Computational fluid dynamics (CFD) and heat transfer simulations are conducted for a novel heat exchanger. The heat exchanger consists of semi-circle cross-sectioned tubes that create narrow slots oriented in the streamwise direction. Numerical simulations are conducted for Reynolds numbers (Re) ranging from 700 to 30,000. Three-dimensional turbulent flows and heat transfer characteristics in the tube bank region are modeled by the k-e Reynolds-averaged Navier-Stokes (RANS) method. The flow structure predicted by the two-dimensional and three-dimensional simulations is compared against that observed by the particle image velocimetry (PIV) for Re of 1500 and 4000. The adequate agreement between the predicted and observed flow characteristics validates the numerical method and the turbulent model employed here. The three-dimensional and the twodimensional steady flow simulations are compared to determine the effects of the wall on the flow structure. The wall influences the spatial structure of the vortices formed in the wake of the tubes and near the exit of the slots. The heat transfer coefficient of the slotted tubes improved by more than 40% compare to the traditional nonslotted tubes.
This paper presents the results of a numerical study on flow characteristics over circular, square, and diamond cross-sectional cylinders. Investigations are performed in a two-dimensional domain using the finite volume discretization method solver for Reynolds number, Re = 20 000. Unsteady Reynolds averaged Navier-Stokes equations with Spalart-Allmaras turbulence model have been used as a turbulence closure. After the validation of the simulations with the available experimental data from the open literature, global characteristics of the flow field around different shaped cylinders near the wall have been presented. Effects of wall proximity on cylinders are investigated for four different gap width (G) to cylinder width (D) ratios. Résumé :Nous présentons ici les résultats d'une étude numérique sur les caractéristiques d'écoulement d'un fluide sur la surface de cylindres de section efficace, circulaire, carrée et en diamant. Ces études se font sur un domaine 2D par voie d'une discrétisation en volumes finis, pour une valeur du nombre de Reynolds, Re = 20 000. Nous utilisons les équations de NavierStokes avec décomposition de Reynolds instable, additionnées du modèle de turbulence de Spalart-Allmaras utilisé pour fermer les équations de turbulence. Après validation des résultats à l'aide des résultats expérimentaux provenant de la littérature disponible, nous présentons les caractéristiques globales du champ d'écoulement autour des cylindres de différentes formes près de la couche limite (mur). Nous étudions l'effet de la proximité du mur sur les cylindres, pour quatre différents rapports de largeur d'espacement (G) sur la largeur du cylindre (D). [Traduit par la Rédaction]
Computational fluid dynamics and heat transfer simulations are conducted for a novel shell-tube type heat exchanger. The heat exchanger consists of tube with a narrow slot oriented in the streamwise direction. Numerical simulations are conducted for the Reynolds number of 1500. The 3D turbulent flow in the tube bank region is modeled by k-ε Reynolds stress averaging method by employing ANSYS FLUENT. 3-D transient flow and heat transfer simulations are conducted to determine the flow structure and temperature profiles in the wake of cylinders in the first row and other rows. The effects of the slot size and the orientation and the arrangement of the cylinder in different configuration will be examined. The slotted tube heat exchanger improved heat transfer by more than 27% compare to the traditional shell-tube heat exchanger without slots. Enhancement in heat transfer is even higher at higher values of Reynolds number.
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