Coupling ground heat exchangers to heat pumps for heating and cooling grants significant energy savings compared to the air heat systems, due to the source higher thermal stability and its better thermophysic properties. A coupled system, consisting of an horizontal ground heat exchanger linked to an ideal heat pump for cooling, is examined here. The thermal exchange problem is solved in transient conditions using a numerical finite element model to evaluate the flow and thermal fields within the porous medium. The soil temperature distribution is calculated for an heterogeneous and equivalent homogeneous porous medium, determining the differences between the two cases in terms of volume, shape and energetic performance. The ground heat exchanger adopted has a specific power between 9 and 14 W/m; the heat exchange is mostly controlled by conduction, even if advection and dispersion phenomena concur in defining the thermal plume. The resulting isothermal lines are very similar between the homogeneous and heterogeneous case, at least in the chosen time frame.
Numerical analysis of heat transfer induced by an horizontal ground heat exchanger in an heterogeneous soil
BOTTARELLI, Michele
2010
Abstract
Coupling ground heat exchangers to heat pumps for heating and cooling grants significant energy savings compared to the air heat systems, due to the source higher thermal stability and its better thermophysic properties. A coupled system, consisting of an horizontal ground heat exchanger linked to an ideal heat pump for cooling, is examined here. The thermal exchange problem is solved in transient conditions using a numerical finite element model to evaluate the flow and thermal fields within the porous medium. The soil temperature distribution is calculated for an heterogeneous and equivalent homogeneous porous medium, determining the differences between the two cases in terms of volume, shape and energetic performance. The ground heat exchanger adopted has a specific power between 9 and 14 W/m; the heat exchange is mostly controlled by conduction, even if advection and dispersion phenomena concur in defining the thermal plume. The resulting isothermal lines are very similar between the homogeneous and heterogeneous case, at least in the chosen time frame.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
