Comparison of Experimental and Numerical Investigation on Local and Global Heat Transfer in Turbulent Square Channel Flow with Roughness Elements in the Form of V Shaped Broken Ribs

摘要

Local and global heat transfer in turbulent square channel flow with roughness elements in the form of V-shaped broken ribs attached at two opposite walls has been investigated experimentally and numerically for the first time. The results of a high resolution (0.063 by 0.063 mm~2) ammonia absorption measurement technique allows a detailed description of the local heat (mass) transfer distribution. These results can be used as a reference to evaluate turbulece heat transfer models. The local heat transfer distributions are compared with numerical results of the well established Low Roynolds Number (LRN) #kappa# - #epsilon# model of Launder and Sharma and a new version of this model category for near wall flow by lien and leschzimer. Both models predict qualitative correct local Nusselt number distribation for the rough and smooth walls. The Line and leschziner model gives better quantitative agreement with experiment than the Launder and Sharma model although still some weaknesses remain. For increased local accuracy the adoption of higher order turbulence models with special regard to near wall effects will be necessary.