• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.4
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• pp.453-462
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• 1994

An unsteady quasi one-dimensional model of momentum, heat and mass transfer in a falling film of a vertical plate absorber which is cooled by air was developed using the integral method. Energy conservation of the absorber wall is considered in the model. The model can predict absorption rate, film thickness and mean velocity as well as concentration and temperature profiles. Predictions of steady state temperature and concentration profiles for LiBr/water system for constant wall temperature condition are in good agreement with the two-dimensional finite difference method solutions. Effects of operating conditions, such as convective heat transfer coefficient between the cooling air and the absorber wall, cooling air temperature and film thickness at inlet, on absorption rate of water vapor into LiBr/water solution were shown.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.782-791
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• 1998

This paper presents a computer simulation of five types of triple effect absorption cycles employ-ing the refrigerant absorbent combinations of NH3/LiNO3 low-pressure type NH3/LiNO3+H2O/LiBr binary two-stage type series flow cycle and two types of parallel flow cycle for H2O/LiBr. The absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature approach temperature of absorber loss temperature of absorber and chilled water outlet temperature. The most important characteristic temperature of absorber and chilled water outlet temperature. The most important characteristic of NH3/LiNO3 low-pressure type and a NH3/LINO3+H2O/LiBr binary two-stage type is that it obtains a coefficient of performance higher than the sum of the performance coefficients of its part operating independently. As a result of this analysis the optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.1
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• pp.1-11
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• 1985

Solar/absorption cooling system was analyzed and its operating condition was examined. For the system, the optimum size of absorption refrigerator and collector area should be determined. As the temperature of water supplied to the generator increases, the collector efficiency decreases whereas the coefficient of performance of absorption refrigerator increases up to a certain point, and vice versa for decreasing of the temperature of water supplied to the generator . Thus if the reeling load is given, the appropriate operating condition can be determined between the two opposing trends by simulation program. As an example of the simulation, the case of Jejudo province was studied. Under the conditions (such as weather data and prices of components, etc.) given en the sample calculation, the result shows that the optimum temperature of water supplied to the generator turned out to be $80.3^{\circ}C$, and still shows a large economical disadvantage in present stage compared to the case of conventional vapor compression cooling/heating combined heat pump system.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.1-11
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• 2009

Although the exterior wood such as column may frequently contact with liquid water, little work has been found to measure liquid water absorption in wood. To investigate the moisture diffusivity of wood in the longitudinal direction including bound water and free water movement, liquid water absorption test was conducted at the room temperature. The order of magnitude for absorption coefficient and diffusivity was Japanese elm, horn beam, hemlock, spruce, radiata pine, and painted maple. The Boltzmann transformation method was used to determine the diffusivity from measured moisture content distributions in the absorption test. The shape of the curve representing the dependence of diffusivity with moisture content was similar in test samples. The diffusivity decreased with increasing moisture content until around the fiber saturation point and then increased at the nonhygroscopic region, which ranged from $10^{-10}$ to $10^{-7}m^2/s$.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.151-159
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• 2018

Annually, the global production of construction aggregates reaches over 40 billion tons, making aggregates the largest mining sector by volume and value. Currently, the aggregate industry is shifting from sand to hard rock as a result of legislation limiting the extraction of natural sands and gravels. A major implication of this change in the aggregate industry is the need for understanding rock fragmentation and energy absorption to produce more cost-effective aggregates. In this paper, we focused on incorporating dynamic rock and soil mechanics to understand the effects of loading rate and water saturation on the rock fragmentation and energy absorption of three different sandstones (Red, Berea and Buff) with different pore sizes. Rock core samples were prepared in accordance to the ASTM standards for compressive strength testing. Saturated and dry samples were subsequently prepared and fragmented via fast and dynamic compressive strength tests. The particle size distributions of the resulting fragments were subsequently analyzed using mechanical gradation tests. Our results indicate that the rock fragment size generally decreased with increasing loading rate and water content. In addition, the fragment sizes in the larger pore size sample (Buff sandstone) were relatively smaller those in the smaller pore size sample (Red sandstone). Notably, energy absorption decreased with increased loading rate, water content and rock pore size. These results support the conclusion that rock fragment size is positively correlated with the energy absorption of rocks. In addition, the rock fragment size increases as the energy absorption increases. Thus, our data provide insightful information for improving cost-effective aggregate production methods.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.844-853
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• 2002

A dynamic model which simulates the coupled heat and mass transfer within a vertical tube absorber was developed. The liquid film is a binary mixture of two components, and both of these components are present in the vapor phase. The pressure, concentration, temperature and mass flow rate of the vapor are obtained by assuming that the pressure is uniform within an absorber. The model was applied to an absorber for an ammonia/water absorption refrigerator. The transient behaviors of the pressure, the outlet temperature and the concentration of the solution and the cooling water outlet temperature on a step change at the absorber inlet of the cooling water temperature, the vapor mass flow rate and the concentration of the solution were shown.

• Journal of the Korean Solar Energy Society
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• v.23 no.4
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• pp.45-54
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• 2003

For cooling of double effect absorption heat pump system of solar heating source, analysis of thermodynamic design data has been done to find the property of Libr-water + ethylene Glycol mixture for working fluid by computer simulation. Derived thermodynamic design data, enthalpy based coefficient of performance and flow ratio for possible combinations of operating temperature for water - LiBr and Ethylene Glycol mixture ($H_2O$ : CHO ratio 10:1 by mole) by computer simulation are done. The obtained results, COP and mass flow ratio of the water - lithium bromide - ethylene glycol system, are compared with data for the water-Libr pair solution.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.51-61
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• 2002

Analysis of thermodynamic design data of double effect solar absorption heat pump system for heating has been done to find the property of Libr-water + ethylene Glycol mixture for working fluid by computer simulation. Derived thermodynamic design data. enthalpy based coefficient of performance and flow ratio for possible combinations of operating temperature for water - LiBr and Ethylene Glycol mixture (H2O: CHO ratio 10:1 by mole) by computer simulation. The obtained results, COP and mass flow ratio of the water-lithium bromide-ethylene glycol system, are compared with data for the water-Libr pair solution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.208-211
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• 2003

In this paper, mechanical property of electric epoxy with water aging was discussed. We studied mechanical property of elastic resin after absorption in water from 0 to 484 hour. As a result, diffusion factor of elastic epoxy showed $20-21{\times}10^{-4}mm^2/s$ and general epoxy showed $9.5{\times}10^{-4}mm^2/s$. Elastic property increased linearly according to amount of addictives and decreased elastic property according to amount of water absorption. Tensile strength was reduced to add to addictives. It was effected by water absorption of micro-void of elastic epoxy. Hardness inclined to decrease after increasing according to absorbed time.

• Journal of the Korea Institute of Building Construction
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• v.7 no.1 s.23
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• pp.115-121
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• 2007

Ordinary concrete uses aggregate sufficiently soaked with water, and is weighed, mixed with other materials and placed in accord with performances required in the construction field. Recently special concrete with high fluidity and durability is required but it is difficult to use top-quality concrete due to lack of high-quality aggregate, delayed transportation because of traffic jam, etc. In addition, sometimes the use of a remicon is inevitable just for small-sized concrete constructions or it is difficult for a remicon to reach remote construction places such as mountainous areas. To solve these problems, this study attempted to pack concrete materials. In other words, it is to instantize concrete. This study dried aggregate, a material of concrete, and compared the change of absorption phase of the aggregate in water and in paste in order to examine the effect of the dryness of aggregate on its absorption rate and, based on the absorption rate, decided water addition ratio necessary for the reduction of unit quantity caused by the use of dry aggregate in designing concrete mixture, and analyzed the properties of unhardened concrete according to water addition ratio in manufacturing concrete using aggregate in the state of absolute dryness and in the state of surface dryness.