The effects of aspect ratio on heat transfer across air layers in a slot-ventilated wall cavity

The effects of aspect ratio on heat transfer across air layers (Pr ̃ 0.71) in a slot-ventilated wall cavity were numerically studied in this paper for Rayleigh number, Ra w in the range of 1.4×10 5 to 12.0×10 5 using the Reynolds-Averaged Navier-Stokes (RANS) methodology. Large horizontal aspect ratios of 40 and 60 for the wall cavities investigated enable a two-dimensional approximation to be employed in the study of the heat transfer characteristics of the air layers over a range of temperature that is representative of extreme winter and summer conditions in the study. Using the RANS-based methodology, a small temperature difference between the front and back wall of the cavity reduces the cost of heating required for remediating moisture and condensation in the wall cavity during the winter in contrast to transferring a similar amount of energy using a large temperature difference. A maximum deviation of about 5.11% obtained between the Nusselt number of the cavity flow at a vertical aspect ratio, H W of 40 and 60 shows that an increase in the vertical aspect ratio of the cavity does not significantly affect the heat transfer rate across the air layers. © 2006-2011 Asian Research Publishing Network (ARPN).