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 electricallyconducting fluid flows under the influence of a transversemagnetic field is investigated in the present work. Thestudy intends to provide useful guidelines to improve efficiencyof MHD cooling systems while also taking into account thatpractical designs should be both thermally efficient and inexpensivein terms of pumping power. A quasi-two-dimensionalMHD model is employed to model the flow using highresolutiondirect numerical simulation. The gap height, incidenceangle and spacing ratio of rectangular cylinders with aspectratio α=1/2 and blockage ratio β=1/4 are independentlyvaried to establish optimal configurations determined by an efficiencyindex; the ratio of heat transfer enhancement to pressuredrop penalty. At gap heights between 2 and 1.5 cylinderlengths L_c from the heated duct wall it was found that 95% ofthe peak heat transfer efficiency can be achieved. Furthermore,cylinders offset at a gap height of G = 1.5L_c experienced noadditional efficiency benefits from cylinder inclination. However,cylinders placed at the duct centreline received improvedthermal efficiency for -15°≤γ≤30°. For upright tandemconfigurations at a gap height of G = 1.5L_c, peak efficiencyηeff = 1.317 and heat transfer HR = 2.541 occurred at spacingsof (S-h_c)/L_c = 6 and (S-h_c)/L_c = 8, respectively.