Characteristics of Flow and Heat Transfer in Stationary Two-Pass Square Duct with Continuous and Broken V-shaped Ribs

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 with different rib arrangements, namely, 60° V, 60° V-IV and broken 60° V-IV ribs. In all ribbed cases, the copper ribs are glued to the heated surface with a fixed rib height-to-hydraulic diameter ratio of 0.125 and a rib pitch-to-height ratio of 10 and 5 for continuous and broken ribs, respectively. In addition to the experimental study, Large Eddy Simulations (LES) with an eddy viscosity-based Smagorinsky-Lilly turbulence model were carried out to assess the fluid flow behaviour and its role in heat transfer enhancement in baseline smooth and 60° V-IV ribbed ducts at a fixed Reynolds number of 45000. The performance of LES results of smooth and 60° V-IV ribbed ducts are checked through the comparison of the time-averaged thermal fields with experimentally obtained Nusselt numbers, friction factors, and thermal performance factors(TPF). In all test cases, the 60° V-IV ribbed duct provides the best TPF compared to the other two ribbed ducts, whereas the smooth duct shows poor TPF. Based on this investigation, the 60° V-IV ribbed arrangement is recommended for the application of the gas turbine internal cooling. A decent match between experiments and numerical predictions was observed. However, the maximum deviation of TPF between smooth and ribbed ducts results is 7.09% and 13.49%, respectively.