• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.422-430
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• 1999

This paper concerns the study of a two-stage absorption heat pump cycle to utilize treated sewage. This two-stage cycle consists of coupling double-effect with parallel or series flow type and single effect cycle so that the first stage absorber and condenser produces hot water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as absorber temperature on the coefficient of performance have been studied for two-stage absorption heat pump cycle. The working fluid is lithium bromide and water solution. The efficiency of the two-stage absorption heat pump cycle has been studied and simulation results show that higher coefficient of performance could be obtained for the first stage with parallel flow type. The optimum ratio of solution distribution can be shown by considering the COP, the crystallization of solution and the generator temperature.

• New & Renewable Energy
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• v.20 no.1
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• pp.110-115
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• 2024

Global sustainable energy needs and carbon neutrality goals make hydrogen a key future energy source. South Korea and Japan lead with proactive hydrogen policies, including South Korea's Hydrogen Law and Japan's strategy updates aiming for a hydrogen-centric society by 2050. A notable advance is the solar thermal chemical water-splitting cycle for green hydrogen production, spotlighted by Korea Institute of Energy Research (KIER) and Niigata University's joint initiative. This method uses solar energy to split water into hydrogen and oxygen, offering a carbon-neutral hydrogen production route. The study focuses on international collaboration in solar energy for thermochemical water-splitting and E-fuel production, highlighting breakthroughs in catalyst and reactor design to enhance solar thermal technology's commercial viability for sustainable fuel production. Collaborations, like ARENA in Australia, target global carbon emission reduction and energy system sustainability, contributing to a cleaner, sustainable energy future.

• Journal of Environmental Science International
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• v.11 no.1
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• pp.25-32
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• 2002

In order to control of water quality in Jeju harbor, variation of physical oceanographic environments was estimated using material cycle model. It is composed of the three-dimensional hydrodynamic model for the simulation at water flow and material cycle model for the simulation of water quality. The three dimensional hydrodynamic model simulation of the circulation and mixing in Jeju Harbor has been conducted forced by Sanzi River Discharge, Tidal elevation, wind and Solar heat in case of August and November, 2000 and February and May, 2001, respectively. The results of numerical model and observation show that the model can produce realistic results of current in the harbor. The monthly variation of velocity pattern are not so much changed are found In Jeju Harbor. The residual current was forced by temperature, salinity, density, wind and tidal current. The residual current of August, 2000 are the strongest among four month. It can be explained that the density effect can be important role in residual current at Jeju Harbor. As the results of salinity distribution simulation, very low concentration of all levels were simulated in August, 2000. The flowrate of Sanzi river was investigated 77,760 ㎥ /d in August, 2000. Therefore, pollutant loadings from Sanzi river should be considered for water quality management in Jeiu harbor.

• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.130-133
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• 2016

The increase in impervious surfaces due to urban development has caused a groundwater drawdown through the reduction of underground infiltration, flood disaster due to increased rainfall runoff and environmental pollution in higher pollutant concentrations of first flush rainwater. As an alternative to these problems, the needs of low impact development (LID) techniques is increasing in urban areas. In this study, the restoration efficiency of water cycle was assessed at a residential site development applied with the LID rainwater management system. The results of monitoring the water cycling showed that the efficiency of water cycle of LID rainwater management system was improved 41% more than that of conventional methods.

• Journal of Environmental Science International
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• v.12 no.3
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• pp.307-317
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• 2003

In this study, the material cycle model was applied to suggest alternative management of water quality for Jeju Harbor. The distribution of COD, DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphorus) concentrations was reasonably reproduced by simulations on the model area of the Jeju Harbor using a material cycle model. The simulations of COD, DIN and DIP concentrations were performed under the conditions of 20∼100% pollution loadings reductions from pollution sources. In case of the 100% reduction of the input loads from Sanzi river, concentrations of COD, DM and DIP were reduced to 39%, 78% and 52%, respectively at Jeju harbor. In contrast, in case of the pollutant loadings reductions from sediment, the effect of DIN and DIP reduction relatively seemed to increase around the center of study area. The 95% reduction of the pollutant loadings from river and sediment is required to meet the COD and nutrients concentration of second grade of ocean water quality criteria.

• Journal of Korea Water Resources Association
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• v.33 no.S1
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• pp.48-56
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• 2000

In this paper, properties of hydrologic cycle in three experimental catchments were compared and different types of a lumped parametric model were applied to understand the hydrologic cycle in the catchments. One of them is a forest catchment and another one includes the reclained upland fields and last one does terraces paddy fields. The comparison of hydrologic properties showed that the differences in land used have great influences on the soil properties of surface layer, which cause changes in hydrologic processes such as evapotranspiration and storm runoff et.al. By the runoff analysis models, good agreements between observed and calculated discharge from the catchments were obtained and it was found that the differences in values of optimized model parameters and water budget components reflect those in the hydrologic cycle among them.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.488-500
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• 1995

An air-cooled ammonia/water GAX(Generator-Absorber heat eXchange) absorption cooling cycle is proposed and its performance is numerically evaluated. It is shown that the performance of the system is greatly dependent on the quality of the refrigerant leaving the evaporator. For any refrigerant concentration in the investigated range(99.1~99.9% ammonia), the cycle COP(coefficient of performance) reaches the highest value, when some amount(about 7%) of refrigerant evaporates in the refrigerant heat exchanger. Among temperature differences in various heat exchangers, the temperature difference between GAX-absorber and the GAX-generator shows the greatest effect on the system performance, whereas pressure losses cause no significant decrease in COP. The system COP increases almost linearly with increasing evaporator temperature, decreasing absorber temperature or decreasing condenser temperature. If both absorber and condenser temperature increase simultaneously, the decrease in the COP becomes larger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.3
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• pp.223-230
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• 2011

The power cycle using ammonia-water mixture as a working fluid is a possible way to improve efficiency of the system of low-temperature source. In this work thermodynamic performance of the ammonia-water regenerative Rankine cycle with partial-boiling flow is analyzed for purpose of extracting maximum power from the source. Effects of the system parameters such as mass fraction of ammonia, turbine inlet pressure or ratio of partial-boiling flow on the system are parametrically investigated. Results show that the power output increases with the mass fraction of ammonia but has a maximum value with respect to the turbine inlet pressure, and is able to reach 22 kW per unit mass flow rate of source air at $180^{\circ}C$.

• Proceedings of the Korea Water Resources Association Conference
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• 2000.05a
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• pp.48-56
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• 2000

In this paper, properties of hydrologic cycle in three experimental catchments were compared and different types of a lumped parametric model were applied to understand the hydrologic cycle in the catchments. One of them is a forest catchment and another one includes the reclaimed upland fields and last one does terraces paddy fields. The comparison of hydrologic properties showed that the differences in land use have great influences on the soil properties of surface layer, which changes in hydrologic processes such as evapotranspiration and storm runoff et. al. By the runoff analysis models, good agreements between observed and calculated discharge from the catchments were obtained and it was found that the differences in values of optimized model parameters and water budget components reflect those in the hydrologic cycle among them.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.763-774
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• 2023

The water availability in a river is related to the return flow of residential water. However it is still difficult to determine the exact return flow. In this study, the residential water-cycle system is defined as a process consisting of water inflow, water transfer and water outflow. The study area is Hampyeong-gun, Jeollanam-do, and is set as a single inflow to a single outflow through the water-cycle system after classification of complete and incomplete measurement points. The time-series prediction models(ARIMA model and TFM) are established with daily inflow and outflow data for 6 years. Inflow and outflow are predicted by dividing into training and test periods. As a result, both models show the feasibility of short-term prediction by deriving stable residuals and securing statistical significance, implementing the preliminary form of the water-cycle system. As a further study, it is suggested to predict the actual return flow of the target basin and efficient water operation by adding input factors and selecting the optimal model.