A CFD Study of Buoyancy Effects on Smoke Spread in a Refuge Floor of a High-rise Building

Abstract

This paper presents a CFD study of wind-smoke spread in a designated refuge floor of a high-rise building and explores the influence of buoyancy on the smoke-flow field. A designated refuge floor is a prescribed requirement stipulated in the Code of Practice on Means of Escape of Hong Kong. It is regarded as an interim safe place for evacuation under fire or other emergency situations in high-rise buildings. In order to prevent smoke logging and causing hazard to the evacuees in the floor, Hong Kong’s code prescribes that cross-ventilation should be provided in such a way that the floor should be open-sided above the parapet on at least two opposite sides. However, whether such requirement is effective has not been analytically studied. A previous study has revealed that smoke may spread into the floor by dint of wind action, and how the buoyancy affects on airflow and smoke is not further studied. We have extended our study and found that the buoyancy could strongly affect the flow pattern. The buoyancy effect could cause a high vertical velocity component inside the refuge floor. The evacuees, while having a rest in the refuge floor, will be substantially affected by the ingress of smoke under a strong wind. It has further been found that the amount of smoke migrating into the refuge floor will be affected by the temperature at the opening of the fire zone immediately below the refuge floor in that it is inversely proportional to the opening temperature.