Gerson Henrique dos Santos

Combined Heat, Air and Moisture (HAM) Transfer Model for Porous Building Materials

In the building science area, mathematical models are developed to provide better indoor thermal comfort with lower energy consumption. Although the fact moisture and air transfer can strongly affect the temperature distribution within constructions, whole-building simulation codes do not take into account the convective air transport in porous materials. In this way, this article presents a heat, air, and moisture (HAM) transfer model based on driving potentials of temperature, air pressure, and water vapor pressure gradients for consolidated porous material in both pendular and funicular states. The solution of the set of governing equations has been simultaneously obtained using the MTDMA (MultiTriDiagonal-Matrix Algorithm) for the three potentials. To conclude, results are presented showing the impact of convective terms on the HAM transfer through a two-layer porous building envelope.

Numerical analysis of thermal transmittance of hollow concrete blocks

Since the 1970s, due to the worldwide energy crisis, some countries have adopted severe legislation to promote energy efficiency in buildings. The electrical power utilized in buildings is directly related to the equipment required to provide thermal comfort to occupants. In this context, one of the most important factors that determine the choice of these systems is the conduction load through the building envelope. In several countries, hollow concrete blocks have become common over the past few years. Therefore, for the assessment of building energy efficiency, the thermal transmittance evaluation of hollow blocks is required. This study obtains values of thermal transmittance for different cavity configurations of concrete blocks by performing computational fluid dynamics simulations. These transmittances are compared to those calculated using the methodology presented in international standards. In the “Results” section, it is shown that large cavities provide higher transmittance values due to convection and that thermal radiation may play an important role in the overall heat transfer through concrete hollow blocks. Some methods used to reduce the thermal transmittance are presented and discussed. Finally, thermal transmittance of cavities with the same wall height has been compared with the ones of a single block and different strategies are considered for reducing the thermal transmittance of concrete hollow blocks.