Experimental and numerical investigations of heat transfer and fluid flow in a rectangular channel with perforated ribs

The present work concentrates on perforated 90 degrees ribs to improve the thermal performances in a rectangular cooling channel with an aspect ratio of 4:1. Three different types of perforated ribbed channels are designed and compared. Steady-state Liquid Crystal Thermography (LCT) is employed to measure surface temperature and derive heat transfer coefficients over the ribbed surfaces in the tested channels. The turbulent flow details are presented by numerical calculations with two established turbulence model, i.e., the k-omega SST (Shear Stress Transportation) model and the DES (Detached Eddy Simulation) model. Compared with the normal rib (Case 1), the low heat transfer behind the ribs is improved by the perforated ribs with slightly reduced pressure drop. This phenomenon is more obvious when the perforated ratio is larger (Case 4). The local heat transfer is enhanced by about 12%-24% and the overall heat transfer is enhanced by about 4%-8%. The overall thermal performance is also improved by the perforated ribs with a slightly reduced pressure drop. The recirculating flows behind the ribs are reduced by the perforated cases. The reduced recirculation flows enhance the local heat transfer in this region. However, the flow reattachment region is disturbed by the perforated ribs and the local heat transfer in this region is slightly decreased. As a perforated rib can improve the overall thermal performance and provide more uniform heat transfer fields, it is promising for applications in internal cooling of turbine blades.