• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2097-2101
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• 2007

This paper presents an optimal design of a micro evaporator which maximizes the heat transfer coefficient. Number of gaps, spanwise distance and streamwise distance are selected as the geometric design parameters. Mass flow rate of the refrigerant is selected as the non-geometric design parameter. Temperature at the surface of the heater is measured to valuate the heat transfer coefficient. Nine experiments are conducted using $L_9(3^4)$ orthogonal array. Maximum heat transfer coefficient is 640 W/$m^2K$ at the parameters of 2 gaps, 0.2 mm spanwise distance, 1.0 mm streamwise distance and 0.72 g/s mass flow rate. Among the 3 geometric parameters, the spanwise distance is the most sensitive parameter influencing the heat transfer coefficient. We conduct a second stage of experiment to increase the heat transfer coefficient by reselecting the mass flow rate. We concluded that 0.87 g/s is the optimized flow rate for an active micro cooler resulting in a heat transfer coefficient of 651 W/$m^2K$.

• Steel and Composite Structures
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• v.7 no.1
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• pp.53-70
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• 2007

This paper presents a analysis of the problem of optimal design of the beams with two I-type cross section shapes. These types of beams are simply supported and subject to pure bending. The strength and stability conditions were formulated and analytically solved in the form of mathematical equations. Both global and selected types of local stability forms were taken into account. The optimization problem was defined as bicriteria. The cross section area of the beam is the first objective function, while the deflection of the beam is the second. The geometric parameters of cross section were selected as the design variables. The set of constraints includes global and local stability conditions, the strength condition, and technological and constructional requirements in the form of geometric relations. The optimization problem was formulated and solved with the help of the Pareto concept of optimality. During the numerical calculations a set of optimal compromise solutions was generated. The numerical procedures include discrete and continuous sets of the design variables. Results of numerical analysis are presented in the form of tables, cross section outlines and diagrams. Results are discussed at the end of the work. These results may be useful for designers in optimal designing of thin-walled beams, increasing information required in the decision-making procedure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.129-136
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• 2006

Optimal design of an air-to-liquid finned plate heat exchanger is considered theoretically in this study. Based on existing correlations for the pressure loss and the heat transfer in channel flows, the optimal configuration of the plate heat exchanger including the optimal plate pitch and the optimal fin pitch is obtained to maximize the heat transfer within the limit of the pressure drop for a given flow depth of the plate heat exchanger. It is found that the optimal fin pitch is about one ninth of the optimal plate pitch. In the optimal configuration, the flow and thermal condition in the channels is just at the boundary between the laminar developing and laminar fully developed states. It is also found when reducing the flow depth of plate heat exchangers for compactness, the heat transfer performance can be maintained exactly the same if the geometric parameters such as the plate thickness, plate pitch, fin thickness, and fin pitch are reduced proportional to the square root of the flow depth as long as the flow keeps laminar within the heat exchangers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1583-1586
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• 2005

Grinding process is different from other machining processes such as turning, milling and drilling because the cutting edges in a grinding wheel doesn't have uniformity and acts differently on the workpiece at each grinding. This study focus on predicting the geometric error produced during surface grinding and selecting an optimal grinding condition to reduce the geometric error. To achieve the aim, the Taguchi design of experiments was applied and the S/N ratios of each grinding was used for evaluating the results. The predicted quantities by the S/N ratios were compared with the experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.125.5-125
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• 2001

Until now, many guidance laws have been developed. They mainly used the classical tail-pursuit guidance method based on geometric angle information, the proportional navigation method based on the line of sight(LOS) rate, and the optimal guidance law based on optimal control theorem. In the augmented guidance law, target acceleration information and autopilot characteristics are added the guidance command. In this study, new guidance laws considering geometric angle are proposed. Two guidance laws are developed for the midcourse guidance law, and a guidance law is developed for the terminal guidance respectively. The proposed guidance laws utilize the LOS rate and the geometric angle information simultaneously. In the midcourse guidance, the guidance command is ...

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.14-24
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• 2011

In this paper, design optimization for mixed-flow pump impellers and diffusers has been studied using a commercial computational fluid dynamics (CFD) code and DOE (design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser. Geometric design variables were defined by the vane plane development, which indicates the blade-angle distributions and length of the impeller and diffusers. The vane plane development was controlled using the blade-angle in a fixed meridional shape. First, the design optimization of the defined impeller geometric variables was achieved, and then the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Next, design optimizations of the defined diffuser shape variables were performed. The importance of the geometric design variables was analyzed using $2^k$ factorial designs, and the design optimization of the geometric variables was determined using the response surface method (RSM). The objective functions were defined as the total head and the total efficiency at the design flow rate. Based on the comparison of CFD results between the optimized pump and base design models, the reason for the performance improvement was discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.443-444
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• 2012

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.386-393
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• 2015

A study is carried out on investigation on pattern costs, identification of geometric parameters for the cost, and development of cost estimation models for casting patterns. Pattern costs for machine tool structures are collected and analyzed to identify the important geometric parameters that affect the costs. The parameters are used for the development of the costing models. It is found that the geometric parameters can be easily obtained from a CAD system and then the costing models estimate a pattern cost in a minimum time. The models are verified with the structures whose pattern cost was used for this study. It is expected that this costing models can evaluate the cost of casting structures of machine tools in search of a near-optimal design based on manufacturing cost and, for example, weight at the design stage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.4
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• pp.13-19
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• 2004

This paper deals with the analysis of geometric error and the optimization of process parameters in surface grinding. Taguchi method which is one of the design of experiments has been introduced in achieving the aims. The process parameters were the grain size, the wheel speed, the depth of cut and the table speed. The effect of the process parameters on the geometric error was examined and an optimal set of the parameters was selected to minimize the geometric error within the controllable range of the used grinding machine. The reliability of the results was evaluated by the ANOVA.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.337-348
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• 2023

The optimization of reinforced concrete (RC) cantilever retaining walls is a complex problem and requires the use of advanced techniques like metaheuristic algorithms. For this purpose, an optimization model must first be developed, which involves mathematical complications, multidisciplinary knowledge, and programming skills. This task has proven to be too arduous and has halted the mainstream acceptance of optimization. Therefore, it is necessary to unravel the complications of optimization into an easily applicable form. Currently, the most commonly used method for designing retaining walls is by following the proportioning limits provided by the ACI handbook. However, these limits, derived manually, are not verified by any optimization technique. There is a need to validate or modify these limits, using optimization algorithms to consider them as optimal limits. Therefore, this study aims to propose updated proportioning limits for the economical design of a RC cantilever retaining wall through a comprehensive parametric investigation using the genetic algorithm (GA). Multiple simulations are run to examine various design parameters, and trends are drawn to determine effective ranges. The optimal limits are derived for 5 geometric and 3 reinforcement variables and validated by comparison with their predecessor, ACI's preliminary proportioning limits. The results indicate close proximity between the optimized and code-provided ranges; however, the use of optimal limits can lead to additional cost optimization. Modifications to achieve further optimization are also discussed. Besides the geometric variables, other design parameters not covered by the ACI building code, like reinforcement ratios, bar diameters, and material strengths, and their effects on cost optimization, are also discussed. The findings of this investigation can be used by experienced engineers to refine their designs, without delving into the complexities of optimization.