Pneumatic and thermal design procedure and analysis of earth-to-air heat exchangers of registry type

Abstract

An analytical pneumatic and thermal design procedure is proposed for earth-to-air heat exchangers (EAHEs) of registry type. The procedure allows to choosing between different EAHE geometrical configurations and between the two usual air circulation paths inside the EAHE (i.e. the Z- and Π-paths, respectively). The implementation of the design procedure is made for the EAHE of a large passive house (PH) built near Bucharest, Romania (AMVIC PH). A time-dependent simulation of EAHE’s operation is performed. It allows to computing the soil temperature profile at the surface and at various depths and the air temperature distribution inside the EAHE. This simulation is validated by comparison with experimental results. The EAHE heating and cooling potential during the year is investigated. The energy delivered by the EAHE depends significantly on its geometrical configuration. A computer fluid dynamics (CFD) analysis is also performed. This analysis is validated by comparison with experimental results. There is good agreement between the results predicted by the design procedure and the CFD analysis concerning the air pressure drops in the EAHE. From a thermal point of view the Z-path should be preferred to the Π-path. The CFD analysis results confirm the conclusions stressed out from the simple analytic design procedure and the time-dependent simulation.