Abstract
This paper investigates numerically the influence of detached square vortex generator (VGs) on the heat transfer and pressure drop inside a square duct. Reynolds number is fixed at 5000. The geometrical parameters in this investigation are: i) The blocking ratios are 0.1, 0.15 and 0.2), ii) Vortex generator numbers are 1, 2, and 3), iii) Attack angles are 0, 30, and 45, iv) The aspect ratios are 1, 1.5 and 2. The numerical simulation is carried out using ANSYS FLUENT 15 . The results show that the rectangular vortex generators have a positive influence on heat transfer as a result of the augmentation in turbulence level. The maximum enhancement in average heat transfer could reach 40%. The heat transfer is found to increase with the blocking ratio. The heat transfer enhanced by 17% for one VG and 28% for 3 VGs for blocking ratio = 0.2. The VGs at angle value of 45° produce the highest heat transfer enhancement. The aspect ratio is found to have an adverse effect on heat transfer rate.
Highlights
Heat transfer enhancement is any process objectives to improve the performance of a heat system or to increase heat transfer coefficient through utilization of various techniques
For Reynolds number in range of 200–1600, the results showed that the rectangular VGs led to the highest heat transfer enhancement and this enhancement increases with the nanofluid volume fraction
The numerical simulation is carried out with the CFD commercial software Ansys Fluent 15. This investigation aims to demonstrate the effect of blocking ratio (BR), VGs number, attack angle (θ) and VGs aspect ratio (AR) as in table 1
Summary
Heat transfer enhancement is any process objectives to improve the performance of a heat system or to increase heat transfer coefficient through utilization of various techniques. In active techniques external power contribution during operation is required to improve heat transfer such as electric or acoustic fields, surface fluid vibration etc.. .In passive techniques, no additional power input during operation is required but special surface geometries were fitted throughout the various industrial processes. The additional power needed to enhance heat transfer is taken from the power in a system, which eventually leads to increase in pressure drop. It is essentially employed by inserting simple geometry in the flow passage or adding fluid additives. These surfaces perform good fluid mixing and increase both turbulence and heat transfer area [2]. Passive techniques can be achieved by providing various roughen surfaces or tabulators in addition to adding vortex generators, which create three-dimensional fluid mixing through generating transverse or longitudinal vortices in the flow field [3]
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