Simulation of dynamic linear thermal bridges using a boundary element method model in the frequency domain

Abstract

Heat losses through thermal bridges often lead to building pathologies generated by moisture condensation. Thus, thermal bridges need to be considered in the building design phase in order to avoid both heat loss and the occurrence of these pathologies later on. The linear thermal bridge is often taken into account at the design stage by using a pre-defined ψ coefficient. This ψ factor is listed in several national regulation/standards for various types of linear thermal bridges on the assumption of a steady state condition. This paper studies linear thermal bridges more realistically by assuming a dynamic behavior that allows the simulation of transient states where the external and internal temperatures may vary over time. The problem is solved by a boundary element model (BEM), formulated in the frequency domain. Time solutions are obtained afterwards by means of inverse Fourier transformations, which can simulate any external temperature variations. After an experimental validation of the BEM model, a series of linear thermal simulations was performed to illustrate the applicability of the proposed model. It further allows the importance of computing thermal bridges to be verified dynamically.