An experimental investigation is made to study the effect of different parameters affecting the process of natural air
flowing through vertical ducts. The experimental setup has been designed and installed in the Air Conditioning
Laboratory, Faculty of Engineering, Mansoura University. The test rig is consisted of mainly of rectangular cross-section
duct of 25 cm width with different heights and gap thicknesses. The air gap thickness ranges from 3 to 20 cm while the
height is ranged from 50 to 200 cm. All duct sides are well insulated with one side heated under heat flux density ranges
from 191.04 to 440.75 ⁄ . Experimental results are plotted to indicate the relation between air volume flow rate
through the vertical duct and different parameters discussed, namely, gap thickness, duct height and heat flux density.
Based on measured results the air volume flow rate increases with increasing both heat flux density and duct height. It is
concluded also that, the air volume flow rate increases with increasing the gap thickness until it reaches maximum
values, namely at gap thickness of 10 cm and then decreases with further increase in gap thickness. The results of the
present study could be useful in the design and application of buoyancy-assisted natural ventilation systems.