• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.04a
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• pp.7-7
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• 1999

충돌/유출냉각은 연소실 벽면 등과 같이 열부하가 많이 걸리는 영역에서 고온의 연소가스로부터 표면을 보호하는 막냉각과 더불어 내부에 다공성 판을 설치하여 충돌제트에 의해 내부표면을 냉각시켜 가스터빈엔진의 고온요소의 냉각성능을 극대화시키는 방법 중의 하나이다. 이와 같은 냉각방법을 적용하면 벽면을 충돌제트에 의한 냉각과 함께 냉각유채를 막냉각에 활용함으로써 냉각효율을 극대화할 수 있다. 본 연구에서는 국소적인 값들을 획득하기 용이한 물질전달실험방법의 하나인 나프탈렌 승화법을 이용하여 수직으로 분사되는 충돌제트에 의한 유출판 내면에서의 열/물질전달특성을 분사판(injection plate)과 유출판(effusion plate) 사이의 높이, 분사제트의 속도, 분사홀간의 배열을 변화시켜가며 유출판만이 있는 경우와 비교, 분석하였다. 분사홀과 유출홀의 관 사이의 간격은 0.33d에서 10d까지 변화시켜가며 그 효과를 관찰하였으며, 홀배열 효과를 보기 위하여 2가지 홀배열(staggered array, shifted array)에 대하여 실험하였다. 또한 분사제트의 속도효과를 고찰하기 위하여 분사제트의 Rc$_{d}$=5,000-12,000까지 변화시켜가며 실험을 수행하였다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.21 no.2
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• pp.105-142
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• 1992

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1501-1509
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• 1995

It is known that the heat and mass transfer characteristics in the absorber are most sensitive of the temperature boost of all the heat exchangers and the development of a more efficient absorber should be highly important. This paper describes absorption experiments made with different inside tube diameters, tube length and tube shapes. The purpose of this study is to acquire basic knowledge about heat and mass transfer in a falling film type absorber with vertical inner tubes. Heat and mass transfer were measured for water vapor absorption into a Lithium Bromide-water solution flowing down an absorber of vertical inner tubes. As a result, insert spring tube compares bare tube and heat transfer improved by order of insert spring tube P2(pitch 20 mm) and P1(pitch 10 mm).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.860-867
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• 2001

Absorption of water vapor into LiBr-$H_2O$ O solution flowing over a finned inclined surface is numerically investigated. The momentum, energy, and diffusion equation are numerically solved using a finite difference method. The four different shapes of the wall surfaces are considered to find the best surface for absorption assuming that the wall temperature and the surface tension are constant. The effects of the fin interval and Reynolds number are investigated. Based on the numerical results, it is known that the parabolic surface shows better absorption performance than the other surfaces, and that water vapor absorption increases gradually with decreasing the fin interval.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1147-1154
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• 2006

An experimental investigation was conducted to enhance the heat/mass transfer for impingement/effusion cooling system when the initial crossflow was formed. For the improvement of heat transfer, the circular guide is installed on the injection hole. At the fixed jet Reynolds number of 10,000, the measurements were carried out for blowing ratios ranging from 0.5 to 1.5. The local heat/mass transfer coefficients on the effusion plate are measured using a naphthalene sublimation method. The result presents that the circular guide protects the injected jet from the initial crossflow, increasing the heat/mass transfer. The heat transfer of stagnation region is hardly changed regardless of the blowing ratio. The secondary peak is obviously formed by flow transition to turbulent flow. At high blowing ratio of 1.5, the circular guide produces $26{\sim}30%$ augmentation on the averaged heat/mass transfer while the case without circular guide leads to the low and non-uniform heat/mass transfer. With the increased heat/mass transfer, the installation of circular guide is accompanied by the increase of pressure loss in the channel. However, the pressure drop caused by the circular guide is lower than that for other cooling technique with the circular pin fin.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1453-1460
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• 2003

The present study investigates the effects of rib arrangements and aspect ratios of a rectangular duct simulating the cooling passage of a gas turbine blade. Two different V-shaped rib configurations are tested with the aspect ratios (W/H) of 3 to 6.82. One is the continuous V-shaped rib configuration with $60^{\circ}$ attack angle, and the other is the discrete V-shaped rib configuration with $45^{\circ}$ attack angle. The square ribs with the pitch to height ratio of 10.0 are installed on the test section in a parallel arrangement for both rib configurations. Reynolds numbers based on the hydraulic diameter are changed from 10,000 to 30,000. A naphthalene sublimation method is used to measure local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices are generated in a duct, and high transfer region is formed at the center of the ribbed walls of the duct. However, for the discrete V-shaped rib configuration with $45^{\circ}$ attack angle, complex secondary flow patterns are generated in the duct due to its geometric feature, and more uniform heat/mass transfer distributions are obtained for all tested cases

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.977-984
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• 2013

A hygroscopic rotor comprises many microchannels with high adsorption characteristics. In this study, the iterative adsorption/desorption processes that were affected by the humid air flow in a channel were numerically simulated. In consideration of the accuracy and computational costs, in the desiccant layer, only surface diffusion was considered in this simulation. The results were compared with the previous numerical results and found to show good agreement. By conjugating the heat and mass transfer between the desiccant and the flow layers, temporal and spatial changes in the vapor mass fraction, adsorbed liquid water mass fraction, and temperature in the channel were presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.102-111
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• 2000

A numerical model which simulates the simultaneous heat and mass transfer within a vertical tube GAX absorber was developed. The ammonia vapor and the solution liquid are in counter-current flow, and the hydronic fluid flows counter to the solution liquid. The film thickness and the velocity distribution of the liquid film were obtained by matching the shear stress at the liquid-vapor interface. Two-dimensional diffusion and energy equations were solved in the liquid film to give the temperature and concentration, and a modified Colburn-Drew analysis was used for the vapor phase to determine the heat and mass fluxes at the liquid-vapor interface. The model was applied to a GAX absorber to investigate the absorption rates, temperature and concentration profiles, and mass flow rates of liquid and vapor phases. It was shown that the mass flux of water was negligible compared with that of ammonia except the region near the liquid inlet. Ammonia absorption rate increases rapidly near the liquid inlet and decrease slowly. Both the absorption rate of ammonia vapor and the desorption rate of water near the liquid inlet increase as the vapor mass flow rate increases, but the mass fluxes of the ammonia and the water near the liquid outlet decrease as the mass flow rate of the vapor increases.

• The Science & Technology
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• v.33 no.10 s.377
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• pp.78-79
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• 2000

나노입자의 제조 및 성장제어와 열 및 물질전달과 에어로솔 공학분야의 연구에 주력하고 있는 최만수 교수(44세). 최근에는 나노입자의 융합속도를 제어하는 새로운 나노입자 성장제어 기술을 개발해 학계의 관심을 모으고 있다. 최교수는 앞으로 융합촉진을 이용하는 나노입자 제어기술을 복합나노입자를 포함한 여러 다양한 나노입자의 제조와 나노물질의 제조에 응용해 나갈 것이며 이론적 모델리의 개발도 병행해 나갈 계획이다.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.73-79
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• 2008

An experimental study was conducted to investigate the effect of a tube row, a fin pitch and an inlet humidity on air-side heat and mass transfer performance of louvered fin-tube heat exchangers under wet conditions. Experimental conditions were varied by three fin pitches, two rows, two inlet relative humidities. Experimental results showed that the heat transfer performance decreased and the friction increased with the decrease of fin pitch, for 2 row heat exchanger. The effect of fin pitch on heat transfer performance was negligible with 3 row heat exchanger. The changes in relative humidity was not affected heat transfer and friction. However, the mass transfer performance was slightly decreased with the increase of relative humidity and with the decrease of fin pitch. The mass transfer performance of the louvered fin-tube heat exchanger decreased with the decrease of the fin pitch and was different according to the number of tube row.