• The Journal of the Acoustical Society of Korea
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• v.31 no.1
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• pp.11-18
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• 2012

In this paper, the occurrence of a stopband phenomenon when an acoustic wave propagates through periodically corrugated ducts is discussed using theoretical and BEM analyses. A 2-D duct with sinusoidally corrugated upper and lower walls is considered. When the magnitude of the sinusoidal corrugation is sufficiently small compared to the duct's height, the wave equation is solved with the multiple scaling perturbation method. Then stopbands for Bragg and non-Bragg resonances are computed from the condition where frequency becomes a complex number. A 2-D BEM analysis is performed to compute insertion loss of the duct, and stopbands are confirmed as predicted by analytical analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.3
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• pp.88-93
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• 2019

This study concerns the distributions of flow in an air conditioning duct used for a marine and oil drilling ship. From the results of carrying out flow analysis and structural analysis of a ventilation duct applied to a marine structure, the following conclusion could be gained. The pressure tended to increase as the flow velocity at the inlet increased and the pressure at the inlet increased. It was recognized that the pressure decreased due to the influence of a corrugated tube when it entered and exited from the duct. As a result of structural analysis, a higher train was generated at the corrugated tube compared with the duct. In addition, in the case of the internal pressure of 0.7MPa, which was the designed load, it was found that there was almost no influence as it was within 0.1mm.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.339-344
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics in wavy ducts of primary surface heat exchanger. Experiments using a naphthalene technique are carried out to determine the local transfer characteristics for flow in the corrugated wall duct. The aspect ratios of the rectangular duct cross-section are 7.3, 4.7 and 1.8 with a corrugation angle of $145^{\circ}$. The Reynolds numbers, based on the duct hydraulic diameter, are ranged from 1000 to 5000. The local heat/mass transfer measurement is conducted in the spanwise directions. The results show that Tayler-Gortler vortices exist on the pressure surface. Flow separation on the suction surface appears at a high Reynolds number resulting in a sharp decrease in the local transfer rates, but relatively high transfer rates are obtained in the reattachment region.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.6
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• pp.569-580
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• 2005

The present study investigates the convective heat/mass transfer characteristics in wavy ducts of a primary surface heat exchanger. The effects of duct aspect ratio and flow velocity on the heat/mass transfer are investigated. Local heat/mass transfer coefficients on the corrugated duct sidewall are determined using a naphthalene sublimation technique. The aspect ratios of the wavy duct are 7.3, 4.7 and 1.8 with the corrugation angle of $145\Omega$. The Reynolds numbers, based on the duct hydraulic diameter, vary from 300 to 3,000. The results show that at the low Re(Re $\leq$ 1000) the secondary vortices called Taylor-Gortler vortices perpendicular to the main flow direction are generated due to effect of duct curvature. By these secondary vortices, non-uniform heat/mass transfer coefficients distributions appear. As the aspect ratio decreases, the number of cells formed by secondary vortices are reduced and secondary vortices and comer vortices mix due to decreased aspect ratio at Re$\leq$1000. At Re >1000, the effects of corner vortices become stronger. The average Sh for the aspect ratio of 7.3 and 4.7 are almost same. But at the small aspect ratio of 1.8, the average Sh decreases due to decreased aspect ratio. More pumping power (pressure loss) is required for the larger aspect ratio due to the higher flow instability.