NUMERICAL SIMULATION OF NATURAL CONVECTION FOR RAISED-CEILING ROOFTOP HEATED FROM BELOW

Abstract

Attic design has a significant impact on buildings’ energy performance thus making investigation of its thermal performance characteristics imperative. Raised-ceiling is among the common complex attic configuration found in pitched-roof buildings. In this study, natural convection inside a raised-ceiling rooftop heated isothermally from the base wall (ceiling) is numerically investigated at a certain pitch angle range while keeping the enclosure base-length unchanged. The results show that the roof pitch and the kinks on the ceiling have a strong influence on the heat and fluid flow patterns. At low roof pitch, high heat transfer rate between the cold and hot walls leads to a multi-cellular flow structure. The number, size and strength of the counter-rotating cells change with the pitch angle. The kinks caused air velocity to double for every 15° increase in the roof pitch. The rate of convective heat transfer is enhanced with decreasing value of the aspect ratio.