• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.700-706
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• 2006

This study presents a numerical procedure to optimize the shape of dimple surface to enhance turbulent heat transfer in a rectangular channel. The response surface based optimization method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter ratio, channel height-to-dimple print diameter ratio, and dimple print diameter-to-pitch ratio are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. full factorial method is used to determine the training points as a mean of design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.285-288
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• 2004

This study presents a numerical procedure to optimize the shape of dimple surface to enhance turbulent heat transfer in rectangular channel. The response surface based optimization method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to -dimple print diameter ratio, channel height- to- dimple print diameter ratio. and dimple print diameter-to-pitch ratio are chosen as design variables. The objective function is defined as a linear combination of heat transfer coefficient and friction drag coefficient with a weighting factor. Full factorial method is used to determine the training points as a mean of design of experiment.

• The KSFM Journal of Fluid Machinery
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• v.10 no.3 s.42
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• pp.39-46
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• 2007

This study presents a numerical procedure to optimize the shape of staggered dimple surface to enhance turbulent heat transfer in a rectangular channel. The RBNN method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter (d/D), channel height-to-dimple print diameter ratio (H/D), and dimple print diameter-to-pitch ratio (D/S) are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Latin Hypercube Sampling (LHS) is used to determine the training points as a mean of the design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

• Tribology and Lubricants
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• v.27 no.6
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• pp.338-343
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• 2011

Laser surface texturing (LST) methods are widely applied now to reduce friction and improve reliability of machine components such as thrust bearings, mechanical face seals and piston rings, etc. In this paper, the effect of dimple shapes on the lubrication characteristics of parallel thrust bearing are studied using a commercial computational fluid dynamics (CFD) code, FLUENT. Pressure and streamline distributions, variations of supporting load, leakage flow rate and friction force, are compared for three different dimple sectional shapes such as circle, pyramid and rectangle type. The lubrication characteristics are highly affected by dimple shapes and number of dimples. The pyramid type dimple shape can support the highest load while the rectangle type is the best in friction reduction.

• Design & Manufacturing
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• v.14 no.4
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• pp.1-10
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• 2020

The seal plays a role in preventing oil leakage when the lip and the rotating shaft come into contact with the fluid and air pressure. Recently, micro dimples or micro pockets are processed and used on the lubrication surfaces of thrust bearings, mechanical bearings, and piston rings. Compared to a smooth surface, micro dimples reduce friction and increase the life of parts. This paper analyzed various kinds of micro dimple shapes on the sealing surface, i.e. circle, rectangle, triangle, and trapezoid. For this purpose, Introduced the design of experiments to work out a micro dimple configuration, unlikely to be damaged from cracks and low in contact stress. As a result, the triangular dimple showed the best results. Optimal factors were dimple size 0.15 mm, dimple depth 0.0383 mm, dimple density 40%, and the maximum equivalent stress was 9.1455 MPa, and the maximum contact pressure was 9.6612 MPa. This paper analyzed the optimal shape of dimples by finite element analysis. As a research project, experiments and comparative analysis of micro dimple shapes are needed.

• The KSFM Journal of Fluid Machinery
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• v.13 no.6
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• pp.42-50
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• 2010

The present analysis deals with a numerical procedure for optimizing the shape of elliptical dimples in a cooling channel. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis is employed in conjunction with the SST model for predictions of the turbulent flow and the heat transfer. Three non-dimensional geometric design variables, such as the ellipse dimple diameter ratio, ratio of the dimple depth to the average diameter, and ratio of the distance between dimples to the pitch are considered in the optimization. Twenty-one experimental points within design space are selected by Latin Hypercube Sampling. Each objective function values at these points are evaluated by RANS analysis and producing optimal point using surrogate model. The linear combination of heat transfer coefficient and friction loss related terms with a weighting factor is defined as the objective function. The results show that the optimized elliptical dimple shape improves considerably the heat transfer performance than the circular dimple shape.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.237-238
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• 2013

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.479-484
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• 2003

In this paper, film thickness and temperature distribution are measured in EHL point contact at high slip ratios. Infrared temperature mapping with two band pass fillers. proposed by Ausherman (1976). is used to measure temperature distribution. And the optical interferornetric method with two filters (red and green filters) is used to measure film thickness. Result of experiment showed that temperature rising at film and ball surface occurred very dramatically in Dimple zone. As slip velocity, slip ratio and load increased, size of Dimple and temperature rising became more large In addition, Position and shape of Dimple we changed by slip ratios, and increasing of Dimple size decreased traction coefficient. In short, it is appointed that the Dimple phenomenon be developed by the effect of viscosity wedge.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.502-507
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• 2000

Fundamental studies on the drag reduction of the circular cylinder having dimple were conducted by the measurement of the fluid force acting on the cylinder and by the flow visualization around the cylinder. The drag coefficients were changed by the shape and the space for the arrangement of the dimple. The drag of the cylinder was reduced about 50% by the proper arrangement of the dimple. The flowfield around the cylinder having dimple, which was the minimum drag, was visualized by the hydrogen bubble technique. In this case, the separation points were moved rearward and the wake region was small in comparison with the cylinder having no dimple.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.700-708
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• 1999

The optimum dimple shape and arrangement in the channel of a plate heat exchanger with staggered dimples are proposed in this study. Four important geometric parameters are selected as design variables, the pressure drop and heat transfer characteristics are examined in the channel of plate heat exchangers. The optimization is accomplished by minimizing the global criterion function which consists of the correlations of Nusselt number and pressure drop. The optimum geometric parameters were found at the dimensionless dimple distance (L) of 0.272, the dimensionless dimple angle ($\beta$) of 0.44, the dimensionless dimple volume (V) of 0.106 and the dimensionless dimple pitch (G) of 0.195. It is found that the heat transfer and pressure drop of the optimum model are increased by approximately 227.9% and 32.9%, respectively, compared to those of the base model.