Heat Transfer Augmentation using Rectangular Cross-Section Turbulence Generators in Confined Quasi-Two-Dimensional Magneto-Hydrodynamic Flows

摘要

Heat transfer efficiency from a duct side-wall in which an electrically conducting fluid flows under the influence of a transverse magnetic field is investigated in the present work. The study intends to provide useful guidelines to improve efficiency of MHD cooling systems while also taking into account that practical designs should be both thermally efficient and inexpensive in terms of pumping power. A quasi-two-dimensional MHD model is employed to model the flow using highresolution direct numerical simulation. The gap height, incidence angle and spacing ratio of rectangular cylinders with aspect ratio α=1/2 and blockage ratio β=1/4 are independently varied to establish optimal configurations determined by an efficiency index; the ratio of heat transfer enhancement to pressure drop penalty. At gap heights between 2 and 1.5 cylinder lengths L_c from the heated duct wall it was found that 95% of the peak heat transfer efficiency can be achieved. Furthermore, cylinders offset at a gap height of G = 1.5L_c experienced no additional efficiency benefits from cylinder inclination. However, cylinders placed at the duct centreline received improved thermal efficiency for -15°≤γ≤30°. For upright tandem configurations at a gap height of G = 1.5L_c, peak efficiency ηeff = 1.317 and heat transfer HR = 2.541 occurred at spacings of (S-h_c)/L_c = 6 and (S-h_c)/L_c = 8, respectively.