• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.287-292
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• 2004

An experimental investigation was carried out to study the performance of a bubble pump for the diffusion absorption refrigerating system. Ammonia was used as the refrigerant and the helium was charged in order to balance the pressure between the low and high pressure side. As experimental variables, the concentration of ammonia charged into system, heat input, and the pressure of helium were selected. Experimental results show that the generation rate of ammonia vapor and the circulation rate of diluted ammonia solution were increased as the heat input increases, but the ratio of the solution to vapor flow rate was decreased. The generation rate of refrigerant vapor and the circulation rate of diluted ammonia solution increased as the system pressure decreased. Finally under the condition of 25 bars, the concentration of rich ammonia solution was not affected by the generation rate of ammonia vapor and the circulation of diluted ammonia solution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.431-438
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• 2000

The major irreversibilities in absorption chillers are associated with the transfer of heat into and out from the machine and irreversible process inside the machine. By modeling only external irreversibilities(endo-reversible), a model was formulated to predict the ideal performance of a single-effect absorption chiller. Its actual performance including both external and internal irreversibilities was calculated with a in-house simulation program. The optimization of heat transfer area distribution was performed for both endo-reversible cycle and actual cycle. The equation of endo-reversible modeling was found to give about 2times higher cooling capacity than the simulation program. At optimal distribution, it was found that heat transfer area of the evaporator was about 30% of total area, that of the generator was 20%, and the rest 50% was for the absorber and condenser. The system COP for endo-reversible cycle was slightly higher than that for actual cycle. In the case of LiBr-water single-effect absorption chiller, the maximum cooling capacity was obtained near the condition that LMTD is same at all heat exchangers.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.89-91
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• 2004

This study examines a regeneration process using hot air heated by solar radiation to recover absorption potential by evaporating moisture in liquid desiccant. More specifically, this study is aimed at finding the optimum operating condition of the regenerator by utilizing a well-established statistical tool, so-called design of experiment, and optimization techniques. It is demonstrated that an optimization model to find the optimum operating condition can be obtained using the functional relationship between regeneration rate and affecting factors which is approximated on the basis experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.26-33
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• 2004

In general, an absorption chiller or heat pump is operated under the constant cooling water flow rate condition even though the system works with a partial load. The objective of this paper is to study the effect of the cooling water flow rates and the temperature of cooling water on the system performance to find the energy saving methode for the partial load operation of the double effect $H_2O$/LiBr absorption chiller. It is found that the performance of the system is sensitive to the temperature of cooling water than the cooling water flow rate, so the decrease of the performance due to reducing the cooling water flow rate can be overcome with the reduction of the cooling water temperature by 1$^{\circ}C$. The flow rate of the cooling water flow rate ranges from 50％ to 100％ of the flow rate at normal conditions with a partial load. It is also found that the operation cost of the cooling water pump and the cooling tower can be reduced by 23％.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.3
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• pp.267-276
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• 2000

A numerical study has been carried out to find out the optimal design condition of a solar absorption cooling system. The system was composed of solar collectors and an absorption chiller with LiBr/water The System performance with commercial single effect(SE) cycle and a new single effect/double lift(SE/DL) cycle utilizing low temperature hot water was calculated and compared. It was found that the required solar collector area grew exponentially as the overall heat loss coefficient of solar collectors increased. For instance, the required area for cooling capacity of 1 USRT was $17m^2$ if heat loss coefficient was 4 W/$m^2\;cdot\;K$. If heat loss coefficient was doubled($8\;W/m^2\;cdot\;$K), the required collector area was increased by 6 times($100m^2$) .It was also found that the SE-cycle as the heat loss coefficient of solar collectors increased. Generally, a SE/DL-cycle seems to be more advantageous than a SE-cycle if loss coefficient of solar collector is greater than 4 W/$m^2\;cdot\;K$.

• Journal of Forest and Environmental Science
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• v.40 no.2
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• pp.90-98
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• 2024

This study analyzes the characteristics of sound-absorbing materials made from forest by-products of the deciduous tree species Zelkova serrata (Z. serrata) by evaluating their sound absorption performance. Accordingly, sound-absorbing materials with varying sample thicknesses, leaf sizes, and drying conditions were fabricated. The sound absorption properties were measured using the impedance tube method via middle-type measurement tube (100 Hz-3,200 Hz). The sound absorption properties were evaluated using the average sound absorption coefficient (ASAC), which was calculated from the measured sound absorption coefficients at 250 Hz, 500 Hz, 1,000 Hz, and 2,000 Hz. The ASAC value significantly improved as the leaf size increased to 0.5×0.5 cm², 1.0×1.0 cm², and 2.0×2.0 cm². The ASAC values under the two drying conditions were similar. There was no significant difference in ASAC according to the leaf size under the air-dried leaf condition, with a thickness of 2.50 cm. The highest ASAC value according to the sound-absorbing material thickness was 0.47 at a thickness of 2.50 cm and leaf size of 2.0×2.0 cm² under the air-dried leaf condition. In addition, the variation in ASAC was 0.23, indicating that the sound absorption performance according to leaf thickness was more significant than the difference in absorption properties according to leaf size. A sound absorption coefficient (SAC) of 0.4 or higher was observed across the measurable frequency band (100 Hz-3,200 Hz). Furthermore, the SAC values with respect to leaf size and thickness were close to 1 in the high-frequency range above 2,000 Hz. Therefore, it is considered that sound-absorbing materials using Z. serrata leaves are advantageous in the field of absorbing noise in a high-frequency band of 2,000 Hz or more, and it is better to manufacture a thickness of 2.50 and 2.0×2.0 cm².

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1241-1248
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• 2002

Performance extension of the absorption refrigerator with LiBr solution is often faced to operate very close to the crystallization limit. Especially in the development of an air-cooled cycle, the crystallization of working solution in the system is a very difficult problem to overcome. This paper describes the cycle of hot water driven absorption system using a new working absorption solution instead of LiBr solution to improve the efficiency. In this study, we found out the characteristics of new working absorption solution through the cycle simulation and compared LiBr solution to evaluate. The effect of cooling water temperature, weak solution flow rate, hot water temperature and hot water flow rate were also examined. The COP is increased 22% higher in the case of LiBr＋Li1＋LiC1＋LiNO$_3$＋$H_2O$, 2% LiBr＋HO(CH$_2$)$_3$OH＋$H_2O$ than that of LiBr solution for the same operation condition.

• Journal of the Korean Society of Visualization
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• v.9 no.3
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• pp.59-64
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• 2011

In this study the change of free surface vortex is expressed through the time volume fraction using multiphase unsteady condition in sump, because in previous studies of the pump sump did not represent the behavior of the free surface vortex exactly due to the reason it was calculated using single phase and steady condition. The reliability of the computational analysis is verified through comparing experimental results with that of present numerical analysis. Homogeneous free surface model is used to apply interactions of air and water. The results show that the free surface vortex can be identified on the isotropic surface at air volume fraction 1%~5%. The vortices make an air column from the free surface to the sump intake and are created and destroyed repeatedly. The behavior of free surface vortex at numerical analysis is quite similar to experimental test. The result of vortex motion according to time, works on a cycle.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.311-318
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• 2006

CFD simulation is a tool very useful to predict the generation and absorption of the contaminant from the construction materials for the single room condition. However, there is a limit in multi-room simulation for analyzing air movement and contaminant concentration at the condition that the door of each room was closed. A lot of network simulation tool were developed which can used to analyze the mass transfer and contaminant concentration as results in the multi-room condition. However, existing network simulation method was not able to analyze the change of the heating and cooling load with the ventilation as though the change of the indoor air-pollution density was predictable. In this study, new approach to predict heating/cooling load and indoor contaminant concentration will be reviewed. New indoor contaminant concentration module reviewed in this study wad coupled with existing ESP-r network simulation method. The validity of new approach will be analysed for comparison the results of simulation and field measurement results.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.195-200
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• 2009

The objectives of this study are to analyze of energy consumption and operation conditions of each cooling system for gas and electric driven systems, and to compare operating cost for five different cooling systems; ice storage system, system air-condition, turbo chiller as the electric driven cooling systems, and absorption chiller and Gas driven Heat Pump (GHP) as the gas driven cooling systems. The sample designs are carried out based on the types of business, capacity, installation region and year.