APPLICATION OF DIMPLES AND HELICAL GROOVES ON THE OUTTER SURFACE OF TUBES TO INCREASE THERMAL-HYDRAULIC EFFICIENCY OF TUBE BUNDLES AT CROSS FLOW

Abstract

The flow structure and thermo-hydraulic efficiency of cross flow of tube bundles with dimples and helical grooves have been analyzed. The Reynolds number range (103-104) was typical for industrial heat exсhangers. It was found that dimples and grooves decrease scientifically the cylinder wake area and reduces the hydraulic losses. The heat transfer augmentation in five-row tube bundle by dimples is 35-40% while pressure drop increase by 10-15%. The hydraulic resistance of two-row bundle of tube with helical grooves is 20% lower than that of a smooth tube bundle, while heat transfer augmentation is absent. The value of Reynolds analogy factor for tube bundles with dimples and helical grooves exceeds unity. The high thermo-hydraulic efficiency of tube bundles with dimples and helical grooves, allows us to recommend it for practical use in the development of modern heat exchange equipment of the tubular type.