NUMERICAL SIMULATION OF ENHANCEMENT OF HEAT TRANSFER IN A TUBE WITH AND WITHOUT ROD HELICAL TAPE SWIRL GENERATORS

The heat transfer augmentation techniques are widely utilized in many applications in the heating process to enable reduction in weight and size or increase the performance of heat exchangers. These techniques are classified as active and passive techniques. The active technique required external power such as surface vibration and electric or acoustic fields, whereas the passive techniques required fluid additives, special surface geometries, or swirl/vortex flow devices, that is, twisted tape inserts. Computational heat transfer flow modeling is one of the great challenges in the classical sciences. As with most problems in engineering, the interest in the heat transfer augmentation is increasing due to its extreme importance in various industrial applications. CFD modeling for the heat transfer augmentation in a circular tube fitted with and without rod helical tape inserts in turbulent flow conditions has been explained in this paper using ANSYS Fluent version 14.0. Numerical simulation analyses will be carried out to study thermal-hydraulic characteristics of air flow inside a circular tube with different tube inserts. The flow rate of the tube is considered in a range of Reynolds number between 2300 and 8800. The swirling flow devices consisting of: the full- length helical tape with or without a centered-rod of a concentric tube heat exchanger. Finally results will be compared to available experimental and analytical calculations. The data obtained by simulation are matching with the literature value for a plain tube with the discrepancy of less than plus or minus 5% for Nusselt number and for the friction factor. Enhanced heat transfer with decreasing twist ratio has been observed. Heat flux is more uniform all along the tube and decreases uniformly towards the center