Longitudinal vortices have a great capability of disrupting the growth of boundary layers and bring about the heat transfer enhancement between the fluid and its neighbouring surface. The potential of a winglet pair type vortex generator for the heat transfer enhancement in a plate fin heat exchanger, with triangular fins as inserts, is numerically evaluated in this article. The rectangular winglet pair is mounted on the triangular fins. The numerical computations are performed by solving an unsteady, three-dimensional Navier-Stokes equation, and an energy equation by using the modified MAC method. Air is taken as the working fluid. This study shows the flow structure and the performance of the winglet pair in improving the heat transfer. The computations are performed at Re = 200 and placing the winglet at an angle of attack, β = 20 • . The results show that the heat transfer is increased by 13 per cent, even at the exit, with the winglet pair. The heat transfer enhancement with a winglet pair for different Re = 200-500 and Pr = 0.71 and for varying heights of the winglet pair is also predicted.
AThis study presents numerical computation results on laminar convection heat transfer in a plate-fin heat exchanger, with triangular fins between the plates of a plate-fin heat exchanger. The rectangular winglet type vortex generator is mounted on these triangular fins. The performance of the vortex generator is evaluated for varying angles of attack of the winglet i.e., 20, 26, and 37° and Reynolds number 100, 150, and 200. The computations are also performed by varying the geometrical size and location of the winglet. The complete Navier-Stokes equation and the energy equation are solved by the (Marker and Cell) MAC algorithm using the staggered grid arrangement. The constant wall temperature thermal boundary conditions are considered. Air is taken as the working fluid. The heat transfer enhancement is seen by introducing the vortex generator. Numerical results show that the average Nusselt number increases with an increase in the angle of attack and Reynolds number. For the same area of the LVG, the increase in length of the LVG brings more heat transfer enhancement than increasing the height. The increase in heat transfer comes with a moderate pressure drop penalty.
The present numerical analysis pertains to the heat transfer enhancement in a plate-fin heat exchanger employing triangular shaped fins with a rectangular wing vortex generator on its slant surfaces. The study has been carried out for three different angles of attack of the wing, i.e., 15°, 20° and 26°. The aspect ratio of the wing is not varied with its angle of attack. The flow considered herein is laminar, incompressible, and viscous with the Reynolds number not exceeding 200. The pressure and the velocity components are obtained by solving the continuity and the Navier-Stokes equations by the Marker and Cell method. The present analysis reveals that the use of a rectangular wing vortex generator at an attack angle of 26° results in about a 35% increase in the combined spanwise average Nusselt number as compared to the plate-triangular fin heat exchanger without any vortex generator.
SUMMARYLongitudinal vortices disrupt the growth of the thermal boundary layer, thereby the vortex generators producing the longitudinal vortices are well known for the enhancement of heat transfer in compact heat exchangers. The present investigation determines the heat transfer characteristics with secondary flow analysis in plate fin triangular ducts with delta wing vortex generators. This geometrical configuration is investigated for various angles of attack of the wing i.e. 15 • , 20 • , 26 • and 37 • and Reynolds numbers 100 and 200. The constant wall temperature boundary condition is used. The solution of the complete Navier Stokes equation and the energy equation is carried out using the staggered grid arrangement. The performance of the combination of triangular secondary fins and delta wing with stamping on slant surfaces has also been studied.
Efforts to meet ever-stringent fuel economy standards has led to increased focus on light weighting technologies, and proliferation of alternative powertrains such as hybrid vehicles. This has significantly increased the complexity of designing exhaust systems to meet high level NVH performances against thin powertrain targets. In this paper, some applications will be presented with latest efforts in addressing some of these challenges. (a) Novel methodologies in predicting exhaust high frequency flow noise using transient CFD simulations will be discussed. (b) Customized tuning applications: Case study in optimization, Daisy-chaining, and positioning of narrow frequency tuning applications (e.g., concentric tube Helmholtz resonators with tuned orifices, pipe length tuning) driven by tighter clearances and directed light weighting efforts will be discussed. (c) Hybrid applications—Hybrid powertrains pose a unique challenge as the engine can function both as power plant and a power generator, both of which have different NVH requirements. Efforts in addressing these challenges with limited packaging space will be discussed.
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