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 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.

摘要 本研究旨在对火灾工况下陶瓷砌块砌体棱柱体的传热过程开展数值分析。本次研究共构建了4种棱柱体构型，分别命名为棱柱"A"、"B"、"C"和"D"。本次研究采用三种不同的数值分析方法：一是基于NBR 15220-2:2022标准的均质化模型，二是热物理属性恒定的精细化模型，三是热物理属性随温度变化的精细化模型。针对均质化流程，本研究提出了一款名为"THC NBR15220-2"的程序。该程序基于Matlab开发，可依据NBR 15220-2:2022标准计算均质化热物理属性。本研究采用有限元法（Finite Element Method, FEM），依托Abaqus软件完成数值建模与求解。火灾工况采用ISO 834:1999标准升温曲线进行模拟。在总暴露时长4小时的工况结束后，采集未受火一侧表面的温度数据。研究结果表明，空腔数量最多、因此净毛面积比最低的棱柱体拥有最优的热工性能。与参照模型——即符合国际标准建议的热物理属性随温度变化的精细化模型——相比，二者的模拟结果差异可达12.79%至29.61%。