• 대한기계학회논문집
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• 제9권1호
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• pp.71-80
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• 1985

본 연구에서는 이중관 열교환기의 내관의 바깥 벽면에 반지 형태의 원형돌기 를 부착하여 굵기와 피치를 변화시키면서 압력손실과 열전달계수의 변화를 실험적으로 고찰하였다.

• 대한건축학회논문집:구조계
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• 제34권3호
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• pp.87-93
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• 2018

Ground source heat pump(GSHP) system is one of the high efficiency heat source systems which utilizes the constant geothermal energy of a underground water or soil. However, the design of conventional GSHP system in the domestic market is dependent on the experience of the designer and the installer, and it causes increase of initial installation cost or degradation of system performance. Therefore, it is necessary to develop a guideline and the optimal design method to maintain stable performance of the system and reduce installation cost. In this study, in order to optimize the GSHP system, design factors according to ground heat exchanger(GHX) type have been examine by simulation tool. Furthermore, the design factors and the correlation of a single U-tube and a double U-tube were analyzed quantitatively through sensitivity analysis. Results indicated that, the length of the ground heat exchanger was greatly influenced by grout thermal conductivity for single U-tube and pipe spacing for double U-tube.

• 반도체디스플레이기술학회지
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• 제15권4호
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• pp.1-9
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• 2016

The warpage on mobile phone camera packages occurs due to the CTE(Coefficient of Thermal Expansion) mismatch between a thin silicon die and a substrate. The warpage in the optical instruments such as camera module has an effect on the field curvature, which is one of the factors degrading the optical performance and the product yield. In this paper, we studied the effect of die bonding epoxy on the package and optical performance of mobile phone camera packages. We calculated the warpages of camera module packages by using a finite element analysis, and their shapes were in good agreement showing parabolic curvature. We also measured the warpages and through-focus MTF of camera module specimens with experiments. The warpage was improved on an epoxy with low elastic modulus at both finite element analysis and experiment results, and the MTF performance increased accordingly. The results show that die bonding epoxy affects the warpage generated on the image sensor during the packaging process, and this warpage eventually affects the optical performance associated with the field curvature.

• 한국화재소방학회논문지
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• 제24권6호
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• pp.69-75
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• 2010

콘크리트가 충전된 각형강관 기둥(CFT)은 외부에 강재가 노출된 형상으로 외측의 강관은 화재시 급격한 온도상승으로 인해 강도가 저하되나, 내부의 콘크리트는 열용량이 큰 재료로써 내화성능을 확보할 수 있는 구조로 구성되어 있다. CFT 기둥을 내화구조로서 적용하기 위해서는 구조적 성능에 영향을 미치는 인자에 대한 연구가 필요하며, 이에 대한 조건별 영향성에 관한 연구가 필요하다. 내화성능에 영향을 주는 주요인자는 콘크리트 압축강도.단면크기.축력비.경계조건이며, 그 중 기둥과 보의 경계조건은 구조적 측면에서 하중지지능력에 영향을 미치므로 내화성능을 지배하는 주요 인자 중에 하나이다. 실험결과 360단면에서는 양단 고정조건에서는 106분의 내화성능이 확보되나 양단 힌지 조건에서는 89분의 내화성능을 확보하는 것으로 나타났다. 280단면에서는 양단 고정조건에서는 113분의 내화성능이 확보되나 양단힌지 조건에서는 78분의 내화성능을 확보하였다.

• International Journal of Concrete Structures and Materials
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• 제6권2호
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• pp.87-100
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• 2012

The process of selecting a repair material is a typical one of multi-criteria decision-making (MCDM) problems. In this study Analytical Hierarch Process was applied to solve this MCDM problem. Many factors affecting a process to select an optimal repair material can be classified into quantitative and qualitative requirements and this study handled only quantitative items. Quantitative requirements in the optimal selection model for repair material were divided into two parts, namely, the required chemical performance and the required physical performance. The former is composed of alkali-resistance, chloride permeability and electrical resistivity. The latter is composed of compressive strength, tensile strength, adhesive strength, drying shrinkage, elasticity and thermal expansion. The result of the study shows that this method is the useful and rational engineering approach in the problem concerning the selection of one out of many candidate repair materials even if this study was limited to repair material only for chloride-deteriorated concrete.

• 설비공학논문집
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• 제12권5호
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• pp.457-465
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• 2000

An experiment was carried out to evaluate the thermal performance of the wire-coil inserts method. Tested were the smooth tubes with the wire-nil inserts of various pitch and helix angle combinations. Test fluids were the 50%-solution of the ethylene glycol and the Hue water. Heat transfer coefficient and friction factors were deduced from the measured values of temperatures, flowrates and pressure drops. A unified dimensionless correlation for the heat transfer coefficients was developed as a function of the pitch to diameter ratio, the Reynolds number and the Prandtl number. An exergy analysis was performed to evaluate an optimal operating condition with the wire-coil inserts.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1451-1460
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• 2004

A two-stroke Schnurle-type gasoline engine was modified to enable compression-ignition in both the port fuel injection and the in-cylinder direct injection. Using the engine, examinations of compression-ignition operation and engine performance tests were carried out. The amount of the residual gas and the in-cylinder mixture conditions were controlled by varying the valve angle rate of the exhaust valve (VAR) and the injection timing for direct injection conditions. It was found that the direct injection system is superior to the port injection system in terms of exhaust gas emissions and thermal efficiency, and that almost the same operational region of compression-ignition at medium speeds and loads was attained. Some interesting combustion characteristics, such as a shorter combustion period in higher engine speed conditions, and factors for the onset of compression-ignition were also examined.

• 태양에너지
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• 제9권1호
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• pp.36-42
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• 1989

Following the oil crisis in 1979, there have been surge of movements by the government in Korea to conserve petroleum-based energy in every sector of society. One of these movements was the application of passive solar technologies into the construction of school buildings. Various passive designs are developed paying special regard to architectural and climatic factors. This paper is related to the application of the passive solar technology to elementary school buildings. It is proposed to place the hallway on the south side of the building to improve the thermal performance as well as indoor lighting effects. The cases have been compared with those of the existing school buildings where substantial improvements are noted. Finally, standard drawings are prepared in detail to promote the application of this passive solar technology in practical school building.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.885-891
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• 2003

Effects of each acoustic property on absorption characteristics of polyester fiber materials has been studied in this paper. It would be impossible for us to measure effects of each acoustic property by experimental method since we cannot make sound-absorbing materials in which only one of the properties is changed. We have adopted a numerical prediction method to carry out parameter studies for each acoustic property. And to get a general behavior of acoustic performance of the materials, the numerical simulation has been repeated to several cases of different bulk density. Finally we have obtained frequency-dependent control factors in the absorption performance which gives us design capability of acoustic absorbing materials.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.13-18
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• 2000

The objective of the Present study is to investigate the performance of electronic scale mitigation unit(ESMU), which reduces the amount of scale in a heat exchanger. A plate heat exchanger with 20 thermal plates is used for the tests. In order to accelerate the rate of fouling in a laboratory test artificial hard water of 2000 ppm(as $CaCO_3$) is recirculated at a flow rate 5L/min throughout the tests. The overall heat trans(or coefficients and fouling factors are examined. Results show that the ESMU technology can significantly reduce the scale deposits.