Effect of Arrangement of Tube Banks on Acoustic Resonance

Hiromitsu Hamakawa,Tatsuaki Nakamura,Eru Kurihara,Eiichi Nishida,Kenta Asakura

doi:10.4236/ojfd.2012.24a038

Abstract

In the present paper the attention is focused on effect of arrangement of tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We have examined the characteristics of vortex shedding and acoustic resonance generated from in-line and staggered tube banks. At the small tube pitch ratio in in-line tube banks, acoustic resonance of third and fourth mode in the transverse direction occurred. As the tube pitch ratio in the flow direction decreased, the vortex shedding frequency became broad-band. The alternative vortex shed from in-line tube banks. The multiple resonance modes were generated within the broad-band vortex shedding frequency. And the acoustic resonances of lower-order modes occurred at the higher gap velocity. On the other hand, at the small tube pitch ratio in staggered tube banks, acoustic resonance did not occurred, although the vortex shed at the resonance frequency in tube banks. The pressure drop at staggered tube banks was larger than that of in-line tube banks. The symmetric vortices were observed inside staggered tube banks at the small tube pitch ratio.

Highlights

In heat exchangers, such as boilers for commercial use, acoustic resonant noise is occasionally generated in the ducts when gas is flowing laterally with respect to the axis of the tubes
We have examined the characteristics of vortex shedding and acoustic resonance generated from in-line and staggered tube banks
The multiple acoustic modes for lower acoustic damping were occurred within the broad-band vortex shedding frequency

Summary

Introduction

In heat exchangers, such as boilers for commercial use, acoustic resonant noise is occasionally generated in the ducts when gas is flowing laterally with respect to the axis of the tubes. The acoustic resonant noise generated from heat exchangers is usually caused by the resonance of acoustic modes inside the boiler and vortex shedding from the tube banks. Many studies have been published on the excitation mechanisms causing acoustic resonance in the tube banks in cross-flow [5,6,7,8]. It is generally known that vortex shedding frequency varies with the pitch ratio of the tube arrangement. There are many studies on the vortex shedding frequency in the tube banks in cross-flow [6,7,9,10,11,12]. The purpose of the present investigation was to clarify experimentally the effect of arrangement of tube banks on acoustic resonance which occurred in the two-dimensional model similar to an actual boiler plant. We have examined the effect of tube pitch ratio on acoustic damping and vortex shedding from tube banks

Experimental Apparatus and Procedure

Acoustic Damping

Acoustic Resonance

Vortex Shedding Characteristics

Conclusions