bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of a Solar Assisted Heat Pump for Building Heating: Control Problems and Improvements
Authors: Tagliafico L. A. , Arteconi A. , Cavalletti A. , Marafioti C. , Marchitto A. 
Published: September 2020

Abstract
Palacus project is a solar assisted heat pump pilot plant in Genoa, Italy. The heat pump combined with solar hybrid photovoltaic thermal panels provides both electrical energy from the solar irradiation and hot water sent into the heat pump circuit. The photovoltaic field covers the energy need of the heat pump and it is even capable of producing extra electrical energy, stored in the national grid through a net-metering, looking for an energetically independent installation. The benefits coming from the net-metering, considered during the design stage, reduced dramatically due to a change in Italian laws concerning feed-in-premium. A brief report on the global facility performance during the past two years is proposed, proving the difficulties of the plant to reach its maximum design potential due to its complexity and problems related to the end users’ “acceptance”. Possible strategies to restore or increase the economic balance of the facility are discussed according to the new feed-in-premium criteria. Supervision and detection of any failure of the plant are performed by means of a large data acquisition system. New related regulation criteria, presented in this work, are compulsory to optimise the plant.
Insight in thermal and fluid-dynamic properties of ribbed ducts by means of a novel clustering method
Authors: Fustinoni Damiano , Vignati Federica , Gramazio Pasqualino , Vitali Luigi , Niro Alfonso 
Published: September 2020

Abstract
The analysis of experimental results on heat transfer by forced convection in diverse ribbed ducts showed that different geometries lead to comparable thermal and fluid-dynamic performances. Moreover, no evident layout has been observed in data, and therefore a statistical clustering analysis is performed to detect the rationale, if any, underlying experimental results. A novel, ad-hoc developed technique is used to disengage the clustering from the data scaling and to account for the measurement uncertainty, consisting of an agglomerative procedure, based on the definition of dynamically-changing bounding boxes, whose size depends on the Nusselt number and the pumping power. Additional informations, such as the the relevance of the diverse geometric parameters and the persistence of similarity among configurations over a range of operating conditions, can be retrieved by means of the developed technique. The described method is applied to a large dataset, obtained during an experimental campaign carried on at ThermALab of Politecnico di Milano, aimed at identifying the Nusselt number and the friction factor for diverse-rib configurations in a large-aspect ratio channel with low-Reynolds flows. The considerations originated from of the results of the clustering analysis suggest the existence of an underlying structure, pointing to a possible unique parameter, termed “generalized blockage”, which is possibly able to describe the global effect of the ribs geometry on forced convection.
Geometric uncertainty propagation in laminar flows solved by RBF-FD meshless technique
Authors: Zamolo R. , Parussini L. 
Published: September 2020

Abstract
The Non-Intrusive Polynomial Chaos method is employed to analyze incompressible and laminar fluid flows in presence of geometric uncertainties on the boundaries, which are described by stochastic variables with known probability distribution. Non-Intrusive methods allow the use of existing deterministic solvers, which are treated as black boxes. Therefore the quantification of the fluid flow uncertainties is based on a set of deterministic response evaluations. The required thermo-fluid dynamics solutions over the deterministic geometries are obtained through a Radial Basis Function-generated Finite Differences (RBF-FD) meshless method. The validation of the presented approach is carried out through analytical test cases (isothermal flow between non-parallel walls) with one geometric uncertainty. The applicability of the presented approach to practical problems is then presented through the prediction of geometric uncertainty effects on the non-isothermal flow over a heated backward-facing step.
Lumped parameter modelling of a thermoelectric cooler for high power electronics
Authors: Casano G , Piva S 
Published: September 2020

Abstract
A detailed analysis based on a lumped parameter model is presented of a cooling system for electronic equipments based on the combination of Peltier cells, air-cooling and liquid cold plate. A comprehensive model, specifically tailored for the cooling system under investigation, is introduced; the whole set of assumptions useful for the description of each element of the lumped parameter model, is described in depth. The model has been calibrated through an exhaustive comparison of numerical results versus experimental data, based on data gathered in experiments already published. Despite the large number of simplifying assumptions, the general good accordance between calculated and measured results demonstrate the reliability of the lumped parameter model, intended to be used for predicting the behaviour of the cooling system for currently untestable experimental conditions. Finally, the model is used as a useful design tool to investigate the cooling circuit under different operating conditions, in order to optimise the cooling solution here proposed.
Thermal properties of wood: measurements by transient plane source method in dry and wet conditions
Authors: Peron F. , Bison P. , De Bei M. , Romagnoni P. 
Published: September 2020

Abstract
Increasing use of wooden material in new constructions and retrofit activities push to a deeper comprehension of properties and specifically thermal properties of different wood species. On one side wooden products on the market are accompanied by few and generic information on the other side analysis of literature confirms a lack of experimental data on thermal conductivity of wood species grown in Italy. In this paper some species of softwood like spruce and larch, and hardwood, like elm, oak and ash are analysed and their thermal conductivities as a function of the equilibrium water content are evaluated by the use of a transient plane source. Results are in line with literature values and, in general, conductivity augments with water content increasing. The relationship between water content and conductivity exploited a linear behaviour for all species.
Saturation temperature effect on heat transfer coefficient during convective boiling in microfin tubes
Authors: Colombo L P M , Lucchini A , Phan T N , Molinaroli L , Niro A , Pozzoni M 
Published: September 2020

Abstract
The growing attention on environmental aspects puts severe constraints on HVAC technology, mainly involving the working fluids and energy efficiency. Both are related to the main limiting factor of HVAC system: the heat transfer process, which, frequently, involves boiling and condensation. To provide suitable tools for the HVAC system design, it is necessary to gather information on the heat transfer characteristics of the new refrigerants. Particular interest is focused on R1234ze(e), because it is one of the viable options to face the R134a phase out. Something similar can be repeated for the low temperature ORC systems using a refrigerant as working fluid. Using a specifically designed test rig, heat transfer coefficient and pressure drop measures were performed during flow boiling of R1234ze(e). The operating conditions were defined by four parameters: the evaporation temperature (5 °C, 35 °C and 45 °C), the mass flux (two values were considered: 160 kg/m2s and 220 kg/m2s), the average thermodynamic quality (which varies between 0.25 and 0.75) and the quality change (which was fixed to 0.2). The uncertainty affecting the pressure drop and the heat transfer coefficient resulted lower than 1% and 5% respectively. The results highlighted that the saturation temperature strongly affects the heat transfer coefficient and the pressure drop: as a consequence of the saturation temperature increase from 5 °C to 45 °C, it was observed up to 40% heat transfer coefficient increase and 90% pressure drop reduction.
Flow boiling of azeotropic and non-azeotropic mixtures. Effect of the glide temperature difference on the nucleate boiling contribution: assessment of methods
Authors: Mastrullo R , Mauro A W , Napoli G , Pelella F , Viscito L 
Published: September 2020

Abstract
Due to the increasing concern about the global warming caused by the use of conventional refrigerants, new HFC/HFO blends are currently proposed to replace high-GWP substances. Most of them, however, present a considerable temperature glide that may negatively affect the nucleate boiling contribution to the heat transfer during evaporation. In this paper, flow boiling data of the new non-azeotropic mixtures R452A and R448A (carrying a high temperature glide of almost 5 °C) and of the conventional quasi-azeotropic blend R404A are provided in a horizontal stainless-steel tube having an internal diameter of 6.0 mm. For all the investigated fluids, the operating conditions explore mass fluxes from 150 to 600 kg/m2s, saturation temperatures from 25 to 55 °C and imposed heat fluxes from 10 to 40 kW/m2, in the whole range of vapor qualities. The nucleative boiling contribution is then isolated from the overall heat transfer coefficient data at disposal and the effect of the heat flux is discussed for both types of blends. Finally, the experimental values and trends are compared to different nucleate boiling correlations taken from literature and conceived for pure fluids, by testing some correction factors explicitly developed for high temperature glide substances.
A new semi-empirical correlation for driving mass-flow rate calculation through ejectors for CO2 heat pumps. Comparison with predictions of other methods.
Authors: Boccardi G , Lillo G , Mastrullo R , Mauro A W , Pieve M , Trinchieri R 
Published: September 2020

Abstract
Carbon dioxide (CO2) is an interesting substitute of traditional HFCs in vapor compression systems, due to its environmentally friendly characteristics: zero ODP and extremely low GWP. Nevertheless, the use of CO2 heat pumps in residential heating and cooling applications actually is still limited, due to the different operating conditions of gas cooling, they can perform significantly worse than conventional.
The use of ejection systems for the fluid expansion in a refrigeration cycle can contribute to recovery part of the mechanical energy otherwise dissipated as friction, leading to significant benefits in terms of performance. The ejector sizing is a critical point for the balancing of components and the correct operation of the CO2 heat pump; in this regard, the availability of reliable methods for calculating the motive flow rate would be useful. In recent years, ENEA Laboratory DTE-PCU-SPCT of the Casaccia research center, along with the Industrial Engineering Department of Federico II University of Naples, carried on a project aimed at evaluating experimentally the effect of several ejectors geometries on the global performance of a CO2 heat pump working with a transcritical cycle.
This paper presents a new semi-empirical correlation for the ejector primary mass flow rate calculation, developed by the experimental data, based on the hypothesis of isentropic and choked flow. The correlation is then tested on other experimental data available in the literature for different ejectors. Finally, the predictions are compared to others semi-empirical correlations present in the literature.
Experimental and numerical activity on a prototype ejector chiller
Authors: Mahmoudian J , Mazzelli F , Milazzo A , Rocchetti A 
Published: September 2020

Abstract
Research activity on ejectors is ongoing at the University of Florence since the late nineties. The most important achievement is a 40 kW ejector chiller designed according to the “CRMC” criterion. The experimentally validated CFD simulations have given some hints about some possible improvements, i.e. refine the surface finish of the ejector, study the effect of heat transfer and improve the final part of the diffuser, which in its present shape does not produce a measurable compression. The prototype has been recently filled with low-GWP refrigerant R1233zd, as a drop-in replacement of previously used R245fa. Both fluids are “dry-expanding” and hence significantly easier to model in CFD simulations. Synthetic low-GWP refrigerants may be an option for ejector chillers, due to their ability to reach below-zero temperature and high volumetric refrigerant capacity. Some lessons learned with synthetic refrigerants can be transferred to the project of a steam ejector chiller, which remains one of our future targets. Herein we resume the principal findings gathered by means of experimental and numerical activity on our prototype and propose a few ideas for the future research.
First experimental results of the use of R1234yf and R1234ze(E) as drop-in substitutes for R134a in a water-to-water heat pump
Authors: Molinaroli L , Lucchini A , Colombo LPM , Bocchinfuso F 
Published: September 2020

Abstract
In the present paper, the first results of an experimental analysis carried out to assess the performance of a water-to-water heat pump in which R1234yf and R1234ze(E) are used as drop-in substitutes of R134a are shown. The heat pump is first tested with R134a to establish a baseline performance and, then, is tested under the same working conditions, i.e. under the same water temperatures at evaporator and condenser outlets, with the above-mentioned HFO refrigerants. The results show that the heating capacity and COP of R1234yf system are up to 9.8% and 6.1% respectively lower than those obtained with R134a. On the other side, the use of R1234ze(E) leads to a capacity reduction and a COP reduction respectively up to 23.1% and 2.5%. A second set of tests is then carried out varying the rotational frequency of the compressor shaft in order to set the heat pump heating capacity to the same value found with R134a. The experimental results demonstrate that increases up to 17% and 50% are respectively needed for R1234yf and R1234ze(E), but subsequent reductions of heat pump COP up to 7.38% and 18.11% arise.
Modelling carbon nano-tubes dynamical behaviour via nonlocal theory – free vibrations and dispersion relations
Authors: Muc A. 
Published: September 2020

Abstract
In the present paper the influence of non-local gradient formulations on the dynamical behaviour (free vibrations and dispersion relations) of carbon nanotubes analysed with the use of 2D shell theory is discussed. At the beginning the compact, consistent approach to the nonlocal (the Mindlin-Tiersten theory) description of 2D carbon nanoshells is shown. The presented results demonstrate the equivalence of free vibration analysis to the normal displacement mode (RBM) of carbon nanoshells. The possible extension of the presented formulations are also discussed.
Development of an Environmental Quality Index to Assess Physical Agents Pollution
Authors: Mancini S , Guida M , Graziuso G , Quartieri J , Guarnaccia C 
Published: September 2020

Abstract
Among the most common techniques and methodologies for the analysis of the exposure to polluting agents, the definition of environmental indexes represents a very useful tool to easily describe the quality of the environment. Based on experimental measurements, an approach using indicators quantitatively and qualitatively describes the ‘health status’ of the environments. For this reason, it is considered one of the most clear and efficient tools to support decisions and actions for the competent control authorities. In this paper the development of a general Physical Agents environmental Quality Index (PAQI) describing the potential impact related to the presence of all the different physical pollutants is discussed. The result is represented by a quantity that measures a weighted combination of sub-indices relating to each pollutant and described by means of an appropriate normalized mathematical function. The main idea is to provide an indicator able to describe, in a clear and concise way, the grade of physical pollution of the environment, suggesting in which areas it would be necessary to intervene or not, in order to improve the general environmental conditions.
Notes on New Physical & Hybrid Modelling Trends for Material Process Simulations
Authors: Horr Amir M 
Published: September 2020

Abstract
The more innovative production techniques for faster, cheaper and better-quality parts have encouraged more ambitious research works on numerical simulation of material & processes designs. A brief description of such ambitious work has been presented in this paper where some explanations of scientific and technical basis for some of latest physical & hybrid trends in material process simulations are concisely discussed. The topics of combining numerical, analytical and data-driven schemes along with evolving & dynamic mesh methods for simulation of dynamic material processes like casting, extrusion, Additive Manufacturing (AM) are also briskly described. Other trends like multi-scale and multi-resolution schemes for solidification (multi-phasing) and cooling applications are addressed, and fresh ideas of hybrid physical-data driven models (using Genetically Algorithm Symbolic Regression, GASR) and their applications are tersely presented. The effects of increasing computational power on hybrid multi-scale modelling and its implications for future of material modellings are also presented shortly. For the short paper herein, it has not been intended to publish the detailed results of new simulation technologies, rather it is focused on describing some new physical & hybrid trends for future of material process simulations.
Nonlocal beam model and FEM of free vibration for pristine and defective CNTs
Authors: Chwał M 
Published: September 2020

Abstract
The natural frequencies of defective single-walled carbon nanotubes are studied and compared with the values for pristine structures. In order to capture the size-dependent effects in carbon nanotubes, nonlocal stress gradient theory within a Euler-Bernoulli beam model is involved. The analytical computations are compared with finite element analysis of a structural model of carbon nanotubes. The numerical analysis of free vibrations is applied to predict the value of the nonlocal parameter. The eigenfrequencies obtained from finite element analysis are much lower compared with analytical computations of local (classical) beam model. For defective structures having small vacancy, a slight decrease in the eigenfrequencies is observed. All studied boundary conditions indicated the higher the nonlocal parameter is, the lower the natural frequencies are.
Modelling nuclear fuel assembly with thermal-hydraulic feedback and burnup using WIMS-PANTHER-Serpent
Authors: Li Jinfeng 
Published: September 2020

Abstract
State-of-the-art deterministic code sequence WIMS-PANTHER and Monte Carlo particle transport code Serpent are employed in this work for computationally modelling the UK EPR nuclear reactor core’s fuel assembly with and without thermal-hydraulic feedback, the results of which targets the government energy policymakers and wider academic community.
Free vibrations and flutter analysis of cylindrical shells
Authors: Augustyn M , Flis J , Muc A 
Published: September 2020

Abstract
The paper present the free vibration and the flutter of multi-layered cylindrical shells using the Rayleigh-Ritz method. The optimal design with constraints imposed on the eigenfrequencies is particularly useful in the selection of dynamic characteristics of structures. For composite cylindrical shells, the fiber orientation variations in individual layers results in an increase (decrease) the critical value of free vibrations. Optimal fibre orientations depends on the shell support and on the geometric parameters of a structure. In the case of the optimal laminate configuration finding, the optimization task cannot be solved using standard FEM software the application and genetic algorithms are required.
Proposal of a simplified Coulomb friction numerical model for the preliminary design of electrohydraulic servomechanisms
Authors: Dalla Vedova M D L , Salente E 
Published: September 2020

Abstract
Electrohydraulic servomechanisms (EHAs) are particularly interesting for aviation application, in fact tanks to the high power to weight ration are widely diffused in medium to large cargo and passengers planes or fighters. This work is focused on the proposal of a new dry friction numerical algorithm, based upon Coulomb’s approach, which can be integrated into simulation algorithms obtained by degrading the systems dynamic models (e.g. an over-damped second-order system reducible to a simpler first-order one). This approach, if correctly applied, significantly reduces the computational burden, without significant losses in simulation accuracy. The authors evaluated the approach proposed by a numerical test bench simulating the behaviour of an electrohydraulic linear actuator commonly used in primary flight controls.
Preparedness for the Emergencies in the City of Kyjov
Authors: Dzermansky M , Pekaj R 
Published: September 2020

Abstract
Population protection represents the fulfillment of tasks in the area of planning, organizing, and carrying out activities to prevent emergence, ensure emergency preparedness and crises and their solution. Among the priorities of individual cities is the protection of the population. For their infantry are planned elements of evacuation, loud warnings, hospital facilities, and more. Extraordinary events may occur unexpectedly, so it is necessary to be prepared for these situations and these purposes are established units of the integrated rescue system.
Analysis of noise annoyance complaints in the city of Milan, Italy
Authors: Zambon G. , Muchetti S.S. , Salvi D. , Angelini F. , Brambilla G. , Benocci R. 
Published: September 2020

Abstract
The paper describes the analysis of noise annoyance complaints submitted by citizens to the Municipality of Milan, Italy, from years 2000 to 2015. These complaints have been organized in a database and analysed according to: i) types of noise sources (technical facilities, music, transport infrastructures, etc.), ii) activities (retail and catering businesses, production, service sector, etc.) and iii) outcomes of the complaints inspection by local authorities. In addition, by means of a Geographic Information System (GIS) software, the spatial distribution of complaints has been determined according to the noise source type and activities, including also a geo-statistical representation by complaints density maps. The results show that, despite the dominant noise source in urban areas is mainly the road traffic, the other noises, such as those from industrial facilities, constructions and social activities (parties, fairs and open air markets, residential noise, etc.), are perceived as more disturbing. Since 2007, the number of noise complaints (about 100-150 complaints/year) is almost constant across the years. However, these complaints are expected to increase due to the growing and spreading of leisure activities, malls, exhibition centres and event venues, observed for the years 2014-2015.