• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.437-439
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 1992.07a
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• pp.397-407
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• 1992

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.21 no.6
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• pp.451-465
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• 1992

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.23 no.3
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• pp.204-211
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• 1994

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.24 no.5
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• pp.539-549
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• 1995

• Journal of Korean Society of Water and Wastewater
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• v.13 no.3
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• pp.61-72
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• 1999

To obtain the experimental data for design and operation of actual filtration processes, a sand filter and three kinds of dual media filters in pilot-plant scale were operated in this study. We analyzed the effect of filter medium composition on the filter performance and the effects of backwash water flow rates, length of stream line and air flow rate on the filter backwash efficiency. We also compared the efficiencies of the combined air-water backwashing and the water backwashing in dual media filters. As the backwash water flow rates or the length of stream line increased, the final turbidity of backwash water was decreased and the filtration duration time after backwash was increased. In the case of the combined air-water backwashing, the backwash water quantity needed for backwashing the dual media filters could be decreased. The total volume of filtered water for the dual media filters during filter run was over three times larger than that for the sand filter. The dual media filters could be operated at a high filtration rate of 360 m/day.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.131-139
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• 2001

Highly accurate control of the air-fuel ratio is important to reduce exhaust gas emissions of the gaseous-fuel engines. In order to achieve this purpose, inlet air mass flow must be measured exactly, and precise engine models are necessary to design engine control systems. In this paper, the effects of water vapor and gaseous fuel that change the air mass flow are studied. The effective air mass ratio is defined as the air mass flow divided by the mixture mass flow, and also it is applied to the estimation of the inlet air mass flow. The presence of the gaseous fuel and the water vapor in the mixture reduces the air partial pressure and the effective air mass ratio of the gaseous-fuel engines. The Experimental results for an LPG engine show that the estimation of the inlet ai mass flow based upon the effective air mass ratio is more accurate than that of the normal air mass flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.1005-1013
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• 2005

The use of river water as a heat source of a heat pump has the advantage in the performance compared to the use of atmospheric air because the temperature variation of river water over the year is relatively small. In this study, the performance of the heat pump system using river water as a heat source was numerically investigated. A simulation model for the 2-stage compression heat pump system was developed with each component model composed of compressors, heat exchangers, a flash tank and electronic expansion devices. The peformance of the heat pump system using river water was improved by $50\%$ compared to that using atmospheric air in winter conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.456-465
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• 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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.4
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• pp.354-362
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• 2000

Optimal supervisory control strategy for the set points of controlled variables in the central cooling system has been studied by computer simulation. A quadratic linear regression equation for predicting the total cooling system power in terms of the controlled and uncontrolled variables was developed using simulated data collected under different values of controlled and uncontrolled variables. The optimal set temperatures such as supply air temperature, chilled water temperature, and condenser water temperature, are determined such that energy consumption is minimized as uncontrolled variables, load, ambient wet bulb temperature, and sensible heat ratio, are changed. The chilled water loop pump and cooling tower fan speeds are controlled by the PID controller such that the supply air and condenser water set temperatures reach the set points designated by the optimal supervisory controller. The influences of the controlled variables on the total system and component power consumption was determined. It is possible to minimize total energy consumption by selecting the optimal set temperatures through the trade-off among the component powers. The total system power is minimized at lower supply, higher chilled water, and lower condenser water set temperature conditions.