• 대한기계학회논문집B
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• 제31권3호
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• pp.256-263
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• 2007

The purpose of this study is to investigate the cooling performance of heat sinks for an electronic telecommunication system by adequate natural convection. Heat generation rates of electronic components and the temperature distributions of heat sinks and surrounding air are analyzed experimentally and numerically. In order to perform the heat transfer analysis for the thermal design of telecommunication system a program is developed. The program used the graphic user interface environment to determine the arrangement of heat sources, interior fan capacity, and heat sink configuration. The simulation results showed that the heat sinks were able to achieve a cooling capacity of up to 230W at the maximum temperature difference of $19^{\circ}C$. To verify the results from the numerical simulation, an experiment was conducted under the same condition as the numerical simulation, and their results were compared. The design program gave good prediction of the effects of various parameters involved in the design of a heat sinks for an electronic telecommunication system.

• 설비공학논문집
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• 제15권10호
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• pp.860-869
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• 2003

Design optimization of the heat sink with 7${\times}$7 square pin-fins is performed numerically using the Computational Fluid Dynamics (CFD) and the Computer Aided Optimization (CAO). In the pin-fins heat sink, the optimum design variables for fin height (h), fin width (w), and fan-to-heat sink distance (c) can be achieved when the thermal resistance ($\theta$$_{j}$) at the junction and the overall pressure drop ($\Delta$p) are minimized simultaneously. To complete the optimization, the finite volume method for calculating the objective functions, the BFGS method for solving the unconstrained non-linear optimization problem, and the weighting method for predicting the multi-objective problem are used. The results show that the optimum design variable for the weighting coefficient of 0.5 are as follows: w=4.653 mm, h=59.215 mm, and c=2.667 mm. In this case, the objective functions are predicted as 0.56K/W of thermal resistance and 6.91 Pa of pressure drop. The Pareto optimal solutions are also presented.re also presented.d.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3092-3097
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• 2007

Although noise of a RAC can be reduced effectively by decreasing RPM, condensation problems can occur to reduce reliability of the RAC for low RPM. Thus, this research has been performed to propose a design guideline of the RAC for low-noise RPM with high reliability. The internal and external flows of the RAC have been visualized and analyzed by a PIV technique to solve the condensation problem at an outlet and impeller. Then, the design guideline has been proposed by the analyzed results and confirmed by wind-tunnel and noise tests to reduce the condensation problem. Finally the shapes of the outlet with reduced condensation problem and the impeller with low noise have been obtained in this study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.494-498
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• 2001

When supersonic jet impinges on wall from the nozzle, complex flow pattern appears such as Mach disc, expansion fan, and jet boundary. The numerical computation of this supersonic jet is important on flame deflecctor design for launch space especially. In this paper, we analyzed supersonic jet structure impinging on deflector wall using three dimensional steady and unsteady compressible equation and showed temperature and pressure distribution on the wall surface. As a result, some dominant factors of jet flows are discussed for conceptual design of flame deflector.

• Journal of Biosystems Engineering
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• 제20권3호
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• pp.217-225
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• 1995

This study was conducted to find design factors of spraying device of the boom sprayer for low volume application. Four types of nozzles(standard flat nozzle, drift guard nozzle, even flat nozzle, and hollow cone nozzle) were used for the spray characteristic experiment. Spray patterns of the nozzles were distinguished by the nozzle type, spray distance, and spray direction. The flow rate was proportional to the square root of spray pressure in all nozzles. Increased nozzle height improved spray distribution at reduced pressures and/or increased spacing. Distribution tended to improve as pressure increased within the range of pressures used for fan nozzles.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권2호
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• pp.149-163
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• 2009

This paper intends to suggest a design to reduce the thermal load of a hand-carried ultrasound (HCU) system, with the aim of increasing the product life. To design ways to reduce the heat load, the surface temperatures of key parts of an HCU system were measured as the 4 system cooling fans, which have a direct relation to the system life, were operated normally. When the derating rate of 80% was applied while the fans of the HCU system were operated abnormally, it was observed that the key image processing parts exceeded the surface temperature (TC) with consideration to derating. Since the part surface temperature did not exceed the derated level when the regulated voltage was derated from 12V to 9V, it is expected to lower the operating voltage of the fans to 9V to increase the fan and HCU system lifetime by 1.8 times.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.448-453
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• 2001

A commercial CFD code is used to compute the 3-D viscous flow field within the inlet flow concentrator of the newly developed AHU(Air Handling Unit). To improve the performance of the AHU, the inlet air needs to be gradually accelerated to the fan's annular velocity without causing turbulence or flow separation. Three major geometric parameters were selected to specify the inlet shape of the AHU. Several numerical calculations are carried out to determine the influence of the geometric parameters on the performance of the AHU. The performance of the AHU could be measured by the inlet and outlet flow uniformity and the total pressure loss through the inlet flow concentrator. The optimized nondimensionalized velocity profile through the inlet flow concentrator were used for the design of the AHU with the various volume flow rates.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.852-855
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• 2002

This paper presents a design of FIR near-equiripple Nyquist filters having zero-intersymbol interference (ISI) and low sensitivity to timing jitter, with coefficients taking only discrete values. Using an affine scaling linear programming algorithm, an optimum discrete coefficient set can be obtained in a feasible computational time. Also presented is a pipelined multiplier-free FIR filter realization with periodically time-varying (PTV) coefficients based on a hybrid form suitable for Nyquist filter. The realization exploits the coefficient symmetry to reduce the hardware by about one half. High speed computation and low power consumption are achieved by its pipelined and low fan-out structure.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2010년도 춘계 종합학술대회 논문집
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• pp.517-519
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• 2010

iphone이 가져다주는 핸드폰 사용자의 체험, 제일 처음으로 제일 많은 스마트폰 시스템 windows mobile의 개명, 새로운 개방적인 스마트폰 시스템 android의 출시, 스마트폰 및 그의 인터페이스 디자인이 가져온 새로운 사용자 체험은 사람들의 눈길을 끄는 화제로 되었습니다. 핸드폰 시장에서 스마트폰의 지위가 날이 갈수록 중요해 짐에 따라, iphone이 가져다주는 핸드폰 사용자의 체험, 제일 처음으로 제일 많은 스마트폰 시스템 windows mobile의 개명, 새로운 개방적인 스마트폰 시스템 android의 출시, 스마트폰 및 그의 인터페이스 디자인이 가져온 새로운 사용자 체험은 사람들의 눈길을 끄는 화제로 되었습니다. 본문에서는 최신 발표한 Windows Mobile시스템의 WPhone7와 Iphone의 핸드폰 인터페이스를 사용하는데 대하여 비교하고 분석하여 미래 핸드폰 인터페이스의 발전 방향과 사용자의 요구 방향에 대하여 탐구 하였습니다.

• 설비공학논문집
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• 제17권3호
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• pp.243-249
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• 2005

The present study has been conducted to simulate dynamics of a gas engine-driven heat pump(GHP) for design of control algorithm. The dynamic modeling of a GHP was based on conservation laws of mass and energy. For automatic control of refrigerant pressures, actuators such as engine speed, outdoor fan, coolant three-way valves and liquid injection valve were PI or P controlled. The simulation results showed physical behavior that is realistic enough to apply for control algorithm design.