Heat Transfer Enhancement by Vortex Generators Consisting of Rectangular Blades Insertion in a Duct

A quantitative estimate of heat transfer enhancement is discussed here based on the measuements of local coefficients of heat transfer and friction for air flow over a range of Reynolds number from Re=9400 to 28200. Pairs of vortex generators consisting of two rectangular blades, increasing linearly in separation downstream, are aligned laterally to the flow with a spacing W. Characteristics of spanwise local heat transfer and pressure coefficients are found to vary differently over two regions of W. For small W, the phase of their distribution is shifted by 180° from the patterns observed just downstream of the blades. For large W, no phase change is observed but changes of the pattern between paired blades are distinctive. Overall heat transfer coefficients are more than double those for a smooth duct without generators. As a result, the performance ratio is greater than unity for all values of W