• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.410-417
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• 2006

The present study predicted the effect of the flow rate of coolant on the absorption performance of a vertical falling film type absorber Heat and mass transfer peformances were numerically investigated. The exit temperatures of solution and coolant were decreased as the flow rate of the coolant was increased at the film Reynolds number of 100. The absorption mass flux was increased and then decreased as the distance from the inlet of the absorber was increased. The distance showing the maximum absorption mass flux was ranged from 0.3 to 0.5m. The heat flux and the absorption mass flux were increased and then slowly decreased as the flow rate of the coolant was increased. The maximum values were obtained at the flow rate of coolant of 2.0L/min.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.41-47
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• 2002

A model of simultaneous heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled vertical plate absorber was developed. The model can predict temperature and concentration profiles as well as the absorption heat and mass fluxes, the total heat and mass transfer rates and the heat and mass transfer coefficients. Besides, the effect of operating condition on absorption mass flux has been investigated, with the result that the absorption mass flux is increased as the inlet cooling water temperature decreases, the system pressure increases and the inlet solution concentration increases. And among the effects of operating parameters on absorption mass flux, the effect of inlet solution concentration is dominant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1428-1436
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• 2000

The absorption of vapor involves simultaneous heat and mass transfer in the vapor/liquid system. In this paper, a numerical study for vapor absorption process into LIBr-H$_2$O solution film flowing over helical absorber has been carried out. Axisymmetric cylindrical coordinate system was adopted to model the helical tube and the transport equations were solved by the finite volume method. The effects of operating conditions, such as the cooling water temperature. the system pressure, the film Reynolds number and the solution inlet concentration have been investigated in view of the absorption mass flux and the total absorption mass flux and the total absorption rate. The results for the temperature and concentration profiles, as well as the local absorption mass flux at the helical absorber are presented. It is shown that solution inlet concentration affected other than operation conditions for a mass flux.

• 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.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.2
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• pp.140-149
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• 1988

The problem of heat and mass transfer accompanying the absorption of water vapor into LiBr-$H_2O$ liquid solution flowing over the outside of the horizontal cylinder was theoretically studied to understand the absorption process occuring in the absorber of the absorption heat pump. Numerical results are presented for various quantities of interest relating to temperature, concentration, heat flux and mass flux. Also, the effects of mass flowrate, initial average velocity, and the radius of the cylinder were investigated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.835-845
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• 1999

The objective of the present study was to investigate heat and mass transfer characteristics in a vertical falling film type absorber using LiBr-$H_2O$ solution with 6owt%. The experimental apparatus consisted of an absorber with inner diameter of 17.2 mm and length of 1150mm, a generator, an evaporator/condenser, a solution tank, a sampling trap etc. The parameters were solution temperature of 45 and $50^{\circ}C$, coolant temperature of 30 and $35^{\circ}C$, and film Reynolds numbers from 50 to 150. Pressure drop in the absorber increased as solution and coolant temperatures decreased. Pressure drop in the absorber increased up to the film Reynolds number of 90, and then decreased at the further increase of the Reynolds number above 90. The maximum absorption mass flux observed at the film Reynolds number of 90. Absorption mass flukes increased as coolant temperature decreased. Absorption mass fluxes and heat transfer coefficients under subcooled condition were larger than those under superheated condition. Heat transfer coefficients were affected by solution temperature more than coolant temperature. The maximum absorption effectiveness under the subcooled condition was 23% for coolant temperature of $30^{\circ}C$ and 31% for coolant temperature of $35^{\circ}C$ under the present experimental conditions.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.213-218
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• 1999

The $LiBr-H_{2}O$ absorption process on a horizontal tube has been analyzed using the numerical method which incorporates the fully elliptic Navier-Stokes equations for the momentum equations, the energy and mass-diffusion equations. On a staggered grid, the SIMPLER algorithm with the QUICK scheme is used to solve these equations along with the MAC method for the free surface tracking. With the assumption that the absorbent is linear, calculations have been made for various inlet temperature and flow-rate conditions. The detailed results of the parametric study, such as the temperature, concentration, absorption mass flux and wall heat flux distributions are presented. The self-sustained feature of the absorption process is clearly elaborated. The analyses have also been carried out for multiple tube arrangement and the results show that the absorption rate converges after a few tube rows.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.2
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• pp.51-59
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• 2000

The purpose of the present study is to investigate the absorbing characteristics in a vertical falling film type absorber using LiBr-H$H_2O$ solution as working fluids with the concentration of 60 wt%. The experimental apparatus consists of an absorber with the diameter of 17.2 mm and the length of 1150 mm, a generator, an evaporator (condenser), a weak solution tank and a sampling trap device and so on. The parameters were the solution temperatures of 45 and 50$^{\circ}$C, coolant temperatures of 30 and 35$^{\circ}$C, and the film Reynolds numbers from 50 to 150. The pressure drop in the absorber increased as the solution and coolant temperatures decreased. The pressure drop in the absorber increased up to the film Reynolds number of 90, however, decreased at the film Reynolds number above 90. The maximum absorption mass flux was observed at the film Reynolds number of 90. Absorption mass fluxes increased as the coolant temperature decreased. Accordingly, absorption mass fluxes and heat transfer coefficients under the subcooled condition increased more than those under the superheated condition. It is claimed that heat transfer coefficients are deeply affected by the solution temperature more than the coolant temperature within the experimental range.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.825-832
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• 2002

The present study investigated the enhancement of the absorption performance by the spring wrapped around the outer surface of the vertical falling film absorber tube. Heat and mass transfer enhancements were experimentally investigated, and flow visualization was performed to observe the wettability and flow pattern of the solution. The key experimental parameters were spring diameter (0.5, 1.0 mm) and spring pitch (1, 3, 10 mm), film Reynolds number (50~150), and concentration of LiBr-$H_2O$ solution (55, 60, 65 wt%). As the spring diameter was increased, the absorption mass flux, Sherwood number, Nusselt number, heat flux, and heat transfer coefficient were increased The Nusselt and Sherwood numbers showed the maximum at the spring pitch of 3mm, and the ratio of pitch to diameter of approximately 3 and 6 for the spring diamter of 0.5 mm, respectively.