Abstract
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.
Highlights
The analysis introduced in this paper aims to explore the thermal performances of a horizontal single-tube earth to air heat exchanger to be placed in the city of Naples (Italy), by varying the most crucial parameters influencing the system
Both geometrical and physical properties are varied in an appropriate range, with the final aim to find the combinations that would optimize the operation of this geothermal system
The burial depth does not affect the thermal performances from 1.5 m onwards because of the typology of the study conducted
Summary
Heating Ventilation and Air Conditioning (HVAC) systems contribute 10–20% to worldwide energy consumption [1]. A relevant amount (20–40%) of the energy consumption attributed to HVAC is required for building air conditioning. In addition to the increase in the use of renewable energy sources, energy saving solutions are being adopted [2,3,4,5,6]. The basic imperative recommended by energy policies is to consider energetically improved solutions that often could not be satisfied only through the vapor compression technology, but which have limits linked to the use of refrigerants with high Global Warming Potential [7,8,9,10]. A viable path is a Not-In-Kind cooling technology [11,12,13]
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