Heat transfer characteristics of a cooling channel with densely arranged, angled rib turbulators were investigated experimentally and numerically. The dense arrangement of the ribs is one of the potential candidates to improve heat transfer performance because of its surface area enlargement effect.
The square test channel consisted of six square ribs, which were placed on one side. The ribs were arranged with a rib height to channel hydraulic diameter ratio (e/Dh) of 0.13, an angle of attack to the mainstream of 60deg, and rib pitch-to-height ratios (P/e) of 3, 6 and 10. Local heat transfer distribution on all surfaces of the rib and the floor surface between the ribs were measured by the naphthalene sublimation method. Channel Reynolds number ranges from 30,000 to 70,000. Measured data showed that the P/e of 3 provided the largest total heat transfer. It was found that 60% of heat flux was transferred through the rib surface.
Numerical simulations using a Reynolds-Averaged Navier-Stokes (RANS) method and a Large Eddy Simulation (LES) were carried out for the above test cases. The RANS underestimated the experimental heat transfer data by 40–50% for all rib surfaces with close rib arrangement. On the other hand, time-averaged heat transfer distribution obtained by LES showed better agreement with experimental data. Moreover, the LES predicted the periodic large vortex structure ranging over several rib pitches. Further investigation is expected on the periodic secondary flow and the application of LES to the prediction of heat transfer in the near future.
Hydrodynamic instabilities and heat transfer characteristics in the duct flow of a fluid in the supercritical thermodynamic regime