Heat Transfer and Fan Power Performance of a Developing Grooved Passage Flow Including Inlet and Exit Effects

Enhanced heat transfer surfaces are used frequently in a variety of practical devices. In the past, transverse surface grooves have shown promise in heat transfer augmentation. These lead to the formation of free shear layers and traveling waves, which augment convective transport normal to the passage walls. In the current work, two-dimensional Navier-Stokes simulations of heat and momentum transport using the spectral element technique are used to investigate the heat transfer and fan power performance of the developing regions of finite-length, grooved channel passage arrays. This study also considers the accelerating and decelerating flows entering and exiting the arrays. The computational domain has in inlet region followed by two passages stacked one above the other with thirty contiguous transverse grooves cut symmetrically into opposite walls and then a sufficiently long exit region that allows pressure recovery to take place. The performance metrics defined in the work include the average array Nusselt number and the total required fan power. The performance of the grooved channel arrays is compared with that of flat passage arrays with the same average wall center-to-center spacing (equal flow volume) for the Reynolds number range 1000 to 3000. The addition of grooves improves the overall heat transfer by a factor of 1.46 at Re=1000 and by a factor of 2.75 at Re=3000. The current calculations will provide guidance for future three-dimensional calculations of heat transfer versus fan power performance of developing flow within grooved passage arrays. Earlier studies show that three-dimensional results more accurately reproduce experimental results for Reynolds numbers greater than roughly 600.