Numerical Simulation On Heat Transfer Performance Of Direct Air-Cooled Condenser With Cylindrical-shell Winglet Vortex Generator

With dimensionless number (j/j0)/(f/f0)1/3, the performances of pressure drop and heat transfer of six kinds of vortex generators in single-row wavy-finned flat tube of direct air-cooled condenser were numerically investigated with Re ranged from600to1800. The considered vortex generators included rectangular winglet, delta winglet, trapezoidal winglet, cylindrical-shell rectangular winglet, cylindrical-shell delta winglet and cylindrical-shell trapezoidal winglet. In order to ensure the reliablity of numerical procedure, the numerical methods and results were verified by the reported experimental results and the grid independence solution. In addition, the effect of parameters of cylindrical-shell trapezoidal winglet were evaluated. The parameters included angle of inclination, the angle of attack, position, installation modes and rows.The simulation results show that rectangular winglet has the best heat transfer enhancement and the largest pressure drop in these vortex generators whose factors j and f are14.27%and18.32%higher than those of the flat tube respectively. The pressure drop and heat transfer of cylindrical-shell trapezoidal winglet are lower than the rectangular winglet by4.7%and1.5%at Re=1729respectively, and then, with regard to the comprehensive factor(j/j0)(f/f0)1/3, cylindrical-shell trapezoidal winglet has the best overall performance in the six kinds of vortex generators. The investigation on paraments of cylindrical-shell trapezoidal winglet shows that for single vortex generator, with the angle of inclination a=12°, the angle of attack β=30°, distance from tube c=2mm, distance from entrance b=50mm, low-tail close to tube, the cylindrical-shell trapezoidal winglet has best overall performance; as a pair in one row, the overall performance of leading edges spacing11mm is better than that of3mm, and three staggered rows is superior to three in-line rows.The dimensionless correlation is developed based on the calculated results. The correlation includes Nusselt number, Reynolds number, angle of inclination, angle of attack, distance from the tube and distance from the entrance about cylindrical-shell trapezoidal winglet in single-row wavy-finned flat tube. This correlation can be helpful to designing and optimizing the single-row wavy-finned flat tube with cylindrical-shell trapezoidal winglet.Finally, with the ω-NTU method it is found that under the condition of the same outlet air temperature, cylindrical-shell trapezoidal winglet can reduce heat transfer area of single-row wavy-finned flat tube of direct air-cooled condenser by12.54%, which indicates its significance for application in engineering.