Location Optimization of Longitudinal Vortex Generators in Finned Tube Bundles

Abstract:

The flow and heat transfer characteristics of the single row finned tube bundle with longitudinal vortex generator are modeled using a validated laminar flow model. The cases of four different distance and five angles from the tube center are studied. It is found that the effect of vortex generator on the finned tube bundle is manifested in two aspects. One is the change of the size of the weak heat exchange zone behind tubes and the other is the change of vorticity intensity along the flow direction. Vortex generators can postpone the pipe flow separated point, mix the fluid of local and core areas, and increase the temperature gradient of the fluid. The results indicate that vortex generators have a good effect with an angle of 130 degrees and a distance ratio of 1.36 for single row finned tube in the Re range of 600 to 2 600, and the corresponding comprehensive performance increased by 7% to 30%. The application of the above optimization theory in 2row find tube heat exchangers indicates that the comprehensive performance of both inclined and staggered tube arrangements reaches the largest when the second row vortex generator is placed about 120 degrees around the related tube center, improving by 15% and 28% respectively.

Key words:laminar flow model; vortex generators; finned tube bundles; location optimization; flow and heat transfer characteristics