Fourier and Biot numbers and the accuracy of conduction modelling

Recent validation work has shown the importance of accurate modelling in order to bring together experimental results and predictions. A number of important areas were identified: heat transfer coefficient, edge effects, etc. This paper dwells on the latter. After a short review of the associated theory the paper concentrates on the effects of Fourier and Biot numbers on the accuracy of the numerical approximation of the diffusion equation for heat flow through solid elements of buildings. Since this is the most widely used method, the paper focusses on finite-difference modelling. However, the main conclusions are applicable to other numerical approaches as well. By practical examples, representing typical building applications, it is demonstrated that it is easy to introduce - but also relatively easy to minimalize - errors due to space and time discretisation of building structures.