Numerical and Experimental Study of Heat Transfer Augmentation Using Pin-in-Dimple Vortex Generators

The article presents the results of a comparative numerical and experimental study of the flow structure and heat transfer during air flow in rectangular channels with cylindrical pin and pin-in-dimple turbulators placed singly and in staggered arrays. Visualization of vortex structures showed that in the case of pin-in-dimple intensifiers, horseshoe vortex has higher size and overall intensity. This effect allows to significantly minimize the stagnation zone behind the pin, due to which it is possible to increase heat transfer. It was found that the use of a single pin-in-dimple turbulator allows to increase the maximum Nusselt number by 10-15% in comparison with the cylindrical pin. Staggered arrays of pin-in-dimple intensifiers also have increased thermal efficiency in comparison with arrays of pin intensifiers: the Nusselt number increases to 10-20% with a maximum increase in the diameter of the dimple and its depth. From the point of view of total thermal-hydraulic efficiency in the range considered, the optimal ones are pin-in-dimple intensifiers installed in staggered arrays with a small relative depth of the dimple, the use of which allows increasing the thermal-hydraulic efficiency coefficient by 4-12% in comparison with arrays of cylindrical intensifiers without a dimple.