• 대한기계학회논문집B
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• 제39권3호
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• pp.271-278
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• 2015

직교류 핀-튜브 열교환기의 대류연절달에 대해 수치해석 연구가 수행되었다. 팬위치에 따른 열전달 성능변화를 조사하기 위하여 분사와 흡입형태로서 몇 가지 팬위치가 선택되었다. 열교환기의 튜브는 엇갈림 배열이며, 튜브의 온도와 유입공기의 온도는 각각 $50^{\circ}C$와 $30^{\circ}C$이다. 해석결과로부터 3차원 유동구조가 검토되었으며, 팬의 다양한 설치 위치에 따른 대류 열전달계수와 열교환기 입출구 사이의 평균 온도차에 대한 분석을 통해 열교환기 성능을 논의되었다.

• Journal of Species Research
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• 제9권1호
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• pp.56-67
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• 2020

Eight new species of two genera Dysidea and Euryspongia (Demospongiae: Dictyoceratida: Dysideidae) are described from Gageodo, Ulleungdo, Geomundo, and Jejudo Islands, Korea. Four new species of the genus Dysidea are differentiated by the fibre structure, cored detritus, and fibre arrangement. Dysidea mureungensis n. sp. is characterized by the honeycomb shape of surface and no distinction between primary and secondary fibres. Dysidea glavea n. sp. differs by large sands cored in fibres and that the membrane easily separates from fibres. Dysidea geomunensis n. sp. has fibres that are thinner than those of D. glavea n. sp.. Dysidea corallina n. sp. is characterized by folded fan shape and the arrangement of secondary fibres. Four new species of the genus Euryspongia are differentiated by the fibre structure, cored detritus, shape of sponge, and fibre arrangement. Euryspongia radicula n. sp. is very different from other species by having regularly arranged fibres. Euryspongia spina n. sp. has a fence-like skeletal structure. Bridged type secondary fibres are arranged near the surface and web types are at the base of fibres. Euryspongia flabellum n. sp. has a very unique wide, thin leaf-like shape. String-like primary fibres of E. linea n. sp. are very unique and cored with large sized sands.

• 설비공학논문집
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• 제30권2호
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• pp.92-99
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• 2018

A numerical analysis of a compressor dehumidifier has been conducted focusing on the air side heat transfer, which is a part of a series research on the dehumidifier. The moving reference frame was applied to the fan modeling, and the porous model was used for the evaporator and condenser modeling. Curve fitting obtained the inertial and viscous resistances parameters to the results of the physical model of the unit cell with actual shape of a fin tube. The porous model was validated within a reasonable computation time for the range of practical inlet velocity of a dehumidifier. A parametric study has been conducted for fin number, fan speed (i.e., air flow rate), and evaporator/condenser tube arrangement. ANOVA analysis showed the dependency of each parameter on the velocity and temperature uniformity, which are desirable for high performance of the dehumidifier.

• 대한안전경영과학회지
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• 제15권2호
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• pp.129-134
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• 2013

In this study, the heat flow analysis compatible commercial code CFX 11 was used to develop the structure inside PCB circuit board devices, which could stable radiant heat as well as the cooling device within it. In case of modifying the arrangement of electronic parts on the PCB inside the multi channel temperature measurement board devices, radiant heat effects did not show a rising tendency, whereas the overall temperature went down in case of installing the vents in the outer case of PCB circuit board devices. In terms of installation location, it was the most appropriate to install it on the electronic parts with no heat. Besides, in case of mounting the fan as a cooling device by considering various user environments for multi channel temperature measurement board devices, the radiant heat effects were shown higher than in case of installing the vents, and the middle sections were the most appropriate to its installation location. In case of changing the wind quantity of the fan from its selected installation location, the best radiant heat effects were shown at high speed as expected.

• 설비공학논문집
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• 제15권7호
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• pp.586-594
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• 2003

The performance of the condenser installed in the air-conditioning plant room of a high-rise building was studied numerically. The effect of the draft direction on the performance of an air-conditioner was analyzed. The on-coil temperature of the condenser was investigated by varying the arrangement and location o( the condenser in the air-conditioning plant room. The performance of an air-conditioner was also evaluated by using COP (coefficient of performance) and CGPI (condenser group performance indicator). The condenser in an air-conditioning plant room should be arranged in such a manner that the fan of the condenser is facing the outside of the building to exhaust the hot air directly, The model by which the condenser is located at the lower-left end of an air-conditioning plant room can prevent the hot air from reentering, and allow indrafting of fresh air. When the direction of draft is to the frontal face of the building, the performance of the condenser above 30th floor is degraded.

• 한국전자통신학회논문지
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• 제9권11호
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• pp.1233-1240
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• 2014

1980년 Toffoli 가역게이트 출현 이후 지난 30년 간 적당한 함수 상에 가역 임베딩을 하는 많은 가역회로 합성법들이 발표되어 오는 동안 소수의 논문만이 가역 임베딩 없이 직접적인 비가역-가역 회로 매핑 방법을 채택해 왔다. 본 논문에서는 가역 임베딩 없는 직접적 가역 매핑에 대한 효과적인 게이트비용 절감 정책을 개발하였다. 새로운 비용절감 정책을 개발하기 위해 고전회로에서 NOT 게이트 배치에 따른 Toffoli 모듈 비용의 영향을 고찰하고, 이것을 기초로 하여 고전적 AND(OR)게이트에 대한 반전입력 추가가 가역 Toffoli 모듈의 비용을 증가(감소)시킨다-라는 고전 게이트 반전입력 수와 가역 Toffoli 모듈 비용 사이의 반비례적 성질을 이끌어내었다. 직접적 가역 매핑에 선행한 반전입력 재배치 정책은 현존하는 팬-아웃 및 슈퍼셀 정책들과 병행할 경우에 가역 Toffoli 모듈의 비용과 복잡성을 개선할 수 있는 효과적인 방법이다.

• 대한기계학회논문집B
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• 제39권1호
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• pp.37-43
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• 2015

현열 뿐만 아니라 잠열을 이용하는 증발냉각은 배기열 회수에 매우 유용하게 사용될 수 있다. 본 연구의 목적은 증발냉각을 이용한 배기열 회수장치의 성능을 실험적으로 규명하는 것이다. 성능실험장치는 플라스틱 열교환기, 물 분무 노즐, 공기유동용 홴, 물 순환용 펌프, 수조, 온도 습도 유량 측정 센서 등으로 구성되었다. 증발이 없는 현열 회수에서의 유용도와 증발을 수반하는 전열 회수에서의 유용도를 여러가지 작동조건에서 측정하여 비교하였다. 현열냉각과 증발냉각의 유용도는 공기의 유량이 증가함에 따라 감소하고, 대향류에서의 유용도가 평행류에서의 유용도 보다 휠씬 높다. 증발냉각의 경우 물 유량이 증가함에 따라 유용도는 증가하고, 평행류가 대향류보다 물 유량에 더 민감함을 알 수 있다.

• Journal of Biosystems Engineering
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• 제34권5호
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• pp.363-370
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• 2009

Hot air heater with light oil combustion is used as the most common heater for greenhouse heating in the winter season. Hot air heaters of 256,246 units have been supplied as main greenhouse heating equipment until 2008 and greenhouse heating cost has reached to 620 billions won in Korea. In order to improve the thermal efficiency of the hot air heater and to reduce the expenses for greenhouse heating, prototype hot air heater was manufactured and tested in this experiment. The heat exchanger of tested prototype hot air heater was circular and hexagonal pipe type and inline and stagger arrangement type. Capacity of the heating was 43,062 kJ/h and total heat transfer area of the heat exchanger was $10.728\;m^2$. According to the performance test, it could supply heat of 38,240 to 35,100 kJ/h depending on the fan motor speed of 1,740~1,220 rpm, respectively. Thermal efficiency of hot air heater was 87.0% to 80.8% in the same conditions. As a result, thermal efficiency of hot air heater with hexagonal pipe-stagger arrangement heat exchanger developed in this study was higher 10.2% than that of conventional hot air heater and heating energy saving rate of 14.3% increased.

• 대한기계학회논문집A
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• 제24권4호
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• pp.1047-1054
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• 2000

A numerical simulation was made to delineate the re-distribution of tonal noise generated from the equally-spaced blade passing frequency (BPF). A pressure-wave model was employed to analyze the tonal noise. An optimal solution for diversifying the tonal peak noise was obtained by rearranging the unequally-spaced blade angles. This was based on the fact that the noise energy is transferred from BPF to the neighboring frequency band. A limit condition for the minimum blade angle spacing was imposed. The unbalancing problem was also considered to avoid the weight bias.

• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.148-154
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• 2008

The Wells turbine rotor consists of several symmetric airfoil blades arranged around a central hub, and the stagger angle is 90 degrees. These characteristics simplify the total construction of OWC type wave energy converters. Although the Wells turbine is simple, the turbine produces a complicated flow field due to the peculiar arrangement of blades, which can rotate in the same direction irrespective of the oscillating airflow. In order to understand these flows, flow visualization is carried out with an oil-film method in the water tunnel. This research aims to analyze the mechanism of the 3-D flows around the turbine with the flow visualization. The flow visualization explained the influence of attack angle, the difference between fan-shaped and rectangular wings, and the sweep angle.