Comparative numerical analysis of heat transfer in masonry prisms in a fire situation

Abstract

This study aims to numerically analyse heat transfer in masonry prisms with ceramic blocks under fire conditions. Four prism configurations, designated as Prism “A”, “B”, “C” and “D”, were modelled. Three different numerical approaches were considered: a homogenized model based on the ABNT NBR 15220-2: 2022 standard, a detailed model with constant thermophysical properties, and a detailed model with properties varying as a function of temperature. For the homogenization process, a programme called “THC NBR15220-2” was proposed. This programme, developed in Matlab, calculates the homogenised properties according to the NBR 15220-2: 2022 standard. Numerical models were performed using the Finite Element Method (FEM) using the Abaqus software. The fire condition was simulated using the ISO 834: 1999 standardised curve. Temperatures were collected on the face not exposed to fire at the final exposure time of 4 hours. The results showed that the prism with the highest number of voids and, consequently, the lowest net to gross area ratio was the one with the best thermal performance. There is a difference of 12,79% to 29,61% when compared to the reference model, which is the detailed model with thermal properties varying with temperature, as suggested in international standards.