An experimental and numerical study of flowand heat transfer in ribbed channels with large rib pitch-to-height ratios

This paper presents an experimental and numerical study of flow and heat transfer char teristics in rectangular crosssection ribbed channels with continuous transverse ribs with large pitch-to-height ratios. Five ribs are regularly placed on the bottom wall of the channels with varied rib pitch-to-height ratios ranging from 10 to 30. The channel inlet Reynolds number ranges from 57,000 to 127,000 based on the channel hydraulic diameter. The studied geometry is relevant for hot internal structures in aircraft engines. In this study, the steady state, liquid crystal thermography (LCT) technique is used to obtain detailed heat transfer coefficients in the inter-rib surface regions. Then a computational fluid dynamics (CFD) technique based on the solution of the Reynolds-averaged Navier-Stokes (RANS) equations is employed to study flow and heat transfer characteristics in ribbed channels. The realizable κ - ε turbulence model is used as the turbulence closure. The numerical results show a good agreement with the experimental data. An important purpose of this study is to investigate the flow and heat transfer behavior between the first repeated ribs, i.e., in the regions where the flow and thermal fields are not yet periodically fully developed.