Heat transfer enhancement using vortex promoters in magneto-hydro-dynamic flows

The effect of vortex promoter orientation on heat transfer enhancement from a duct side-wall in which an electrically conducting fluid flows under the influence of a transverse magnetic field is investigated. A quasi-two-dimensional magneto-hydrodynamic model is employed to model the flow using high resolution numerical simulation. The gap height and angle of attack of a cylinder with rectangular cross-section (aspect ratio 휶=ퟏ/ퟐ) and blockage ratio 휷=ퟏ/ퟒ, were independently varied to establish relationships between obstacle configuration and heat transfer efficiency. The heat transfer efficiency is measured through an efficiency index defined by the ratio of heat transfer enhancement to pressure drop penalty in comparison to an empty duct case. At gap height ratios ퟏ.ퟏퟓ≤푮/푳풄<ퟐ for an upright cylinder above a heated lower wall, thermal enhancement and efficiency can be improved, with a peak thermal efficiency of 휼=ퟏ.ퟔ occurring at 푮푳풄⁄=ퟏ.ퟓ. For a cylinder offset at 푮푳풄⁄=ퟏ.ퟓ, varying the incidence angle through −ퟑퟕ.ퟓ°<휸≤ퟐퟐ.ퟓ°, −ퟕ.ퟓ°<휸<ퟎ° and ퟎ°<휸≤ퟏퟓ° can lead to additional thermal efficiency benefits, with a global peak efficiency of 휼=ퟏ.ퟕ occurring at 휸= −ퟑퟕ.ퟓ° .