1,721,000 research outputs found
Feasibility study of solar cooling thermally driven system configurations for an office building in mediterranean area
No full textThe high temperature values in the summer time in southern Europe involve a high demand of energy for air conditioning. The advantage of solar cooling is the simultaneity of strong sunlight and cooling requirement. In fact, when the demand of electricity reaches extreme peaks for the excessive use of air conditioners, heat energy from the sun it is available. In this paper, an analysis with NEGST (New Generation of Solar Thermal System) feasibility study for a solar cooling plant in southern part of Italy (Naples) is carried out. The building is an office of a chemical industry. It is 48 m long, 23 m wide and 3.5 m high, and 200 people work inside. Thermal loads by machines, people, PC etc. were evaluated by means the software Energy Plus. It is considered three different type of collectors (FPC, ETC and PTC) and two different chillers: single effect for collectors FPC and ETC and double effect (H2O-BrLi) for the collectors PTC. Results are given in terms of solar fraction and PE-Saving for three different configurations. Then, it calculated the payback time for the best plant configuration
Numerical Analysis on the Exploitation of Niti-Based Shape Memory Alloys in an Elastocaloric Device for Air Conditioning
No full textElastocaloric is a promising cooling technique that offers a solid-state alternative to vapor compression. The elastoCaloric Effect (eCE) refers to the reversible changes in temperature and entropy that occur in Shape Memory Alloy (SMA) when loaded/unloaded by an external mechanical load. The research introduced in this paper compares vari-ous Ni–Ti-based SMAs to determine the optimal one to be exploited in an experimental air conditioner. The device can lodge 600 SMA wires in the space stacked by two cylin-ders concentrically arranged, with inner/outer diameter of 250/280mm. Tests are performed while the device rotates at variable frequencies ranging from 0.3Hz to 0.7Hz. A rotary meshing two-dimensional tool has been developed and used to perform the test campaign under variable working condi-tions and NiTi-based SMAs. The energy performances are evaluated and (Ni50Mn31.5Ti18.5)99.8B0.2 resulted in the most suitable SMA showing 2.13kW as peak of cooling power (at a cycle frequency of 0.6Hz and a utilization factor of 0.7) and a maximum COP of 8.35 (at 0.3Hz and 0.7 as utilization factor). This work demonstrates that the use of the (Ni50Mn31.5Ti18.5)99.8B0.2 alloy can enable the device to achieve performances superior to vapor compression-based devices
Developing a prototype of a Not in Kind Heat Pump based on elastocaloric effect
No full textElastocaloric is an emerging cooling solution that, as possible alternative to vapor compression, employs solid-state refrigerants exhibiting the property of changing their temperature as a consequence of a variation of a mechanical stress applied, i.e. elastocaloric effect. The materials showing caloric effects have solid state and therefore they are not provided by Global Warming Potential. The above-mentioned characteristic reflects in the absence of any direct contribution on Total Equivalent Warming Impact (TEWI) for an elastocaloric cooling system. These features attributed to solid-state elastocaloric heat pumping and air conditioning the role of breakthrough ecofriendly technology and the development of sustainable performing prototypes can represent a turning point in the history of refrigeration and heat pumping. The elastocaloric devices developed in the world up to now are a dozen. Among them just one is rotative and Italy has not presented its first elastocaloric prototype, yet. This paper aims to introduce the design and development of SUSSTAIN-EL, the first Italian Not in kind Heat Pump based on elastocaloric technology, whose rotative design coupled with hydraulic pistons represent an innovation in research
Numerical modeling and design of regenerative electrocaloric coolers
No full textThis chapter aims to become a reference point for numerical modeling of regenerative electrocaloric coolers. After having underlined the importance of developing tools to predict the performances of electrocaloric devices, a brief focus on correctly choosing the parameters for developing a consistent model is provided. The core of the chapter is a presentation of the state of the art, in which the most salient, prominent numerical models of regenerative electrocaloric coolers are illustrated and the main results obtained are introduced. At the end, general considerations about the results achieved by the scientific community and future perspectives for this aspect of electrocaloric research are drawn
2D thermo-fluidynamic rotary model of an elastocaloric cooling device: The energy performances
No full textElastocaloric cooling has been considered a promising solid-state technology for cooling and heat pumping among the alternatives to vapor compression, at room temperature range. The technology is based on elastocaloric effect that is a thermophysical phenomenon occurring in materials like Shape Memory Alloys (SMA). The effect is detectable as a temperature change in the material if adiabatically subjected to a forcing field of mechanical nature. The latter provokes to the materials a stress that can derive from tension, compression, bending, torsion solicitations. As a result, the SMA experiments a structural phase change from austenite to martensite (coupled with heat addition) and temperature rise. Dually when the stress is removed, the SMA releases heat with a temperature decrease. In this paper the SUSSTAIN-EL rotary elastocaloric heat pump has been deeply investigated to test the energy performances while it works on open loop and closed loop, through a 2D numerical model based on the finite element method, for cooling and heating operation modes. The device employs a binary NiTi SMA as elastocaloric refrigerant and air as heat transfer medium. A wide set of working conditions has been considered like variable inlet mass flow rate, rotation frequency and thermal loads. The acquired results demonstrate that, both in open and closed loop, the prototype's energy performances are promising and highly favourable for the intended macroscale collocation of the device
Optimized Design of a Rotary elastoCaloric Heat Pump Using Thermofluid-dynamic Analysis
No full textThe most recent information made available to the scientific community claims that a prototype elastocaloric device provides a number of benefits over conventional systems based on vapor compression. Greater energy efficiency is one of the key benefits, as the elastocaloric device method uses less energy than conventional systems. This is accomplished without the use of chemical refrigerants thanks to the elastic deformation of a solid substance utilized as a heat transfer medium. Despite the many benefits, the technology is still in its infancy, and further investigation is required to answer worries about prices, efficiency, and scalability. In general, this technology exhibits potential as a viable and alluring replacement for conventional refrigeration systems. An accurate two-dimensional rotating model of the device's behavior is presented in this paper. The model that can accurately represent the device's dynamic behavior is described. This study presents an optimized geometric configuration of the device that maximizes the energy performance. Along with preliminary performance numbers for cooling power and coefficient of performance, the findings are reported in terms of temperature, velocity, and pressure
Comparison Between Two Different Rotary Configurations of an Elastocaloric Cooling Device
No full textThis paper presents a numerical study of the elastocaloric effect in NiTi wire using two different configu-rations in a rotary prototype, analyzed through a 2D model solved via the finite element method. The focus is on the design of the device’s cold and hot channels, comparing two configurations: the obstacle configuration and the cross-con-figuration. The obstacle configuration includes barriers in the transition area to prevent unwanted mixing between the inlet and outlet air from the cold and hot regenerators, while the cross-configuration features an equidistant arrangement between the inlet and outlet sections to avoid suction phe-nomena at the outlet sections
Experimental Investigation on Fluid Dynamic and Thermal Behavior in Confined Impinging Round Jets in Aluminum Foam
Full text linkIn this paper an experimental investigation is carried out on impinging jets in porous media with the wall heated from below with a uniform heat flux. The fluid is air. The experimental apparatus is made up of a fun systems, a test section, a tube, to reduce the section in a circular section. The tube is long 1.0 m and diameter of 0.012 m. The test section has a diameter of 0.10 m and it has the thickness of 10, 20 and 40 mm. In the test section the lower plate is in aluminum and is heated by an electrical resistances whereas the upper plate is in Plexiglas. The experiments are carried out employing aluminum foams with 5, 10 and 40 PPI and three thickness over the heated circular plate. Results are obtained in a Reynolds number range from 500 to 1500 and wall heat flux from 500 W/m2 to 1400 W/m2. Results are given in terms of wall temperature profiles, local and average Nusselt numbers, pressure drops, friction factor and Richardson number. Moreover, to evaluate the improvement due to the presence of the metal foam, it is necessary a quantitative methodology. In this work an energy performance ratio is employed to compare the performances of surface with and without foams in terms of heat transfer coefficients and pressure drops. Preliminarily experimental results has confirmed that the use of the porous medium improves the heat transfer promoting the heat dissipation of the surface with high efficacy but determines an increase in pressure drops
A Synergistic Multi-Agent Framework for Resilient and Traceable Operational Scheduling from Unstructured Knowledge
No full textIn capital-intensive industries, operational knowledge is often trapped in unstructured technical manuals, creating a barrier to efficient and reliable maintenance planning. This work addresses the need for an integrated system that can automate knowledge extraction and generate optimized, resilient, operational plans. A synergistic multi-agent framework is introduced that transforms unstructured documents into a structured knowledge base using a self-validating pipeline. This validated knowledge feeds a scheduling engine that combines multi-objective optimization with discrete-event simulation to generate robust, capacity-aware plans. The framework was validated on a complex maritime case study. The system successfully constructed a high-fidelity knowledge base from unstructured manuals and the scheduling engine produced a viable, capacity-aware operational plan for 118 interventions. The optimized plan respected all daily (6) and weekly (28) task limits, executing 64 tasks on their nominal date, bringing 8 forward, and deferring 46 by an average of only 2.0 days (95th percentile 4.8 days) to smooth the workload and avoid bottlenecks. An interactive user interface with a chatbot and planning calendar provides verifiable “plan-to-page” traceability, demonstrating a novel, end-to-end synthesis of document intelligence, agentic AI, and simulation to unlock strategic value from legacy documentation in high-stakes environments
elastoCaloric (eC) Cooling: recent studies and preliminary results on materials and devices
No full textRefrigeration is a process aimed at lowering the temperature of an environment compared to the outside temperature. It has always played a fundamental role in modern industry: food, for the preservation of food; in the air conditioning of buildings, to make them habitable and even in the field of medicine and biology, for the preservation of samples and particular therapies. Today refrigeration systems, are responsible for about 17% of the world's electricity consumption. Therefore, the scientific community is researching solid-state refrigeration, which is 50% more efficient than vapour compression systems. Solid-state refrigeration is based on some materials' caloric effect, which can release or absorb latent heat when subjected to an external field (magnetic, electric, pressure or strain) release. Elastocaloric Refrigeration is one of the most minor explored frontiers, unlike magnetocaloric and electro-caloric systems. Some preliminary studies confirm that the eC systems have the advantage of being able to decrease the intensity of the external field (with a relative increase of the COP). In this work, a review on Ec systems is carried out, with particular attention to the description of the properties of the materials used, the various types of stress application. The results have been presented in terms of temperature, entropy, latent heat and COP
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