Aerothermal Characteristics of Surface-Mounted Round-Edged Slit Ribs With Performance Optimization Using Response Surface Methodology

The author has investigated the aerothermal characteristics of round-edged ribs with a continuous slit. The experiments have been performed by mounting an array of ribs on the bottom wall inside a rectangular duct. Heat transfer characteristics have been measured using liquid crystal thermography (LCT), whereas flow characteristics have been measured using two-dimensional particle image velocimetry (2D-PIV) technique. Experiments have been performed for flow over a rib having ∼20% blockage ratio and 10% open area ratio. Geometrical parameters considered for the study are slit angle (α) and rib pitch-to-height ratio (p/e). Experiments have been performed for three distinct rib configurations having α values, i.e., 0 deg, 5 deg, and 10 deg with different arrangements having p/e values of 5, 10, and 15, at four Reynolds number ranges from 6200 to 12200. The heat transfer results are evaluated by examining the surface and spanwise-averaged distribution of augmented Nusselt number (Nu/Nu₀, and $Nux¯/Nuo,x¯$ respectively). Flow field results are explained within the inter-rib region by examining the time-averaged normalized velocity fields, streamlines, fluctuation statistics, and vorticity distribution. The results show that the flow coming out from the rib geometry significantly affects the heat transfer and flow behavior. Further, the impact of geometrical design parameters (α and p/e) on different performance parameters, i.e., overall averaged augmented Nusselt number $(Nu/Nu0¯)$⁠, friction factor ratio (f/f₀), and thermal performance factor (TPF) has been analyzed at all four Reynolds numbers using Response Surface Methodology (RSM). Finally, the desired correlations for the performance parameters have been documented and found in accord with an uncertainty range of ±10%.