A Novel Ladder-Shaped Bridge Finned Tube for Convective Heat Transfer Enhancement

Abstract

Abstract In order to improve the convective heat transfer efficiency of a shell-and-tube heat exchanger, a novel ladder-shaped bridge finned tube (LBFT) is presented. The LBFT possesses outer low helical integral fins, two layers of staggered transverse bridge, upper passage, middle passage, and bottom passage. The convective heat transfer performance of the LBFT is studied and experimental results show that the Nusselt numbers outside the tube and the overall heat transfer coefficients of the LBFT are significantly greater than those of the smooth tube. The bridges, bridge roots, and pores formed on the outer fins contribute to the larger heat transfer coefficient. Both the Nusselt number and the overall heat transfer coefficient decrease, while the friction resistance coefficient increases with outer helical fin pitch increasing and bridge width increasing. As the Reynolds number increases, the comprehensive performance evaluation criterion (PEC) decreases at first and then increases. The maximum PEC occurs at the Re number of 2300 and is up to 1.34.