Vortex Shedding from Tube Banks with Closely Mounted Serrated Fin

Abstract

This paper focuses on the vortex shedding from tube banks with closely mounted serrated fin. The tube banks were installed rigidly in the test section of a wind tunnel. We measured the mean velocity, the velocity fluctuation spectrum, and the gap velocity in the model tube banks that had the same pitch ratio as a boiler heat exchanger. We found two types of vortex shedding with different Strouhal numbers S t of 0.40 and 0.20 in the case of Reynolds numbers R e in the range 2.8 × 10 4 to 6.2 × 10 4. Strouhal numbers were calculated by using the measured values of the vortex shedding frequency, the gap velocity, and the equivalent diameter. The vortex shedding for S t = 0.40 was mainly formed within the finned tube banks and the other vortex shedding for S t = 0.20 was in the wake of the finned tube banks. The Strouhal number of the vortex shedding inside the finned tube banks changed from 0.40 to 0.32 for R e = 6.2 × 10 4. The applicability of the equivalent diameter, obtained from a single circular cylinder with a serrated fin, to the finned tube banks was examined. The calculated Strouhal number of 0.32 agreed with a Strouhal number of 0.30 obtained from Fitz-hugh's map for bare-tube banks. The Strouhal number of 0.20 is similar to that for vortex shedding from a circular cylinder.

Design Optimization of Shell and Tube Heat Exchanger by Vibration Analysis

“…The characteristics of vortex shedding from tube banks with closely mounted serrated fin was investigated in [1] where the relationship between the Strouhal number defined by the equivalent diameter as the characteristic length of a finned tube in the tube banks and the Strouhal number map for bare-tube banks was examined. Whereas in [2] the author has presented various outlet conditions of a shell and tube heat exchanger theoretically and experimentally in which it is observed that prime parameter geometry of outlet affects the performance, maintenance and life span of a vertical shell and tube evaporator.…”

“…In this proposed work design, development & testing of STHE is carried out. Along with the parameter considered in [1][2][3][4][5][6][7][8], vibration analysis is performed to optimized unsupported span of tube by using HTRI software. Detail overview on work carried out by researchers is presented in Section 1, Section 2 & 3 states mechanics of flow-induced vibration and the current problem definition & objective, details of STHE is given in Section 4.…”