• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.2
• /
• pp.144-152
• /
• 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
• /
• v.10 no.4
• /
• pp.456-465
• /
• 1998

Effect of a non-absorbable gas on the absorption process in a vertical tube absorber was investigated numerically. The water vapor mined with air as the non-absorbable gas is absorbed into LiBr/water solution film. The flow is assumed to be laminar and fully developed in both liquid and gas phases. The diffusion and energy equations were solved in both phases to give the temperature and concentrations, from which heat and mass fluxes were determined. It was shown that the local absorption rate decreases as the mass fraction of air in water vapor increases. The vapor pressure of water at the liquid-vapor interface reduces significantly since the non-absorbable gas is accumulated near the interface. The effect of non-absorbable gases on absorption rate becomes larger as the mass flow rate of the vapor decreases. For small amount of non-absorbable gases the total absorption rate of water vapor increases as the mass flow rate of the vapor decreases. Total absorption rate increases as the mass flow rate of the vapor increases for large concentration of non-absorbables at the inlet of an absorber.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.7
• /
• pp.69-78
• /
• 1999

Effects of a non-absorbable gas on the absorption process in a vertical tube absorber has been investigated numerically. The water vapor mixed with air is absorbed into LiBr/water solution film. The flow is assumed to be laminar and fully developed in both liquid and gas phases. The diffusion and energy equations were solved in both phases to give the temperature and concentrations, from which heat and mass fluxes were determined. The local absorption rate has been shown to decrease as the mass fraction of air in the water vapor increases. The vapor pressure of water at the liquid-vapor is interface reduced significantly since the non-absorbable gas accumulates near the interface. The effects of non-absorbable gases on absorption rate become larger as the mass flow rate of the vapor decreases. For a small amount of non-absorbable gases, the total absorption rate of water vapor increases as the mass flow rate of the vapor decreases. The total absorption rate increases as the mass flow rate of the vapor increases for large concentrations of non-absorbable gases at the inlet of an absorber.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.2
• /
• pp.65-71
• /
• 1992

In most absorption machines, absorption enhancement has been achieved by adding small amount of surfactant additive, which introduced the surface tension difference between absorbent and surfactant droplets in the vapor absorption. The aim of this study is to understand a basic mechanism of Marangoni convection and its effectiveness in the vapor absorption enhancement. In this study, nonflowing aqueous solution of LiBr 60 mass% was exposed to saturated water vapor under the condition that two dropwises surfactant were fixed on the absorbent surface. Our experiments achieved to visualize the enhanced heat and mass transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also, Marangoni convection behavior was obtained by using tracer method.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.24 no.6
• /
• pp.810-818
• /
• 2000

The purpose of this study was to analyze the effect of geometrical structure on the moisture transport properties of nonwoven batting materials. Two types of nonwovens were used such as single and double layered nonwovens. Steady and dynamic state water vapor transport properties were measured by absorption, evaporation and cobaltous chloride method respectively. The results of this study were as follows: 1) Geometrical structure affected water vapor evaporation, but there were no differences between single and double layered nonwovens in moisture absorption. Thickness and air permeability were influencing factor on water vapor transport rate. 2) Directionality of double layered nonwoven was observed both in steady and dynamic state moisture transport. There were differences between upper and lower layer of double layered nonwoven both in moisture absorption rate and color change by cobaltous chloride method. 3) In dynamic state of water vapor transport rate, single layered nonwoven reached more rapidly at the established relative humidity. It was confirmed that geometrical structure affected water vapor evaporation and hydrophilicity of fiber affected moisture absorption because there were much more water vapor transport rate by evaporation than absorption within the same period of time.

• Preventive Nutrition and Food Science
• /
• v.13 no.1
• /
• pp.28-32
• /
• 2008

Water vapor sorption by sodium alginate-based films may result in swelling and conformational changes in the molecular structure and affecting the water vapor barrier properties. Sodium alginate film specimens were dried in a vacuum freeze dryer and their moisture content was determined by an air-oven method. The water vapor absorption was determined at two different levels of water activities (0.727 and 0.995) and at three temperatures (10, 20, and $30^{\circ}C$), and kinetics were analyzed using a simple empirical model. Reasonably good straight lines were obtained with plotting of 1/($m-m_0$) vs 1/t. It was found that water vapor absorption kinetics of sodium alginate films were accurately described by a simple empirical model. The rate of water vapor sorption increased with increase in temperature and it showed temperature dependency following the Arrhenius equation. The activation energies varied from 49.18$\sim$149.55 kJ/mol depending on the relative humidity.

• Journal of the Korean Vacuum Society
• /
• v.13 no.2
• /
• pp.59-64
• /
• 2004

A study on the semiconductor laser-based atomic absorption spectroscopy was performed for monitoring physical vapor deposition process. Gadolinium metal was vaporized with a high evaporation rate by electron beam heating. Real-time atomic absorption spectra were measured by using tunable semiconductor laser beam at 770-794 nm (center wavelength of 780 nm) and its second harmonic at 388-396 nm. Atomic densities of metal vapor can be calculated from the absorption spectra measured. We plot the atomic densities as a function of the electron beam power and compare with the evaporation rates measured by quartz crystal monitor. We demonstrate that the semiconductor laser-based spectroscopic system developed in this study can be applied to monitor the physical vapor deposition process for other metals such as titanium.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.2
• /
• pp.122-133
• /
• 1997

Numerical analysis using finite volume method has been carried out to examine the effect of degree of superheat of LiBr aqueous solution on heat and mass transfer occurred in absorption process. According to the result of this study, it was found that refrigerant vaper was generated at the entrance region of absorber when LiBr aqueous soltion was superheated. As the degree of superheat increases, heat transfer rate increases and vapor absorption rate decreases. The increase in averaged Nusselt and Sherwood numbers could be found as film Reynolds number increases. The larger the degree of superheat, the greater the averaged Nusselt and Sherwood numbers.

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

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.33 no.3
• /
• pp.43-49
• /
• 2004

This article reviews R＆D of triple effect cycle developed in Japan. Most of the refrigeration and heat pump technologies are dominated by vapor compressor system. The vapor compressor system, however, is highly concerned with the environmental regulations , as most of the vapor compressor technologies are using CFCs or HCFCs which are known as ozone depleting and global warming gases. As a consequence, refrigeration technologists are trying to invent or to develop an alternative to vapor compressor refrigeration devices. Thermally driven, absorption technology is one of the possible alternatives. At the moment, absorption cycle is most promising technology The paper summarizes briefly the current research and development in advanced technologies of triple effect absorption chiller-heater in Japan.(omitted)