• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.7
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• pp.380-394
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• 2015

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

• Advances in Energy Research
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• v.4 no.3
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• pp.189-202
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• 2016

This work emphasized optimum production of biodiesel using non-edible Prunus armeniaca (Bitter Apricot) oil via transesterification collected from the high altitude areas of Himachal Pradesh, India. In this study the author produced biodiesel through the process of transesterification by using an alkali catalyst with alcohol (methanol and ethanol), under the varying molar ratio (1:6, 1:9, 1:12), variable catalyst percentage (1% and 2%) and temperature ($70^{\circ}C$, $75^{\circ}C$, $80^{\circ}C$, $85^{\circ}C$). Furthermore, a few strong base catalysts were used that includes sodium hydroxide, potassium hydroxide, sodium metal and freshly prepared sodium methoxide. After screening the catalyst, response surface methodology (RSM) in connection with the central composite design (CCD) was used to statistically evaluate and optimize the biodiesel production operation using NaOH as catalyst. It was found that the production of biodiesel achieved an optimum level biodiesel yield with 97.30% FAME conversion under the following reaction conditions: 1) Methanol/oil molar ratio: 1:6, 2) Reaction time: 3h, 3) Catalyst amount: NaOH 2 wt. %, and 4) Reaction temperature: $85^{\circ}C$. The experimental results showed that the optimum production and conversion of biodiesel through the process of transesterification could be achieved under an optimal set of reaction conditions. The biodiesel obtained showed appropriate fuel properties as specified in ASTM, BIS and En- standards.

• Journal of Bio-Environment Control
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• v.28 no.3
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• pp.243-254
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• 2019

With the recent accelerated policy-making and interests in new renewable energy, plans to develop and supply the new renewable energy have been devised across multiple regions in Korea. Solar energy, in particular, is being applied to small-scale power supply in provincial areas, as solar cells are used to convert solar energy into electric energy to produce electric power. Nonetheless, in the case of solar power plants, the need for a large stretch of land and considerable sum of financial support implies that the planning step should take into consideration the most suitable meteorological and geographical factors. In this study, the proxy variables of meteorological and geographical factors associated with solar energy were considered in analyzing the vulnerable areas regarding the photovoltaic power generation facility across the nation. GIS was used in the spatial analysis to develop a map for assessing the optimal location for photovoltaic power generation facility. The final vulnerability map developed in this study did not reveal any areas that exhibit vulnerability level 5 (very high) or 1 (very low). Jeollanam-do showed the largest value of vulnerability level 4 (high), while a large value of vulnerability level 3 (moderate) was shown by several administrative districts including Gwangju metropolitan city, Jeollabuk-do, Chungcheongbuk-do, and Gangwon-do. A value of vulnerability level 2 (low) was shown by the metropolitan cities including Daegu, Ulsan, and Incheon. When the 30 currently operating solar power plants were compared and reviewed, most were found to be in an area of vulnerability level 2 or 3, indicating that the locations were relatively suitable for solar energy. However, the limited data quantity for solar power plants, which is the limitation of this study, prevents the accuracy of the findings to be clearly established. Nevertheless, the significance of this study lies in that an attempt has been made to assess the vulnerability map for photovoltaic power generation facility targeting various regions across the nation, through the use of the GIS-based spatial analysis technique that takes into account the diverse meteorological and geographical factors. Furthermore, by presenting the data obtained for all regions across the nation, the findings of this study are likely to prove useful as the basic data in fields related to the photovoltaic power generation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.12
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• pp.715-732
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• 2009

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2008. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends in thermal and fluid engineering have been surveyed in the categories of general fluid flow, fluid machinery and piping, new and renewable energy, and fire. Well-developed CFD technologies were widely applied in developing facilities and their systems. New research topics include fire, fuel cell, and solar energy. Research was mainly focused on flow distribution and optimization in the fields of fluid machinery and piping. Topics related to the development of fans and compressors had been popular, but were no longer investigated widely. Research papers on micro heat exchangers using nanofluids and micro pumps were also not presented during this period. There were some studies on thermal reliability and performance in the fields of new and renewable energy. Numerical simulations of smoke ventilation and the spread of fire were the main topics in the field of fire. (2) Research works on heat transfer presented in 2008 have been reviewed in the categories of heat transfer characteristics, industrial heat exchangers, and ground heat exchangers. Research on heat transfer characteristics included thermal transport in cryogenic vessels, dish solar collectors, radiative thermal reflectors, variable conductance heat pipes, and flow condensation and evaporation of refrigerants. In the area of industrial heat exchangers, examined are research on micro-channel plate heat exchangers, liquid cooled cold plates, fin-tube heat exchangers, and frost behavior of heat exchanger fins. Measurements on ground thermal conductivity and on the thermal diffusion characteristics of ground heat exchangers were reported. (3) In the field of refrigeration, many studies were presented on simultaneous heating and cooling heat pump systems. Switching between various operation modes and optimizing the refrigerant charge were considered in this research. Studies of heat pump systems using unutilized energy sources such as sewage water and river water were reported. Evaporative cooling was studied both theoretically and experimentally as a potential alternative to the conventional methods. (4) Research papers on building facilities have been reviewed and divided into studies on heat and cold sources, air conditioning and air cleaning, ventilation, automatic control of heat sources with piping systems, and sound reduction in hydraulic turbine dynamo rooms. In particular, considered were efficient and effective uses of energy resulting in reduced environmental pollution and operating costs. (5) In the field of building environments, many studies focused on health and comfort. Ventilation. system performance was considered to be important in improving indoor air conditions. Due to high oil prices, various tests were planned to examine building energy consumption and to cut life cycle costs.

• Clean Technology
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• v.20 no.1
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• pp.13-21
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• 2014

Because of the water scarcity caused by the increase of salinity in the underground water, seawater desalination stands out as one of the most promising solution. As there are so much energy costs in operating desalination plants, new hybrid process which is more effective should be researched. A geothermal VMD (vacuum membrane distillation) hybrid process is a competitive alternative for seawater desalination. Because geothermal energy has significant characteristics of high capacity factor to operate the power plant at full capacity for 24 hour per day, it can be a priority heat source of VMD superior to any other renewable energies such as solar and wind power. In this study, we design a geothermal VMD hybrid process, analyze it economically and finally compare the result with a case of conventional VMD process. Geothermal VMD hybrid process generates $23,822,409 of NPV (net present value) more than the conventional VMD process in case of 5% discount rate. The break-even point between these processes is 5.36 year. Sensitivity analysis indicates that steam cost is the most decisive influence variable to the economic outcome.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.491-494
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• 2009

This paper introduces the design concepts and characteristics of WinDS3000$^{TM}$ which is a trade mark of Doosan's 3MW offshore/onshore wind turbine. WinDS3000$^{TM}$ has been designed in consideration of high RAMS (Reliability, Availability, Maintainability and Serviceability) and cost effectiveness for the TC Ia condition in GL guideline. An integrated drive train design with an innovative three-stage gearbox has been introduced to minimize nacelle weight of the wind turbine and to enhance a high reliability for transmission. A permanent magnet generator with full converter system has been introduced to get higher efficiency in part load operation, and grid friendliness use of 50 Hz and 60 Hz grid. A pitch regulated variable speed power control with individual pitch system has been introduced to regulate rotor torque while generator reaction torque can be adjusted almost instantaneously by the associated power electronics. An individual pitch control system has been introduced to reduce fatigue loads of blade and system. The wind turbine has been also equipped with condition monitoring and diagnostic systems in order to meet maintainability requirements. And internal maintenance crane in nacelle has been developed. As a result, the maintenance cost was dramatically reduced and maintenance convenience also enhanced in offshore condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.258-264
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• 2018

This paper presents application of a differential search (DS) meta-heuristic optimization algorithm for optimal operation of a micro grid system. The DS algorithm simulates the Brownian-like random-walk movement used by an organism to migrate. The micro grid system consists of a wind turbine, a diesel generator, a fuel cell, and a photovoltaic system. The wind turbine generator is modeled by considering the characteristics of variable output. Optimization is aimed at minimizing the cost function of the system, including fuel costs and maximizing fuel efficiency to generate electric power. The simulation was applied to a micro grid system only. This study applies the DS algorithm with excellence and efficiency in terms of coding simplicity, fast convergence speed, and accuracy in the optimal operation of micro grids based on renewable energy resources, and we compared its optimum value to other algorithms to prove its superiority.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.3
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• pp.19-27
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• 2012

Wind is an important variable for various scientific communities such as meteorology, climatology, and renewable energy. In this study, numerical simulations using WRF mesoscale model were performed to produce temporal and spatial wind information over the Republic of Korea during 2006. Although the spatial features and monthly variations of the near-surface wind speed were well simulated in the model, the simulated results overestimated the observed values as a whole. To correct these simulated wind speeds, a regression-based statistical algorithm with different constants and coefficients by land cover type was developed using the satellite-derived LST and NDWI. The corrected wind speeds for the algorithm validation showed strong correlation and close agreement with the observed values for each land cover type, with nearly zero mean bias and less than 0.4 m/s RMSE. Therefore, the proposed algorithm using remotely sensed surface observations may be useful for correcting simulated near-surface wind speeds and producing more accurate wind information over the Republic of Korea.

• Mycobiology
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• v.48 no.5
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• pp.351-363
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• 2020

Here, we investigated fungal microbiota in the understory root layer of representative well-conserved geographically segregated natural wetlands in the Korean Peninsula. We obtained 574,143 quality fungal sequences in total from soil samples in three wetlands, which were classified into 563 operational taxonomic units (OTU), 5 phyla, 84 genera. Soil texture, total nitrogen, organic carbon, pH, and electrical conductivity of soil were variable between geographical sites. We found significant differences in fungal phyla distribution and ratio, as well as genera variation and richness between the wetlands. Diversity was greater in the Jangdo islands wetland than in the other sites (Chao richness/Shannon/Simpson's for wetland of the Jangdo islands: 283/6.45/0.97 > wetland of the Mt. Gariwang primeval forest: 169/1.17/0.22 > wetland of the Hanbando geology: 145/4.85/0.91), and this variance corresponded to the confirmed number of fungal genera or OTUs (wetlands of Jangdo islands: 42/283> of Mt. Gariwang primeval forest: 32/169> of the Hanbando geology: 25/145). To assess the uniqueness of the understory root layer fungus taxa, we analyzed fungal genera distribution. We found that the percentage of fungal genera common to two or three wetland sites was relatively low at 32.3%, while fungal genera unique to each wetland site was 67.7% of the total number of identified fungal species. The Jangdo island wetland had higher fungal diversity than did the other sites and showed the highest level of uniqueness among fungal genera (Is. Jangdo wetland: 34.5% > wetland of Mt. Gariwang primeval forest: 28.6% > wetland of the Hanbando geology: 16.7%).

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.187-191
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• 2006

Sputter deposition followed by surface treatment was studied using reactive RF plasma as a method for preparing titanium oxide $(TiO_2)$ films on the FTO $(SnO_2: F)$ substrate for dye-sensitized solar cells (DSCs). Anatase structure $TiO_2$ films deposited by reactive RF magnetron sputtering under the conditions of $Ar/O_2(5%)$ mixtures, RF power of 600W and substrate temperature of $400^{\circ}C$ were surface-treated by inductive coupled plasma (ICP) with $Ar/O_2$ mixtures at substrate temperature of $400^{\circ}C$, and thus the films were applied to the DSCs. We have chosen a solar cell width as a variable of a large-scaled DSCs and confirmed electric characteristics of an individual cell. As a result, the higher the internal resistance of DSC becomes, the wider the width gets. Internal resistance makes it difficult to collect photoelectron generated from dye. Ultimately up sizing DSC causes the increase of internal resistance and then has a bad effect on the cell characteristics.