• 한국지열·수열에너지학회논문집
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• 제15권1호
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• pp.9-17
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• 2019

Reducing global warming potential has become important, and as one of those methods for reducing it, economic evaluation by applying ice thermal storage air conditioning system was performed. The floor area and height of the subject building was assumed $5,000m^2$ and 20 m. Absorption chillerheater system and air source heat pump system was used for comparing to the subject system, and payback period method was used to perform economic evaluation. Although the running cost of ice thermal storage system is reduced compared to two systems, the ratio is not significant compared to the increase of initial construction expenses, and payback period was calculated to be about 7.7 and 79.3 years. However, the heat storage system should be approached from the viewpoint of long term rather than the economic standard in the present standard.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.3-32
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• 2008

The potential deep geothermal resources span a wide range of heat sources from the earth, including not only the more easily developed, currently economic hydrothermal resources; but also the earth's deeper, stored thermal energy, which is present anywhere. At shallow depths of 3,000~10,000m, the coincidence of substantial amounts heat in hot rock, fluids that heat up while flowing through the rock and permeability of connected fractures can result in natural hot water reservoirs. Although conventional hydrothermal resources which contain sufficient fluids at high temperatures and geo-pressures are used effectively for both electric and nonelectric applications in the world, they are somewhat limited in their location and ultimate potential for supplying electricity. A large portion of the world's geothermal resource base consists of hot dry rock(HDR) with limited permeability and porosity, an inadquate recharge of fluids and/or insufficient water for heat transport. An alternative known as engineered or enhanced geothermal systems(EGS), to dependence on naturally occurring hydrothermal reservoirs involves human intervention to engineer hydrothermal reservoirs in hot rocks for commercial use. Therefore EGS resources are with enormous potential for primary energy recovery using an engineered heat mining technology, which is designed to extract and utilize the earth's stored inexthermal energy. Because EGS resources have a large potential for the long term, United States focused his effort to provide 100GW of 24-hour-a-day base load electric-generating capacity by 2050.

• International Journal of Automotive Technology
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• 제1권2호
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• pp.71-77
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• 2000

High temperature materials in service are subjected to mechanical damage due to operating load and metallurgical damage due to operating temperature. Therefore, when designing or assessing life of high temperature components, both factors must be considered. In this paper, the effect of tensile hold time on high temperature fatigue crack growth and long term prior thermal aging heat treatment on creep rupture behavior were investigated using STS 316L and STS 316 austenitic stainless steels, which are widely used for high temperature components like in automotive exhaust and piping systems. In high temperature fatigue crack growth tests using STS 316L, as tensile hold time increased, crack growth rate decreased in relatively short tensile hold time region. In long term aged specimens, cavity type microcracks have been observed at the interface of grain boundary and coarsened carbide.

• 한국지열·수열에너지학회논문집
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• 제13권3호
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• pp.1-8
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• 2017

Variable refrigerant flow (VRF) systems have recently attracted attention in many countries due to a variety of advantages over conventional system. Especially, the water-cooled VRF heat pump, including geothermal heat pump, is a system that accurately controls the flow rate of refrigerant for the improved efficiency under part load operation. This paper describe the process of generating the cooling and heating energy performance curve coefficients and performance expressions for modeling water cooled VRF system using EnergyPlus. Through this study, the process for generating performance curves can be implemented into EnergyPlus or other comparable building energy analysis tools for the long-term evaluation of heat pump under dynamic conditions.

• 한국도로학회논문집
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• 제7권4호
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• pp.69-77
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• 2005

줄눈 콘크리트포장에서 적정한 줄눈간격은 슬래브의 거동에 의해 발생하는 인장응력 줄눈채움재의 파손과 다웰바의 하중전달율(LTE)의 저하를 방지하여 도로포장의 장기 공용성 증가에 큰 영향을 미친다. 하지만 국내 줄눈간격은 경험적이고 획일적으로 이루어진다. 그러므로 본 연구는 국내 권역별 기후조건을 토대로 합리적인 줄눈간격 산정에 대한 방안을 제시하였다. 합리적인 줄눈간격은 초기거동에서 환경하중의 영향에 따른 건조수축과 수화열에 의해 무작위 균열 발생하지 않도록 산정하였다. 그리고 장기거동에서 줄눈폭의 과도한 움직임에 따른 LTE 저하로 인해 포장파손이 발생하지 않도록 줄눈간격을 산정하였다. 본 연구에서 산정된 줄눈간격 잠정안은 6$\sim$8m이며, 포장파손 예측 모델을 통해 줄눈간격을 8m로 증가시켜도 포장 공용성엔 큰 차이가 없었다.

• KIEAE Journal
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• 제17권4호
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• pp.33-39
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• 2017

Purpose: The use of renewable energy system is essential for building energy independence and saving energy consumption in the building sector. Among renewable energy technologies, ground source heat pump(GSHP) system is more energy-efficient and environmental-friendly than other heat source systems due to utilize stable ground heat source. However, the GSHP system requires a high initial installation cost and installation space in limited urban area, so it is difficult to have superiority in the market of heat source system. Therefore, it is necessary to develop the installation method of low-cost and improve system performance. This paper aims to evaluate the performance of double u-tube ground heat exchanger(GHX) and verify system feasibility through real-scale experiment. Method: In this study, the real-scale experiment of vertical closed-type GSHP system was conducted using double u-tube GHX and high-efficiency grout. Through the verification experiment, heat source temperature, heat exchange rate(HER) and seasonal performance factor(SPF) were measured according to the long-term operation. In addition, the feasibility analysis was conducted comparing to the single u-tube system. Result: In the results of experiment, average HER was 136.27 W/m and average SPF was 5.41. Furthermore, compared to the single u-tube, the installation cost of the developed system could be reduced about 70% in the same heating load condition.

• KIEAE Journal
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• 제1권1호
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• pp.17-26
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• 2001

The purpose of this study is to develop an underground Building. Population tends to concentrate in large cities. In result, the cities lacks housings. Underground space may be a attractive space by being able to gain alternative energy and get a cheap site, protect environment at the same time. The earth or ground is a useful medium for a long-term heat source and storage of it's heat. Also the underground space has the status of stabilization, the lower heating load and the similar heat transfer coefficient of the inside wall surface comparing to that of residential space. Utilization of underground space has many advantages to cope with lack of building sites and energy conservation, etc. As a result, it is expected to provide a useful information for the practical use of Underground building.

• 설비공학논문집
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• 제7권2호
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• pp.234-248
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• 1995

A super-heat pump system composed of a suction line heat exchanger, low and high stage economizers, and a screw compressor is simulated to examine the energy performance and design options. CFC12, HCFC22, HFC134a, HCFC22/HCFC142b, HFC32/HFC134a, and HFC125/HFC134a are used as working fluids for comparison. The results indicate that the proposed system charged with appropriate mixtures is up to 33.4% more energy efficient than the normal system with CFC12. The performance of the super-heat pump system charged with mixtures was influenced by such factors as the temperature matching, heat source temperature difference, low stage economizer, and high stage economizer. The fluids with a larger liquid specific heat such as HFC134a would have more benefits when a suction line heat exchanger is installed. 40%HCFC22/60%HCFC142b mixture seems to be a good candidate to replace CFC12. On the other hand, 25%HFC32/75% HFC134a would be a good long term candidate to replace HCFC22.

• 한국지열·수열에너지학회논문집
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• 제17권4호
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• pp.68-78
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• 2021

In order to solve the increasing deterioration of the energy shortage problem, ground-source heat pump (GSHP) systems have been widely installed. The control method is a significant component for maintaining the long-term performance and for reducing operation cost of GSHP systems. This paper presents the measurement and analysis results of the cooling performance of a GSHP system using capacity control with outdoor air temperature. For this, we installed monitoring equipments including sensors for measuring temperature, flow rate and power consumption, and then monitored operation parameters from July 9, 2021 to October 2, 2021. From measurement results, we analyze the effect of capacity control with outdoor air temperature on the cooling performance of the system. The average performace factor (PF) of the heat pump was 6.95, while the whole system was 5.54 over the measurement period. Because there was no performance data of the existing GSHP system, it was not possible to directly compare the existing control method and the outdoor air temperature method. However, it is expected that the performance of the entire system will be improved by adjusting the temperature of cold water produced by the heat pump, that is, the temperature of cold water on the load side according to the outside air temperature.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.617-620
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• 1997

In this paper, the thermal stress analysis of spent nuclear fuel disposal canister in a deep repository at 500m underground is done for the underground pressure variation. Since the nuclear fuel disposal usually emits much heat and radiation, its careful treatment is required. And so a long term safe repository at a deep bedrock is used. Under this situation, the canister experiences some mechanical external loads such as hydrostatic pressure of underground water, swelling pressure of bentonite buffer, and the thermal load due to the heat generation of spent nuclear fuel in the basket etc.. Hence, the canister should be designed to designed to withstand these loads. In this paper, the thermal stress analysis is done using the finite element analysis code, NISA.