1,721,091 research outputs found
Experimental study of a phase change material storage for low-temperature applications
Full text linkThermal energy storage technologies are matter of intense research and discussion, in the broader framework of decoupling the "demand-side" and the "supply-side". This topic is of paramount importance to support the large-scale deployment of renewable energy-based technologies in the residential sector, to support the decarbonisation pathways. In this perspective, a promising solution concerns solar-assisted heat pumps. This paper contributes to the existing discussion by developing, building and testing a "pilot-scale" finned-and-tube phase change material storage for solar-assisted heat pumps applications (viz.,low temperature applications, in the range of 20 - 30 °C). The proposed storage unit is tested, under real boundary conditions and it is able to store 65 % higher thermal energy stored compared with an equivalent water storage unit
Experimental study of a pilot-scale fin-and-tube phase change material storage
Full text linkThe large-scale deployment of solar-assisted systems in the residential sector relies on innovative thermal energy storage units. This paper contributes to the present-day discussion by proposing a pilot-scale phase change material storage, whose size has been selected to be coupled with solar-assisted heat pumps. The storage unit consists of a fin-and-tube heat exchanger placed within a tank: water is circulated on one side of the heat exchanger and, on the other side, commercial paraffin RT26 is employed. The storage system is operated considering two heat exchanger configurations (viz., parallel and series configurations) and implementing a broad set of boundary conditions, to test the storage unit under relevant operating conditions. To this end, a novel test rig with electrical resistances (to provide the heating load) and a heat pump (to provide the cooling load) has been designed and build. The results were commented in terms of global and local performances; it was found that the proposed storage, compared with a volume-equivalent water storage, is able to store 65% higher thermal energy. In addition, the dataset obtained in this research is attractive to validate numerical codes of phase change material storage units
Valutazione di alcune metodiche peer il recupero di enterovirus da molluschi sperimentalmente contaminati
No full textSolar-assisted dual-source multifunctional heat pump: Field tests results and thermodynamic analysis
Full text linkThe integration between heat pumps and renewable energy sources (i.e., solar energy) is a promising and recognised technology to reduce primary energy consumption for building cooling/heating. This paper contributes to the existing discussion concerning field performances of multifunctional solar-assisted heat pumps, for cooling/heating applications, and for the production of domestic hot water. The proposed system has been tested experimentally, in a detached house in Milan, to obtain the seasonal performances; in particular, based on experimental observations, energy and exergy analyses have been formulated and applied to the heat pump control volume and to the whole system control volume. The results of the energy analysis have demonstrated that the system was able to maintain high efficiency in the different seasons. The exergy efficiencies of the heat pump and of the whole system were similar in their values, thus suggesting that the heat pump control volume is the location where most of the exergy losses occur, thus pointing out where the future research activities should focus to improve the performance of the proposed system
La scelta green che non ti lascia al verde
No full textCasa dolce casa! Al di là degli slogan, è un dato di fatto che l’edificio costituisca parte integrante della vita stessa dell’uomo e come tale sia cambiato nel tempo, nelle sue caratteristiche intrinseche e nella capacità di soddisfare bisogni e nuove aspettative
A screening of low-GWP refrigerant for ejector refrigeration
Full text linkEjector refrigeration is a promising technology to reduce primary energy consumption for building cooling. Unfortunately, a change in the design criteria (i.e., geometry, working fluid, operating conditions) influences the system performance owing to variations in the local fluid dynamic phenomena at the "local-scale". For this reason, a general agreement on ejector performance is far from being reached. In addition, a general assessment of ejector performance is even more challenging when considering the recent regulations concerning the working fluids, which are going to phase-out most of the refrigerants commonly used in refrigeration and air conditioning systems. Despite there are different options to replace them, no refrigerant has yet imposed. This paper contributes to the discussion on the screening of working fluids, using a previouslyvalidated lumped parameter model. The modelling approach has been applied to sub-critic ejector refrigeration systems and some alternatives to high GWP refrigerants are considered. The influence of the generator, the evaporator and the condenser temperatures over the ejector performance, for the different working fluids, have been presented and commented. The results are comments in terms of entrainment ratio and coefficient of performance, to provide indications and guidelines for refrigerant selection in prospective ejector refrigeration systems
Sub-critic and trans-critic cjector refrigeration: A screening of IIFC/HFO mixtures as alternatives of high GWP refrigerants
No full textExperimental tests on the performance of an economic model predictive control system in a lightweight building
Full text linkEuropean policies are fostering the electrification of energy use, including space heating and cooling systems, in order to decarbonise the building stock. The significant penetration of electrical loads and domestic photovoltaic (PV) plants has therefore become an important topic for researchers and engineers working in the building sector. In this context, this paper presents a recently constructed laboratory for testing efficient management strategies in all-electric houses. The article describes the laboratory and the Model Predictive Control (MPC) strategy developed to minimize economic costs for space heating while ensuring thermal comfort in the indoor environment with a simulated rooftop PV system. The proposed controller leverages prior knowledge about the physical and geometric properties of the building and the optimization problem is formulated using mixed-integer quadratic programming. This article reports the results of calibration and optimization performed in open loop, as well as two closed loop tests where the MPC controls the HVAC system using receding horizon. The predictive controller was able to substantially increase PV self-consumption in both tests compared to a conventional thermostat, thus cutting electricity costs for heat pump by 10–17%. Such improvement was obtained at the price of a higher thermal comfort violations, mainly due to oversimplified HVAC system models. In light of these findings, the article analyses the effect of such simplifications and suggests possible alternative modelling approaches
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
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