No abstract

The energy demand in residential sector constitutes an important fraction of the entire energy consumption (40% in EU). Solar district heating (SDH) is a key strategy to reduce use of fossil fuels in buildings. Inside the European project REPLICATE, financed by Horizon 2020 SCC1 Smart Cities and Communities, a SDH with a seasonal storage (STES) has been designed to be realized in the city of Florence. It is the first example of solar district heating with a STES in Italy. The design phase has aimed to size properly the extension of solar field and the volume of seasonal storage based on several parameters such as number of dwellings to feed, heat demand, solar resource, geology of the location and economic reasons. The paper deals with the model that has been realized through TRNSYS to describe the energy fluxes of heating plant andtheir optimization process. The computational model depicts the possible operating conditions and leads to define the control strategies of solar field and seasonal storage, integrated with commercial components that complete theplant such as gas boiler, heat pump and overall circuit. Hot water tank TES has been selected as the appropriate typology of storage for this application based on geological considerations. The thickness of insulation material and various layers have been determined. The numerical analysis fixes the volume of TES to be 3800 m3 and a solar field of about 1000 m2. The solar fraction expected by the district heating is 44%.

No abstract

In EU, the residential sector is responsible for the 40% of the total energy consumption. The integration of solar technologies in buildings is therefore necessary in order to reduce the use of fossil fuels. Concentrating collectors could offer an interesting solution but nowadays their application in buildings is rare due to high costs, large dimensions and complexity of the system. A novel small parabolic trough collector (PTC) has been conceived to overcome these limits and to allow the integration in buildings. The main features of realized prototype are the compact dimensions, strongly reduced compared to the PTC standards, and modularity. The paper deals with the numerical analysis necessary to design the concentrating collector properly and its validation with experimental results. An optical analysis has allowed to select the optimum values for the parameters of the parabola, aperture and rim angle. A thermo-fluid dynamics finite element model has been developed with Comsol Multiphysics, to analyse the relevant physical characteristics and to predict the performance of the receiver tube. The efficiency curve of the collector has been extracted. Successively a receiver tube has been built based on the indications of FEM model for what concerns geometry and materials. In order to evaluate the heat loss of the receiver and to validate the finite element model, a test bench has been realized. The results of off-sun heat loss tests on the receiver tube are reported for several temperatures. The computational model is in good agreement with experimental results and therefore it is validated.

Acoustic liners can represent an effective strategy for noise reduction in aero engines. To assess the sound absorption effectiveness under representative operating conditions and to validate numerical methods, the treatments shall be characterized by using grazing flow rigs. Purpose of this survey is to describe the design solutions adopted in a brand-new test rig aimed at evaluating the performance of the liners under testing conditions representative of the turbine exhaust in an aircraft engine, i.e. high flow speed and temperature. The main components of the rig have been numerically investigated from an aerodynamic, thermostructural and acoustic perspective. The relevant outcomes are reported in the paper. After the rig has been manufactured and assembled, a preliminary commissioning has been performed to verify the rig operability and performance, with special focus on the acoustic behavior.