Study of thermal comfort: numerical simulation in a closed cavity using the lattice Boltzmann method

Abstract

In this work, a study on thermal comfort in building is presented as it has great interest given its impact on the quality of indoor environments. The thermal comfort depends on several parameters such as air temperature and velocity, relative humidity and so on. With this in mind, numerical investigation is carried out on natural convection induced by temperature gradient between the lower and upper walls in a square enclosure filled with a Newtonian fluid. To approach the real case of underfloor heating subject to real weather conditions, periodic time varying temperature is imposed on the lower wall of the enclosure. The mathematical problem has been formulated by considering the Boussinesq’s approximation, and the resulted governing equations are solved using the Lattice Boltzmann Method. The study has been carried out for Rayleigh numbers in the range 103 ≤ Ra ≤ 106, while Prandtl number and aspect ratio are kept constant at 0.71 and 1, respectively. The results obtained show that the flow’s behaviour is strongly dependent on the values of Rayleigh numbers and heating amplitude. The temporal evolution of the spatially averaged Nusselt number indicate that the transfer regime is periodic for low values of Ra and switches to a perturbed unsteady flow for hight values.