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• Realization of an experimental heat pump based on elastocaloric effect. • The device is made of elastocaloric wires crossed by air as heat transfer fluid. • The energy and environmental impacts of the device with many elastocaloric materials were tested. • Evaluation of the environmental impact through a TEWI analysis compared with a HFC32 heat pump. • Ni 55.92 Ti 44.08 and (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 provide a significant reduction of the environmental impact (−50/−60 %) with respect to HFC32 heat pump. Solid-state refrigeration can constitute a breakthrough point since based on solid-state refrigerants that do not have any direct greenhouse effect (GWP = 0). The refrigeration systems based on caloric effect can be categorized as: magnetocaloric, electrocaloric, elastocaloric or barocaloric. The theme of interest for the investigation introduced in this paper is elastoCaloric Effect (eCE). In this paper the environmental impact in terms of Total Equivalent Warming Impact (TEWI) of an elastocaloric rotary device ensuring continuous fluxes of cold/hot air for the air conditioning applications is evaluated. The final aim is the construction of an experimental device based on eCE working as a heat pump that operates at peak performance and that would be eco-friendly. Indeed, a rotary two-dimensional model based on finite element method was developed to couple with the device during its realization. The device has been virtually tested while mounting various elastocaloric effect materials to examine and select the ones resulting most suitable both from energetical and environmental points of view. The evaluation of the environmental impact has been perpetuated through a TEWI analysis comparing the indexes of the elastocaloric prototype operating with different elastocaloric materials (Ni 50.8 Ti 49.2 , Ni 55.9 Ti 44.1 , Ni 45 Ti 47.2 Cu 5 V 2.75 , (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 and PbTiO 3) and a vapor compression heat pump (A ++/ A +) working with HFC32. The analysis was perpetuated for both the functioning modes: cooling and heating modes. The most remarkable data on the analysis is that only Ni 55.92 Ti 44.08 and (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 provide a significant reduction of the environmental impact (−50/−60 %) appropriately selecting the operative conditions (air velocity ranging from 9 to 12 ms−1 and cycle frequency 0.4 ÷ 0.5 Hz). [ABSTRACT FROM AUTHOR]

The aim of this paper is to research the parameters that optimize the thermal performances of a horizontal single-duct Earth to Air Heat eXchanger (EAHX). In this analysis, the EAHX is intended to be installed in the city of Naples (Italy). The study is conducted by varying the most crucial parameters influencing the heat exchange between the air flowing in the duct and the ground. The effect of the geometrical characteristics of the duct (pipe length, diameter, burial depth), and the thermal and flow parameter of humid air (inlet temperature and velocity) has been studied in order to optimize the operation of this geothermal system. The results reveal that the thermal performance increases with length until the saturation distance is reached. Moreover, if the pipe is designed with smaller diameters and slower air flows, if other conditions remain equal, the outlet temperatures come closer to the ground temperature. The combination that optimizes the performance of the system, carried out by forcing the EAHX with the design conditions for cooling and heating, is: D = 0.1 m s−1; v = 1.5 m s−1; L = 50 m. This solution could also be extended to horizontal multi-tube EAHX systems. [ABSTRACT FROM AUTHOR]

This paper is focused on the resort to geothermal energy, through the employment of an Earth-to-Air-Heat Exchanger (EAHX) positioned upstream of the air-handling unit of an air conditioning system, for an office building in Naples (South Italy). The aim is to evaluate the energy performances of this unusual system compared to the common solution of external air directly entering the air-handling unit. The EAHX is extensively designed and two-dimensionally modeled, and the analysis is solved with finite element method. The model is validated with experimental data and this comparison shows good agreement. With the requirement of providing the building with 1300 m3 h−1 of external airflow, different design solutions for the EAHX are studied, by varying the diameter (in the range 0.2–0.5 m) and length (between 20 and 140 m) of the buried pipes. The results indicate that: smaller tube diameters enhance the heat transfer; a tube length between 80 and 100 m is recommended. Using the EAHX, the reduction of the thermal power of the coils in the air-handling unit is greater than 40% in most cases. Finally, the efficiency of the EAHX is assessed as a function of the tube length and diameter, reaching values up to 0.9. [ABSTRACT FROM AUTHOR]

In this paper the results of a wide investigation on a geothermal-integrated air HVAC system are reported: in the first part, the energy performances of an Earth to Air Heat eXchanger (EAHX) operating in Pomezia (a locality of the area of Rome, Italy) are carried out through a comprehensive numerical two-dimensional model based on the finite element method and the system is forced under real time-changing weather conditions over 1 year. The model is able to reproduce the time- and space- dependent thermo-fluid-dynamic behavior of the EAHX system, the humid air flux and the surrounding soil, as well as to account for the mass of condensed water in the tubes. In the second part of the investigation, the EAHX is coupled to an air handling unit of a company building for office use and tested while operating both in cooling and heating mode. The hourly results, in terms of power savings and energy consumption were reported for representative days of all the months belonging to the cooling or the heating working seasons, monthly and seasonal assessment. The convenience in terms of seasonal energy savings is +40.8% in cooling mode and +44.1% in heating mode. Then, the economic impact in terms of payback time and net present value was investigated through a cost analysis to examine the return of the economic investment under two possible soil morphologies and different prices of electrical energy in Italy. The simple payback with the real price of energy in Italy (0.50 €/kWh) is 3.3 years for the tufa-soil and 5.8 years for soft rock-soil; the economic return in terms of net present value is around 500 k€ for both the morphologies (560 k€ for the tufa; 446 k€ for the soft rock), per effect of the energy saving and, consequently, for a reduced expense of electrical energy. Therefore, in all the considered cases the installation of EAHX systems in support of traditional systems would generate both energy and economic advantages. [ABSTRACT FROM AUTHOR]