylated ERK due to FGF-8b leads to the inhibition of adipogenesis in FIBs and SCs maintenance and myofiber formation in MPCs. Together, these findings demonstrate the powerful potential of FGF-8b for rotator cuff repair by altering the fate of muscle undergoing degeneration.
Local thermal conductivity of inhomogeneous nano-fluidic films: A density functional theory perspective
Authors: Sun 孙 Zongli 宗利 , Kang 康 Yanshuang 艳霜 , Kang 康 Yanmei 艳梅
Published: December 2023

Combining the mean field Pozhar–Gubbins (PG) theory and the weighted density approximation, a novel method for local thermal conductivity of inhomogeneous fluids is proposed. The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations. The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results, and that it performs better than the original PG theory as well as the local averaged density model (LADM). In its further application to the nano-fluidic films, the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated. It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters. Specifically, in the supercritical states, the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature. However, when the bulk density is small, the thermal conductivity exhibits a decrease-increase transition as the temperature is increased. This is also the case in which the temperature is low. In fact, the decrease–increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore. Furthermore, smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation, and then are beneficial to the enhancement of the thermal conductivity. These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.
Formation and dissociation of carbon dioxide hydrate in presence of (NH4)2SO4: experimental characterization of the inhibition produced on the process.
Authors: Gambelli Alberto Maria , Domenighini Piergiovanni , Gigliotti Giovanni , Rossi Federico
Published: December 2023

Gas hydrates are mainly known as potentially alternative energy source and the research is mainly focused in making this source accessible, competitive and carbon neutral, by accompanying the recovery of methane with the permanent disposal of carbon dioxide. However, hydrates formation and dissociation can be advantageously applied in several key processes, such as gas mixture separation, gas storage and transportation, cold energy storage, desalination and waste water treatment. This study deals with these wo latter processes. Carbon dioxide hydrates were formed and dissociated in a pure water mixed with (NH4)2SO4. Two different scopes were pursued: the thermodynamic characterization of the inhibiting action due to the presence of electrolytes diffused in the aqueous phase and the possibility of considering hydrates formation as a potential strategy for NH4
+ removal from water, since the formation of clathrate structures rarely involves ions and other particles diffused in water. A lab – scale apparatus was used for the production of hydrates.
Numerical modelling and process simulation of a post-combustion CO2 capture pilot plant based on a membrane contactor unit
Authors: Cremona Riccardo , Conversano Antonio , Gatti Manuele
Published: December 2023

Hollow fiber membrane contactors (HFMC) have gained prominence in post-combustion CO2 capture applications due to their potential for high mass transfer rates, compactness, modularity and versatility. In this work, two pilot plant design have been proposed, an innovative solution which foresees the membrane contactor as CO2 absorption reactor, and a conventional one based on a packed column absorber. A one-dimensional model based on the resistance-in-series method has been developed for the membrane module and validated against experimental data from literature. The other process units have been simulated in Aspen Plus V11. According to the model results the membrane contactor unit is able to guarantee same levels of CO2 removal rates with improved energy performances compared to the conventional packed column absorber. In particular, if the same reactor volume is considered for the two absorber configurations, a reduction in the specific reboiler duty (SRD) of 8.5% is estimated. On the other hand, if the same liquid-to-gas (L/G) ratio is applied, the HFMC is able to guarantee a required reactor volume almost halved (45% reduction). These substantial improvements of the CO2 capture process could lead to lower investment cost and better economic indicators of the CO2 capture plant.
A simplified approach for energy system design in buildings and its application to a case study
Authors: Migliari L , Cau G , Cocco D , Tola V
Published: December 2023

The present study proposes an easy-to-use procedure for the preliminary design of energy systems for existing buildings based on easily available consumption data. The approach is then applied to a case study represented by the Rector’s headquarter of the University of Cagliari. With the aim of analysing a complex case, the building has been chosen among those with unknown thermal and electrical load subdivision. The feasibility study and subsequent preliminary sizing of a Combined Heat and Power (CHP) system serving the building started through seasonal comparison of electricity consumption data, which also allowed for the subdivision of the building’s electrical and thermal loads and the definition of the electrical base load. The design of the cogeneration system was conducted through the analysis of the electric and thermal demand of the building with quarter-hour resolution, compared among different seasons. The application of the model to the case study allowed for a preliminary design and techno-economic feasibility assessment of implementing a Combined Cooling, Heating and Power (CCHP) system. Besides highlighting the valuable insights that can be obtained through observation and analysis of energy power curves, this paper presents energy indicators that can be utilized to populate benchmarks’ databases for comparable buildings.
To What Extent Is Aeroelasticity Impacting Multi-Megawatt Wind Turbine Upscaling? A Critical Assessment
Authors: Pagamonci L. , Papi F. , Balduzzi F. , Xie S. , Sadique J. , Scienza P. , Bianchini A.
Published: December 2023

Aeroelasticity is recognized as the key enabler that allowed for the massive upscaling of wind turbines in the last decade, leading to long, slender, and flexible blades that equip rotors with lower specific power and unprecedented energy conversion capabilities. In this study, a selection of case studies with increasing size, specifically the NREL 5 MW, the DTU 10 MW, and the IEA 15 MW Reference Wind Turbines (RWTs) is considered to explore to what extent aeroelastic effects impact the functioning of these rotors. The rotors are not only different in size, with the 15 MW having blades nearly double the length of its 5 MW predecessor, but also in technological level as they belong to different phases of wind turbine development. To evaluate how these machines interact with complex inflow conditions, equivalent boundary conditions have been considered for all simulations, including a realistic atmospheric boundary layer, atmospheric turbulence, and wind shear. To carry out the comparative study, a new aero-servo-elastic module called CALMA is introduced herein, by coupling the engineering software OpenFAST with the CFD software CONVERGE, which solves the wind field and provides inflow conditions for the calculation of loads. Results show how not only aeroelasticity increasingly affects the power performance of the new-generation rotors, but is also a key driver of structural design, for example allowing for an alleviation of 1P load variations due to a sheared and turbulent inflow, thus proving that the inclusion of aeroelasticity in the design process is a key enabler to current and future upscaling trends.
Behaviour of a tidal turbine system using a diffuser in waters characterized by low speeds and the presence of surface waves typical of the Mediterranean Sea
Authors: Pucci Micol , Zanforlin Stefania , Conte Valerio Maiorino , Saccardi Alessandro
Published: December 2023

The exploitation of the kinetic energy of the Mediterranean Sea tidal currents is hindered by low speed values. Therefore, it is useful to investigate methods for accelerating the flow to increase both the power generated by the single machine and the specific power, i.e. related to a certain sea surface. The aim of the study is predicting the power gain achievable by means of a diffuser in very low speed conditions and also to analyse the behaviour of the diffuser in the presence of small amplitude and high frequency surface waves, typical of the Mediterranean. Using 3D CFD simulations we predicted the performance of a system of 2 counter-rotating turbines, coupled side-by-side, equipped with a symmetrical convergent-divergent diffuser. The fluid dynamic interaction with the rotating blades is just mimicked by adopting the momentum source low-order approach, that in our case is based on the Virtual Blade Model (VBM). The diffuser not only enables more than doubled power output, but also dampens the relative fluctuation of torque in case of very low wave amplitude; however, in case of significant amplitudes the turbine angular speed needs to be increased in order to avoid stall, and therefore to preserve the blade structural integrity.
Bell-Metha Power Augmented Savonius turbine as Take-off in OWC Systems
Authors: Brusca Sebastian , Galvagno Antonio , Mauro Stefano , Messina Michele , Lanzafame Rosario
Published: December 2023

The present paper deals with the study of ducted Savonius turbine performance to be used as power take-off in oscillating water column systems equipped with a power booster. Two converging sections with a Bell-Metha profile have been used to increase the mass flow rate on the active side of the turbine while masking the resistant part. The Bell-Metha profile was chosen with the aim of reducing vortices immediately upstream of the turbine, avoiding both disturbance and energy loss. A laboratory scale Savonius turbine with a diameter of 0.09 m with an aspect ratio of 1 and an overlap ratio of 1/3 was tested. Performance was tested using a laboratory scale oscillating flow simulator. All tests were performed at fixed air velocity of 5 m/s. Based on the results, it is possible to state that ducted turbine with power augmenter performance is higher than plain ducted turbine ones, at all tip speed ratios.
Climatic change mitigation: analysis of electrical fans usage impact on dwellers heat stress
Authors: Manzan M , Ramezani A , Stella A Buoite
Published: December 2023

Climate change is responsible for a consistent increase in ambient temperatures, leading to social and health problems for individuals residing indoors. The effect should be seriously considered by authorities, especially regarding people’s health; high temperatures can be very dangerous for elder people and in general for vulnerable categories. Mitigation approaches are important in case of heat waves that are expected to increase in frequency and intensity due to climatic change effects. One approach for avoiding such a problem is to install cooling systems, but sometimes this isn’t a viable solution, for example in case of low-income families which cannot afford the expense for the installation and the bill costs for running such systems. An alternative solution is using electric ventilators and the main objective of this paper is to revise the effect of electric fans and assess if they can be useful for mitigating the heat effect on people inside buildings. The results showed that the number of hours with people exposed to heat strain, in the worst-case scenario, dropped from 168 without a fan to 13 with an active fan, confirming the positive effect of this system.
Comparison of Desalination Technologies and Assessment of Their Sustainability
Authors: Chebli Hiba , Fornarelli Francesco , Bellantuono Nicola
Published: December 2023

Water scarcity is a major issue in socioeconomic progress and a threat to livelihood. Overexploitation of freshwater resources threatens food security and sustainable water usage. Countries, therefore, are looking for new ways to ensure the long-term availability of drinking water sources, among which desalination has a prominent role. Several desalination technologies have been proposed during the last decade, which can be classified into two primary categories, i.e. thermal technologies, and membrane technologies. The former include Multi-Stages Flash distillation (MSF), Multi-Effect Distillation (MED), and Mechanical Vapor Compression (MVC), whereas the membrane technologies include Reverse Osmosis (RO), Electrodialysis (ED), and Forward Osmosis (FO). However, all these technologies are energy-intensive and can have significant environmental impacts. In this context, sustainable desalination technologies, such as solar desalination, are essential in solving this issue. The main objective of this paper is to compare the different desalination technologies based on their environmental, technical, and economic aspect. Based on the results, when considering energy consumption, water cost, and carbon dioxide emissions, membrane technology is the most promising option. However, thermal desalination technologies, particularly MED, coupled with Solar energy are technically more interesting compared to the RO.
Supercritical carbon dioxide recovery system applied to cement industries
Authors: Cevolani G , Giovannelli A , Messina G
Published: December 2023

The paper addresses the potential heat-to-power application of supercritical CO2 (sCO2) plants to the cement industry, thereby reducing their electricity demand and improving energy efficiency. The research was conducted as part of the European project CO2OLHEAT (G.A. 101022831), which involves the installation of a 2 MW Waste-Heat-to-Power (WH2P) skid based on a sCO2 cycle in a cement plant, the first of its kind with a MW-scale power output. The paper summarizes technologies and processes employed in the Italian cement production sector, detecting where the waste heat can be successfully extracted to feed the recovery plant without compromising the industrial process. Moreover, the paper discusses the national cement market and explores the potential advantages and limitations of integrating sCO2 recovery plants within the national cement context, considering production and energy-related data. The final finding reveals the percentage of recoverable electricity per technological class for the cement production sector in Italy with a potential application of the sCO2 recovery plant, aiming at identifying the potential market penetration of the CO2OLHEAT installation.
Numerical verification of the condenser finite volume model
Authors: Giovannini Michael , Lorenzini Marco
Published: December 2023

Numerical modelling of vapour compression systems is very useful for performance optimization through the implementation of suitable model-based control applications; in this context the heat exchangers are the most challenging component to devise, due to phase transition and ensuing discontinuities of the physical properties, and one tool which has proven itself suitable for the task is the finite volume method. A numerical verification of a finite volume model of a brazed plate condenser in counterflow arrangement is carried out, employing a fixed timestep solver; some useful guidelines are suggested to properly choose the solver order, the integration step size and the number of grid elements, balancing the accuracy of the predictions with computational time and model stability and flexibility during the transients, with the ultimate goal to provide a model suited for real-time simulations and control-oriented applications.
A Numerical Investigation on Laminar Flame Speed of Syngas in Air with Ozone Addition
Authors: D’Amato Marco , Magi Vinicio , Viggiano Annarita
Published: December 2023

In the context of energy and propulsion systems, in recent years engineering research has increased its efforts to develop more efficient technologies with a lower environmental impact. Specifically, new combustion systems have been investigated, such as ultra-lean combustion and Homogeneous Charge Compression Ignition (HCCI) combustion, and sustainable fuels have been employed. With respect to the latter option, syngas and hydrogen have emerged as attractive choices. However, the low specific energy of syngas and the presence of diluents can cause flame failure and instability. On the other hand, it is well known that ozone-assisted combustion enhances the Laminar Flame Speed (LFS), reduces the ignition delay time, and improves the flame stabilization of fuels such as methane, n-heptane and iso-octane, since it affects the chemistry in the Low Temperature Combustion (LTC) regime. In this context, the aim of the present work is to evaluate the effect of ozone on the LFS of syngas/ozone/air mixtures. Specifically, 1-D simulations have been carried out to compute the LFS of CO/H2
and CO/H2/N2
syngas mixtures. The model has been validated against experimental data available in the scientific literature by considering four different reaction mechanisms. Then, the model has been used to perform a parametric analysis by considering different conditions in terms of syngas composition (three different CO/H2
ratios) and equivalence ratio (from 0.5 to 5). The results show that the addition of 2500 ppm of ozone in air results in an increase in LFS for all equivalence ratios examined. The four different mechanisms give comparable results in terms of LFS and LFS increase for CO/H2
syngas, and are also able to predict ozone effect on LFS enhancement for CO/H2/N2
mixtures. Finally, the results show that the influence of ozone, in terms of LFS percentage increase, is greater for CO/H2
ultra lean mixtures with a lower CO/H2
ratio.
Improving the energy performance of healthcare buildings: a case study
Authors: Grignaffini L. , Grignaffini S. , Vallati A. , Romagna M.
Published: December 2023

The energy issue due to dependence on fossil fuels, pollution, and problems due to climate change are closely related issues. To address them, in recent years, solutions are being studied that provide for different methodologies that exploit alternative sources and technologies capable of reducing the environmental impact. One of the sectors most affected by the problem linked to environmental sustainability is the building sector, as can be read in the European Union directive 91 of 2002: “the energy used in the residential, healthcare and service sectors, made up for the most part of buildings, represents more than 40% of the total energy consumption”. To reduce the environmental load due to construction, it is necessary to study the energy performance of buildings, understand their critical issues and improve their efficiency using systems that exploit renewable energy sources and new construction techniques. In this study, a methodology will be developed to analyse the plant and energy characteristics of healthcare facilities, referring to the “target” buildings of a healthcare complex of Central Italy that will be used as a case study, highlighting all the problems and critical issues. Solutions will be proposed to improve the energy performance of the healthcare buildings, indicating the interventions to be implemented.
A preliminary analysis of the potential reduction of CO2 emissions by using high temperature heat pumps in residential buildings in Italy
Authors: Mongelli D C , Carnieletto L , De Carli M , Busato F
Published: December 2023

The present research aims to provide an innovative contribution to the reduction of fossil fuels and the consequent reduction of CO2eq emissions for each Italian region. Simulations have been carried out to replace space heating boilers supplied with fossil fuels with air to water heat pumps, when the environmental conditions (external temperature, temperature of the water in the emission systems, etc. ) allow it. In order to estimate the potential covering of high temperature heat pumps in Italy energy profiles of buildings have been considered together with the potential COP of heat pumps working with variable climatic control supply temperature. The potential electrification for buildings’ space heating has been estimated subdividing Italy into 21 territorial units. The work has shown that 83% of heating energy which can be covered by the heat pumps in Milan and almost 100% in Lecce. Overall, in Italy 146 TWh of current energy consumed by fossil fuels could be covered by heat pumps; at the same time 45 TWh of electric energy has to be generated to drive the heat pumps.
A numerical study on thermal control of batteries by phase change materials with liquid cooling
Authors: Arumugam A , Buonomo B , D’Arienzo C , Romano P , Manca O
Published: December 2023

The thermal control of the battery system concerns about reduction in heat generation during the operation of battery and the limitations of the vehicles due to the external climatic factors. This study focuses on the attempt to control the battery from external climatic factors and temperature peaks during its operation by the principle of passive thermal management system using phase-change material. A numerical investigation of a three-dimensional model for a cylindrical lithium-polymer battery as a single module is done. The thermal control is realized by a phase-change material for a battery placed inside a parallelopiped and cooled by convective tubes placed at constant temperature and the surface of the module is considered as adiabatic. The governing equations are solved using the Finite Volume method using Ansys-Fluent. The investigation involves 3 different C-rates for two different phase change materials. The results analyse the maximum temperature, temperature distribution and liquid fraction fields for the different cases. The obtained results indicated that for the two different PCM materials namely RT25HC and RT35HC used for the cooling of the batteries the maximum temperature reached by battery and the average temperature of the PCM materials used was observed to be higher in RT35HC.
Modelling of a Gerotor pump including the evaluation of the micro-movements of the external gear
Authors: Totaro G , Zardin B , Borghi M , Scolari F
Published: December 2023

Gerotor pumps are positive displacement pumps used in many applications thanks to their compact size and low cost. On the other side the efficiency of the machine is not so brilliant. In order to study design modifications to decrease energy consumption, a lumped parameter model is a useful tool since it allows predicting and enhancing pump performance. This type of model can be used, once complete, to analyse various phenomena such as cavitation, the chambers’ pressure transient, the flow and pressure ripple, the leakages, and the noise emissions. This work presents a lumped parameter model for the analysis of a Gerotor pump, including the evaluation of the micro movements of the external gear. These micro-movements potentially affect the gap geometry at the internal gear tooth tips and have an impact on the pump’s performance. We modelled the behaviour of the external gear as a journal bearing under dynamic load and then we compared various methods to solve the problem and to find the most suitable method to be coupled with the lumped parameters model of the pump. We incorporated the methods into our global model and evaluated their performance in terms of accuracy and required computational times. The results obtained and the impact on the teeth gaps geometry are finally compared and discussed.
Application of a hydraulic gas bladder suppressor for pressure ripple reduction in gear pumps
Authors: Casoli Paolo , Vescovini Carlo Maria
Published: December 2023

Gear pumps are widely employed in hydraulic circuit but they carry the major drawback represented by the pulsating flow they produce. To improve the capability of the pump to produce a clean and smooth flow rate, many methods have been investigated over time: from the optimization of pump features itself to the introduction of additional systems on the pump delivery side. One system that has demonstrated to be particularly effective is the in-line bladder hydraulic pulsation suppressor, which is part of the passive systems category. This device consists of a bladder gas accumulator with a particularly clever geometry and is the focus of many studies. The study illustrated in this paper has the aim of proposing a lumped parameter model capable of predicting the hydraulic suppressor ripple reduction performance. To test the actual performance of the suppressor and validate the lumped parameter model, an experimental study was conducted, which demonstrated the good effectiveness of device, while a good agreement between modeling results and experimental data was obtained.
Analysis of Flow Rate Distribution in Progressive Divider for Reciprocating Compressor Lubrication
Authors: Benedetti I , Chiavola O , Palmieri F , Tundo L
Published: December 2023

Reciprocating compressors require a correct fluid delivery to each lubrication point. Lubricant defeat means higher component wear and damages, whereas lubricant excess leads to undesired contamination of the processed gas, energy waste and ambient pollution. Two main lubrication systems are used for reciprocating compressors, namely “Pump To Point” (PTP) and “Progressive Divider” (PD) systems. In the first one, there are as many pumps as lubrication points and on each pump unit it is possible to adjust the flow rate delivery. In the second one, a single pump delivers the lubricant to a volumetric flow divider, which provides the metered amount to each lubrication point. A Progressive Divider is modelled under lumped parameter approach, with the aim to highlight its sensitivity to the main operating parameters and to provide awareness about its available operating range. The model is built in Amesim environment and validated thanks to a specific experimental activity that allows to relate the distributed amounts to the lubrication points. The model allows to simulate the PD system under the typical conditions of reciprocating compressors, pointing out its sensitivity on the pressure unbalance among the lubrication points and on the fluid properties. The lumped parameter modelling of PD systems is found to provide reliable information on fluid distribution, effective for design and diagnose activities and for research and development in the field of hydraulic progressive dividers.
Thermal Energy Storage technologies for the optimal management of metal hydride hydrogen storage systems
Authors: Barberis Stefano , Rivarolo Massimo , Sorce Alessandro
Published: December 2023

Hydrogen is an excellent energy carrier that could enable the energy transition, however, storing it in a proper and effective way is one of hydrogen key issues. Storing hydrogen via metal hydrides (MH) can be considered a potential solution to avoid problems (safety, pressurization/liquefaction costs) related to conventional storage systems. A thermal energy storage could be coupled to the MH one, to store the heat obtained from the hydrogen absorption reaction and subsequently to release it to start and support the desorption reaction. This technology allows not to use external sources of heat or of compression, guaranteeing significant energy savings. In this work a MH hydrogen storage system (coupled to a 1 MW electrolyser used in an industrial use case) is studied, focusing on its thermal management supported by a Latent Heat Thermal Energy Storage (LTES) via Phase Change Materials (PCM). The study analyses three different metal hydrides, namely LaNi5, TiFe, TiMn1.5, and phase change materials produced by Rubitherm® Technologies GmbH. A model representing a specific electrolyser case study is then built up, enabling the evaluation of the hourly behaviour of the integrated system, the sizing of the thermal energy storage and to conduct a sensitivity analysis towards the identification of most relevant geometry parameters which affect the techno-economic performances of the system, whose are reported in the concluding part of the paper.
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

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

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

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

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

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

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

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

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

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

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.