Numerical Investigation of Flow Structures and Their Impact on Heat Transfer Performance in a Staggered Arrangement of Rectangular Winglet Pair Vortex Generators in a Fully Developed Channel Flow

Christoffersen, Kristian Fodgaard ; Bjerg, Allan

4. term

Energy Engineering, Master

2018

2018-06-01

108 pages

Heat exchangers are used in many practical applications throughout the world. For applications involving liquidto-gas heat transfer, the gas-side accounts for the vast majority of the thermal resistance. One way of improving the heat transfer is by the use of vortex generators (VGs) such as winglets. VGs generate vortices that interact with the thermal boundary layer and thereby enhance the heat transfer. The present work investigates how variations in winglet height and longitudinal pitch distance affect the flow phenomena and resulting heat transfer and pressure loss for rectangular winglet pair VGs in a staggered periodic arrangement. A Large Eddy Simulation (LES) model to simulate periodic flow and heat transfer is developed for the numerical investigations. To validate the LES model, an experimental setup is developed to facilitate Laser Doppler Anemometry (LDA) measurements. The LDA measurements and LES simulations show good correspondence with a mean deviation of ≈ 5 %. The numerical investigations prove the highest performance at a smaller winglet height and larger longitudinal pitch distance, which is attributed to the fact that the generated vortices in this configuration have a good interaction with the thermal boundary layer without causing a significant pressure loss.

Vortex generator ; Large Eddy Simulation ; CFD ; Laser Doppler Anemometry ; Streamlines ; iso-contour

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