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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Natural Convection in an Open-Ended Channel Under Staggered Thermal Boundary Conditions. Application to the Control of the Free Cooling in Photovoltaic Double-Skin Facades.

Get access (open in a dialog) DOI: 10.1615/IHTC15.hte.009969
pages 4201-4214

Sinopsis

This paper is dedicated to investigate the effect of the non-uniformity of the wall heat flux distribution on the natural convection flow and heat transfer within an open-ended vertical channel. The aim of our research is to provide information regarding the link between the kinematical flow behavior and heat transfer at the walls. Different periodic and asymmetric heating modes have been carried out on both walls of an air apparatus for the same aspect ratio of 1/15. Heat transfer and PIV flow measurements are conducted for two different periodicities of heated/unheated zones (1/15 and 4/15) imposed alternatively from one wall to the other and two levels of Joule heating inputs, 233 W and 500 W. As set of results obtained for the two different heat flux configurations, there is an increase of both convective heat transfer on heated zones and global chimney effect in comparison with uniform injected flux configuration. Depending on the repartition of heated/non heated areas, this enhancement may reach 30% on heat transfer and 12% more on mass flow rate. Concerning the physical mechanisms which are involved, we highlight that the natural convection flow does not necessarily undergo transition but a disruption of the boundary layer that induce a better mixing and higher Reynolds stresses over most of the width of the channel. The rate of turbulent production increases gradually with the height of the channel through these mechanisms, especially in the upper part of the channel. Finally, global thermal and kinematical quantities are linked through correlations.