Flow Felid and Heat Transfer Enhancement Investigations by using a Combination of Corrugated Tubes with a Twisted Tape Within 3D Circular Tube Based on Different Dimple Configurations

Different dimple geometrical configurations with a combination of corrugated tubes and twisted tape are numerically investigated. Water is used as a working fluid for constant heat flux heat transfer condition at the pipe wall. The diameter of the dimples used in this work are 1, 2, 3 and 4 mm. However, the corrugation configuration diameters are 1 mm and twisted tape of 2 mm inside the pipe are kept constant. The numerical simulations are carried out at the Reynolds number in the range of 1500 to 14000. The results reveal that the friction factor (f) and Nu number are augmented as the dimple diameter increase. The Nu number ratio of 1.25 is found for dimple pipe tube with a diameter of 4 mm. The numerical outcome presented that there is more mixing, secondary and vortex produced in the main flow direction and near the pipe wall due to the rotating flow induced by twisted tape. Moreover, mixing, secondary vortices and rotational flow are originated behind the dimple, twisted tape, and corrugation surfaces. These rotational and vortices can promote mixing in flow between the thermal boundary layer and velocity boundary layer. So, increase the heat transfer enhancement. The improved pipes with different dimple diameters produce the maximum PEF of 1.25.