Abstract:
Night natural ventilation systems have been receiving increased attention in recent years because of their
energy saving potential and environmental protection when used in passive instead of active cooling. A
novel system recently proposed for cooling the building concrete slab is studied numerically in the present
work. The system relies only on night ventilation as a means for cooling down the structure of the
building. It consists of a new type of suspended ceiling with a peripheral gap between it and the walls
combined with the positioning of the air supply and extraction grilles between the ceiling slab and the
suspended ceiling. This study focuses on the use of Computational Fluid Dynamics (CFD) to predict the
airflow and thermal performance of this strategy for an office room. Ansys-Fluent is used to perform
the calculations both for a reduced and a full-scale room. Transient simulations were performed for a period
of 24 h and the predictions for the reduced-scale model were validated by experiments under different
operating conditions. The results show that the mathematical and numerical models provide
satisfactory predictions of the temperature evolution in the reduced-scale model, allowing the analysis
to be extended for full scale. The predictions for the office room at full scale confirm the effectiveness
of the proposed cooling technique, revealing that the air peak temperature during the day is lower, as
well as the temperature of the slab and the temperature of the air in the plenum during the night.