• KIEAE Journal
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• v.16 no.6
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• pp.109-114
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• 2016

Purpose: The underground air is the warm air discharged from the porous volcano bedrock 30-50m underground in Jeju, including excessive humidity. The temperature of the underground air is $15-20^{\circ}C$ throughout the year. In Jeju, the underground air was used for heating greenhouses by supplying into greenhouses directly. This heating method by supplying the underground air into greenhouses directly had several problems. The study was conducted to develop the heat pump system using underground air as heat source for resolving excessive humidity problem of the underground air, adopting the underground air as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) and saving heating cost for agricultural facilities. Method: 35kW scale(10 RT) heat pump system using underground air installed in a greenhouse of area $330m^2$ in Jeju-Special Self-Governing Province Agricultural Research & Extension Services, Seogwipo-si, Jeju. The inlet and outlet water temperature of the condenser, the evaporator and the thermal storage tank and the underground air temperature and the air temperature in the greenhouse were measured by T type thermocouples. The data were collected and saved in a data logger(MV200, Yokogawa, Japan). Flow rates of water flowing in the condenser, the evaporator and the thermal storage tank were measured by an ultrasonic flow meter(PT868, Panametrics, Norway). The total electric power that consumed by the system was measured by a wattmeter(CW240, Yokogawa, Japan). Heating COP, rejection heat of condenser, extraction heat of evaporator and heating cost were analyzed. Result: The underground air in Jeju was adopted as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) in 2010. From 2011, the heat pump systems using underground air as a heat source were installed in 12 farms(16.3ha) in Jeju.

• Tunnel and Underground Space
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• v.1
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• pp.32-38
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• 1991

9 nuclear power plants are presently in operation in Korea. They produce radioactive waste of which the most long-lived radioactive elements need to be safely stored for hundreds of thousands of years, isolated from humanity and the environment. The safe disposal of high level radioactive waste in mined cavities requires knowledge of the mechanical. thermal and fluid flow characteristics of rock as perturbed by a thermal pulse The literature review was performed to assemble data on the following properties: modulus tensile strength compressive strength thermal expansion specific heat, thermal conductivity thermal diffusivity and permeability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.2
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• pp.57-64
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• 2016

Power demand has continuously increased with technological and economical development. The load density is also growing in the center of downtown area. In particular, underground facilities have been increased on the purpose of the prevention of urban disasters and pedestrian environment improvement. Based on this situation, the underground space in urban surroundings has gradually decreased because of the limited space. The ampacity of buried cables is affected by various factors such as cable size, soil thermal resistance, burial depth and filling material. The thermal capacity of the facilities is determined by the absorb heat surrounding the cable and the soil. The maximum operating temperature of cable is the highest temperature when the insulator of cable is not damaged in the case of high enough temperature. In this paper, the most effective cabling configuration is suggested using the duct array adjustment. It was also considered to increase the number of cable line. This underground distribution system was simulated by using ETAP(Electrical Transient Analysis Program).

• KIEAE Journal
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• v.8 no.4
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• pp.3-9
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• 2008

The rapid urbanization after 1970s caused the shortage of dwellings in urban areas. As the result, the underground dwellings were developed to compensate for the insufficient dwelling spaces. While the underground dwellings have some advantage in the respect of thermal and acoustic environment, they usually have the basic problems in the indoor air quality because of the lack of natural ventilation through small window areas. The purpose of this study is to investigate and to improve the indoor air quality of underground dwellings. Thirty Units in Seoul and Gyung-Gi Province were investigated into the indoor environmental conditions. For the purpose of the improvement of their indoor air quality, Automatically-operated ventilating fan was installed in a sample unit which has worst indoor environmental condition. Then the indoor air quality was monitored when it was operated by $CO_2$ control system and timer. Finally economic feasibility study was made considering the effect of the improvement of indoor air quality. The extra cost for installing timer could be paid back only in 10 months, so timer-installed automatic fan is recommended to improve the indoor air quality of underground dwellings.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.1-23
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• 2015

In this technical report we summarize the observational data on thermal and mechanical properties of rocks reported by over 70 best published papers. The experimental results reported individually are integrated and presented in tables and figures here, which will provide fundamental data to fairly determine and evaluate the rock properties at the initial design stage of underground structures exposed to high temperature environment.

• Journal of the Korean Society of Safety
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• v.10 no.3
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• pp.96-105
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• 1995

The better industry develops, the more spaces need but in the limited area. Most building become larger and more complicated if the more spaces need in the constant area. And this leads to do underground work in long period generally six(6) months for 6 basement stories due to the selection of TOP DOWN technique. Working environment in this underground area can be problems and should not be overlooked, because air quality in underground spaces become quickly worse. Recently, department name to control construction safety has been changed to ENVIRONMENT & SAFETY TEAM from SAFETY TEAM. This means that it is very important to control against environmental condition at site so much. Overall construction work as well as underground work should conform to the requirement of working environment, particularly against inhabitants around the construction area. Strut protection, one of earth protection method, in case to 40m long strut may become weaker due to thermal stress or its longitudinally compressive strain and the another one, earth anchor protection may not be applied to the site In case of encroaching on vertical underground borderline because of regulation to prohibit it. It is necessary that TOP DOWN technique should be introduced in order to solve the external and internal problem of the site such as difficulty level of the work, potential danger with excavating depth, and shortening workperiod. It is needed that improving way of working condition should be shown and simplified computer simulation program should be also provided for checking pollution level & ventilation, excluding of lighting problem here. Results measured with conformance to the Regulation for Working Environment Measurement, enforced by Ministry of Labor have been applied to the computer program developed here. Sample air taken at unit workplace which was considered as exposing condition of pollutant at breathing point and within a range of behavior of the workers, Identified exposing group in underground work, using Moded Flow Life Finally, three types of ventilation system, type I with blower & ventilator, type II natural supply with mechanical ventilation system, and type I mechanical ventilation with Drivent Fan Unit System are selected for this study.

• KIEAE Journal
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• v.13 no.2
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• pp.107-112
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• 2013

The purpose of this study is to analyze an insulation property and to establish a design standard for the underground space in architecture. Insulation materials for this study are 12 kinds of Insulation which qualified KS standards(3 classes of EPS type 1, 3 classes of EPS type 2(Neopor), 3 classes of XPS and 3 classes of PU Boards). For insulation materials of underground space, insulating and water tightening property are desired. So conductivity for insulating and water absorption for water tightening are measured in this study. Temperature, insulation is exposed to in the underground space, is different from temperature above the ground. Conductivity is measured in a temperature of $17^{\circ}C$, $20^{\circ}C$, $23^{\circ}C$ and $26^{\circ}C$. In KS standards, water absorption are measure after 24 hours, but insulation is exposed to water for a long time in the underground. So after 110 days, water absorption are measured. As time goes by, increasing of water absorption means decreasing of water tightening and insulating. So after water absorption had measured for 110 days, conductivity has measured again. As a result, XPS is selected as optimized insulation for underground. And Conductivity of XPS insulation with water should be added by 20%.

• Tunnel and Underground Space
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• v.24 no.2
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• pp.166-175
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• 2014

In this study, the thermal environment in a large scale coal mine located in Taebaek, Gangwondo was assessed by a field survey. In order to estimate the thermal environment, various heat stress indices such as WBGT, HSI, ESI, KATA index and effective temperature were investigated. Correlation analysis was also conducted. It was found that the thermal environment in most workplace was high. In particular, the correlation coefficient between HSI reflected in physiological fatigue characteristic and the maximum sweat evaporation heat was -0.834. This shows that the correlation coefficient have the most influence on HSI index. The factor which has the most influence on the maximum sweat evaporation heat is velocity of air. The thermal environment of high-depth coal mines is likely to be improved by installing a structure that enables the maximum prevention of extended digging, air doors, or the leakage of the inflow of air in the first shaft.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.04a
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• pp.15-19
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• 1999

IMF 이후 시설원예분야에 있어 생에너지, 에너지 절약형, 대체에너지 개발 등의 용어들이 자주 등장하고 하고 있다. 이는 시설원예 난방에너지원의 대부분을 수입에 의존함에 따라 지난 2년간에 걸친 유가의 상승으로 인한 온실경영의 어려움을 단적으로 보여주고 있는 것이라 하겠다. 따라서, 난방연료비의 상승에 대응하여 시설원예의 안정적인 유지 발전과 장기적으로 환경보존이라는 측면에서 난방에너지를 줄이고 대체에너지의 개발 등을 통한 난방비 부담의 감소와 안정된 생산기술을 확립하여야 한다. (중략)

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2001.04b
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• pp.86-87
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• 2001

자갈축열 태양열온실의 기본원리는 주간에 일사로 데워진 온실내부공기를 자갈축열층사이로 순환시켜 이때 자갈층에 축열된 에너지를 난방에 이용하는 것이므로 축열층 사이로 충분한 공기순환이 이루어져야 한다. 따라서, 자갈축열층내로 순환되는 공기의 풍량이 축열성능과 밀접한 관계가 있으며 효과적인 공기 순환방식을 분석하고자 자갈축열성능실험을 수행하였다. (중략)