Studying the evolution of both thermal and kinetic boundary layers in the vicinity of a vertical conductive gypsum plate under dynamic time-depending conditions at the building scale

In this paper, a vertical gypsum plate with thermal capacity placed in an open cavity under dynamic temperature decrease is numerically investigated in order to assess the evolution of the thermal and kinetic structure of the boundary layer and the convective heat transfer coefficient h over time. The particularity of this work resides in the fact that the system was made to simulate the case of a plate with thermal capacity under nocturnal conditions where the temperature is constantly decreasing. Thus, a two-dimensional CFD model is developed under the Ansys Fluent 14.5 environment and is validated using experimental data obtained for a plasterboard studied under dynamic temperature changes. This study contributes to give precise results about temperature, flux, convective heat transfer coefficient and velocity in the vicinity of a vertical wall with a thermal conductivity at the building scale. All the phenomena that occur in the vicinity of the heat capacitive vertical plate (gypsum) are analyzed and explicitly discussed. The main results of this study show that after simulating 1 h real time we observe that turbulent flow begins to appear at the top level of the plate and after this moment the three flows (laminar, transitional and turbulent) coexist. Finally, mean convective heat transfer coefficient depends on the thermal storage capacity of the adjacent material. The average value of convective heat transfer coefficient increases over time by obtaining for a plasterboard (Cp = 1100 J/kg K) value of 1.8 W/m2 K and for a phase change material in a solid state (Cp = 4350 J/kg K) value of 2.4 W/m2 K at steady state.