Papers by Giuseppe Starace
Journal of Heat Transfer, 2016
The thermal–hydraulic phenomena in a pebble bed modular reactor (PBMR) core have been simulated u... more The thermal–hydraulic phenomena in a pebble bed modular reactor (PBMR) core have been simulated under steady-state and transient conditions. The PBMR core is basically a long right circular cylinder with a fuel effective height of 11 m and a diameter of 3.7 m. It contains approximately 452,000 fuel pebbles. A three-dimensional computational fluid dynamic (CFD) model of the PBMR core has been developed to study the influence of porosity on the core performance after reactor shutdown. The developed model was carried out on a personal computer using ANSYS fluent 14.5. Several important heat transfer and fluid flow parameters have been examined under steady-state and transient conditions, including the coolant temperature, effective thermal conductivity of the pebble bed, and the decay heat. Porosity was found to have a significant influence on the coolant temperature, on the effective thermal conductivity of the pebble bed, on the decay heat, and on the required time for heat removal.
Cooling Technologies - Technologies and Systems to Guarantee Thermal Comfort in Efficient Buildings [Working Title]
The hybrid method allows the overall performance of a fin and tube evaporator to be determined be... more The hybrid method allows the overall performance of a fin and tube evaporator to be determined beginning from local analysis results and combining the accuracy of the data obtained with a small-scale numerical approach with the low processing costs of the analytical approaches. The program calculates heat transfer rates, pressure drops, and temperature fields for both sides of the heat exchanger using regression equations derived from known data (analytical, experimental, or numerical).The hybrid method has been progressively refined and enhanced with the goal of modeling heat exchangers more closely to actual typologies often used for HVAC application that involve intricate circuit arrangements. In order to aid designers to choose the optimal configuration, various refrigerant circuitry layout choices were examined as well as a proper trade-off analysis was performed.
Volume 3: Engineering Systems; Heat Transfer and Thermal Engineering; Materials and Tribology; Mechatronics; Robotics, 2014
ABSTRACT Evaporative condensers operate at lower temperatures and with a higher efficiency compar... more ABSTRACT Evaporative condensers operate at lower temperatures and with a higher efficiency compared to air condensers, as heat rejection is limited by air wet bulb temperature and mainly caused by water vaporization. This reduces the compressor pressure-lift and improves refrigeration cycle performance. Due to complex phenomena of heat and mass transfer on the tube bundles, modeling the evaporative condensers is a hard task and fine grids in numerical simulations are requested to reach acceptable results. A two-dimensional steady state numerical model at the single tube scale has been developed in Ansys-Fluent (release- 14.5), adopting the VOF multiphase model. Moist air has been treated as a mixture of air and water vapor species, while water vaporization and latent heat have been modeled with a C++ User Defined Function. The tube wall temperature has been assumed constant. The aim of this work is to describe the developed numerical model and to validate it by comparing results obtained at different operating conditions with empirical relationships found in the literature in terms of combined and overall heat transfer coefficients. Combined heat transfer coefficient variation along the tube surface has been analyzed, observing that the heat transfer coefficient is higher in the impingement zone, becomes approximately uniform and rises approaching the trailing edge. Moisture content distributions at different sections through the heat exchanger have been examined in detail as well. This study will be the basis to investigate the performance of the whole condenser taking into account the real evolution of the operating conditions of each single tube in the bundle, whatever its arrangement.
Energies
Finned tube heat exchangers are used in many technological applications in both civil and industr... more Finned tube heat exchangers are used in many technological applications in both civil and industrial sectors. Their large-scale use requires a design aimed at reaching high thermal efficiency as well as avoiding unnecessary waste of resources in terms of time and costs. Therefore, in the last decades, research in this area has developed considerably and numerous studies have been conducted on modeling in order to predict heat exchangers (HXs) performance and to optimize design parameters. In this paper, the main studies carried out on plate-finned tube HXs have been collected, analyzed, and summarized, classifying existing models by their scale approach (small, large, or multi-scale). In addition, the main methods of design optimization with a focus on circuitry configurations have been illustrated. Finally, future developments and research areas that need more in-depth analysis have been identified and discussed.
Biosystems Engineering, 2016
Fifteen HDPE agricultural nets were tested inside a micro wind tunnel (0.1345 m diameter) to esta... more Fifteen HDPE agricultural nets were tested inside a micro wind tunnel (0.1345 m diameter) to establish their characteristic air flow rate vs pressure drop curves with velocities > 4 m s-1. The air pressure drop through the net was accounted for, with reference to the Bernoulli scheme, by means of the loss coefficient. Experimental results confirmed those available in the literature, in terms of the dependence of the pressure drop on the velocity squared and the net porosity, , by means of the function ℎ() = (1 − 2) 2 ⁄. The influence of the orifice geometry was investigated and an effect equivalent to the increase in net porosity was identified in textile pores with elongated shapes. As with previous studies, the loss coefficient trend was found to fit the product of two functions, one depending on the porosity, and the other on the Reynolds number defined using the pore equivalent diameter. The calculated values of the loss coefficient show deviations from experimental results in the range of 19.9 to 41.1%. In addition, a new formulation for the loss coefficient, dependent only on the porosity and wet perimeter was proposed. Except for higher
Experimental and Computational Multiphase Flow, 2019
In this work, a thermal-hydraulic investigation of N2 as a coolant in a pebble bed reactor core h... more In this work, a thermal-hydraulic investigation of N2 as a coolant in a pebble bed reactor core has been performed using a porous media approach. Three different diameters of fuel sphere have been employed for the numerical simulations. The pebble bed reactor is a kind of packed bed reactor whose core is a long right circular cylinder with a height of 3.5 m and an outer diameter of 3.7 m. The finite volume method was used to solve the governing equations using ANSYS FLUENT 14.5. Several important thermal-hydraulic parameters have been investigated consisting of the coolant and solid temperatures, density, pressure drop, and the coolant temperature. Results show that when the fuel sphere diameter increases, the coolant temperature is almost the same, but the solid temperature increases and the pressure drop decreases.
Energies
The global energy and environmental crises are the most urgent issues confronting humanity in the... more The global energy and environmental crises are the most urgent issues confronting humanity in the coming years [...]
Sustainability
This paper focuses on the study of the “greenium”, i.e., the premium on Green Bonds (GBs) vs. Tra... more This paper focuses on the study of the “greenium”, i.e., the premium on Green Bonds (GBs) vs. Traditional Bonds (TBs) whereby investors accept lower yields of GBs vs. TBs, which is caused by the important difference between them with reference to their contribution to the green transition, specifically paying attention to the influence of the COVID-19 pandemic on it. The conjecture of this paper is that the negative shock of rates due to the pandemic crisis has increased the greenium, as it has also increased the interest in projects of the green transition. In addition, a hypothesis is made that the risk of breaking the green promises might be higher for corporations than for governments and, hence, that the greenium would be lower for corporate GBs than for government GBs. Finally, the possibility that the post-pandemic changes of the greenium might vary depending on individual GBs’ liquidity is considered. The empirical analyses provide support for the first two hypotheses but no...
Journal of Cleaner Production, 2023
In the current scenario of transition to a Europe-wide circular economy (CE), the Waste-to-Energy... more In the current scenario of transition to a Europe-wide circular economy (CE), the Waste-to-Energy (WtE) treatments represent a smart solution to generate renewable energy, reduce landfills and ensure sustainable waste management. The costs and environmental impacts of existing WtE treatments are very different for each available technology. In many cases, their identification is affected by a set of variable boundary conditions strongly dependent on local municipal requirements. In light of these considerations, the paper aims to compare the investment in three different WtE treatments (i.e., incineration, gasification, and flameless oxy-combustion) to identify the best solution to support the current transitional phase towards a CE condition. An overall yearly cost analysis was developed by varying local municipal requirements, including investment, operating, and carbon emissions costs. The overall yearly cost and the revenues, due to energy sales and tipping fees, allowed to evaluate the profitability of the investment in the plant lifetime to identify the best WtE treatment. The investment profitability was evaluated by adopting the Net Present Value (NPV) method by estimating the cash flow statement over the entire plant lifetime. The performance of the three WtE treatments, classified as “conventional” (i.e., gasification and incineration) and “innovative” (i.e., flameless oxy-combustion), were compared in a case study concerning Southern Italy's Metropolitan City of Bari. The applied methodology showed, in this case, that gasification, at the moment, has to be deemed as the most sustainable treatment for MSW management. Moreover, the study proved a high dependence between the carbon price and the profitability of the investment and, thus, in the next future the innovative oxy-combustion technology will gain an advantage over all the other technologies, when carbon price will be higher than 44 €/tonnesCO2.
Journal of Cleaner Production, 2023
In the current scenario of transition to a Europe-wide circular economy (CE), the Waste-to-Energy... more In the current scenario of transition to a Europe-wide circular economy (CE), the Waste-to-Energy (WtE) treatments represent a smart solution to generate renewable energy, reduce landfills and ensure sustainable waste management. The costs and environmental impacts of existing WtE treatments are very different for each available technology. In many cases, their identification is affected by a set of variable boundary conditions strongly dependent on local municipal requirements. In light of these considerations, the paper aims to compare the investment in three different WtE treatments (i.e., incineration, gasification, and flameless oxy-combustion) to identify the best solution to support the current transitional phase towards a CE condition. An overall yearly cost analysis was developed by varying local municipal requirements, including investment, operating, and carbon emissions costs. The overall yearly cost and the revenues, due to energy sales and tipping fees, allowed to evaluate the profitability of the investment in the plant lifetime to identify the best WtE treatment. The investment profitability was evaluated by adopting the Net Present Value (NPV) method by estimating the cash flow statement over the entire plant lifetime. The performance of the three WtE treatments, classified as “conventional” (i.e., gasification and incineration) and “innovative” (i.e., flameless oxy-combustion), were compared in a case study concerning Southern Italy's Metropolitan City of Bari. The applied methodology showed, in this case, that gasification, at the moment, has to be deemed as the most sustainable treatment for MSW management. Moreover, the study proved a high dependence between the carbon price and the profitability of the investment and, thus, in the next future the innovative oxy-combustion technology will gain an advantage over all the other technologies, when carbon price will be higher than 44 €/tonnesCO2.
E' oggetto di questo studio l'elaborazione di un modello matematico sviluppato in ambient... more E' oggetto di questo studio l'elaborazione di un modello matematico sviluppato in ambiente Mathcad in grado di simulare il funzionamento di scrubber verticali ad acqua in controcorrente (torri di lavaggio) per la pulizia di syngas da gassificazione di biomasse lignocellulosiche, al fini del suo utilizzo in un motore a combustione interna. Il modello calcola il numero di stadi necessario a soddisfare le specifiche prestazionali dello scrubber in termini di efficienza di abbattimento del particolato e di raffreddamento della corrente gassosa e fornisce indicazioni progettuali sulla scelta dei parametri geometrici e funzionali. La variazione imposta dei parametri funzionali consente, poi, di condurre un'analisi dell'output progettuale, in particolare al variare del rapporto tra portata d'acqua immessa e polverizzata e portat di syngas, della dimensione media dei contaminanti da rimuovere e della temperatura d'ingresso nello scrubber.
Journal of Food Engineering, 2003
The thermo-fluid-dynamic behavior of a dryer, used for the production of a special kind of alimen... more The thermo-fluid-dynamic behavior of a dryer, used for the production of a special kind of alimentary pasta (lasagna), was analyzed, performing both numerical simulations and experimental investigations, in order to improve the dryer thermal performance. In particular, the achievable improvements in terms of temperature distribution, obtained by modifying the control of air distribution and the geometry of air distribution channels, were analyzed. The numerical simulation suggested the design of some modifications of the actual dryer. Particularly, the air distribution was improved and the natural vertical stratification of the drying air was reduced, implementing a new geometrical configuration with some vertical and horizontal panels. An experimental campaign on the dryer was carried out, confirming the trends obtained using the computer code. The percentage of pasta defects was reduced from 30% down to 10% thanks to a more controlled air distribution.
Electronics
This work discusses smart building applications involving the Internet of Things (IoT) which are ... more This work discusses smart building applications involving the Internet of Things (IoT) which are focused on energy consumption monitoring and forecasting systems, as well as indoor air quality (IAQ) control. Low-cost hardware integrating sensors and open source platforms are implemented for cloud data transmission, data storage and data processing. Advanced data analytics is performed by the seasonal autoregressive integrated moving average (SARIMA) method and a long short-term memory (LSTM) neural network with an accurate calculation performance about energy predictions. The proposed results are developed within the framework of the R&D project Data System Platform for Smart Communities (D-SySCOM), which is oriented to a smart public building application. The main goal of the work was to define a guideline-matching energy efficiency with wellness in public indoor environments, by providing modular low-cost solutions which are easily implementable for advanced data processing. The i...
Handbook of Research on Advances and Applications in Refrigeration Systems and Technologies
This chapter focuses on the Diffusion Absorption Refrigerator (DAR) cycle and describes a new adv... more This chapter focuses on the Diffusion Absorption Refrigerator (DAR) cycle and describes a new advanced thermodynamic model which allows good predictions of the chiller performance in terms of efficiency and cooling capacity, starting from a precise evaluation of the thermo-physical properties of the working mixture at each point of the circuit. A steady state thermodynamic analytical model of the thermal pump driving the DAR is also included. In addition, the experimental validation of the model, performed on a prototype built coupling a domestic 750 W-magnetron with a small purposely modified commercial DAR to activate the thermal pump, is here included: a maximum mismatch of 2.32% in the weak mixture mass flow rate and lower than 5% in COP between the predicted and measured data were found.
Sensors
Complex energy monitoring and control systems have been widely studied as the related topics incl... more Complex energy monitoring and control systems have been widely studied as the related topics include different approaches, advanced sensors, and technologies applied to a strongly varying amount of application fields. This paper is a systematic review of what has been done regarding energy metering system issues about (i) sensors, (ii) the choice of their technology and their characterization depending on the application fields, (iii) advanced measurement approaches and methodologies, and (iv) the setup of energy Key Performance Indicators (KPIs). The paper provides models about KPI estimation, by highlighting design criteria of complex energy networks. The proposed study is carried out to give useful elements to build models and to simulate in detail energy systems for performance prediction purposes. Some examples of energy complex KPIs based on the integration of the Artificial Intelligence (AI) concept and on basic KPIs or variables are provided in order to define innovative for...
Antioxidants, 2021
Tomato (Solanum lycopersicum L.) is one of the most consumed vegetables worldwide due to its low ... more Tomato (Solanum lycopersicum L.) is one of the most consumed vegetables worldwide due to its low caloric intake and high fiber, minerals, and phenolic compounds, making it a high-quality functional food. However, fruit quality attributes can be affected by pre-harvest factors, especially environmental stresses. This research aimed to evaluate the influence of two shading nets (white net −30% and pearl grey net −40% shading degree) on the yield and phytochemical profile of tomato fruits grown in summer under the Mediterranean climate. Mineral and organic acid content (by ion chromatography-IC), phenolic profile (by ultra-high performance liquid chromatography-UHPLC coupled with an Orbitrap high-resolution mass spectrometry-HRMS), carotenoid content (by high-performance liquid chromatography with diode array detection-HPLC-DAD), and antioxidant activities DPPH, ABTS, and FRAP (by UV-VIS spectrophotometry) were determined. Tomato fruits grown under the pearl grey net recorded the highe...
Journal of Thermal Analysis and Calorimetry, 2021
In refrigeration systems, evaporative condensers have two main advantages compared to other conde... more In refrigeration systems, evaporative condensers have two main advantages compared to other condensation heat exchangers: They operate at lower condensation temperature than traditional air-cooled condensers and require a lower quantity of water and pumping power compared to evaporative towers. The heat and mass transfer that occur on tube batteries are difficult to study. The aim of this work is to apply an experimental approach to investigate the performance of an evaporative condenser on a reduced scale by means of a test bench, consisting of a transparent duct with a rectangular test section in which electric heaters, inside elliptical pipes (major axis 32 mm, minor axis 23 mm), simulate the presence of the refrigerant during condensation. By keeping the water conditions fixed and constant, the operating conditions of the air and the inclination of the heat transfer geometry were varied, and this allowed to carry out a sensitivity analysis, depending on some of the main paramete...
Agriculture, 2019
The effectiveness of experimental nets in preventing the access of adult meadow spittlebug Philae... more The effectiveness of experimental nets in preventing the access of adult meadow spittlebug Philaenus spumarius L., the main vector of Xylella fastidiosa Wells et al. subspecies pauca, sequence type (ST) 53, in olive tree nurseries and orchards was evaluated. To optimize the net design, mesh size, kind of fabric, thread typology, and radiometric properties, six nets with different mesh sizes and kinds of fabric were evaluated in laboratory and in field experiments. Laboratory bioassays evaluating the capability of adult spittlebugs to pass through nets with different mesh sizes (1.2, 1.8, 2.4 mm) showed that all nets with a mesh size equal to or lower than 2.4 mm prevented insect crossing. These results were confirmed in field conditions using an experimental net box apparatus. Further laboratory tests showed a positive correlation between porosity and radiometric properties of the nets. Three prototypes of thermally stabilized flat woven nets made of circular cross-sectional yarns, ...
E3S Web of Conferences, 2021
The plate-finned tube evaporator performance, in terms of heat transfer rate and refrigerant pres... more The plate-finned tube evaporator performance, in terms of heat transfer rate and refrigerant pressure drops, is influenced by several choices done during the design process to be carried out complying with different constraints. In this paper different refrigerant circuitry layout options together with other parameters variations were investigated with the purpose of supporting designers. Performance predictions were calculated using the hybrid method as well as appropriate Performance Evaluation Criteria (PEC) were adopted to select the best layout. The hybrid method has been here revised and improved aiming at modelling heat exchangers with an approach closer to real configurations that include complex circuit layouts. The method was chosen as its main advantage (high accuracy in the results with low computational costs) allowed to easily perform operating conditions modifications to be compared.
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Papers by Giuseppe Starace