الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Experimental investigations are made to study the effect of different parameters affecting the process of natural air flow 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 mainly of rectangular cross-section duct of 25 cm width with different heights and air gap thicknesses .All duct sides are well insulated except one side heated under constant heat flux ranges nearly from 191. to 441. w⁄m^2 . The air gap thickness is varried with the values 3, 5, 7, 10, 15 and 20 cm. A number of 4 duct parts of height 50 cm with equal width and equal gap thickness are used to form total duct height of 50, 100, 150 and 200 cm. This enables using the duct parts heated or unheated to show the chimney effect and the effect of heat added on air volume flow rate. Experimental results are plotted to indicate the relation between air volume flow rate through the vertical duct , convective heat transfer coefficient, Reynolds number of air and Nusselt number and different parameters discussed, namely, gap thickness, heat flux, duct height, and modified Rayleigh number . Based on measured results the air volume flow rate increases with increasing both heat flux density and heated duct height. In case of heating a lower percentage area of the duct with remaining area of the duct unheated, the air volume flow rate increases with the unheated area of the duct due to the chimney effect. It is concluded also that, the air volume flow rate increases with 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 show also that the Nusselt number increases with Reynolds number and has the same trend of air flow rate with gap thickness values. The results of the present study could be useful in the design and application of buoyancy-assisted natural ventilation systems.