• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.546-552
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• 2001

The heat transfer and flow measurements on a pedestal encountered in chip cooling. A uniform wall temperature boundary condition at the plate surface and on a pedestal was created using shroud method. Liquid crystal was used to measure the plate surface temperature. The jet Reynolds number (Re) ranges from 11,000 to 50,000, the dimensionless nozzle-to-surface distance (L/d) from 2 to 10, and the dimensionless pedestal diameter-to-height (H/D) from 0 to 1.0. The results show that the Nusselt number distributions at the near the pedestal exhibit secondary maxima at $r/d{\cong}1.0\;and\;1.5$. The formation of the secondary maxima is attributed to an create in the vortex by the pedestal.

• 대한기계학회논문집B
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• 제27권1호
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• pp.1-8
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• 2003

The heat transfer and flow measurements on a cylindrical pedestal mounted on a flat surface with a turbulent impinging jet were made. The experiments were made for the jet Reynolds number of Re = 23,000, the dimensionless nozzle-to-surface distance of L/d = 2~10, the dimensionless pedestal height of H/D = 0~1.5. Measurements of the surface temperature and the Nusselt number distributions on the plate surface were made using liquid crystal and shroud-transient technique. Flow measurements involve smoke flow visualization and the wall pressure coefficient. The results show that the wall pressure coefficient sharply decreases along the upper surface of the pedestal. However, the pressure increases when the fluid escapes from the pedestal and then collides on the plate surface. The secondary maxima in the Nusselt numbers occur in the region of 1.0 $\leq$ r/d $\leq$ 1.9. Their values for the case of H/D = 0.5 are maximum 80% higher than those for other cases. The formation of the secondary maxima may be attributed to the reattachment of flow on the plate surface which was separated at the edge of the pedestal.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.124-130
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• 2001

The heat transfer and flow measurements were made on a cylindrical pedestal mounted on a flat plate with a turbulent impinging air jet. The heat transfer coefficient distributions on the flat plate were measured using the shroud-transient technique and liquid crystal was used to measure the surface temperature. The jet Reynolds number (Re) is 23,000, the dimensionless nozzle-to-surface distance (L/d) from 2 to 10, the dimensionless pedestal diameter-to-height (H/D) from 0 to 1.5, the dimensionless 2nd pedestal diameter-to-height ($H/D_2$) from 0 to 0.4 and the distance from the stagnation point to 2nd pedestal (p/D). The results show that for H/D = 0.5 to 1.5, the Nusselt number distributions on the plate surface exhibit a maximum between $r/d\;{\cong}\;1.0$ and 1.5. The presence of the pedestal appears to cause the flow separation and reattachment on the plate surface, which results in the maximum heal transfer coefficient. Also, for p/D = 2.5 and $H/D_2$ = 0.3, the local Nusselt number in the region corresponding to $r/d\;{\cong}\;1.1$ was increased up to 50% compared to that for $H/D_2=0$.

• 한국전산유체공학회지
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• 제17권1호
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• pp.16-22
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• 2012

Acoustic pressure field around the centrifugal fan is predicted by a aero-acoustic splitting method. Unsteady flow field is obtained by solving the incompressible Navier-Stokes equations using commercial code, while the acoustic waves generated inside the centrifugal fan and shroud are predicted by solving the far field acoustics analysis. Computational results show that the acoustic waves of BPF tone are generated by interactions of the blades with the shroud. Acoustic results is validated by experimental results This paper describes the influence of geometric parameters on the noise generation from the section of blades and shroud. One of the effective ways to reduce BPF noise is optimization method using Genetic Algorithm, which effectively minimize eccentricity, is suggested. New improving design was developed by optimization method.