1,720,963 research outputs found
An experimental set up for dynamic multi-control investigation on vapour compression heat pumps
No full textDirect expansion solar assisted heat pumps - A clean steady state approach for overall performance analysis
No full textTraditional thermal solar panel technologies have limited efficiency and the required economic investments make them noncompetitive in the space heating market. The greatest limit to the diffusion of thermal solar systems is the characteristic temperatures they can reach: the strong connection between the user temperature and the collector temperature makes it possible to achieve high thermal (collector) efficiency only at low, often useless, user temperatures.
By using solar collectors as thermal exchange units (evaporators) in a heat pump system (direct expansion solar assisted heat pump, DX-SAHP), the overall efficiency greatly increases with a significative cut of the associated investment in terms of pay-back time.
In this study, an approach is proposed to the steady state analysis of DX-SAHP, which is based on the simplified inverse Carnot cycle and on the second law efficiency concept. This method, without the need of calculating the refrigerant fluid properties and the detailed processes occurring in the refrigeration device, allows us to link the main features of the plant to its relevant interactions with the surroundings. The very nature of the proposed method makes the relationship explicit and meaningful among all the involved variables.
The paper, after the description of the method, presents an explanatory application of this technique by reviewing various aspects of the performance of a typical DX-SAHP in which the savings on primary energy consumption is regarded as the main feature of the plant and highlighted in a monthly averaged analysis.
Results agree to those coming from a common standard steady state thermodynamic analysis. The application to a typical DX-SAHP system demonstrates that a mean saved primary energy of about 50% with respect to standard gas burner can be achieved for the same user needs. Such a result is almost independent from the type of flat plate solar panel used (double or single glazed, or even bare panels) as a result of using an optimal collector working temperature
DYNAMIC SUMULATION OF A SOLAR ASSISTED HEAT PUMP SWIMMING POOL WATER HEATING PILOT PLANT
No full textLiquefied natural gas submerged combustion vaporization facilities: process integration with power conversion units
No full textLiquefied natural gas (LNG) vaporization facilities offer an excellent opportunity of primary energy saving by means of integration with power conversion units that is still weakly exploited in actual installations. This work focuses on the evaluation of primary energy saving achievable by the integration of an LNG vaporization facility with a gas turbine and with a cogenerative combined gas-steam power plant. The fuel energy saving ratio is used as the main performance parameter to evaluate the primary energy saving derived by system integration, with respect to conventional submerged combustion vaporization. Twelve possible configurations are analyzed with steady-state calculations. Results show that a primary energy saving greater than 15% with peak values up to 27%, corresponding to 2.98TJ/year, is achievable. The paper shows that the fuel energy saving ratio can be used as a synthetic and effective parameter to estimate the energy-saving potential of different plant configurations. © 2011 John Wiley & Sons, Ltd
Photovoltaic co-generation with solar-assisted heat pumps
No full textThe main technological issues related to the development of PVT hybrid panels is de-scribed and the main achievements and studies being developed at DIME are reported, with particular reference to solar assisted heat pump (SAHP) heating systems, both with PVT or thermal SAHP systems
Preliminary experimental results from a linear reciprocating magnetic refrigerator prototype
No full textA linear reciprocating magnetic refrigerator prototype was designed and built with the aid of an industrial
partner. The refrigerator is based on the Active Magnetic Regenerative cycle, and exploits two
regenerators working in parallel. The active material is Gadolinium in plates, 0.8 mm thick, for a total
mass of 0.36 kg. The device is described and results about magnetic field and temperature span measurements
are presented. The designed permanent magnet structure, based on an improved cross-type
arrangement, generates a maximum magnetic field intensity of 1.55 T in air, over a gap of
(13 50 100) mm3. The maximum temperature span achieved is 5.0 K, in a free run condition
Bare panels for the exergy exploitation of ambient (air vapour content) humidity with solar assisted heat pumps
No full textThermodynamic and economic model of solar assisted heat pumps for water and space heating
No full textAn approach to energy saving assessment of solar assisted heat pumps for swimming pool water heating
No full textA steady state off-design model of a Water Solar Assisted Heat Pump (W-SAHP) and the results of monthly-based averaged simulations are presented. The W-SAHP system is arranged with a commercial water- towater heat pump, coupled with unglazed flat plate solar collectors. The study is purposely developed for swimming pools, however most of the analysis criteria and outcomes are valid for any building (user) having hot water needs. Calculations are made for given thermal load and user operating temperatures with reference to the climatic data of all Italian Municipalities, that is degree days (DD) in the range from 700 to 3000, altitude from 0 to 1500m (above sea level), and latitude from 36.5°N to 46.3°N.
The primary energy saving capability of the W-SAHP solution, compared to a traditional gas-boiler plant, is analyzed as a function of the DD index of each site. Despite the large spread of climatic and altitude data, the results show that the W-SAHP performance are usually well correlated to DD, which can therefore be assumed as the main independent variable for the energy saving assessment of these systems, and make the results easily extended to other possible geographical locations
METODO DI IMPIEGO DI TUBI METALLICI NON COIBENTATI COME COLLETTORI DI ENERGIA SOLARE E AMBIENTALE ABBINATI A SISTEMI A POMPA DI CALORE
No full textMetodo di impiego di tubi metallici non coibentati (1) da installarsi direttamente su superfici isolate in esterno ovvero su elementi architettonici di edifici civili ed industriali (quali coperture di tetti, tettoie e coperture in genere), in grado di captare l'energia raggiante del sole, sia direttamente sia indirettamente dalla copertura (4) (operante come superficie estesa aderente al tubo) mediante opportuno impianto idraulico in accoppiamento a pompa di calore (9) (del tipo a compressione di vapore acqua-acqua od acqua aria, ovvero del tipo ad assorbimento, sempre con acqua od altro fluido antigelo circolante nei tubi (1)). La distesa di tubi può sfruttare, oltre all'energia solare, anche le altre fonti exergetiche ambientali quali l'irraggiamento ambientale, la convezione con l'aria, la convezione con l'acqua della pioggia o la potenza termica ottenibile dalla condensazione del vapore contenuto nell'aria ambiente
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