101,901 research outputs found
Development and numerical modelling of a supercharging technique for positive displacement expanders
No full textThis study presents a novel strategy to enhance the recovery performance of any positive displacement expander technology which aims at the maximization of the power output rather than solely its efficiency. The approach is based on an auxiliary injection of fluid under the same suction conditions as the main intake but during the closed volume expansion phase. The operating principle of the supercharging technology is firstly outlined in theoretical terms, while the benefits over a conventional configuration are numerically assessed with reference to a sliding vane expander for applications based on Organic Rankine Cycles (ORC). The holistic modelling platform used for the benchmarking is preliminarily validated over an experimental campaign in which the vane expander was installed in a heavy-duty automotive ORC system and generated up to 1.9 kW (3% of the engine mechanical power) with an overall efficiency of 51.2%. After the simulation platform is validated, the auxiliary intake line is parameterized in terms of four geometrical quantities and the effects of the supercharging with respect to baseline angular pressure trace are shown. An optimization based on a genetic algorithm is eventually performed and the resulting optimized design led to an average mechanical power increase of 50.6%
UTILIZZO DELLA SPETTROSCOPIA RAMAN E FT IR (ATR) SU UN DIPINTO SU TAVOLA DI SCUOLA NAPOLETANA DEL SECOLO XVII:ANALISI E RESTAURO DEL SAN GEROLAMO NEL DESERTO.
No full textLa ricerca illustra l’importanza della collaborazione tra scienza e restauro. Come caso esplicativo si presenta l’analisi e il restauro del “San Gerolamo nel deserto”, un dipinto su tavola del XVII secolo di scuola napoletana. Si indica un percorso da leggere come una “stratigrafia” in cui, dal supporto alla vernice protettiva, si analizzano in successione le tipologie dei materiali artistici e le tecniche di esecuzione, il tutto costantemente supportato dalle indagini diagnostiche. Una volta terminata la fase conoscitiva del manufatto, ossia integrando le ricerche scientifiche con accurate ricerche storiche, storico-artistiche e archivistiche, si è proceduto con la stesura del progetto e la realizzazione dei restauri
Model-based optimisation of solar-assisted ORC-based power unit for domestic micro-cogeneration
No full textIntegrating flat solar thermal collectors and organic Rankine cycle (ORC)-based power units in microcogeneration systems ensures a reduction in CO2 emissions in domestic applications. The key component of these systems is the expander, which must withstand frequent off-design operating conditions owing to the intermittent nature of the solar source. Despite being in the first stage of technological development, scroll expanders are widely adopted in small-scale applications owing to their operating flexibility and robustness. In this study, a domestic micro-cogeneration unit equipped with a scroll expander is characterised experimentally. The experimental data are used to calibrate the expander and ORC unit models. The models are used to evaluate the operating limits of the units as functions of the main operating parameters. The maximum power and efficiency are obtained as 300 W and 3 %, respectively, for hot water temperatures between 90 degrees C and 100 degrees C, close to the rated performances. Finally, the effect of adopting a dual-intake port on the expander and unit performance is assessed. The technology facilitates the widening of the operating range (20-140 g/s mass flow rate of WF) and a peak power production of 1.2 kW
Design improvement of volumetric pump for engine cooling in the transportation sector
No full textInternal combustion engine (ICE) thermal management is one of the most attractive methods for reducing both fuel consumption and harmful emissions. Conventional ICE cooling uses a dynamic centrifugal pump, which is generally designed based on the maximum ICE power. Unfortunately, such devices present significant efficiency reductions when they are operated far from the design point. Therefore, a sliding vane rotating pump (SVRP) has been considered as a substitute for the centrifugal pump because its efficiency is not dependent on the revolution speed and head pressure. This study developed a mathematical model that could be used for designing and simulating an SVRP. Then, an SVRP was built and tested, and the results validated the model under a wide range of operating conditions. Once validated, the model was used as a software platform to improve the SVRP design using a novel approach based on the optimisation of the ports and shape. Moreover, the benefits of this SVRP were assessed by comparing electrical and mechanical actuation using the Worldwide Harmonised Light Vehicles Test Procedure (WLTP). A pump energy reduction of approximately 30% and a CO2 emission reduction of up to 1.4 g/km were obtained
Experimentation of a PVA-Borax hydrogel for the removal of Paraloid B72® from artifacts of archaeological interest from the National Archaeological Museum in Naples, Italy
No full textThis paper shows the results of an experimentation aimed at the removal of a polymeric film of aged Paraloid B72® originally placed to protect some wooden artifacts belonging to the Egyptian collection of the National Archaeological Museum of Naples (MANN). The study was conducted on two shabtis dated to the 19th Dynasty and a sculpture of Ptah-Sokar-Osiris dating to the late period. Thanks to the collaboration between the National Archaeological Museum of Naples and the Laboratory of Restoration of Wooden Artifacts of the University of Naples Suor Orsola Benincasa, it was possible to conduct an in-depth study of the artifacts, from both an archaeological-historical point of view and from a conservation point of view. This led to the development of the above-mentioned experimentation and to the planning of a proper restoration intervention. The study and experimentation were supported by several diagnostic techniques. In a first stage, non-invasive investigations were carried out to study the execution technique and the state of conservation of the artifacts. This allowed the recognition of the wood species that constituted the three sculptures through optical microscopy, whereas IR reflectography, UV induced fluorescence and X-ray radiation (XRF) were conducted to identify the type and the chemical nature of the pigments. Based on the above analysis, different restoration strategies, based on the removal of Paraloid B72® through a methodology that would act in full respect of the wooden support of the artifacts, were considered. Pros and cons of the different methodologies applied in the recent past for the removal of aged Paraloid from artifact surfaces were analysed. A removal technique based on the use PVA-Borax hydrogel loaded with a solvent mixture was selected. Experiments were conducted to validate the effectiveness of the selected method
Modeling and Experimental Activities on a Small-scale Sliding Vane Pump for ORC-based Waste heat Recovery Applications
No full textPumping work in energy recovery units based on Organic Rankine Cycles (ORC) can severely affect the net power output
recovered. Nevertheless, in recent years scientific and industrial communities mainly focused on expanders’ development. In
order to address this lack of know-how and equipment, the current paper presents the development of a positive displacement
ORC pump based on the sliding vane rotary technology. The machine was installed in a power unit for low-medium grade
thermal energy recovery that operated with oil at 70-120°C as upper thermal source and tap water as lower one. Working fluid
was R236fa while cycle pressure ratio ranged from 2.8 to 3.7. The ORC pump was also tested at different revolution speeds such
that mass flow rate varied between 0.05 kg/s and 0.12 kg/s. These experimental data were further used to validate a
comprehensive one-dimensional model that takes into account fluid dynamic filling and emptying processes, closed vane
transformation and leakages at blade tip, rotor slots and end walls clearances. Viscous and dry friction phenomena occurring
between components in relative motion were additionally considered. A full operating map of the sliding vane pump was
eventually retrieved to explore multiple off-design operating conditions. The parametric and modular structure of the model will
act as a design platform to outline enhanced ORC sliding vane pump prototypes
Design and analysis of a sliding vane pump for waste heat to power conversion systems using organic fluids
No full textThe current research work assesses the relevance of pumping work in energy recovery systems based on bottoming Organic Rankine Cycles (ORC) and presents the development of a sliding vane pump prototype for small scale units. The novel device was installed on an ORC-based power unit for waste heat to power conversion in compressed air applications in which the heat source was a compressor lubricant while the heat sink was tap water. Tests were performed with R236fa as working fluid at different pressure rises (3.9-9.7) and revolution speeds (500-1300 RPM). The experimental dataset was used to validate a numerical one-dimensional CFD model of the sliding vane pump developed in the GT-SUITE™ environment. The model takes into account the fluid dynamics and friction phenomena that are involved in the pump operation such as vane filling and emptying, leakages as well as dry and viscous friction between components in relative motion. The modelling platform was further exploited to retrieve performance maps of the pump, angular vane pressure evolution as well as to break down leakage and friction losses. The effects of geometrical features on the pump performance were eventually investigated through variations of the aspect ratio. With reference to the best experimental operating point (pressure rise 9.7, revolution speed 1250 RPM), simulations showed that, with a stator 5% bigger than the nominal one and the length almost halved, overall pump efficiency could be increased from the experimental 36.9% to a value of 48.0%. © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (https://
creativecommons.org/licenses/by/4.0/)
A procedure for combining the removal and the identification of a patina on a 15Th century byzantine icon
No full textIn our paper, we report a workflow, which combines cleaning procedures and Gas Chromatography Mass Spectrometry (GC-MS) for the removal and the identification of a patina from a byzantine 15th century icon representing the Virgin and Child. Our strategy suggest a convenient interaction between restoration procedures and analytical methodologies aimed at the cleaning of the surface of the artwork and the identification of unknown compounds responsible for its alteration. These informations can be very useful not only to return the colors to their original brightness but to reconstruct the story of the icon to
Experimental and theoretical analysis of a micro-cogenerative solar ORC-based unit equipped with a variable speed sliding rotary vane expander
No full textA promising solution for the Combined Heat and Power (CHP) micro production is certainly represented by Organic Rankine Cycle (ORC)-based power units. In the domestic appliances with electrical power range of the units below 1 kW, the reduced dimensions of the components represent a critical aspect as well as the need to guarantee a high reliability. When the hot source is represented by solar energy, the optimization of the electricity production keeping insured the thermal energy availability represents an aspect which invites to a proper management of the unit. Solar-based ORC-recovery units frequently work in off-design conditions due to the variability of the hot source and to the Domestic Hot Water (DHW) requirements. For this reason, the design and the selection of the components should be carefully performed. The expander is commonly retained the key component of the unit being the one that mainly affects the behaviour. For the mentioned power ranges, the volumetric expander is the best technological option and, among those available, Sliding Rotary Vane Expander (SVRE) are gaining a sensible interest. At off design conditions, according to permeability theory, the expander intake pressure linearly varies with mass flow rate of the Working Fluid (WF) which is the most suitable and easiest parameter to be changed. This modifies the performances of the unit, both from a thermodynamic and technological point of view. In this paper, the speed variation of the expander is considered as control parameter to restore design expander intake pressure. In order to assess a strategy for the speed variation of the expander, in this paper a comprehensive model of the SVRE is presented when it operates in a solar-driven ORC-based unit. The model is physically based and recovers and widens the permeability theory developed by the authors in previous works. An experimental ORC-based unit was fully instrumented and operated, coupled with a reservoir, usually present when flat plate solar collectors are used, which store the thermal energy which fulfils thermal energy requests and feeds the generating unit. The model was widely validated with the experimental data properly conceived for the purpose. In the unit the expander speed was varied and, thanks to the permeability theory, the relationships between WF flowrate variations, inlet expander pressure and expander speed variation were investigated. The potentiality of a control strategy of the expander revolution speed of the expander was fixed as well as a deeper understanding of the SVRE behaviour and relationships between operating variables. In particular, it was observed that varying the speed from 1000 RPM up to 2000 RPM, the expander behaviour was optimized ensuring proper working condition matching with a (30-100 g/s) flowrate range
Experimental characterization of a small-scale solar Organic Rankine Cycle (ORC) based unit for domestic microcogeneration
No full textThe integration of a Micro-Organic Rankine Cycle (ORC) power unit with conventional solar flat plate collectors ensures the simultaneous fulfillment of electricity and domestic hot water (DHW) demands. Due to the variability of the solar source, despite the introduction of a thermal storage unit, the plant is subject to severe off design operating conditions. A small-scale ORC-based was designed, built and fully tested, to experimentally assess the performance and operating robustness of the plant in steady and dynamic off-design condition. The unit is fed by hot water from a 135 L reservoir. Dedicated electric heaters (12 kW each one) reproduce the thermal availability from 15 m2 of standard solar thermal collectors for domestic applications. The test bench underwent an extensive experimental assessment in both stationary conditions of the hot source and in presence of a variable thermal load at the evaporator. Due to the plant architecture and components, the control of the unit is based on the variation of the mass flow rate of the working fluid (R245fa) matching the thermal equilibrium at the evaporator in each operating condition of the system. The variation of the flow rate, in fact, must fit with thermal power available. The off-design steady state assessment allows the understanding of the wide operability of the plant (17–62 g/s), with power and efficiency varying between 150 and 500 W and 2.4–4%, respectively. The dynamic testing of the pilot unit points out the plant consistency and robustness to severe off-design operation, mostly due to the 1 kW scroll expander, very suitable for time-varying operating conditions. Both the option of a full discharge of the thermal energy of the reservoir and the option of a split discharge to the evaporator were investigated and provided a clear indication on the CHP feasibility when no addition of thermal energy takes place at the reservoir. It was observed that during a complete reservoir thermal discharge, the plant works for 3000–3300 s continuously, with a slow power decrease from 500 W to 100 W. Considering the thermal energy recharging time, the plant could be averagely operated up to 7 times during the day if a partial discharge was performed. Each plant activation lasts 900 s producing a power ranging from 500 W to 200 W. This operating strategy allows to cover up to 11.2% of the whole electric energy yearly required by an average European household
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