Fitting conduction transfer function method to low Fourier numbers: application to ground-coupled floors

Abstract

This paper proposes a practical solution to the problems arising when the conduction transfer function (CTF) method is applied to solve the 1D transient component of heat transfer in the internal zone of ground-coupled floors. The lower boundary condition for these problems must be imposed at a depth of several metres. The proposed method is based on the division of the ground domain into a number of layers that allows calculation of transfer function coefficients while keeping the first cross coefficient negligible. A mathematical expression is proposed for the proper layer thickness that assures the applicability of the CTF method to thick ground domains. A numerical validation for a slab-on-grade configuration has been carried out showing maximum errors of 0.09°C (0.42%) and 0.73 W/m2 (2.24%) for temperature and heat flow rates on the floor surface, respectively.