Natural ventilation of atrium spaces

This research is aimed to develop a series of design guidelines and relevant prediction tools for the incorporation of natural ventilation in atrium spaces as a passive cooling strategy. Focused on the geometrical and thermal characteristics of atrium buildings, four issues related to this purpose are investigated in this work including thermal comfort, wind-induced ventilation, buoyancy-induced ventilation and combined buoyancy and wind driven ventilation: In order to identify when passive cooling strategies are needed for atrium spaces, a new thermal comfort assessment method which enables the treatment of the solar radiation and non-uniform environment is developed using M.ATLAB as the data exchange platform. It is found that high mean radiant temperature (MRT) can be a more significant factor contributing to the thermal discomfort of the space when the internal occupants' level is irradiated by the sun rays. It is also shown that the air temperature at the occupants' level is mostly affected by the temperatures of the surfaces at lower levels and the temperatures at the roof level and the upper areas generally have little influence on the air temperature at the occupants' level. The study of wind-induced ventilation is concerned with the airflow through roof openings since the atrium is' often placed in the centre of a building and· as a result the openings at lower levels are not available. In this way the air movement in the space is actually driven by the recirculation rather than the direct main flow from the wind. Three. possible flow patterns, and related controlling forces for each flow pattern are defined first, based on which the impacts of the design parameters on the ventilation performance are investigated by CFD techniques and design guidelines are developed accordingly. The effects of the location of heat source and the control of the neutral level when bidirectional flow occurs are studied for buoyancy-driven natural ventilation of atrium spaces. The tendency of the heat source efficiency with the variation of. its location is examined and the optimised location for the heat source is suggested, based on which the guidelines for the selection of materials for the atrium internal surfaces are made. A series of new' algorithms are also developed for the prediction of neutral level when bi-directional flows occur and validated with CFD simulations. The investigation of the combined ventilation focuses on the condition where wind forces and buoyancy forces partly assist each other and partly oppose each other, and it is found that the phenomenon of solution multiplicity still exists for this condition and different solutions may have different ventilation performance depending on the initial conditions.