Numerical study of fluid flow and heat transfer over a series of in-line noncircular tubes confined in a parallel-plate channel

Two-dimensional steady developing fluid flow and heat transfer across five in-line tubes confined in a channel were studied numerically for a fluid with a Prandlt number of 0.7. The tube cross-sectional shapes studied were circular, flat, oval, and diamond. Domain disrectization was carried out in body-fitted coordinate system. The contravariant components of velocities were used as the dependent variables. The governing equations were solved using a finite-volume technique. Grid independence study was carried out by running the developed code for several different grid sizes for each of the four geometric configurations and monitoring module average Nusselt number and normalized pressure drop. The results for flat, oval, and diamond tubes were compared with each other and with those for circular tubes. Flat and oval tubes offered greater flow resistance and heat transfer rate when compared to circular tubes for all values of Reynolds number (Re) considered in this study. Diamond tubes offered less resistance to flow compared to circular tubes for Re <= 250. For all values of Re, diamond tubes exhibited the lowest heat transfer rate. When both the flow resistance and heat transfer rate were considered, diamond tubes were better than flat and oval tubes for Re < 40. For Re > 50, flat and oval tubes performed better. Both geometry and flow field were major factors affecting the heat transfer performance for Re > 50, whereas geometric shape was found to affect performance for Re > 50 more significantly.