• 한국지반신소재학회논문집
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• 제12권2호
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• pp.13-23
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• 2013

겨울에는 시베리아기단에 의해 한랭 건조한 대륙성 고기압의 영향을 받는 계절동토지역인 우리나라는 춥고 건조하여 1월 평균기온이 $-6{\sim}-7^{\circ}C$의 영하의 온도로 낮아져 지반동결시 수분이동으로 동상현상이 발생하여 지반구조물의 불균형 동결팽창을 초래한다. 동상 발생시 토립자는 모관력에 의해 지하수를 흡수하여 아이스렌즈를 형성하며, 이 모관 흡수력은 토립자의 크기에 영향을 받는다. 본 연구에서는 흙의 종류에 따른 동상민감성의 차이를 알아보기 위하여 공학적 특성이 다른 10종류의 흙시료에 대하여 물리적 특성 파악과 통일분류법에 의한 흙 분류를 통해 실내동상실험을 실시하였다. 이에 각각 흙의 종류에 따른 동결깊이, 동상팽창량, 부동수분, 아이스렌즈와 같은 동상특성을 확인하여 시료의 동상민감성을 평가하였다.

• 한국지반신소재학회논문집
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• 제12권3호
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• pp.23-29
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• 2013

동결토는 물과 얼음의 상변화에 따라 일반적인 흙과는 다른 거동을 보이며, 동결토의 강도는 온도, 함수비, 시간, 토질 특성 등 다양한 인자에 의해 영향을 받는다. 특히 지반이 동결되는 경우, 얼음과 흙 입자의 결합력에 의해 높은 강도 특성을 보이며, 이때의 전단강도는 흙의 구조적 결합에 영향을 미치는 얼음과 세립분의 함량에 따라 달라지며, 이로 인해 점착력이 동결토의 전단강도에 미치는 영향은 증가한다. 본 논문에서는 동결조건에서 직접전단시험과 일축압축강도시험을 실시하여 온도에 따른 흙의 강도 특성을 확인하였으며, 점착력과 일축압축강도와의 상관관계를 확인하였다.

• 설비공학논문집
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• 제25권3호
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• pp.126-130
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• 2013

In this study, a shape-stabilized phase change material (SSPCM) was prepared by octadecane and exfoliated graphite nanoplate (xGnP) in a vacuum, to improve thermal storage performance. The octadecane as an organic phase change material (PCM) is very stable against phase separation of PCM, and has the proper temperature range for thermal comfort in the building; and the xGnP is a porous carbon nano-material. Scanning electron microscope (SEM) and Fourier transformation infrared spectrophotometer (FT-IR) were used to confirm the chemical and physical stability of the Ocatadecane/xGnP SSPCM. In addition, thermal properties were determined by Deferential scanning calorimeter (DSC), and Thermogravimetric analysis (TGA). The specific heat of Octadecane/xGnP SSPCM was $14.1J/g{\cdot}K$ at $31.3^{\circ}C$. The melting temperature ranges of melting and freezing were found to be $26{\sim}35^{\circ}C$ and $26{\sim}19^{\circ}C$, respectively. At this time, the latent heats of melting and freezing were 110.9 J/g and 104.5 J/g, respectively. The Octadecane was impregnated into xGnP by as much as about 56.0% of the Octadecane/xGnP SSPCM's mass fraction.

• 대한조선학회논문집
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• 제50권6호
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• pp.414-420
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• 2013

Generation and measurement methods of EG/AD model ice, which is used in KIOST ice model basin are investigated for improvement of its properties. Temperature of seed water, air temperature in the freezing phase and the target air temperature in the tempering phase were changed in the cold room, and the properties of model ice was measured in this conditions. We also verified a conventional measuring method of flexural strength of model ice caused a little measuring error in cold room, so that we suggested a new measuring method that must be used higher supports than double the thickness of the model ice. In this study, we improved the generation and measurement technique of EG/AD model ice, and the developed procedure at cold room can be applied to the KIOST ice model basin.

• 한국농공학회지
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• 제41권4호
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• pp.37-46
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• 1999

Field experimnet of constructed wetland for rural wastewater treatment was performed from July 1998 to April 1999 including winter to examine the seasonal effect on the wetland performance. The system worked without freezing even under $-10^{\circ}C$ of air temperature as long as watewater was flowing. BOD removal rates varied in similar pattern as the air temperature, and winter performance was relatively lower than that in the growing season. However, removing performance during winter was still significant, and BOD removal rates were almost the the same as in the growing season. SS removal rate was relativelyless affected by temmperature, but lower decay rate during the winter can result in accumulation of the SS in the system, which releases constituents in the next spring and can affect whole system performance. The winter removal rates of nutrients like T-N and T-P were decreased about half compared to the growing season and low temperature. To maintain stabilized wetland performanced including winter time, supplying minimum heating for plants could be an alternative in field application. Experimental data was compared with NADB(North Americal Wetlands for Water Quality treatment database), and general performance of the system was within the reasonable range. The pollutant loading and effluent concentration of the experimented system were in high margin. Base on the experiment and databases, the required effluent water quality could be achieved if loading rate adjusted as ilulstrated in the database.

• 콘크리트학회지
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• 제10권4호
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• pp.153-161
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• 1998

콘크리트 구조물은 자연적인 혹은 인위적인 온도의 승, 강하로 인하여 동결-융해 작용을 받게 되어 구조물의 성능저하를 야기시킨다. 현대에 들어서면서 콘크리트의 내구특성을 파악하기 위한 연구적 요구가 증가되고 있다. 따라서 폐주물사 콘크리트를 실제 구조물에 적용하기 위해서는 내구특성에 대한 연구가 반드시 이루어져야 한다. 폐주물사를 혼입한 콘크리트의 내구특성을 파악하기 위한 동결-융해 실험은 폐주물사의 잔골재 치환율, 물-시멘트비, AE제 사용 여부를 주요 변수로 하여 실시하였다. 원형공시체를 제작하여, 동결-융해 시험기에 넣어 -18~4$^{\circ}C$로 급속 동결-융해를 진행시키면서 매 23싸이클마다 동탄성계수를 측정하였다. 실험결과 AE제를 첨가했을 때 물-시멘트비가 적을수록, 폐주물사의 치환율이 클수록 전반적으로 강도가 증가하는 것으로 나타났으며, 물-시멘트비가 증가함에 따라, AE제를 사용한 콘크리트가 동결-융해 저항성이 증가하는 것으로 나타났다. 특히 폐주물사 치환율이 50%일때가 동결-융해 저항성이 가장 좋은 것으로 나타났으며 그 다음으로 25, 0% 순으로 저항성이 좋은 것으로 나타났다. 따라서 폐주물사 콘크리트가 내구성이 우수한 것으로 나타나 폐주물사를 콘크리트에 재활용할 수 있는것으로나타났다.

• 설비공학논문집
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• 제12권10호
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• pp.925-931
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• 2000

Refrigerating ability of vapor compression refrigerator is decided by the harmonic work of it's components such as compressor, condenser, evaporator, expansion device, and so on. In this study, choosing refrigerant injectors as a new one of expansion device, temperature change of the cold room, ice freezing ability, and power consumption on flowrate of injector and refrigerant charging condition are evaluated experimentally. As the results of this study, it is verified that the spray injection type refrigeration system has some merits according to the flowrate and spray pattern of injector and charging quantum of refrigerant. And there are some design factors such as spray pattern and shape of spray chamber to utilize and fabricate this refrigerant injection type refrigerator.

• 설비공학논문집
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• 제13권12호
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• pp.1175-1183
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• 2001

Recently, a great attention has been paid to the ice thermal storage system for the purpose of energy saving and reduction in peak electrical demand. In the present study, it has been investigated the freezing behavior of several kinds of water solutions with nonionic surfactant. In order to prevent ice blockage in a cooled pipe, the amount and wall adhesion behavior of ice of the test fluids were observed experimentally under different concentration of water solution with surfactant, temperature of cooled wall, and the shear velocity of test fluids. The results showed that the size of ice crystal became smaller at higher shear velocity at wall. And the lowest limit of wall adhesion of ice in water solution with surfactant was found at 230 W/$m^2$ of heat flux.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1689-1696
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• 2008

Heat pumps transfer heat by circulating a substance called a refrigerant through a cycle of evaporation and condensation. But Heat pumps system by only using heat-source is not efficient. Because the mean temperature of North Korean winter season is low, economy of air heat-source heat pump descend. This paper is practiced the simulation on evaluation criteria for Heat pump heating and cooling systems to Rolling Stock. Efficiency of the heat pump in order improving from certainly the development of the technique will be able to prevent a freezing actual condition must proceed. As a result, Below $-10^{\circ}C$ used heating and cooling systems of heat pump format even in cold winter season and is serviceable confirmed with heat source supply circle of the Rolling Stock.

• 수산해양기술연구
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• 제50권1호
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• pp.67-74
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• 2014

Most of steam power plants in Korea are using the method of heating the feed water whenever the ambient temperature around the power plant area below $5^{\circ}C$ to prevent freezing water flowing in the pipe in winter time. But this kind of heat supplying system is not useful to save energy. If we take the method that the temperature of the each pipe is controled by direct measure of temperature by attaching sensor on the outside surface of the feed water tubes, then we can expect that a plenty of energy can be saved. In this study, the computer simulation is used to compare the energy consumption loads of both systems. Energy saving rate is calculated for the location of Incheon area in winter season. Four convection heat transfer coefficients for the ambient air and three initial flowing water temperature inside the tube were used. The result shows that the temperature control system using sensor represents more than 95% of energy saving rate in Incheon area. Even in the severe January weather condition, the energy saving rate is almost 75% in two days basis and even 83% in one day basis.