CFD Study of the Effects of Groove Geometries on Heat Transfer for Internally Grooved Tubes

The CFD study investigated three different groove geometries: circular, rectangular, and trapezoidal grooves, and these results were compared to a smooth tube. The results obtained from this CFD study were compared with experimental work completed for Reynolds numbers of 10,000, 22,000, 34,000, and 38,000. A CFD analysis for Reynolds numbers between 10,000 and 50,000 were performed to further investigate the effects of heat transfer on these geometries. This CFD work validated the experimental results and analyzed three additional Reynolds numbers of 42,000, 46,000, and 50,000 to further evaluate the turbulence effect on heat transfer. For increasing Reynolds numbers in the turbulence region, the Nusselt number significantly increased. The Nusselt number for the grooved geometries was significantly greater than that of the smooth tube. The augmented grooves resulted in the greatest enhancement of heat transfer for the circular, rectangular, and trapezoidal grooves at a Reynolds number of 34,000 and were 63%, 31%, and 58%, respectively. These results are consistent with the experimentally obtained results for the circular, rectangular, and trapezoidal grooves of 63%, 47%, and 58%, when compared to the smooth tube. It was observed that overall thermal enhancement was greatest for the augmented grooves in the Reynolds number range between 10,000 and 20,000. The friction factor for each grooved tube increased with higher Reynolds numbers, while the smooth tube showed a reduction in friction factor for the range 10,000 < Re < 38,000. All three grooves had greater axial pressure drop than the compared smooth tube. The rectangular groove exhibited the greatest axial pressure drop, while the circular and trapezoidal grooves were similar in their results. The mean heat enhancement factors for the circular, rectangular, and trapezoidal grooves were determined to be 1.40, 1.12, and 1.25, respectively. Therefore, all three grooved geometries proved to be thermodynamically advantageous when compared to the smooth tube.