Heat Transfer of Few Row Bundles of Screw-shaped Tubes

Abstract

The article is devoted to assessing the impact of a number of transverse rows of tubes on heat transfer in heat exchangers with helical tubes in order to create a generalized dependence for calculating the correction factor that takes into account the impact of transverse rows of helical tubes z2 on heat transfer of bundles.The studies of the convective heat transfer of the staggered bundles of helical tubes with cross flow of air were carried out in a pilot plant, represented by the open-type wind tunnel of rectangular cross section in the range of the Reynolds numbers from 5,000 to 70,000.The article describes the generalized dependence to calculate the factor that takes into account the impact of the transverse rows of helical tubes on heat transfer of the bundles. The findings showed an increase of heat intensity during the transition from the first to the second and the third rows of the bundle, which is explained by the increase of the degree of turbulence of the flow as it travels deep into the bundle. To calculate the correction factor for few row bundles of helical tubes it is recommended to use the dependence obtained for the staggered bundles of round tubes with washer and helical ribbing in case of S1/S2g 2.The studies can be used to select the solutions when designing new heat exchangers of heat exchange elements in the form of helical tubes, used in air heaters- regenerators of gas turbine installations.The results can form the basis of thermal calculations when designing new heat exchangers of helical tubes.