Scale modeling studies on stack effect in tall vertical shafts

Natural ventilation was provided by tall vertical shafts such as solar chimney while designing some green buildings. For buildings with a tall vertical shaft located in very cold countries, measured pressure difference due to stack effect was up to 300 Pa. Air motion induced by stack effect would give adequate ventilation flow rate. However, stack effect would also give adverse effect if not utilized properly in this green design. Smoke would spread faster to other parts of the building in an accidental fire. Therefore, estimations of stack pressure by simple hydrostatic equation used to be criticized in performance-based design. Further studies are required and will be justified by scale model experiments in this article. Stack effect in a vertical shaft was studied experimentally by a model shaft of size 0.05 × 0.05 m2 and height 2.0 m. Air temperature inside the model was kept at constant values above outdoor by wounding hot electric wires. Vertical air temperature profiles inside and outside of the model at different heights were measured. Measured air pressure difference profiles between indoor and outdoor were then compared with those estimated from the air temperature difference. Results were then applied to justify stack pressure estimations by the hydrostatic models. From this study, hydrostatic equations are confirmed to be acceptable for studying stack pressure in tall vertical shafts.