• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.8
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• pp.605-611
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• 2012

The objective of this study is to investigate the influence of the cooling performance for a water-to-water 10 RT ground source heat pump by using the water switching and refrigerant switching method. The test of water-to-water ground source heat pump was measured by varying the compressor speed, load side inlet temperature, and ground heat source side temperature. The cooling capacity and refrigerant mass flow rate of the heat pump increased with increasing ground heat source temperature. But COP of the heat pump decreased with increasing ground heat source temperature. As a result, the water switching method with counter flow, compared to a refrigerant switching method, improves the cooling capacity and COP by approximately 6~9% in average, respectively.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.5
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• pp.83-91
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• 2017

Recently, ground subsidence frequently occurs in downtown area. The major causes of the subsidence on the subsurface were the damages of the water supply and sewer pipelines and excavation works in adjacent areas, etc. Because of these various factors, it is not easy to analyze the tendency of occurrence of ground subsidence. The purpose of this study is to clarify the effect of ground subsidence by the change of the fine particle content and ground water level and to establish the ground subsidence mechanism. In this study, a model soil-box was manufactured to simulate the failure of the old sewer pipe which is one of the causes on ground subsidence. And a model test was conducted to investigate the effects of fine contents and ground water level on the cavity occurrence. From the test results, firstly the higher the ground water level, the faster the primary cavity is formed as the seepage stress increases. As a result, the secondary cavity and the ground subsidence rapidly progress due to the relaxation of the surrounding ground. The total amount of discharged soil was decreased as the fine content increased.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.99-106
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• 2010

We investigated springs in Seoul in 2009 to know the change of water quality according to storage method of spring water, the concentration of chemical compounds and their correlation. Even spring water that originally satisfied national standard for drinking water could be exceeded national standard for drinking water by storage method such as storage bottle, temperature and period; especially used PET bottles could affect the increase of total colony counts. Therefore, spring water is desirable to be consumed on the spot, or to be stored in sterilized bottles in refrigerator rather than room temperature at home, and also to be consumed shortly not exceeding 24 hours. Total colony counts, coliform, yersinia, $F^-$, $Cl^-$, $NO_3^--N$, hardness, total Solids, pH, color and Al were exceeded national standard for drinking water at some springs. The result of correlation analysis shows that hardness and total solids, which are caused by several ionic compounds, had relatively high correlations with other chemical compounds.

• Journal of Bio-Environment Control
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• v.2 no.1
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• pp.1-8
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• 1993

Experimental and theoretical analyses were carried out to investigate the heat exchange characteristics of the nutrient solution cooling system utilizing ground water. The material of heat exchanger used in the experiment was polyethylene and the cross-flow type was adapted in which nutrient solution was mixed and ground water unmixed. For the exchanger surface area of 0.33$m^2$ and flow rates of ground water of 1-6$\ell$/min, NTU(number of transfer units) and effectiveness of experimental heat exchanger were 0.1-0.45 and 10-35％, respectively. Therefore these results showed that the hydroponic greenhouse of 1,000$m^2$(300 pyong) with the ground water of 10$m^2$/day could cover about 55-70％ of maximum cooling load in summer.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.268-275
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• 2006

Excavation works of cylindrical shafts and tunnels for the construction of a variety of infrastructures have been frequently going on in the urban areas. When ground excavations of cylindrical shafts and shallow tunnels proceed in the ground condition of high water level and silt particle component, ground water drawdown involving soil particle migration causes loosening of ground around tunnels and shafts, causes settlement and deformation of ground. Damages due to ground sinking and differential settlement can occur in the adjacent ground and structures. The extent and possibility of damage relevant to ground water drawdown and soil particle migration can't be so precisely expected in advance that we will face terrible damages in case of minor carefulness. This paper introduces two examples of construction management where using incremental deformation graph of inclinometer, we noticed the possibility of soil migration due to ground water drawdown in the excavation process of vertical shaft and shallow tunnel, analysed a series of measurement data in coupled connection, properly prepared countermeasures, so came into safe and successful completion of excavation work without terrible damages. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.1
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• pp.95-107
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• 2016

Ground water is one of important parameters in the designs of underpass structures because urban areas are characterized by soil ground which is relatively permeable than rock ground and a high level of ground water due to low elevation. Therefore, it is important properly to predict variations of the ground water when they can affect underpass structures. In this study, a series of numerical analyses are performed to predict the variations of ground water levels considering the degree of surface imperviousness and LID(Low Impact Development) application. In turn the stability of underground structure is assessed using predicted ground water level. The results show that an increase in the impervious surface area decreases the ground water level. The application of permeable pavement as a LID facility increases the ground water level, improving the infiltration capacity of rainfall into the ground. Seasonal variations of the ground water level are also verified in numerical simulation. The results of this study suggest that reasonable designs of underpass structures can be obtained with the suitable prediction and application of the ground water level considering the surface characteristics.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.57-62
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• 1999

The study has been performed to estimated the quantity of ground water recharge using the DAWAST model for water balance analysis in the Youngsan & Sumjin watersheds. The mean safe yield of ground water is annually 41.3mm, corresponding to 85 $\times$106 ㎥ at the Naju station in the Youngsan watershed, and 76.6mm corresponding to 343 $\times$ 106 ㎥ at the Songjung station in the Sumjin watershed. It is remarkable because safe yield of ground water are estimated 44 to 64 % less than the quantities estimated in the other researches.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.4
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• pp.59-67
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• 2021

In this study, the performance of the single heat source system and the hybrid system was comparatively analyzed. Case 1 is a ground heat source system, and Case 2 is a water heat source system. Case 3, a hybrid system, reduced the capacity of the ground heat source and applied a water heat source as an auxiliary heat source, and Case 4 was composed of a system that applied a water heat source as an auxiliary heat source to the ground heat source system. As a result of the simulation, in case 3, energy consumption was reduced by up to 2.67% compared to ground sources for cooling. In Case 4, COP was improved by up to 10.02% compared to ground sources during cooling, and EST was calculated to be 2.42℃ lower. During heating, 0.83% was improved compared to the water heat source. At this time, the EST was calculated to be 2.25℃ higher than the water heat source.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.1
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• pp.5-13
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• 1997

The Island of Cheju plans massive ground water development to meet predicted water demand. Effective management of ground water resources requires impact assessment study. Due to the nature of the island, effects of sea water must be considered. In this work, salt water intrusion, due to hypothetical ground water development in Eastern and Central Cheju Watersheds, is predicted using a sharp-interface model. The model considers simultaneously hydrodynamics of both freshwater and saltwater. The hypothetical ground water development was designed such that it follows closely the regional ground water development plan. The numerical model predicted that the saltwater wedge may intude over 1km depending on the location. This observation leaves doubt on impact assement studies based on freshwater-flow only modeling.

• Economic and Environmental Geology
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• v.9 no.4
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• pp.225-240
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• 1976

This study deals with the flow of bed rock ground water of Banyaweol Formation, which is presently cleared up as a laminar flow. The result obtained may be summarized as the following. 1) The Banyaweol Formation consists mainly of thin-bedded, green to blackish green shale, mudstone, and marl. The marl and mudstone alternatively occur with shale. The marl and mudstone form a aquifer of Banyaweol Formation. In this study, a group of aquifer is in convenience named as a aquifer zone. The aquifer occurs in lenticular form. The aquifer seems to be a type of artesian aquifer because it is covered with aquicludes, but it actually forms a unconfined aquifer because its piezometric surface stays under the lower aquiclude. The lowering of piezometric level is formed because of leakage of the ground water to the lower aquifer undersaturated. 2) The coefficient of permeability of Banyaweol Formation's ground water body (K) is derived by using Dupuit's equation as the following ${\log}K=\frac{CK^2-dK+f}{aK-b}\;\(M=1.365(2H-s)s\\M={\log}1.956s{\sqrt{H}}r\)$ here, $$a=\sum_{1}M_iG_i$$ $$b={\frac{1}{2}log{\sum_{i}}Q_i{^2}$$ $$c=2{\sum_{i}}M_i{^2}$$ $$d=loge{\sum_{i}}M_{i}Q_{i}+2{{\sum_{i}}N_{i}Q_{i}$$ $$f=loge{\sum_{i}}Q_i{^2}N_i$$ If the measured values substituted for the above equation, the coefficient of permeability of the aquifer is 4.1m/day. The coefficient of storge of the aquifer is $2.8{\times}10^{-4}$ if the measured values substituted for Theis's equation. Using the above constants, the filtration velocity of the aquifer is $2.1{\times}1O^{-1}m/day$and the daily flow quantity of the ground water is $847.38m^{3}/day$. 3) In order to understand the time necessary for a circulation of ground water body, the contents of tritum contained in the ground water are measured as 2.3 T.U. at the Korea Atomic Energy Research Institute. Before 1952, the average concentration of tritium per year in groundwater was reported as 10T. u., taking it as the standard, the groundwater of the present study 26.25 years old. Therofore, the groundwater of the Banyaweol Formation is judged as an relatively old groundwater. It is characteristic that the ground water of Banyawol Formation is laminar flow as well as unconfined aquifer and ground water flow of relatively long time. 4) The nature, means of flow, and circulation of Banyaweol Formation's ground water body make it possible set up this ground water body as a ground water system.