• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.502-507
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• 2014

In this paper, performance characteristics of cycles were studied when mixed working fluid was used for ocean thermal energy conversion (OTEC). Among the various mixed refrigerants for industrial heat-pump, R32/R152a used in ocean thermal energy conversion system. For simulations, R32/R152a were used in existing closed cycle and Kalina cycle which is used only ammonia and water as mixed refrigerant. Temperature of the warm heat source was 26 and 29 celsius degree, temperature of the cold heat source was 5 celsius degree. In results of simulation, Gross power of the closed cycle on R32 was 22kW, and efficiency of the cycle was 2.02%. When the mixed refrigerant of R32/R152a, in the ratio of 90 to 10, gross power of the closed cycle was 29.93kW, and efficiency of the cycle was 2.78%. Gross power and cycle efficiency of R32/R152a increased by 36% and 37% than those of existing single refrigerant. Additionally, the same simulations were conducted in Kalina cycle with the same various composition ratio of mixed refrigerant.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.16-29
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• 2017

It is known that large-scale deforestation has occurred in North Korea due to economic failures since the 1990s, and this is expected to greatly change the characteristics of the hydrological cycle. In this study, hydrological cycle simulation was carried out for the period of about 30 years from 1981 to 2013 for the entire Korean peninsula using the VIC model, a land surface hydrology model. The simulation results are summarized as follow. First, the runoff ratio is 55%~70% in South Korea and 38~56% in North Korea. In particular, it is worth noting that despite the small runoff ratio, the variation is about 28% larger than the South Korea's 15%. The rate of evapotranspiration was larger than that of South Korea. That is, the rate of evapotranspiration in South Korea is 20~35% and in North Korea it is 25~46%. However, the rate of change was 21% in the case of North Korea and slightly larger than 15% in South Korea. Third, South Korea has an average of 34% in soil moisture and 27% in North Korea. However, unlike the simulated results of the runoff ratio and the evapotranspiration rate, the difference in the variation of soil moisture in South Korea and North Korea over the entire period was similar with 8%. As a result, we can confirm that the difference of hydrological cycle characteristics between South Korea and North Korea has been increased since the 1990s, when the forest destruction of North Korea became serious. In the case of South Korea, there is little difference in the hydrological cycle characteristics. In North Korea, however, there is a distinct difference, which is also a result reflecting the difference in the effects of forest destruction.

• Journal of Biosystems Engineering
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• v.8 no.1
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• pp.38-46
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• 1983

This study was carried out to investigate the possibility of improving the performance of a kerosene engine with water addition. The engine used in this study was a single-cylinder, four-cycle kerosene engine with the compression ratio of 4.5. Water could be successfully added into the inlet manifold by an extra carburetor for the volumetric ratios of 5, 10, 20, and 30 percents. Variable speed tests at wide-open throttle were performed for five speed levels in the range of 1,000 to 2,200rpm for each fuel type. Volumetric efficiency and brake specific fuel consumption were determined, and brake thermal efficiency based on the lower heats of combustion of kerosene was calculated. To examine variation in fuel consumption, CO concentration, and cooling water temperature, part load tests were also performed. The results obtained are summarized as follow. (1) Brake torque increased almost in proportion to volumetric efficiency. But the ratio of increase in torque was greater than that of volumetric efficiency. Mean torque over the speed range of 1,000 to 2,200rpm increased 1, 3, 7, and 2 percents for 5, 10, 20, and 30 percents water addition, respectively. The increase in brake torque with water addition was greater at lower speeds. (2) Mean brake specific fuel consumption over the speed range of 1,000 to 2,200rpm decreased 1, 2, 3, and 3 percents for 5, 10, 20, and 30 percents water addition, respectively. (3) Mean temperature of cooling water over the speed range of 1,000 to 2,200rpm decreased 2, 4, 8, and 12 percents for 5, 10, 20, and 30 percents water addition, respectively. (4) The effects of decreasing CO concentration in the exhaust emissions with water addition were significant. At the speed range of 1,000 to 2,200rpm, CO concentration in the exhaust emissions decreased 2, 10, 23, percents for 5, 10, and 20 percents water addition, respectively. (5) Deposits were not discovered in the combustion chamber during the experiment. However, a little rust was formed in the water-supply carburetor.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4287-4294
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• 2023

In order to meet the energy demand, energy production must be done continuously. Hydrogen seems to be the best alternative for this energy production, because it is both an environmentally friendly and renewable energy source. In this study, the hydrogen fuel production of the peaceful nuclear explosives (PACER) fusion blanket as the energy source integrated with Fe-Cl thermochemical water splitting cycle have been investigated. Firstly, neutronic analyzes of the PACER fusion blanket were performed. Necessary neutronic studies were performed in the Monte Carlo calculation method. Molten salt fuel has been considered mole-fractions of heavy metal salt (ThF₄, UF₄ and ThF₄+UF₄) by 2, 6 and 12 mol. % with Flibe as the main constituent. Secondly, potential of the hydrogen fuel production as a result of the neutronic evaluations of the PACER fusion blanket integrated with Fe-Cl thermochemical cycle have been performed. In these calculations, tritium breeding (TBR), energy multiplication factor (M), thermal power ratio (1 - 𝜓), total thermal power (P_hpf) and mass flow rate of hydrogen (ṁ_H2) have been computed. As a results, the amount of the hydrogen production (ṁ_H2) have been obtained in the range of 232.24x10⁶ kg/year and 345.79 x10⁶ kg/year for the all mole-fractions of heavy metal salts using in the blanket.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.373-378
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• 2011

The freeze desalination cycle with seawater heat pump system is simulated and designed for the basic data for the design of freeze desalination system. The basic model of seawater heat pump system is refrigeration cycle and indirect freeze desalination method is used for seawater desalination. The cycle performance of seawater heat pump such as COP, compressor work, condensing capacity was analyzed and the desalination performance such as fresh water productivity and energy per unit fresh water productivity was compared with respect to the seawater temperature of condenser inlet and ice ratio in the evaporator. The compressor work and condensing capacity decreased with respect to the decrease of seawater inlet temperature. The energy per unit fresh water productivity in case of $8^{\circ}C$ seawater inlet temperature showed 28.9% lower than that of $20^{\circ}C$.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.607-612
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• 2007

In this study, we investigated the variations of the kinetic coefficients and Chemical Oxygen Demand (COD), N and P mass used for assimilation of a sequencing batch reactor (SBR) system with the variation of SRTs; SRTs of 7.5, 10.0, 12.5, 15.0 and 20.0 days were tested in one cycle of SBR operation to determine the optimum conditions for the operation of the SBR and estimate its COD, nitrogen and phosphorus removal efficiencies. The SBR system was operated under the conditions as follows: an operation time of 6 hours per cycle, a hydraulic retention time (HRT) of 12 hours, an influent COD loading of $0.4kg/m^3/day$, and an influent nitrogen loading of $0.068kgT-N/m^3/day$. The yield coefficient (Y) and decay rate coefficient ($k_d$) were estimated to be 0.4198 kgMLVSS/kgCOD and $0.0107day^{-1}$ by calculating the removal rate of substrate according to the variation of SRT. Considering total nitrogen amount removed by sludge waste process, eliminated by denitrification, and in clarified water effluent with reference to 150 mg/cycle of influent nitrogen amount, the percentage of nitrogen mass balance from the ratio of the nitrogen amount in effluent (N output) to that in influent (N input) for Runs 1~5 were 95.5, 97.0, 95.5, 99.5, and 95.5%, respectively, which is well accounted for, with mass balances close to 100%.

• Plant Journal
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• v.14 no.4
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• pp.33-38
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• 2018

In this study, it was confirmed whether the cooling water bypass ratio of packing for plume abatement matched designed value during winter operation of combined cycle power plant. Designed operating wet bulb temperature of the plume abatement cooling tower with 29 Gcal/h capacity had a range from $13^{\circ}C$ to $-20^{\circ}C$, while its designed bypass ratio was from 0 % to 78%, so that increasing rate of the designed bypass ratio was $2.36%/^{\circ}C$ when the external temperature decreased. When the wet bulb temperature at cooling tower inlet had a range from $7.8^{\circ}C$ to $-11.8^{\circ}C$ in a normal operation, it was measured that actual bypass ratio of packing for plume abatement had a range from 23.8 % to 74.3%. While increasing rate of the actual bypass ratio was $2.71%/^{\circ}C$ in a range from $7.8^{\circ}C$ to $-9.55^{\circ}C$, it was $1.61%/^{\circ}C$ under $-10^{\circ}C$ in cold weather condition according to atmospheric temperature drop, therefore it was confirmed that the increasing rate of the bypass ratio for packing was lowered than its design.

• Journal of People, Plants, and Environment
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• v.23 no.2
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• pp.179-189
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• 2020

In order to increase the indoor air purification effect of plants, plants need to be placed on 5-10% of indoor spaces. To increase the density and utilization of plants in indoor spaces, studies on bio-wall, a vertical green wall system, have been recently conducted. The purpose of this study was to investigate the growth characteristics of 7 indoor plants introduced to the system and their rooting zones at different irrigation cycles. This study was conducted to investigate a proper irrigation cycle for the continuous maintenance of bio-wall systems. The conditions of their growth environment were maintained as follows: light intensity, 20-50 μmol·m^-2·s^-1 PPFD; and temperature, 20 - 25℃. For fertilization, Hyponex diluted with water at the ratio of 1:1,000 was supplied to plants. Irrigation was treated at intervals of 1, 3, 5, and 7 days for 1 hour at a time. As a result, there was no significant difference in the growth of plants between different irrigation cycles. Dieffenbachia 'Marianne' showed a significant decrease in the number of leaves at the irrigation cycle of 7 days. In addition, the chlorophyll content was relatively low at the irrigation cycle of 7 days. In terms of the color of leaves, a decrease in L value and b value and an increase in a value were observed, resulting in changes in brightness and color. Ardisia pusilla 'Variegata' showed a slightly higher photosynthetic activity and stomatal conductance when it was watered every day and once per 5 days, while Epipremnum aureum showed a relatively higher photosynthetic activity and stomatal conductance at the irrigation cycle of 3 days. In the case of root activity, it was found that the longer irrigation cycle, the higher root activity compared to daily irrigation. The development of roots of Peperomia clusiifolia was promoted by watering at long intervals. However, in the case of Aglaonema 'Siam-Aurora', the total number of roots decreased at the interval of 7 days. In conclusion, a proper irrigation cycle for the sustainable maintenance of vertical bio-wall systems seems to be 3 days.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.924-927
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• 2003

Aluminium-doped ZnO (ZnO:Al) films were grown by atomic layer-controlled deposition on glass substrates at temperature of 200 $^{\circ}C$ using diethylzinc($Zn(C_{2}H_{2})_{2}$; DEtZn), water($H_{2}O$) and trimethylaluminium ($Al(CH_{3})_{3}$; TMA) as precursors. As the cycle ratio of TMA to DEZn(TMA/DEZn) increased, the resistivity of the films decreased and the roughness increased. In the case of TMA/DEZn pulse ratio of 1 to 10, the film had a resistivity of $9.7{\times}l0^{-4}{\Omega}{\cdot}cm$ and a roughness of 2.25nm(rms), while in the case of only DEZ injection the film had a resistivity of $3.5{\times}10^{-3}{\Omega}{\cdot}cm$ and a roughness of 1.07nm(rms)

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.158-162
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• 2014

A series of numerical simulation has been carried out to study thermo-hydraulic characteristics of a primary surface type heat exchanger, which is designed for the evaporator and condenser of a geothermal ORC. Working fluid is geothermal water at hot side and R-245fa, which is a refrigerant designed for ORC, at cold side. Amplitude ratio of the channel and Reynolds number are considered as design parameters. Nusselt number is presented for the Reynolds number ranging from 50 to 150 and compared to analytic solutions. The result shows that higher amplitude ratio channel gives better heat transfer performance within the range of investigation.