CFD Modelling and Thermal Performance Analysis of Ventilated Double Skin Roof Structure

Abstract

Air conditioning is a serious issue in hot areas. The demand to live in more comfortable buildings,
which is understandable, has resulted in an increase in energy consumption by air conditioning.
However, in Djibouti, one of the world's most expensive electricity countries, this demand is
exacerbated by building that is inadequate and unfit for the climate. This paper investigates the design
of the roof which is the surface receiving the most solar radiation and which determines the general
behaviour of the building. The energy performance of a double skin ventilated roof is modeled and
analysed using Computational Fluid Dynamics (CFD). This study looks at Djibouti's climate, which is
hot and humid in the winter and extremely hot and humid in the summer. To characterize the flow and
heat transfer induced in the ventilated roof in a steady state, roof simulations are carried out using the
Ansys Fluent software. The effects of numerous parameters on heat gain through the roof are
compared, including the internal emissivity of the upper surface, the thickness of the roof insulation,
and the thickness of the vented channel. The energy saving potential is also studied and presented in
comparison to the current constructions in Djibouti.