Temperatures in and under a slab-on-ground floor: two- and three-dimensional numerical simulations and comparison with experimental data

This paper presents the results of a numerical simulation of measured temperatures in a ground floor slab and the soil beneath it. Two- and three-dimensional calculations (2D and 3D) are performed using a widely utilised whole building thermal simulation program. A multi-dimensional numerical conductive heat transfer module has been added to this program and this current work is intended to show (i) whether the model is capable of successfully modelling the system and (ii) whether the use of 2D analysis is justified or if a 3D simulation is more appropriate for this type of slab. The predictions of the finite-volume model are compared with one year of measured data from a real building. A Differential Sensitivity Analysis is made in an attempt to account for uncertainties in some input parameters (i.e. thermal conductivities). It seems that in this case, where the slab is large, the 2D model is capable of satisfactorily predicting the transient temperature variations in the soil. However, it is shown that near the corners of the slab a 3D model is necessary to accurately simulate heat flows for periods involving high heat fluxes; i.e. during the heating season.