bluuebunny/crossref_metadata_2025 huggingface dataset:
Historical analysis and refurbishment proposal of the “Red schools” in Viterbo
Authors: Romano Giada , Pennacchia Elisa , Agostinelli Sofia
Published: October 2020

To hinder climate change, EU legislation requires that by 2020 each European state achieves the objectives set by the 2020 Climate and Energy Package. Particular attention is paid not only to new constructed buildings, the so-called Near Zero Energy Buildings, but also to the existing building stock: in Italy in fact, in addition to the National Action Plan to increase the NZEB buildings (PANZEB), the Strategy for Energy Renewal of the National Real Estate Park (STERPIN) is planned. The aim of the thesis work is a primary school built in 1938 within the historical centre of Viterbo. The work touched on three different areas of design: the design of the internal and external spaces, annexed to the school building, finding solutions for a flexible and functional distribution in line with the theories of modern pedagogy, moving from a school of homologation to a school of diversity enhancement.

This was joined by a study concerning the original elevations and constructive features, bearers of historical and aesthetic values, which resulted in the proposal for conservative restoration of the Terranova plaster and the original iron-window profiles.

Finally, attention was paid to energy upgrading and efficiency, in line with regulatory provisions.

The interventions did not only concern the building envelope (through a thermal upgrading of the original iron-windows, the insulation of the flat roof and the indoor thermal coat of the perimeter walls), but also the system (through the replacement of the boiler with a heat pump, integrated with the photovoltaic system placed on the roof, the inclusion of thermostatic valves and lighting design with the replacement of fluorescent lamps with LED ones).
On the optimisation of a direct current (dc) hot-wall refrigerator
Authors: Aprea Ciro , Maiorino Angelo
Published: October 2020

This study presents an experimental investigation conducted on a refrigerator powered by direct current and composed of a 166L cabinet, a condenser embedded in the external wall of the compartment (hot-wall), an internal static evaporator, a hermetic variable speed compressor. The refrigerant fluid used is the R290a, a natural fluid. By placing the refrigerator in a temperature-controlled environment, four external temperatures have experimented: 22, 25, 29 and 32 °C. Three different temperature setpoints have been set for each temperature: -5, -10, -20 °C. In this way, 12 test conditions were defined, and each of them was repeated by imposing four different compressor rotation speeds: 2000, 2500, 3000, 3500 rpm. The set of tests allowed to identify for each operating condition the optimal number of operating revolutions aimed at minimising the energy consumption of the analysed device.
Passive solar systems for buildings: performance indicators analysis and guidelines for the design
Authors: Cillari Giacomo , Fantozzi Fabio , Franco Alessandro
Published: October 2020

Data from the International Energy Agency confirm that in a zero-energy perspective the integration of solar systems in buildings is essential. The development of passive solar strategies has suffered the lack of standard performance indicators and design guidelines. The aim of this paper is to provide a critical analysis of the main passive solar design strategies based on their classification, performance evaluation and selection methods, with a focus on integrability. Climate and latitude affect the amount of incident solar radiation and the heat losses, while integrability mainly depends on the building structure. For existing buildings, shading and direct systems represent the easiest and most effective passive strategies, while building orientation and shape are limited to new constructions: proper design can reduce building energy demand around 40%. Commercial buildings prefer direct use systems while massive ones with integrated heat storage are more suitable for family houses. A proper selection must consider the energy and economic balance of different building services involved: a multi-objective evaluation method represents the most valid tool to determine the overall performance of passive solar strategies.
Refurbishment of a house in a historical building: energy saving, electrification and flexibility
Authors: Romano Giada , Pennacchia Elisa , Agostinelli Sofia
Published: October 2020

Buildings with architectural constraints and recognized historical values require a careful design process, aiming to combine the needs of conservation and the adaptation of the buildings to the modern use and its accessibility. The feasible interventions consist in improving the energy performance of the building envelope, in inserting efficient technological systems and using renewable energy sources where possible. The compatibility between the architectural constraints of the building and its more sustainable future use represents a crucial challenge. This work presents the interventions designed and realized on a small villa located in the Prati district, in Rome. Starting from the requests of the client, the primary objective was to create a comfortable house both in the winter and in the summer season, with widespread use of automation systems for managing the utilities. In line with the current energy scenario, the interventions were oriented to energy efficiency, the reduction of polluting emissions, the electrification of utilities and the use of renewable energy sources. The proposed solutions showed high gains in terms of energy saving even if the changes to the building envelope were limited by the desire to preserve the values of the cultural heritage. Therefore, a virtuous refurbishment can effectively respond to current energy efficiency goals.
Shading and layout influence on flats energy performance of an apartment building
Authors: Nardi Iole , Sarcina Marialisa
Published: October 2020

Giving the need for environment protection and energy need reduction, especially in the building sector, it is important to clearly understand what influences, and to what extent, buildings’ energy performance. In this work, an apartment building has been considered, and the influence of shadings and of flats layout on the energy performance ratings are evaluated. The case study is a building of the ‘90s, which has been demolished and re-built (2016) according to the actual energy requirements. For each of the 16 flats of the building, the energy certificate has been retrieved in the two configurations: before and after reconstruction. From the analysis of the specific energy consumption, and of their components (i.e. energy need for ventilation, transmission losses, solar gains), in the two configurations, a comparison amongst the flats has been drawn. Results show that the apartment layout influences the solar gains, but this influence (in percentage) is higher in the “ex-ante” configuration than in the “ex-post”. Similarly, the energy gains are more relevant in the “expost” configuration, in which some apartments, although having higher dispersing surface, result to be more efficient due to their favourable exposition.
A Machine Learning approach for personal thermal comfort perception evaluation: experimental campaign under real and virtual scenarios
Authors: Salamone Francesco , Bellazzi Alice , Belussi Lorenzo , Damato Gianfranco , Danza Ludovico , Dell’Aquila Federico , Ghellere Matteo , Megale Valentino , Meroni Italo , Vitaletti Walter
Published: October 2020

Personal Thermal Comfort models differ from the steady-state methods because they consider personal user feedback as target value. Today, the availability of integrated “smart” devices following the concept of the Internet of Things and Machine Learning (ML) techniques allows developing frameworks reaching optimized indoor thermal comfort conditions. The article investigates the potential of such approach through an experimental campaign in a test cell, involving 25 participants in a Real (R) and Virtual (VR) scenario, aiming at evaluating the effect of external stimuli on personal thermal perception, such as the variation of colours and images of the environment. A dataset with environmental parameters, biometric data and the perceived comfort feedbacks of the participants is defined and managed with ML algorithms in order to identify the most suitable one and the most influential variables that can be used to predict the Personal Thermal Comfort Perception (PTCP). The results identify the Extra Trees classifier as the best algorithm. In both R and VR scenario a different group of variables allows predicting PTCP with high accuracy.
Control Oriented Modelling of a Turboshaft Engine for Hybrid Electric Urban Air-Mobility
Authors: Donateo Teresa , Cucciniello Ludovico , Strafella Luciano , Ficarella Antonio
Published: October 2020

The electrification of aircraft is a well-established trend in recent years in order to achieve economic and environmental sustainability. In this framework, an application particularly interesting for hybrid electric power system is represented by urban air-mobility. For this application, the authors presented a parallel hybrid electric power system including a turboshaft engine and two electric motors and proposed a quasi-stationary simulation tool. As a further step, this paper deals with the dynamic modelling of the same turboshaft engine within the framework of a hybrid electric system where the pilot command is interpreted as a power request to be satisfied by the engine and the electric machine according to the selected energy management strategy. In this work, the dynamic behaviour of the turboshaft engine is analysed with and without the help of the electric motors to satisfy the power demand.
Feasibility analysis of a hybrid auxiliary power unit for pleasure boats
Authors: Ferrari Lorenzo , Frate Guido Francesco , Giglioli Romano , Girolami Alessia , Pasini Gianluca , Tocchi Federico
Published: October 2020

To reduce the pollutant emissions in the naval sector, the use of alternative fuels and new power generator systems are both promising solutions. In this study, the feasibility of replacing a pleasure boat Auxiliary Power Unit (APU) with a hybrid solution is studied from the economic and technical points of view. Several power generation technologies and layouts are considered. Many configurations were investigated, from hybrid battery/diesel generator to innovative layouts including fuel cell with onboard Liquified Natural Gas (LNG) reforming for hydrogen production. Since hybrid APUs may yield significant advantages in terms of both environmental and noise pollution, the opportunity of operating the system for several hours without powering up the traditional generators is also considered. For each configuration, CO2 and NOx emissions, purchasing and operating costs, as well as weight and volume, are estimated. Emissions may be reduced up to 20 % and 60 % for CO2 and NOx, respectively, and fuel cost reductions up to 35 % may be achieved.
Passenger Car Energy Demand Assessment: a New Approach Based on Road Traffic Data
Authors: Previti Umberto , Brusca Sebastian , Galvagno Antonio
Published: October 2020

Nowadays the automotive market is oriented to the production of hybrid or electric propulsion vehicle equipped with Energy Management System that aims to minimize the consumption of fossil fuel. The EMS, generally, performs a local and not global optimization of energy management due to the impossibility of predicting the user’s energy demand and driving conditions. The aim of this research is to define a driving cycle (speed time) knowing only the starting and the arrival point defined by the driver, considering satellite data and previous experiences. To achieve this goal, the data relating to the energy expenditure of a car (e.g. speed, acceleration, road inclination) will be acquired, using on-board acquisition system, during road sections in the city of Messina. At the same time, the traffic level counterplot and others information provided, for these specific sections, from GPS acquisition software will be collected. On-board and GPS data will be compared and, after considering an adequate number of acquisitions, each value of the traffic level will be associated with a driving cycle obtained by processing the acquired data. After that, the numerical model of a car will be created which will be used to compare the energy demand of two driving cycles. The first one acquired on a section with a random starting and destination point inside the historic city centre of Messina. The second is the one assigned, for that same section, considering only the value of the traffic level counterplot.
Analysis of the integration of the three-way catalyst thermal management in the on-line supervisory control strategy of a gasoline full hybrid vehicle
Authors: Benegiamo Marco , Carlucci Paolo , Mulone Vincenzo , Valletta Andrea
Published: October 2020

Full hybrid electric vehicles have proven to be a midterm viable solution to fulfil stricter regulations, such as those regarding carbon dioxide abatement. Although fuel economy directly benefits from hybridization, the use of the electric machine for propulsion may hinder an appropriate warming of the aftertreatment system, whose temperature is directly related to the emissions conversion efficiency. The present work evaluates the efficacy of a supervisory energy management strategy based on Equivalent Minimization Consumption Strategy (ECMS) which incorporates a temperature-based control for the thermal management of the Three-Way Catalyst (TWC). The impact of using only the midspan temperature of TWC is compared against the case where temperature at three different sampling points along the TWC length are used. Moreover, a penalty term based on TWC temperature has been introduced in the cost functional of the ECMS to allow the control of the TWC temperature operating window. In fact, beyond a certain threshold, the increase of the engine load, requested to speed up TWC warming, does not translate into a better catalyst efficiency, because the TWC gets close to its highest conversion rate. A gasoline P2 parallel full hybrid powertrain has been considered as test case. Results show that the effects of the different calibrations strategies are negligible on the TWC thermal management, as they do not provide any improvements in the fuel economy nor in the emissions abatement of the hybrid powertrain. This effect can be explained by the fact that the charge sustaining condition has a greater weight on the energy management strategy than the effects deriving from the addition of the soft constraints to control the TWC thermal management. These results hence encourage the use of simple setups to deal with the control of the TWC in supervisory control strategies for full hybrid electric vehicles.
Impact of Grid Density on the Analysis of the In-Cylinder Flow of an Optical Engine
Authors: Barbato Alessio , Iacovano Clara , Cicci Francesco
Published: October 2020

The evaluation of Internal Combustion Engine (ICE) flows by 3D-CFD strongly depends on a combination of mutually interacting factors, among which grid resolution, closure model, numerics. A careful choice should be made in order to limit the extremely high computational cost and numerical problems arising from the combination of refined grids, high-order numeric schemes and complex geometries typical of ICEs. The paper focuses on the comparison between different grid strategies: in particular, attention is focused firstly on near-wall grid through the comparison between multi-layer and single-layer grids, and secondly on core grid density. The performance of each grid strategy is assessed in terms of accuracy and computational efficiency. A detailed comparison is presented against PIV flow measurements of the Spray Guided Darmstadt Engine available at the Darmstadt University of Technology. As many research groups are simultaneously working on the Darmstadt engine using different CFD codes and meshing approaches, it constitutes a perfect environment for both method validation and scientific cooperation. A motored engine condition is chosen and the flow evolution throughout the engine cycle is evaluated on two different section planes. Pros and cons of each grid strategy are highlighted and motivated.
Standard and consistent Detached-Eddy Simulation for turbulent engine flow modeling: an application to the TCC-III engine
Authors: Krastev Vesselin Krassimirov , Di Ilio Giovanni , Iacovano Clara , d’Adamo Alessandro , Fontanesi Stefano
Published: October 2020

Multidimensional modeling of Cycle-to-Cycle Variability (CCV) has become a crucial support for the development and optimization of modern direct-injection turbocharged engines. In that sense, the only viable modeling options is represented by scale-resolving approaches such as Large Eddy Simulation (LES) or hybrid URANS/LES methods.

Among other hybrid approaches, Detached-Eddy Simulation (DES) has the longest development story and is therefore commonly regarded as the most reliable choice for engineering-grade simulation. As such, in the last decade DESbased methods have found their way through the engine modeling community, showing a good potential in describing turbulence-related CCV in realistic engine configurations and at reasonable computational costs.

In the present work we investigate the in-cylinder modeling capabilites of a standard two-equation DES formulation, compared to a more recent one which we call DESx. The DESx form differs from standard DES in the turbulent viscosity switch from URANS to LES-like behavior, which for DESx is fully consistent with Yoshizawa’s one-equation sub-grid scale model. The two formulations are part of a more general Zonal-DES (ZDES) methodology, developed and validated by the authors in a series of previous publications. Both variants are applied to the multi-cycle simulation of the TCC-III experimental engine setup, using sub-optimal grid refinement levels in order to stress the model limitations in URANS-like numerical resolution scenarios. Outcomes from this study show that, although both alternatives are able to ouperform URANS even in coarse grid arrangements, DESx emerges as sligthly superior and thus it can be recommended as the default option for in-cylinder flow simulation.
Theoretical and experimental control strategies assessment of a Sliding Vane Oil Pump
Authors: Fatigati Fabio , Di Bartolomeo Marco , Lo Biundo Giuseppe , Pallante Francesco , Cipollone Roberto
Published: October 2020

To date, Sliding Vane Pump (SVP) technology is one of the most attractive solution in different technical applications thanks to its reliability and compactness and capability to keep a high efficiency even when it is working far from rated condition. In particular, this feature makes the SVP suitable to be employed for the oil circulation (SVOP) in Internal Combustion Engine (ICE) which is characterized by a wide oil flow rates variation, delivered pressure and temperature variation which causes operating conditions of the pump far from the design point. Flow delivered changes in these machines are produced by varying the eccentricity for a mechanical connection with the engine - or by varying the speed of revolution. The mild hybridization of the powertrains calls for a strong development of electrically assisted engine auxiliaries which undoubtedly makes the flow variations easier to be done, but the presence of an electric motor requires some technological choices not fully assessed, a cost increase and a reliability decrease. The paper presents a mathematical model of a SVOP for oil circulation in ICE, suitably validated by a wide experimental activity. The model integrates a mono and zero-dimensional fluid-dynamic analysis and allows to represent the intimate behaviour of the machine. Moreover, it was employed as virtual platform to discuss pros and cons of different flow rate variation strategies and their effect on the efficiency of the SVOP.
3D CFD numerical analysis of vane dynamic effects on the pressure ripple in a variable displacement vane pump
Authors: Marinaro Gianluca , Frosina Emma , Senatore Adolfo , Stelson Kim A. , Feng Yuhao
Published: October 2020

A numerical three-dimensional CFD analysis of a variable displacement vane pump has been conducted, investigating the effects on the pressure ripple caused by the vane detaching from the pressure ring. The volume of the fluid over the vane tip has been re-meshed at every time step as a function of the forces acting on the bottom and the top of each vane. The numerical model has been developed using the commercial tool, Simerics MP+, including turbulence and cavitation models. The validation of the model has been done comparing numerical and experimental data. It has been observed that the detachment of the vane occurs during the transition zones when unwanted pressure spikes are generated by a nonoptimized valve plate design. The prediction of vane detachment is crucial for designing a quieter and more durable pump. Vane collision on the stator ring can be a source of noise producing premature wear of both components. Vane detachment from the stator ring has a large effect on pressure ripple even if the volumetric efficiency is only slightly influenced.
On the Design of a Diaphragm Valve for Aerostatic Bearings
Authors: Lentini Luigi , Colombo Federico , Trivella Andrea , Raparelli Terenziano , Viktorov Vladimir
Published: October 2020

Because of their almost zero friction, cleanness and long life, aerostatic bearings are commonly used in many applications where high precision of positioning is required, e.g. machine tools, measuring machines, semiconductor manufacturing and power board testing. However, air bearings suffer from low relative stiffness and poor damping. Active and passive compensation are two effective methods to enhance the static and dynamic performance of these kinds of bearings. Despite their higher performance, active compensation solutions are too expensive to be used in industrial applications, as a consequence of the costs related to their controllers, actuators and sensors. This paper presents the design and performance of a passive compensation method that exploits a diaphragm valve. Thanks to its ease of integration, satisfactory performance and relatively low cost, this method could be a valuable solution to increasing the stiffness of aerostatic bearings. This work provides a procedure to design diaphragm valves depending on the type of the integrated pad and the desired nominal air gap height. Results demonstrate that, once correctly designed, the diaphragm valve makes it possible to obtain bearings with quasi-static infinite stiffness at the selected air gap height.
The Hydraulic Power Generation and Transmission on Agricultural Tractors: feasible architectures to reduce dissipation and fuel consumption – Part I
Authors: Gaiola Andrea , Zardin Barbara , Casoli Paolo , Borghi Massimo , Mazzali Francesca , Pintore Francesco , Fiorati Stefano
Published: October 2020

This paper is aimed at investigating the benefits in terms of energy efficiency of new electro-hydraulic architectures for power distribution systems of a medium-size agricultural tractor, with a focus on the hydraulic high-pressure circuit. The work is part of a wider industrial research project called TASC (Smart and Clean Agricultural Tractors [1]). Traditional and alternative architectures have been modelled and energetically compared through simulation, using a lumped parameter approach. Experimental data previously acquired have been used to validate the models and to replicate real working conditions of the machine in the simulation environment. A typical on-field manoeuvre has been used as duty cycle, to perform an effective energetic analysis. The standard hydraulic circuit is a multi-users load sensing system that uses a single variable displacement pump to feed steering, trailer brake and auxiliary utilities in that order. The key idea of the proposed solutions is the separation of steering from the other implements, to optimize the entire energy management. In particular, the paper investigates new and flexible solutions for the auxiliary utilities, including an electro-hydraulic load sensing architecture with variable pump margin, an electronic flow matching and flow sharing architecture, and an electronic strategy for automatic pressure compensation. The simulation results show that good energy saving can be achieved with the alternative architectures, so that physical prototyping of the most promising solutions will be realized as next step of the project.
Applying Spiroid Winglet on The Tip of NREL 5 MW Offshore Wind Turbine’s Blade to Investigate Vortex Effects
Authors: Fathi Behrouz
Published: October 2020

The present research describes the numerical investigation of the aerodynamics around a wind turbine blade with a winglet using Computational Fluid Dynamics, CFD. In this project our goal is to applying spiroid winglet to examine of the vortex effects on the tip of wind turbine’s blade known as “NREL offshore 5-MW baseline wind turbine”. At present this method has not yet been implemented in the wind energy sector, in particular because their production still involves excessive costs, compared to the benefits obtainable in terms of wind energy field. A spiroid winglet was investigated with different twist distribution and camber in which pointing towards the suction side (downstream). The comparisons have been done between two operating conditions in terms of pressure, thrust, torque, relative velocity, streamlines, vorticity and then mechanical power.
Calcium Looping technology demonstration in industrial environment: the CLEANKER project and status of the CLEANKER pilot plant
Authors: Fantini Martina , Spinelli Maurizio , Magli Francesco , Consonni Stefano
Published: October 2020

The CLEANKER (CLEAN clinKER production by calcium looping process) project got EC support from October 2017 to September 2021 under the Horizon 2020 call LCE 29 – 2017. CLEANKER (www.cleanker.eu) aims at demonstrating at TRL7 (Technology Readiness Level) the Calcium Looping (CaL) concept in a configuration highly integrated with the cement production process, making use of entrained flow reactors.

There are currently no feasible methods to produce clinker, and thus cement, without releasing CO2 from CaCO3, and, given the lifetime of a cement plant, the technologies to be developed have to be retrofittable. In addition to oxyfuel combustion and post-combustion solvent-based capture technologies, which have attracted most of the research efforts up to now, Calcium Looping is recognized as another very promising emerging technology for CO2 capture in cement plants.

The core activity of the project is the design, construction and operation of a CaL demonstration system including the entrained-flow carbonator (the CO2 absorber) and the entrained-flow oxyfuel calciner (the sorbent regenerator). This demonstration system, connected to the Buzzi Unicem kiln of the Vernasca cement plant (Italy), will capture the CO2 from a portion of the flue gases of the kiln, using as CO2 sorbent the same raw meal that is used for clinker production.

The CLEANKER implementation plan spans four years from October 2017 to September 2021.The project is in its crucial phase: the erection of the demo plant is going to be completed by the end of August 2020 and the experimental campaigns will start immediately after.
Multi-Variable Control and Optimization Strategy for Domestic Solar-ORC Combined Heat and Power Generation System
Authors: Vittorini Diego , Antonini Alessio , Cipollone Roberto , Carapellucci Roberto
Published: October 2020

The feasibility of a solar-ORC system for domestic combined heat and power generation (CHP) is deeply affected by both the time-varying ambient conditions (e.g. solar irradiance, temperature, wind speed) and the thermal and electrical load profiles variability of the final application. The definition of a proper control strategy is proven to be a major design-challenge for successful operation of solar-ORC systems, with the main goal of assuring that the thermal power demand for space heating and Domestic Hot Water (DHW) production and the electricity needs are simultaneously satisfied. The rising demand for energy-autonomous systems also calls for the inclusion of a storage system within the base-layout, that could assure the electricity demand is properly matched after sunset or in very-low irradiance conditions, such as cloudy days. A comprehensive model accounts for the dynamic of the plant-integrated unit, featuring an ORC-based plant that bottoms a flat plate solar thermal collector: a parametric study is presented, and an off-design analysis is performed to properly assess the energy performance of the system. The heat availability to the ORC heat exchanger is evaluated, based on solar availability, thermal losses in the pipes and plant requirements, in terms of operating temperature and pressures and organic fluid mass flowrate. R245fa is selected as working fluid in the ORC-section. Sliding vanes machines expander and pump – are considered as rotary equipment. Flat plate heat exchangers complete the base layout, the analysis accounts for. Due to the need for DHW production, a storage unit for hot water is present, upstream the recovery branch: dependently on the ability the fluid at the collector outlet has to meet the ORC requirements for proper operation (about 110°C), the ORC evaporator is fed and the recovery section enabled. Both continuous and unsteady operation underwent an in-depth analysis, as well as the benefits associated with different discharge times for the storage unit. A dedicated control strategy is defined, dependently on whether the electrical output or the thermal one need to be maximized, and accounts for either a flash or a progressive tank discharge. A virtual platform allowed the setting-up of a pilot plant, for direct performance assessment, in presence of different amounts of tank discharges per day and different lower temperatures at the storage tank.
On the wake effect in wind farm power forecasting: a new data-driven approach
Authors: Famoso Fabio , Brusca Sebastian , Galvagno Antonio , Messina Michele , Lanzafame Rosario
Published: October 2020

Wind power generation differs from other energy sources, such as thermal, solar or hydro, due to the inherent stochastic nature of wind. For this reason wind power forecasting, especially for wind farms, is a complex task that cannot be accurately solved with traditional statistical methods or needs large computational systems if physical models are used. Recently, the so-called learning approaches are considered a good compromise among the previous methods since they are able to integrate physical phenomena such as wake effects without presenting heavy computational loads. The present work deals with an innovative method to forecast wind power generation in a wind farm with a combination of GISbased methods, neural network approach and a wake physical model. This innovative method was tested with a wind farm located in Sicily (Italy), used as a case study. It consists of 30 identical wind turbines (850 kW each one), located at different heights, for an overall Power peak of 25 MW. The time series dataset consists of one year with a sampling time of 10 minutes considering wind speeds and wind directions. The output of this innovative model leaded to good results, especially for medium-term overall energy production forecast for the case study.
Optimization and performance assessment of Solar Towers
Authors: Ghirardi Elisa , Brumana Giovanni , Franchini Giuseppe
Published: October 2020

The present paper investigates possible strategies to improve the competitiveness of Solar Towers, considered the best option over CSP technologies. Nevertheless, many aspects still penalize the tower systems, mainly the higher installation costs and the lower energy density. The optimal design of the heliostat layout and the selection of the optimal tower height are fundamental to improve the performance of CRS. A new model for optimizing and simulating solar tower plants, based on an in-house Matlab® code, has been developed and validated. A technical and an economic optimization procedure allows to select the plant configuration with the maximum efficiency or the minimum LCOE, respectively. The case study is focused on a solar field of 6000 heliostats, corresponding to a nominal power of 100 MWe. The tower height shows a strong influence on the heliostat layout and solar field performance; however, the annual energy yield shows a nearly asymptotic behavior when the tower height is increased. An economic optimization leads to a less dense layout to limit the tower impact on the cost; a penalty in efficiency of around 6% can reduce the LCOE of more than 5%. The minimization of land utilization, saving 24% of the occupied area, has a penalization of about 8% in terms of LCOE.
Analysis of Solar District Cooling systems: the Effect of Heat Rejection
Authors: Brumana Giovanni , Franchini Giuseppe , Ghirardi Elisa , Perdichizzi Antonio
Published: October 2020

The paper presents the performance assessment of a solar district cooling system with special attention to the heat rejection process. The investigation includes energetic, economic and environmental aspects. The district cooling network is driven by two-stage Li-Br absorption chillers coupled with parabolic trough solar collectors. The whole system, including solar field, storage tanks and chilled water pipeline, has been modelled in Trnsys. The focus is on the heat rejection systems, and their impact on the performance of the cooling plant. Four different types of heat rejection systems are considered: Air Cooling (AC), Evaporative Cooling Tower (ECT), Groundwater Heat Exchanger (GHE) and Geothermal Boreholes (GB). The paper presents two case studies in the Gulf region: the warm climate is compared for two condition of humidity, dry (Riyadh) and humid (Abu Dhabi). Furthermore, the work presents a multivariable optimization procedure based on GenOpt software interacting with Trnsys model under the constraint of a 70% annual solar fraction. The best option resulted to be the one based on absorption chillers coupled with Groundwater Heat Exchanger in both locations. The annual power consumption is reduced by 83% in Abu Dhabi and 82% in Riyadh compared to conventional cooling systems.
Performance and Emissions Comparison between Biomethane and Natural Gas Fuel in Passenger Vehicles
Authors: Cignini Fabio , Genovese Antonino , Ortenzi Fernando , Valentini Stefano , Caprioli Alberto
Published: October 2020

Bio-methane as fuel in a natural gas engine is a viable solution to reduce greenhouse gas emissions. The present paper illustrates the results of the first set of measurements carried out in the BiomethER project (EULIFE). BiomethER aimed to design and build two innovative bio-methane production plants, located in Emilia Romagna region (Italy), fed by different feedstock: the first one with sewage sludge and the other with landfill waste. Biogas extracted by the anaerobic digester was cleaned and upgraded to biomethane for road vehicles application. To verify the compatibility of biomethane in conventional compressed natural gas engine (CNG) vehicles, three passenger cars have been tested with two gases: conventional natural gas and bio-methane coming by BiomethER sewage sludge plant. Test concerned dynamic performances and exhaust emissions and was operated on the chassis dynamometer facility, in ENEA Casaccia Research Centre. Preliminary results showed no appreciable deviation was noticeable for fuel consumption and CO2 emissions between the two fuels, acceleration and maximum power were almost the same for the three vehicles tested. The WTW evaluation of GHG emissions for the biomethane resulted in up to 79% lower in comparison with natural gas provided by the Italian pipeline.
Analysis of citrus peels-based polygeneration plant for hydrogen, heat, power and DME production: energy and exergy analysis
Authors: Prestipino Mauro , Chiodo Vitaliano , Bonura Giuseppe , Maisano Susanna , Brusca Sebastian , Galvagno Antonio
Published: October 2020

The energy sustainability of producing biofuel from wet bioresidues needs proper energy integration to ensure sustainable exploitation. This study analyses the potentials of combined hydrogen, heat, power, and LOHC (Liquid Organic Hydrogen Carrier) production from the residues of citrus juice production, at a factory scale. In this work, the main constituents of LOHC are DME (Dimethyl ether) and methanol. The proposed system is based on air-steam gasification and direct CO2-to-DME process, integrated with hydrogen purification and a CHP unit. The DME reactor is operated at 30 bar in the temperature range 493-533 K. A thermodynamic model, which is validated experimentally, simulates the proposed polygeneration system. In addition to the potential amount of biofuel, hydrogen production, and net power production, the energy and exergy efficiencies are analyzed. Despite the variation of LOHC yield with the temperature, the results show that the whole system’s energy efficiency is not affected, while the small difference among the exergy efficiencies is negligible.
Port Energy Supply Through An LNG-Powered Integrated Grid
Authors: Borelli Davide , Devia Francesco , Schenone Corrado , Silenzi Federico , Tagliafico Luca
Published: October 2020

Ports are primary importance infrastructures when considering the transportation of people and goods across the planet. Two of the biggest issues linked to harbor areas are the pollutant emissions from moored ships, as well as the huge energy demand coming from ships and other activities that take place inside of the port boundaries. To tackle these challenges, the effort on the ship-side is to promote the transition to Liquefied Natural Gas (LNG) propulsion, while on the harbor-side is to implement electrical ship feeding. In general, using LNG for bunkering purposes implies its storage onshore using dedicated tanks. The regasification of LNG in situ can be exploited to cool down a water-brine flow (i.e. ethyl-alcohol and water). The cold brine can be used to increase the efficiency of a standard inverse cycle to produce cold (i.e. -30°C) used for refrigeration purposes inside ports. Then, the NG flow can be used to produce electrical energy with a standard turbogas cycle with energy recovery from flue gases. The generated electricity directly runs the standard inverse cycle with ethyl-alcohol and water brine to completely fulfill the energy demand for cold thermal power. The electricity still available is then used to supply the onboard systems of moored ships, or otherwise is sold to the users operating in the port. The flue gas coming from the turbogas plant can be used to provide both heating and process heat, through a dedicated heat exchanger and a natural gas boiler. The new envisaged plant can exploit all possible useful effects coming from the regasification process, helping to push towards a greener energy management system in harbor areas, through smart operative integration of the several available energy systems and the implementation of efficient energy smart grids.
CFD analysis of the combustion in the BERL burner fueled with a hydrogen-natural gas mixture
Authors: Capurso Tommaso , Ceglie Vito , Fornarelli Francesco , Torresi Marco , Camporeale Sergio M.
Published: October 2020

The regulatory restrictions, currently acting, impose a significant reduction of the Greenhouse Gas (GHG) emissions. After the coal-to-gas transition of the last decades, the fossil fuel-to-renewables switching is the current perspective. However, the variability of energy production related to Renewable Energy Sources requires the fundamental contribution of thermal power plants in order to guaranty the grid stability. Moving toward a low-carbon society, the industry is looking at a reduction of high carbon content fuels, pointing to Natural Gas (NG) and more recently to hydrogen-NG mixtures. In this scenario, a preliminary study of the BERL swirled stabilized burner is carried out in order to understand the impact of blending natural gas with hydrogen on the flame morphology and CO emissions. Preliminary 3D CFD simulations have been run with the purpose to assess the best combination of combustion model (Non Premixed and Partially Premixed Falmelets), turbulence model (Realizable k ɛ and the Reynolds Stress equation model) and chemical kinetic mechanism (GriMech3.0, GriMech 1.2 and Frassoldati). The numerical results of the BERL burner fueled with natural gas have been compared with experimental data in terms of flow patterns, radial temperature profiles, O2, CO and CO2 concentrations. Finally, a 30% hydrogen in natural gas mixture has been considered, keeping fixed the thermal power output of the burner and the global equivalence ratio.
Investigation on Thermal and Fluid Dynamic Behaviors in Mixed Convection in Horizontal Channels with Aluminum Foam and Heated from Below
Authors: Buonomo Bernardo , Fardella Vincenzo , Manca Oronzio , Nardini Sergio , Vigna Silvio
Published: October 2020

In this paper, mixed convection in a horizontal channel partially filled with a porous medium and the lower wall heated at uniform heat flux is studied experimentally and numerically. A simplified two-dimensional problem is modelled and solved numerically. The domain is made of a principal channel and two channels with adiabatic walls, one upstream and the other one downstream the principal channel. The heated wall temperature profiles as a function of the Ri values are presented. Average Nusselt numbers are evaluated. The experimental test section is made up of a horizontal wall and a parallel adiabatic wall. The distance between the horizontal walls is equal to 40 mm. The porous medium is an aluminium foam and it is placed over the heated lower wall. The porous plate has a thickness equal to 20 mm. The aluminium foam has 10, 20 and 40 PPI. The experiments are performed with working fluid air. The Reynolds numbers investigated are between 5.0 and 250, these being in the laminar regime. The Richardson number, Ri, holds values in the range 1 2000. Results in terms of wall temperature profiles, local and average Nusselt numbers are presented for different Reynolds and Rayleigh number values. Some comparison between experimental and numerical results are accomplished.
Numerical and experimental analysis of thermal penetration depth in bare reinforced concrete structures during fire accidents
Authors: Tagliafico Luca Antonio , Cavalletti Paolo , Cavalletti Alessandro , Marafioti Chiara , Poma Francesco , Sterpi Enrico
Published: October 2020

This work faces the problem of fire resistance and temperature penetration depth in reinforced concrete under construction subjected to fire. Indeed, the design approaches always neglect the fire-induced effects on the structures under construction. In current applications, a lot of information about working boundary conditions during fire, actual material parameters and geometrical details lacks. The paper presents an original approach for the case study of a vertical reinforced concrete element (a stack under construction of the new bridge “Viadotto Polcevera”, Genoa) subjected to a fire accident. Lacking information was retrieved and integrated following a multi-reference approach (numerical simulation, design and operational data, norms). The critical areas of the stack, identified by means of a simplified numerical model, were compared to samples of materials extracted from the construction site and tested in laboratory. Particular attention was given to the model sensitivity to data uncertainties about component geometry, material thermophysical properties and possible thermal effects due to the reinforcement bars extruding from the cast of concrete, acting like fins. The very good agreement between the model and experimental data allowed to identify the minimum volume of stack to be demolished and rebuilt with a significant saving in time and money.
Numerical Investigation on Heat Transfer in Confined Impinging Slot Jets with Nanofluids in Partially Filled Configuration of Metal Foam
Authors: Buonomo Bernardo , Cascetta Furio , di Pasqua Anna , Manca Oronzio , Nappo Sergio
Published: October 2020

In this paper a numerical investigation on mixed convection in confined slot jets impinging on a partially filled configuration of porous medium by considering pure water or Al2O3/water based nanofluids is described. A two-dimensional model is developed and different Peclet numbers are considered. Rayleigh numbers is imposed equal to 30000. The particle volume concentration ranges from 0% to 4% and the particle diameter is assumed equal to 20, 30 and 80 nm. The target surface is heated at constant temperature value, calculated according to the value of Rayleigh number. The distance of the target surface is five times greater than the slot jet width. Three different values of the ratio between the total system length and metal foam length are considered. A single-phase model approach is employed in order to describe the nanofluid behaviour while the hypothesis of non-local thermal equilibrium is assumed to simulate the thermal behaviour in the metal foam. The foam is characterized by a number of pores per inch equal to 5, 10, 20 and 40 and a porosity around 0.90. The aim of the paper consists to study the thermal and fluid-dynamic behaviour of the impinging jet system with nanofluids. Results show increasing values of the Nusselt number for increasing values of Peclet number and nanoparticle concentration. In addition, the ratio between the thermal and pumping power is evaluated to find a trade-off between the increase of heat transfer and pressure drop.
Investigation of a Radial Turbines Compatibility for Small Rocket Engine
Authors: Leto Angelo
Published: October 2020

In the radial turbine preliminary design for an expander rocket engine, a comparison was made with axial turbine used in Pratt & Whitney RL10 engine.

One of the primary requirements of a liquid propellant rocket engine is the generation of a high thrust, which depends on both the mass flow rate of the propellant and the pressure in the thrust chamber.

In expander-cycle engines, which are the subject of the present study, the liquid propellant is first compressed using centrifugal turbo-pumps, then it is used to cool the combustion chamber and the nozzle and, once vaporized, it flows through the turbines used to drive the turbo-pumps.

The aim was to demonstrate the greater efficiency of the radial turbine with a reduction of the pressure ratio with respect to the axial turbine.
Numerical Study of Entropy Wave Evolution within a HPT Stage
Authors: Pinelli Lorenzo , Lilli Leonardo , Arnone Andrea , Gaetani Paolo , Persico Giacomo
Published: October 2020

Component reciprocal interaction and aero-thermal coupling are critical aspects in modern turbomachinery design. Combustors and highpressure turbine (HPT) interaction is extremely critical due to the compact and lightweight system design. In this context, computational and experimental analyses are thus necessary to study the interaction of the high temperature gas coming from combustor systems and entering the turbine in order to avoid engine mis-operations and to lower the indirect core noise generation. This paper presents a numerical study of pulsating temperature distortion (entropy wave) evolution within a high pressure turbine stage. Four different clocking positions between the 11 temperature spots and the 22 stators have been studied. The numerical results, obtained by URANS computations (TRAF code) and by a dedicated post-processing based on Fourier coefficients, have been compared with experimental measurements coming from the Laboratorio di Fluidodinamica delle Macchine (LFM) of the Politecnico di Milano (Italy) where the HP stage rig is located. The excellent agreement between numerical results and experimental acquisitions confirms the accuracy of the numerical approach. Such results also suggest recommendations for the thermal design of the rows and are the main prerequisite for the study of the indirect core noise generation.