The Influence of Detached Rib Locations on the Channel Thermal Performance

The study describes a numerical investigation of the flow and heat transfer characteristics in a rectangular channel with detached ribs. Eight different detached locations are studied and a channel with traditional attached ribs serves as a baseline. The detached location is represented by the detached distance off the ribbed surface and the detached distance is denoted by d. The flow structure, heat transfer characteristics, pressure loss penalty, and thermal performance index in the rectangular channel with detached ribs are obtained with Reynolds numbers ranging from 8000 to 27,000. The results obtained show that part of the fluid and recirculation flow B leaks from the clearance, generating a clearance flow. The clearance flow impinges on recirculation flow A and is compelled to lift, disturbing and mixing with mainstream. The highest level of the averaged Nusselt number is in the case with d/Dh = 0.0075 (where Dh is the hydraulic diameter), while the case with d/Dh = 0.05 gives the lowest Nusselt number. The case with d/Dh = 0.0075 yields best thermal performance at a Reynolds number of 8000, and the highest thermal performance enhancement at a Reynolds number of 16,000, 4.42% higher than that in baseline, owing to the highest averaged Nusselt number and limited pressure loss penalty.