Kátia Cordeiro Mendonça

Study of moisture transfer in a double-layered wall with imperfect thermal and hydraulic contact resistances

The objective of this work is to study the effect of taking into account interface contact resistance on the prediction of moisture distribution through multilayered building envelope. Therefore, two mathematical models to describe coupled heat and mass transfer in double-layered porous materials have been investigated: one that considers imperfect contact between layers and another that ignores this phenomenon. Both models are one-dimensional and were implemented using finite difference technique with an implicit scheme. Numerical results are presented in terms of moisture distribution for a double-layered wall and compared with the experimental data available in the current literature. The comparison has shown that the model that disregards interface contact resistance between layers cannot predict correctly one-dimensional heat and moisture transfer within double-layered porous materials. The sensitivity analysis of the simulation parameters and the impact of contact resistances at the whole building level are presented in detail and their effect on the whole building level was analysed. Our results suggest that the thermal contact resistance is the most influent parameter on the moisture flux across the hydraulic contact interface. On the whole building level, simulations indicate that taking into account contact resistances had a slight effect on the indoor relative humidity but a noticeable effect on heating input energy. A decrease of 10% in energy consumption is obtained when contact resistances are considered.

Effects of Coupled Heat and Moisture Transfers through Walls upon Indoor Environment Predictions

Abstract The non-uniform behaviour of the air inside a room, which is important in comfort analysis, can be evaluated by zonal models. While not as fine-grained as CFD simulation, they do give useful information about temperature and moisture distributions that is not available from lumped-parameter models. Therefore, we have developed a tool, called SimSPARK, to automatically build dynamic zonal simulations of a building zone. Its model library includes different models to describe heat and moisture transfers across the building zone envelope, with two of them taking into account moisture adsorption/desorption by building materials. To illustrate the applicability of this tool, we compare two zonal models including adsorption and desorption processes with one that ignores these phenomena, in a ventilated room modelled using 27 cells. The results indicate that adsorption/desorption by building materials does affect indoor air behaviour in a hot and humid climate.