الفهرس 
Chapter 1: Introduction and Literature Review
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Abstract
This study presents an experimental and computational investigation on turbulent flow and heat transfer in rectangular duct with attached and detached square and trapezoidal ribs for Reynolds numbers from 36700 to 82900. The rectangular duct has an aspect ratio of 4. The rib height-to-hydraulic diameter ratio is 0.125, the rib pitch-to-height ratio equals 10 and the clearance-to-rib height ratio is 0.5.
Six different rib shapes are employed; attached square ribs, detached square ribs, attached trapezoidal with increasing height in the flow direction ribs, detached trapezoidal with increasing height in the flow direction ribs, attached trapezoidal with decreasing height in the flow direction ribs and detached trapezoidal with decreasing height in the flow direction ribs.
RNG k-ε with enhanced wall treatment and SST k-ω with transitional flow turbulence models in the FLUENT code are used to simulate heat transfer and fluid flow fields at the given range of Reynolds numbers.
The results show that the attached ribs enhance heat transfer more than the detached ribs. The average Nusselt numbers and friction coefficients of the attached trapezoidal ribs with decreasing height in the flow direction rib provides the highest heat transfer enhancement. This enhancement has 1.52-1.92 times heat transfer augmentation with 6.97-7.037 times pressure DROP penalty compared with smooth duct followed by the attached trapezoidal with increasing height in the flow direction and then the attached square ribs.
The comparison of computational and experimental results reveals that the RNG k-ε turbulence model is suitable for the predictions of flow and heat transfer in the ribbed ducts more than the SST k-ω turbulence model, however the predicted values of the thermo-hydraulic performance showed that the SST k-ω model have the same trend of the experimental results but at relatively lower levels.