Noise prevention in tube-type heat exchangers employed in gas turbines.

Adachi

Matsuoka

et al. 2014

JFST

Weaver, 1993, Ziada and Oengören, 1993). The vortex excitation has been shown to result from the formation of periodic vortices in the space between the tubes (Weaver, 1993, Ziada and Oengören, 1993). Recently, finned tubes have been used in heat recovery steam generator to enhance heat transfer. The fins are mounted spirally around a bare tube surface so as to simplify the production process. It is generally believed that vortex-induced vibration can be suppressed by mounting helical strakes around a bare tube (Blevins, 1986, Zdravkovich, 1981). Zdravkovich (1981) showed that helical strakes consisting of several fins acting as surface protrusions around a bare tube can also reduce vibration. However, acoustic resonance and vortex shedding phenomena still occur occasionally in the

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

Aeolian tone radiated from a circular cylinder with solid spiral fin in cross flow

Adachi

Matsuoka

et al. 2014

JFST

“…Some studies have reported the characteristics of the acoustic resonance and vortex shedding generated from finned tube banks. Suzuki et al (12) and Nemoto et al (13)~ (15) suggested that acoustic resonance was generated also in finned tube banks. Chen (5) , Mair (16) , Kouba (17) , Kawaguchi et al (18)~ (20) , Hirota et al (21) , Ziada et al (22) , and Hamakawa et al (23) observed significant vortex shedding in finned tube banks and also in the wake of a single finned tube.…”

Section: Introductionmentioning

confidence: 98%

Vortex Shedding from Tube Banks with Closely Mounted Serrated Fin

Muraoka

Nishida

et al. 2011

JEE

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.

“…Chen (6) , Kouba (7) , Hamakawa et al (8) , Kawaguchi et al (9) and Ziada et al (10) have shown that the vortex shedding was remarkably observed in fin tube banks or in the wake of a single fin tube. Mair et al (11) , Suzuki et al (12) , Hamakawa et al (13) and Ziada et al (10) have reported that the vortex shedding frequency was correlated with the tube effective diameter.…”

Section: Introductionmentioning

confidence: 99%

Vortex Shedding from a Circular Cylinder with Spiral Fin

Nakashima

Kudo

et al. 2008

JFST

The effect of simple spiral fin around a bare tube on Karman vortex shedding was experimentally investigated. We measured the distributions of the mean velocity, the intensity of velocity fluctuation, the spectrum of velocity fluctuation and the coherence distribution of Karman vortex in the spanwise direction. And the flow around a fin tube was visualized by using smoke wire technique. As a result it was made clear that the periodic velocity fluctuation caused by Karman vortex was remarkably observed in the wake of the fin tube although the fin was mounted around a bare tube with a large pitch along the tube axis. The vortices in the near-wake of the fin tube make cells structure with the scale of the pitch length of the fins. The rotation axis of each vortex was inclined against the tube axis. The large scale vortex was formed by the coalescence of the vortex cells. Therefore, the spanwise scale of the vortex in the wake of the fin tube was larger than one pitch of the fins.