• Journal of Energy Engineering
• /
• v.27 no.1
• /
• pp.59-64
• /
• 2018

In this paper, we investigated the alternative sources of limestone. Oyster shell waste originated from aquaculture that causes a major disposal landfill problem in coastal sectors in southeast Korea. Their inadequate disposal causes a significant environmental problems araised. Bio mineralization leads to the formation of oyster shells and consists $CaCO_3$ as a major phase with a small amount of organic matter. It is a good alternative material source instead of natural lime stone. The utilization of oyster shell waste for industrial applications instead of natural limestone is major advantage for conservation of natural limestone. The present work describes the limestone and oyster shells hydraulic activity and chemical composition and characteristics are most similar for utilization of oyster shell waste instead of natural limestone.

• Nuclear Engineering and Technology
• /
• v.53 no.2
• /
• pp.446-454
• /
• 2021

Critical heat flux (CHF) has traditionally been evaluated using look-up tables or empirical correlations for nuclear power plants. However, under complex moving condition, it is necessary to reconsider the CHF characteristics since the conventional CHF prediction methods would no longer be applicable. In this paper, the additional forces caused by motions have been added to the annular film dryout (AFD) mechanistic model to investigate the effect of moving condition on CHF. Moreover, a theoretical model of the natural circulation loop with additional forces is established to reflect the natural circulation characteristics of the loop system. By coupling the system loop with the AFD mechanistic model, a CHF prediction program called NACOM for natural circulation loop under moving condition is developed. The effects of three operating conditions, namely stationary, inclination and rolling, on the CHF of the loop are then analyzed. It can be clearly seen that the moving condition has an adverse effect on the CHF in the natural circulation system. For the calculation parameters in this paper, the CHF can be reduced by 25% compared with the static value, which indicates that it is important to consider the effects of moving condition to retain adequate safety margin in subsequent thermal-hydraulic designs.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.600-603
• /
• 2005

U.S. National Research Council proposed benefits framework for energy R&D project as economic benefits, environmental benefits, security benefits and knowledge benefits. Following this framework, U.S. National Renewable Energy Laboratory evaluated the projected benefits of Federal Energy Efficiency and Renewable Energy Programs in the indicators of energy-expenditure savings, energy system cost savings, $CO_2$ emissions reductions. oil savings, natural gas saving and avoided additions to central conventional power. As this result, geothermal energy have predominant position in the energy-expenditure savings, natural gas saving and avoided addi t ions to central conventional power to FY2050. The projected benefits, in monetary value, of the whole supply-potential of geothermal energy in Korea were evaluated as 480.2 billion Won, 43.1 billion Won and 135.8 billion Won for the private energy-cost savings, social environmental-cost savings, and import energy-cost saving, respectively.

• Journal of Energy Engineering
• /
• v.23 no.3
• /
• pp.36-41
• /
• 2014

The world's overall need for natural gas (NG) has been growing up fast, especially in the residential sector. The better the estimation of residential NG consumption (RNGC) distribution, the better decision-making for a residential NG policy such as pricing, demand estimation, management options and so on. Approximating the distribution of RNGC is complicated by zero observations in the sample. To deal with the zero observations by allowing a point mass at zero, a mixture model of RNGC distributions is proposed and applied. The RNGC distribution is specified as a mixture of two distributions, one with a point mass at zero and the other with full support on the positive half of the real line. The model is empirically verified for household RNGC survey data collected in Korea. The mixture model can easily capture the common bimodality feature of the RNGC distribution. In addition, when covariates were added to the model, it was found that the probability that a household has non-expenditure significantly varies with some variables. Finally, the goodness-of-fit test suggests that the data are well represented by the mixture model.

• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.4
• /
• pp.464-480
• /
• 2007

There are several methods for the hydrogen production such as steam reforming of natural gas, photochemical method, biological method, electrolysis and thermochemical method, etc. These days it has been widely studied for the hydrogen production method having low hydrogen production cost and high efficiency. In this paper, patents in the hydrogen production by steam reforming of natural gas were gathered and analyzed. The search range was limited in the open patents of USA(US), European Union(EP), Japan(JP), and Korea(KR) from 1996 to 2006. Patents were gathered by using key-words searching and extracted by filtering criteria. The trends of the patents was analyzed by the years, countries, companies, and technologies.

• Structural Engineering and Mechanics
• /
• v.52 no.4
• /
• pp.687-699
• /
• 2014

Based on the energy method considering the second order effects, the natural frequencies of externally prestressed simply supported beam and the compression softening effect of external prestress force were analyzed. It is concluded that the compression softening effect depends on the loss of external tendon eccentricity. As the number of deviators increases from zero to a large number, the compression softening effect of external prestress force decreases from the effect of axial compression to almost zero, which is consistent with the conclusion mathematically rigorously proven. The frequencies calculated by the energy method conform well to the frequencies by FEM which can simulate the frictionless slide between the external tendon and deviator, the accuracy of the energy method is validated. The calculation results show that the compression softening effect of external prestress force is negligible for the beam with 2 or more deviators due to slight loss of external tendon eccentricity. As the eccentricity and area of tendon increase, the first natural frequency of the simply supported beams noticeably increases, however the effect of the external tendon on other frequencies is negligible.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.459-466
• /
• 2006

The objective of this study is to improve the accuracy of damage detection using natural frequency and modal strain energy. The following approaches are used to achieve the goal. First, modal strain energy is introduced and newly GA-based damage detection technique using natural frequency and modal strain energy is proposed. Next, to verify efficiency of the proposed technique, damage scenarios for free-free beams are designed and the vibration modal tests as damage cases are conducted. Finally, feasibility of proposed technique is verified in comparison with a GA-based damage detection technique using natural frequency and mode shape.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.10a
• /
• pp.451-456
• /
• 1997

Temperature distribution measurements in the mockup apparatus of reactor vessel were performed to determine the effective thermal conductivity of porous media with different geometry and to obtain the experimental data for the heat transfer processes by natural convection occurring in the air duct. The temperature distributions at four separated sections with different arrangements of porous media have different slopes according to the geometrical configuration. From the measured temperature distribution, effective thermal conductivity have been derived using the least square fitting method. The test at air duct was performed to the high heat removal at 3.4kW/$m^2$ by the natural convection from the outer wall to the air. And also the temperature distributions in the air duct agree well with the 1/7th power-law turbulent temperature distribution. The obtained heat transfer data have been compared with the Shin's and Sieger's correlations.

• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.1
• /
• pp.12-25
• /
• 2007

Numerical simulation of the natural gas steam reforming process for on-site hydrogen production in a $H_2$ fueling station was conducted on the basis of process material and heat balances. The effects of reforming parameters on the process efficiency of hydrogen production were investigated, and set-point values of each of the parameters to minimize the sizes of unit process equipments and to secure a stable operability of the reforming process were suggested. S/C ratio of the reforming reactants was found to be a crucial parameter in the reforming process mostly governing both the hydrogen production efficiency and the stable operability of the process. The operation of the process was regarded to be stable if the feed water(WR) as a reforming reactant could evaporate completely to dry steam through HRSG. The optimum S/C ratio was 3.0 where the process efficiency of hydrogen production was maximized and the stable operability of the process was secured. The optimum feed rates of natural gas(NGR) and WR as reforming reactants and natural gas(NGB) as a burner fuel were also determined for the hydrogen production rate of $27\;Nm^3/h$.

• Industrial Engineering and Management Systems
• /
• v.15 no.4
• /
• pp.307-317
• /
• 2016

According to most of energy sector experts, at least in the next two decades, fossil energy plays important role in fulfilling required energy in the world. Based on these conditions, the investigation of the conditions of major countries providing natural gas in the world can be useful in analysis of future development of this clean fuel. According to the latest estimations of British Petroleum Company, Iran with 18.2% natural gas reservoirs has the first natural gas reservoirs in the world. The main purpose of this paper is developing scenarios of gas industry in Iran. To achieve the mentioned goals, besides investigation of existing methods of scenario design and existing production scenarios, natural gas export and consumption in Iran and the world in 2035, the most important scenarios of gas industry in Iran are formulated by critical uncertainty analysis approach using quantitative advanced time based impact analysis in 2035 horizon.