Application with Winglet-Type Vortex Generators in an In-line Tube Arrangement

Heat transfer enhancement and pressure loss penalty caused by three-row winglets built in three-row tube-bundles in an in-line arrangement, are compared between 'common flow up' and 'common flow down' winglet configurations. The 'common flow down' winglet-pairs recommended by the previous researchers bring about to increase in heat transfer enhancement and to increase in pressure loss penalty, in comparison with fin-tube bundles without winglets. For the 'common flow up' winglet-pairs, the spanwise distance between the trailing edges () of winglet pairs was changed and investigated. Two types ot winglet are applied for triangular and rectangular shapes. In the triangular winglets with =5 mm in in-line tube bundles, the heat transfer increased up to , and simultaneously the pressure loss decreased by to for the Reynolds number (based on two times channel height) ranging from 300 to 2700, when the 'common flow up' winglets were built in. The performance of fin-tube bundles with triangular winglets is much superior to the rectangular one, because of the smaller pressure-loss penalty.