Characteristics of Flow and Heat Transfer in Stationary Two-Pass Square Duct With Continuous and Broken V-Shaped Ribs Ramesh Erelli, Arun K. Saha Journal of Thermal Science and Engineering Applications, 2025 Turbulent flow and heat transfer were investigated in stationary two-pass square ducts through experiments and computations. Forced convection measurements were performed using the infrared thermography technique (IRT) with three different rib arrangements, namely, 60 deg V, 60 deg V–IV, and broken 60 deg V–IV ribs. In all ribbed cases, the copper ribs are adhered to the heated surface using a particular rib height-to-hydraulic diameter (e/Dh) ratio of 0.125. For continuous and broken ribs, the corresponding rib pitch-to-height ratios are 10 and 5, respectively. In addition to the experimental study, large eddy simulations (LES) with an eddy viscosity-based Smagorinsky–Lilly turbulence model was performed to assess the fluid flow behavior and its role in heat transfer enhancement in baseline smooth and 60 deg V–IV ribbed ducts at a fixed Reynolds number of 45,000. The performance of LES results of smooth and 60 deg V–IV ribbed ducts are checked through The time-averaged thermal fields have been compared with experimentally obtained Nusselt numbers (Nu), friction factors (f), and thermal performance factors (TPFs). In all test cases, the 60 deg V–IV ribbed duct offers the greatest TPF compared to the other two ribbed ducts, whereas the smooth duct exhibits a minimal TPF. Based on this investigation, the 60 deg V–IV ribbed arrangement is recommended for the application of the gas turbine internal cooling. A decent match, both qualitatively and quantitatively, between experiments and numerical predictions was also observed. However, the maximum deviation of TPF between smooth and ribbed ducts results is 7.09% and 13.49%, respectively.
Experimental and Numerical Investigation of Flow and Heat Transfer in Stationary Two-Pass Rectangular Duct (AR=1:2) with Continuous and Broken V-Shaped Ribs Ramesh Erelli, Arun K. Saha Journal of Thermal Science and Engineering Applications, 2021 The combined experimental and large eddy simulations (LES) were performed in the stationary two-pass duct of aspect ratio (AR) 1:2. The experiments were conducted with three different rib arrangements, namely, 60 deg V, 60 deg V–IV, and broken 60 deg V–IV ribs, and the analysis was carried out with Reynolds numbers of 45,000, 60,000, and 75,000. The infrared thermography (IRT) technique is employed to obtain the local temperature distribution on heated smooth and ribbed surfaces. In all ribbed cases, the copper ribs are glued to the heated surface with a fixed rib height-to-hydraulic diameter (e/Dh) ratio of 0.125 and the rib pitch-to-height ratio (P/e) of 10 and 5 for continuous and broken ribs, respectively. In addition, the LES turbulence model was adopted for carrying out a simulation to understand the flow and heat transfer behavior in ducts populated with all three V-shaped ribs. The comparison of the time-averaged thermal fields generated using computations has been made with experimentally measured Nusselt numbers, friction factors, thermal performance factor (TPF), and Reynolds analogy performance parameter (RAPP) for all cases. The overall thermal performance factor was found to be quantitatively within 8.0–10.66% between experimental and numerical results. Among all the cases, the 60 deg V–IV ribbed duct provides the best TPF and RAPP than the other two ribbed ducts, whereas the smooth duct shows poor TPF.
