• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.79-79
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• 2017

국내 여름철의 고온다습한 기후환경으로 인하여 온실 내부의 냉방 및 제습이 필수적인데, 온실 냉방 방식 중 증발냉각 시스템이 가장 효율이 높다고 알려져 있다. 하지만 증발냉각 시스템은 건조한 기후 지역에서 발달한 방식으로, 작물의 증산작용으로 인한 온실 내부 습도 상승에 따른 문제점이 발생되어 다습한 여름철 국내 기후에는 반드시 냉각과 제습이 동시에 필요하다. 따라서 증발냉각 방식 중 Fan and Pad 방식과 리튬브로마이드 수용액을 이용한 온실 냉방 및 제습을 위한 복합시스템에 관한 연구가 진행중이다. 현재 리튬브로마이드 수용액 제습 시 발생되는 발열량과 수용액의 무게변화와 같은 수용액의 흡습성질 대한 정확한 지표가 나타나 있지 않다. 이에 연구를 진행하기에 앞서 리튬브로마이드 흡습성질에 관한 데이터 자료가 필요하다고 판단되어 기초실험을 진행하였고, 본 연구에서는 Pilot Scale의 재생 순환시스템을 통해 리튬브로마이드 수용액의 흡습성질을 이용한 재사용 방안을 제시하였고, 시스템 내에서 외부투입공기와 작동유체의 흡습성질에 의한 반응 전후 온도변화 예측 모델을 수립하였다. 따라서 본 연구를 통해 리튬브로마이드 수용액의 흡습성질을 분석하고, 이를 이 용한 재생 순환 시스템에 관한 연구를 진행할 예정이다.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.337-341
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• 2014

Due to the nature of the ambient air temperature in summer in korea, the growth of crops in greenhouse normally requires cooling and dehumidification. Even though various cooling and dehumidification methods have been presented, there are many obstacles to figure out in practical application such as excessive energy use, cost, and performance. To overcome this problem, the lab scale experiments using lithium bromide(LiBr) solution and cooling coil for dehumidification and cooling in greenhouses were performed. In this study, preliminary experiment of dehumidification and cooling for the greenhouse was done using LiBr solution as the dehumidifying materials, and cooling coil separately and then combined system was tested as well. Hot and humid air was dehumidified from 85% to 70% by passing through a pad soaked with LiBr, and cooled from 308K to 299K through the cooling coil. computational Fluid Dynamics(CFD) analysis and analytical solution were done for the change of air temperature by heat transfer. Simulation results showed that the final air temperature was calculated 299.7K and 299.9K respectively with the deviation of 0.7K comparing the experimental value having good agreement. From this result, LiBr solution with cooling coil system could be applicable in the greenhouse.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.05a
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• pp.103-108
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• 1994

리튬브로마이드 수용액이 수직관내면을 따라 액막의 형태로 흘러 내릴때 수증기와의 흡수과정에 대하여 열 및 물질전달 특성을 실험하였다. 실험에서 열 및 물질전달계수는 막레이놀즈수를 30에서 200까지 변화시키면서 실시하였다. 일정한 냉방능력에서 시스템 압력을 변화시켰을 때의 열 및 물질전달계수를 측정하였다. 액막의 열전달계수는 레이놀즈수가 증가함에 따라 감소하였다. 최대 질량유량에서 최적의 막레이놀즈수가 존재하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.144-152
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• 1997

Film absorption involves simultaneous heat and mass transfer in the vapor-liquid system. In the present work, the absorption process of water vapor by an aqueous soluton of LiBr flowing inside of the vertical tube was investigated. The continuity, momentum, energy and diffusion equations for the solution film and vapor were formulated in integral forms and solved numerically. The model could predict the film thickness, the pressure gradient, and the heat and mass transfer rate. Particularly the effects of vapor flow conditions on the absorption process were investigated in terms of the vapor Reynolds number. As the vapor Reynolds number increased, the shear stress at the vapor-solution interface also increased. Consequently solution film became thinner at higher vapor flowrate under the co-currentflow condition. Thinner film was capable of higher heat transfer to the wall and leaded to higher absorption rate of the water vapor into the solution film.

• 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
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• v.19 no.4
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• pp.1071-1082
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• 1995

Numerical analyses have been performed to obtain the absorption heat and mass transfer coefficients and the absorption mass flux from a falling film of the LiBr aqueous solution which is cooled by cooling air. Heat flux at the wall is specified in terms of the heat transfer coefficient of cooling air and the cooling air temperature. Effects of operating conditions, such as the heat transfer coefficient, the cooling air temperature, the system pressure and the solution inlet concentration have been investigated in view of the local absorption mass flux and the total mass transfer rate. Effects of film thickness and film Reynolds number on the heat and mass transfer coefficients have been also estimated. Analyses for the constant wall temperature condition have been also carried out to examine the reliability of present numerical method by comparing with previous investigations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1214-1222
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• 2001

The present study investigated the effect of diameter and length on the absorption performance of a vertical falling film type absorber using $LiBr-H_2$O solution of 60 wt%. The parameters were diameter of absorber (17.2, 23.4, 31.1 mm), length of absorber (771, 1150, 1528 mm), and film Reynolds numbers (50, 70, 90, 110, 130, 150). As the diameter of the absorber was increased, the absorption mass flux, Sherwood number, heat flux, and heat transfer coefficient were increased, in which Sherwood number and heat transfer coefficient were increased up to 13% and 30% respectively. As the length of the absorber was increased, the total absorption rate and heat transfer coefficient were increased by 37% and 35% respectively, while the absorption mass flux was decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1267-1276
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• 1998

Falling-film evaporation experiments with aqueous lithium bromide (LiBr) solution were performed to investigate the heat transfer characteristics of enhanced copper tubes. Enhanced tubes (a knurled tube, a spirally grooved tube, and a tube coated with $20{\mu}m$ aluminum particles) and a bare tube were selected as test specimens. Averaged evaporation fluxes of water were obtained from horizontal tubes with various film Reynolds numbers, system pressures, LiBr concentrations and degrees of wall superheat. The enhanced performance of steam generation was compared between tubes with varying parameters. The knurled tube geometry showed the most excellent performance among the tubes tested. The specified enhanced tubes were more useful for generating steam on a low grade heat source such as waste heat.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3293-3303
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• 1996

Numerical analyses have been performed to estimate the absorption heat and mass transfer coefficients in absorption process of the LiBr aqueous solution and the total heat and mass transfer rates in a vertical tube absorber which is coolING ed by air. Axisymmetric cylindrical coordinate system was adopted to model the circular tube and the transport equations were solved by the finite volume method. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by water vapor in tube. Effects of film Reynolds number on heat and mass transfer coefficients have been also investigated. Especially, effects of tube diameter have been considered to observe the total heat and mass transfer rates through falling film along the tube. Based on the analysis it has been found that the total mass transfer rate increases rapidly in a region with low film Reynolds number(10 ~ 40) as the film Reynolds number increases, while decreases beyond that region. The total heat and mass transfer rates increase with increasing the tube diameter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.670-679
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• 1996

A numerical study for vapor absorption into LiBr-H$_{2}$O solution film flowing over horizontal circular tubes has been carried out. The momentum, energy and diffusion equations, which are parabolized by the boundary- layer approximation, are solved simultaneously for various mass-flow rates and inlet conditions. The results for the velocity, temperature and concentration fields, as well as the heat and mass flux at the free surface are presented. The effects of inlet conditions, i.e., flow rate, temperature and concentration, on the absorption process are also examined and discussed.