1,721,189 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Evaluation of Thermomechanical Properties in a 2D Rotational Elastocaloric Prototype: A Numerical Study for Enhanced Energy Efficiency
No full textSo far, much of the research on the caloric effect has focused on the magnetocaloric effect, which was the first investigated chronologically, in the field of room temperature for about 40 years. Subsequently and especially in the last decade, scientific research has focused on the development of solid-state technologies other than the magnetocaloric one, including the one of interest for this work: elastocaloric technology. This work is part of the “SUSSTAINEBLE” project of the Department of Industrial Engineering at the University Federico II of Naples, aimed at developing the first Italian prototype of an elastocaloric device for environmental conditioning. The prototype is currently in the experimental development phase and its design and construction are dynamically accompanied by a two-dimensional numerical model that fully reproduces its thermo-fluid dynamic operation. The rotary-type prototype consists of 600 Nickel Titanium wires subjected to loading and unloading phases controlled by a properly programmed optical encoder. The thermo-fluidic medium that regulates heat transfer is air. The aim is to characterize the operation of the elastocaloric device using numerical analysis software in order to optimize its geometric, operational, and environmental parameters, to maximize its energy performance in terms of temperature difference, useful thermal power, and coefficient of performance
The energy performances of an elastocaloric device for air conditioning through numerical investigation
Full text linkThe urgent needing to address global warming and the rapid depletion of fossil fuel reserves has led to a demand for immediate research in sustainable and clean energy technologies. Elastocaloric cooling is a promising proposal for clean refrigeration because of the zero global warming potential of the shape memory alloys, which are solid-state materials showing elastocaloric effect. The latter manifests when the shape memory alloys are stressed through a mechanical loading, transforming from the austenite phase toward the martensite one and releasing heat, dually transforming from the martensite phase into the austenite phase and absorbing heat. The updated literature accounts for 15 elastocaloric cooling devices, but none is close to commercialization. The efforts are devoted to making this decisive step by implementing new efficient devices.
This paper analyses the energy performances of an elastocaloric rotary prototype employing binary NiTi wires through the first rotary bidimensional numerical model based on the finite element method to attain the device's potential cooling and heating capacities. In this paper, the energy performances of an elastocaloric rotary prototype employing binary NiTi wires are analyzed through a 2D numerical model based on the finite element method to attain the device's potential cooling and heating capacities. The model reproduces the thermo-fluid-dynamic behaviour of an experimental rotary device for air conditioning; meanwhile, the secondary fluid in the device is air. The accuracy of the rotary model easily allows to optimize the operating parameters of the elastocaloric prototype under construction.
Results in terms of outlet air temperature, cooling power and coefficient of performance are presented for different air velocities inside the air channel and different rotation frequencies of the device. A performance map has been obtained by exploring the device's behaviour in the cooling mode under variable working conditions to identify the optimal configuration. A maximum COP of 6.22 (corresponding to a second law analysis efficiency of 60%) was evaluated under an airflow speed of 6 m s−1 and a frequency of 0.3 Hz, corresponding to
. 28.5 K and 5400 W kg−1 are the reached peaks of temperature span and cooling power
The Application of Barocaloric Solid-State Cooling in the Cold Food Chain for Carbon Footprint Reduction
Full text linkIn this paper, the application of solid-state cooling based on the barocaloric effect in the cold food supply chain is investigated. Barocaloric solid-state technology is applied to the final links of the cold food supply chain regarding the steps of retail and domestic conservation. In this context, effective barocaloric cooling entails the refrigeration of food at 5 °C (273 K) and as such is a promising cooling technology due to its energy efficiency and environmental friendliness. The categories of food involved in this investigation are meat and fresh food products like soft cheese, yogurt, and milk. The energy performance of the barocaloric system is analyzed and compared with a commercial vapor compression refrigerator of a similar size, both operating using R600a under the same working conditions. Based on the results of this comparison, it is concluded that barocaloric cooling is a favorable technology for application in the final links of the cold food supply chain if the system operates in an ABR cycle at frequencies between 1.25 and 1.50 Hz with a regenerator comprising acetoxy silicone rubber as the solid-state refrigerant and a 50%EG–50% water mixture as the heat transfer fluid flowing at an optimal velocity of 0.15 m s−1. Thus, an appropriate tradeoff between the temperature span, cooling power, and coefficient of performance is guaranteed. Under these conditions, the barocaloric system outperforms the domestic vapor compression cooler operating using R600a
CHECK TEMPERATURE: A Small-Scale Elastocaloric Device for the Cooling of the Electronic Circuits
No full textElastocaloric is a technology to the class of solid-state cooling based on caloric-effects have attracted great interest in recent years, representing a new and viable alternative to vapour-compression. The physical phenomenon on which elastocaloric systems are based is elastocaloric effect: a physical-thermal phenomenon manifesting in some materials called shape memory alloys where, consequently to an adiabatic variation of the intensity of an external field, a temperature variation (ΔTad), occurs. If the intensity of the field is increasing, a temperature rise is observed in the elastocaloric material; conversely, to a decreasing intensity a temperature fall corresponds. Controlling the temperature of electronic equipment is also essential and, currently, there are not elastocaloric devices specifically addressed to this application. In this context CHECK TEMPERATURE (acronym of “Controlling the Heating of Electronic Circuits: a Key-approach Through Elastocaloric Materials in a Prototype Employing them as Refrigerants of an AcTive Ultrasmall Refrigerator”) project was born: the main purpose of this project is to develop an elastocaloric device targeted on miniature scale for environmentally friendly cooling of electronic components. In this paper all the aspect concerning the development are described
The Development of a 2D Numerical Model of a Device Using the Elastocaloric Effect to Cool Electronic Circuits
No full textThe scientific community has been working hard lately to develop fresh, environmentally friendly refrigeration technologies. Those based on solid-state refrigerants are among the Not-In-Kind Refrigeration Technologies that show great promises. The one based on the elastoCaloric Effect is among the most interesting of them. This paper presents the development of a 2D numerical model for a device harnessing the elastocaloric effect with the primary objective of cooling electronic circuits. The study focuses on the intricate interplay between mechanical and thermal aspects, capturing the dynamic behavior of the elastocaloric material in response to cyclic mechanical loading. The numerical model incorporates detailed descriptions of the electronic circuits, accounting for heat dissipation and thermal management. Through simulations, the optimal configuration for efficient cooling is explored, considering various operative conditions and mechanical loading conditions (tensile and bending). The findings contribute to the advancement of elastocaloric cooling technology, offering insights into the design and optimization of devices aimed at enhancing electronic circuit performance through effective thermal control. The results that the most promising configuration is based on bending, a design choice resulting appropriate for cooling the electronic circuits
A Numerical Analysis on a Single Bunch of Wires of Susstain-El: The First Italian Elastocaloric Device
No full textRefrigeration is responsible of twenty percent of the worldwide energy consumption and the majority of the systems are based on vapor compression. In the scientific community, elastocaloric refrigeration, belonging to solid-state refrigeration technologies, is increasingly attracting interest, as a valid alternative to vapour compression. It is based on the latent heat generated as a consequence of the austenite-martensite transformation phase, a phenomenon shown by Shape Memory Alloys (SMA) as a consequence of cycles of stress/unstress under adiabatic conditions. The main SMA property is the capability of keeping memory of the initial form and being able to recover it after the remotion of the uniaxial stress (unloading). The elastocaloric effect can be exploited in a regenerative thermodynamic cycle called Active elastocaloric regenerative refrigeration cycle (AeR). The paper reports the data coming out though a numerical analysis by modelling a single bunch of elastocaloric wires crossed by air. The heat transfer and the energy performances have been investigated under a wide set of conditions: different geometrical parameters of the wires and many air flow speed
Development of an electronic circuit cooling system using elastocaloric effect: a FEM comparison among different configurations
No full textIn recent years the scientific community has been committed to finding new eco-friendly solutions for refrigeration. Among the Not-In-Kind Refrigeration Technologies very promising are those based on solid-state refrigerants. Solid-state refrigeration technologies are based on the caloric effect. The nature of the applied field (magnetic, electric, mechanical) particularizes it in: magneto -, electro -, mechano - (elasto - or baro -) caloric effect. Among these, very interesting is the elastoCaloric Effect (eCE) -based one. The aim of the study introduced in this paper is to design and build an elastocaloric device specifically aimed at the cooling of the electronic circuits. At the best of our knowledge, there are not any other caloric solid-state systems specifically developed for this application in open literature. Furthermore, there are not any elastocaloric devices yet developed basing on bending as loading/unloading operation and at the same time thermodynamically exploiting the Active elastocaloric Regenerative refrigeration cycle. This paper reports a preliminary study where two different configurations are compared based on a two-dimensional numerical model. The substantial difference between the two configurations lies in the application of wires loading/unloading: tensile or bending. The device consists of 240 wires of Ni50.8Ti49.2 alloy, for a total mass of 61 g, with a diameter of 0.5 mm and a length of 300 mm crossed by air as heat transfer fluid. In this paper a comparison between the energy performances of the two configurations has been carried out (in terms of temperature span, cooling power and COP): the results reveal that the device based on wires bending gives the best performances (+50 % as COP with bending rather than loading)
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