• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.7
• /
• pp.862-872
• /
• 1997

Ice formation in a horizontal circular cylinder has been studied numerically. From the numerical analysis results, it was found that there were three types of freezing pattern and that freezing phenomenon was affected largely by density inversion and cooling rate. The type of freezing pattern largely depends on the secondary flow which is generated by density inversion. When supercooling energy is released before the development of the secondary flow, the annular ice layer grows. If the energy is released when the secondary flow is considerably developed and the supercooled region is removed to the upper half part of the cylinder, an asymmetric ice layer grows. And if the energy is released after perfect development of the secondary flow, instantaneous dendritic ice formation over the full region occurs. Furthermore, this secondary flow was found to have an effect on heat transfer characteristics. The heat transfer rate becomes small at the instant when the secondary flow is generated, but becomes large with the development of the flow. It's concluded that for the facilitation of heat transfer it is desirable to keep water in liquid phase until the secondary flow is perfectly developed. This study gave an instruction of performance improvement of capsule type ice storage tank.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2004.06a
• /
• pp.167-173
• /
• 2004

The amount of cesium released from the leaching of spent fuels in contact with and without the compacted bentonite bloc]t which was compacted as the density of $1.4g/\textrm{cm}^3$, up to 5.7 years were measured and the empirical formula of the fractional release rate of cesium were derived from these measured values. The empirical formulas show that the long-term release rate of cesium under a repository would become a constant, as about $3{\times}10_{-6}$ fraction/day, after a certain period. The cumulative fractions of cesium released from the spent fuel with bentonite and with copper and stainless steel sheets were steadily increased, but the fraction from bare fuel was rapidly increased and then sluggishly increased. However, the remained value except its gap inventory from the cumulative fraction of cesium released from bare fuel was almost very close to the others. This suggests that the initial release of cesium from bare fuel might be dependant on its gap inventory.

• Journal of Radiation Protection and Research
• /
• v.29 no.3
• /
• pp.157-163
• /
• 2004

Atmospheric dispersion modelling has been widely used to predict the fate and transport of radioactive or toxic materials released from nuclear facilities which is an unlikely accidental event. To improve the forecasting performance of the dispersion model, it is required that source rate and dispersion characteristics must be defined appropriately. Generally, source term of the radioactive materials is much uncertain at the early phase of an accidental event. In this study, we computed the source rate with the experimental field data monitored at the Yeoung-Kwang nuclear site and obtained the optimal source rate to minimize the errors between the measured concentrations and the computed ones by the Gaussian plume model. Computed source term showed a good result within 24% of the artificially released source rate.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 1997.11a
• /
• pp.77-84
• /
• 1997

Cone calorimeter measurements can be used for the calculation of effective material properties, which can be used as input parameters in modeling of fire. Main parameter measured in Cone calorimeter is heat release rate. Some other parameters as time to ignition, effective heat of combustion, mass loss rate or total heat released is also measured in Cone calorimeter. Total heat released is important from the point of view of total energy available in material in Fire situation. Cone calorimeter. measurements were done on several wood species (oak, beech, spruce, poplar). Measurements were provided at external irradiances 30, 50 and 65 ㎾/$m_2$ in horizontal orientation. Heat release rate data were evaluated and compared as a function of external irradiance for various species of wood. furthermore the influence of external irradiance on effective heat of combustion and total heat release was also evaluated for the period of flame combustion.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.10
• /
• pp.860-867
• /
• 2007

Heat pump drying has a great potential for energy saving due to its high energy efficiency in comparison with conventional air drying. In the present study, the performance simulation for the basic design of a heat pump dryer has been carried out. The simulation includes one-stage heat pump cycle, simple drying process using the drying efficiency. As an example, the heat pump cycle with Refrigerant 134a has been investigated. For the operating conditions such as the average temperature of the condenser, the heat rate released in the condenser, the flow rate of drying air, and drying efficiency, the simulation has been carried out to figure out the performance of the dryer. The parameters considered in the design of the dryer are COP, MER, SMER, the rate of dehumidification, the temperature and humidity of drying air and those parameters are compared for different conditions after carrying out the simulation.

• Nuclear Engineering and Technology
• /
• v.34 no.3
• /
• pp.242-249
• /
• 2002

The relationship between the tritium release rate from the nuclear power plant and tritium concentration in the environment around the Kori site was modeled. The tritium concentration in the atmosphere was calculated by multiplying the release rates and $\chi$/Q values, and the d3V deposition rate at each sector according to the direction and the distance was obtained using a dry deposition velocity. The area around Kori site was divided into 6 zones according to the deposition rate. The six zones were divided into 14 compartments for the numerical simulation. Transfer coefficients between the compartments were derived using site characterization data. Source terms were calculated from the dry deposition rates. Tritium concentration in surface soil water and groundwater was calculated based upon a compartment model. The semi-analytical solution of the compartment model was obtained with a computer program, AMBER. The results showed that most of tritium deposited onto the land released into the atmosphere and the sea. Also, the estimated concentration in the top soil agreed well to that measured. Using the model, tritium concentration was predicted in the case that the tritium release rates were doubled.

• KIEAE Journal
• /
• v.13 no.4
• /
• pp.49-54
• /
• 2013

released by IEA, 2010, indicated that Korea's GDP, of 8 countries surveyed-Korea, Frans, Germany, Italy, Japan, the UK, the USA, and Australia-was the lowest, but the electric consumption per head was third, following America and Australia. Thus, our government has been striving to reduce energy usage and especially to lessen the energy used in buildings, proposing a variety of road maps such as 'building energy efficiency rating' and 'energy saving design standards of buildings'. Accordingly, this study investigated the effect of the items of machine part among EPI items on the energy saving rate. I measured energy usage by ECO2 program, for simulation program, that is used for the building energy efficiency rating. Result showed that items concerning control of pumps and fans had much more saving rate than the ones concerning efficiency of heater and cooler that had bigger scores assigned among EPI items. Result showed that items concerning control of pumps and fans had much more saving rate than the ones concerning efficiency of heater and cooler that had bigger scores assigned among EPI items. Therefore, I think that grades assigned to items in energy performance index need to be corrected.

• New & Renewable Energy
• /
• v.20 no.1
• /
• pp.175-181
• /
• 2024

This study analyzed the hydrogen conversion rate and microbial community in conjunction with changes in carbohydrate concentration during hydrogen fermentation using food waste, and presented comprehensive research results for the condition 80 g Carbo COD/L, which showed the highest efficiency with a carbohydrate removal rate of 98.1% and a hydrogen conversion rate of 1.76 mol H₂/mol. The microbial community analysis found that Clostridium sp., widely known as a hydrogen-producing microorganism, was released in 80 g Carbo COD/L and confirmed that it was a dominant species at 98.1%. Conversely, in 100 g Carbo. Under COD/L conditions, Leuconostoc sp. showed the maximun prevalence, which is believed to hinder hydrogen production.

• Journal of Advanced Marine Engineering and Technology
• /
• v.41 no.3
• /
• pp.182-190
• /
• 2017

All liquids contain a small amount of gaseous components and the amount of gases dissolved in a liquid is in accordance with Henry's Law. In a multi-stage thermal-type seawater desalination plant, as the supplied seawater undergoes variations in temperature and pressure in each evaporator, the gases dissolved in the seawater are discharged from the liquid. The discharged gases are carbon dioxide, nitrogen, oxygen, and argon, and these emitted gases are non-condensable. From the viewpoint of convective heat transfer, the evaluation of non-condensable gas released during a vacuum evaporation process is a very important design factor because the non-condensable gases degrade the performance of the cooler. Furthermore, in a thermal-type seawater desalination plant, most evaporators operate under vacuum, which maintained through vacuum system such as a steam ejector or a vacuum pump. Therefore, for the proper design of a vacuum system, estimating the non-condensable gases released from seawater is highly crucial. In the study, non-condensable gases released in a thermal-type seawater desalination plant were calculated quantitatively. The calculation results showed that the NCG releasing rate decreased as the stage comes getting a downstream and it was proportional to the freshwater production rate.

• Journal of the Korean Solar Energy Society
• /
• v.22 no.1
• /
• pp.9-21
• /
• 2002

To develope chemical heat pump using available energy sources, solar heat and other kinds of waste thermal energy, we have studied the heat transfer rate in cylindrical bed reactor packed with calcined Dolomite. Two dimensional (radial and circumferential) Partial differential equations, concerning heat and mass transfer in packed bed of calcined Dolomite, are solved numerically to describe the characteristics of the reaction of calcined Dolomite and heat transfer. The results obtained by numerical analysis about two dimensional profiles of temperature and conversion of reactant in the packed bed reactor and the amount of exothermic heat released from the reactor are follows. It was found that all of calcined Dolomite packed bed kept the reaction temperature of about 750K throughout the entire part of the bed, immediately after the steam was introduced exothermic reaction of hydration was proceeded from the packed bed inpu to output and from wall side to center. The rate of thermochemical reaction depends on the temperature and concentration and it is also governed by the boundary conditions and heat transfer rate in the particle packed bed.