Abstract:

In tube bank heat exchangers, heat transfer is carried out with another fluid which is passed around in the cross direction to the fluid inside the tubes. The fluid that passes through the outside of the tube in the cross direction is also mostly gas fluids. In tubes placed one after another, the highest heat transfer is usually obtained in the first tube. The heat and flow characteristics become similar to each other after the first tube. In this case, periodic flow is obtained by repeating the velocity and temperature contours. Ensuring that the boundary layer is constantly renewed in successive tubes allows obtaining high heat transfer in the other tubes, as in the first tube. While improving heat transfer, the most important problem is the increase in pressure drop. In this study, a numerical optimization was carried out in order to increase the heat transfer and reduce the pressure drop by using tubes of four different diameters placed in an in-line arrangement. Comparisons are made assuming that the heat transfer surface area is constant and the longitudinal and transversal distances between the tubes are the same. If the diameters of four tubes are placed successively where D_1=5 mm,D_2=15 mm,D_3=6 mm,D_4=14 mm, the heat transfer increases by 14.5% and the pressure drop increases by 377%.

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