• 설비공학논문집
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• 제21권12호
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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.

• 터널과지하공간
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• 제12권3호
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• pp.142-151
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• 2002

대전 식품냉동저장창고 파일럿 공동주위의 거리에 따른 비정상상태의 온도 분포를 산정하기 위해 Claesson(2001)의 해석해 및 Dirichlet과 Neuman 내부 경계조건을 갖는 수치모델들을 검토하였다. 온도 강하 단계동안 일정 표면 온도 경계조건에 기초하고 있는 Claesson의 해석해를 활용한 결과, 실제 암반에서의 온도 계측결과를 오차 평균 0.89$^{\circ}C$ 수준으로서 비교적 정확히 예측할 수 있었는데, $0^{\circ}C$근처의 실험실 암석 열물성을 입력하였고 현지 암반 조건을 표현하기 위한 특별한 물성 보정을 하지 않았다. 내부 공동 암반 벽면을 통한 열유속을 갖는 수치해석의 경우, 대류 열전달계수와 공동 내부 온도가 냉각시간에 따라 변화하기 때문에 경계조건을 가하기 어려운 단점을 극복하기 위해 새로운 경계조건 설정 기법을 제안하였다. 그 결과 오차 평균 1.58$^{\circ}C$의 수준으로서 온도 계측치와 부합하였다. 또한 공동 벽면에서 고정 온도 조건을 갖는 수치해와 비교하였다. 마지막으로 Claesson의 해석해 및 다양한 내부 경계조건을 갖는 수치모델을 활용하여, 공동 주변의 온도 분포를 정확히 예측할 수 있는 일련의 해석 단계 프로그램을 제안하였다.

• 한국연소학회지
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• 제13권2호
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• pp.33-41
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• 2008

The high permeability of the gas in the molten iron of the dripping zone of the blast furnace is a major factor in achieving the stable operation of a furnace with high productivity. Basic studies of the liquid flow behavior in a packed bed are necessary to grasp the effect of various operational changes on conditions in the dropping zone. Molten iron and slag together playa critical role in the lower zone, transporting mass and energy, while impairing and redistributing the gas flow. In turn, molten iron and slag undergo physical and chemical changes, and are redistributed radially as they descend to the hearth. In this research, mathematical formulations are derived for the gas and the liquid. The solid phase is fixed with constant porosity. The information for the molten iron and slag includes the hold-up, velocity, pressure, and information related to the areas of interaction between the gas and the liquid, and the solid and the liquid. Predictable results include the velocity, pressure and temperature distribution. Additional parameters include the packed particle size and the air blast rate.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.24-29
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• 2003

Deep sea water has cold temperature, abundant nutrients and minerals, and good water quality that is pathogen-free and stable. Compared with surface water, deep sea water contains more nutrition salt, such as nitrogen and phosphor. Moreover, if has the good balance of minerals. Because of the ability of the spray drying process to produce a free-flowing power considering of spherical particles with a well-defined size distribution and the rapid drying times for heat-sensitive material, spray drying is attractive for a wide range of applications spray drying is a unique unit operation in which powders are produced from a liquid feed in a single processing step. Key component of the process are atomizer, spray chamber. Design of spray chamber should be based on the atomizer type, the production rate, and the particle size required. Because of the complex processes taking place during spray drying, traditional design method are based on pilot-plant tests and empirical scale-up rules. Modern technique such as CFD have a role to play in design and troubleshooting.

• 대한조선학회논문집
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• 제50권3호
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• pp.167-174
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• 2013

Model ice forming process in ice tank needs several steps of seeding, freezing, tempering. In those process, one of the most important factors to affect the accuracy of experiment is the homogeneity of the ice thickness and the temperature. This paper investigated a computational and statistical method to assess the uniformity of the model ice. In addition, the different configurations of freezing systems were considered to improve the uniformity. Qualitative assessment using streamlines from the cooling units was carried out by computational fluid dynamics (CFD) and the quantitative evaluations of the homogeneity were compared using the temperature distribution on the ice surface. In addition, multi species transport analysis is introduced to understand the circulation efficiency of cold air from the cooling units. As the results, optimized configurations were determined by adjusting the angles of vane in the cooling units.

• 한국자동차공학회논문집
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• 제20권5호
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• pp.95-101
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• 2012

An electric water pump for engine cooling system has an advantage which particularly in the cold start, the use of the electric water pump saves fuel and leads to a corresponding reduction in emissions. The canned type electric water pump without mechanical sealing elements was selected to meet the requirements for operational reliability and life. However, the electric water pump for internal combustion engine generates much more heat loss than for hybrid electric vehicle since it is operated by the electric power of high current and low voltage. In this study, the fluid flow and thermal characteristics of the canned type electric water pump as an inverter integrated water pump has been investigated under the effects of heat generation. The analysis conditions such as outdoor air temperature of $125^{\circ}C$, water pump speed of 6000 rpm, coolant temperature of $106^{\circ}C$ and coolant flow rate of 120 L/min was used as a standard condition. Therefore, flow fields and temperature distribution inside the water pump were obtained. Also, we checked the feasibility of the canned type for the electric water pump in comparison with the mechanical seal type.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.389-394
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• 2008

Nowadays Plate Heat Exchanger (PHE) is widely used in different industries such as chemical, food and pharmaceutical process and refrigeration due to the efficient heat transfer performance, extreme compact design and efficient use of the construction material. In present work, PHE is applied in the fresh water generator system. Fresh water generators or desalinators are installed in ship to convert seawater to fresh water using heat from engines. PHE is an important part of a condensing or evaporating system. Among many of factors which should be concentrated on, the heat transfer and pressure drop is most important parts during sizing and rating the performance of PHE. Flow maldistribution is common but it will significantly reduce the heat exchanger performance. In this paper provide a overview of PHE cover basic of theory and conduct a numerical approach for flow distribution in plate channel. An experimental study on the performance of fresh water generator system which developed by plate heat exchanger will presented in future research. Thus, extensive experiment and analysis is required to study the thermal and fluid flow characteristics of PHE.

• Journal of Periodontal and Implant Science
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• 제36권1호
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• pp.51-60
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• 2006

Gingival recession is clinically manifested by an apical displacement of the gingival tissue and dentin hypersensitivity is often used to describe a painful condition in which exposed dentin is unduly sensitive to intraoral stimuli. The objects of this study were primarily to investigate the prevalence and distribution of gingival recession and hypersensitivity and secondarily to determine whether a relationship exists between gingival recession and hypersensitivity. The study population was 195 patients (102 males, 93 females) who were attended the department of periodontology, Pusan National University Hospital. 189 patients exhibited gingival recession at least more than 1 tooth, the prevalence was 96.9%. The maxillary and mandibular first premolar and mandibular incisors had the highest prevalence. The majority of patients (139 patients, 71.3%) were diagnosed as having dentin hypersensitivity. Dentin hypersensitivity was determined to 3 seconds application of cold air to the exposed root surface after isolating the test tooth and was commonest in maxillary and mandibular first premolars and mandibular incisors. Relationship between recession and hypersensitivity was analyzed using chi-square test (p=0.05), significant relation (p=0.000) was existed. Gingival recession was more severe, the prevalence of hypersensitivity was higher.

• 혜화의학회지
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• 제9권1호
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• pp.503-511
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• 2000

This case study was done on a 37 year old female patient at the department for rehabilitation in Bundang Cha Oriental hospital who was treated for 70 days by traditional Acupuncture and Herbal medicine therapy as well as fasting with saengshig(生食), air bath(風浴) and cold-hot-bath(冷溫浴) for skin revitalisation, furthermore by Doinangyo and exercise for improvement of general condition and colon-hydrocleansing. The results are as following: 1. The body weigth was reduced by 14.5kg from 87.4kg to 72.9kg 2. The obesity degree reduced from 159% to 133% 3. The BMI reduced from 33.3 to 27.8 4. The WHR reduced from 0.96 to 0.88 5. The amount of body fat reduced by 7.7kg from 27.2kg to 19.5kg 6. The fat distribution of the abdomen reduced from 0.92 to 0.85 7. The percent body fat was reduced from 31.1% to 26.7 % 8. Except of a mild systemic pruritus the clinical symtoms like kneepain, fatigue, chilling, headache, indigestion, menorrhalaia improved significantly.

• 한국태양에너지학회 논문집
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• 제27권1호
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• pp.91-98
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• 2007

Perimeter zone is one of the weakest area in buildings and it makes an increase of heating and cooling loads, in addition to condensation or discomfort with cold-draft to residents in winter. Because of this, it needs to be reinforced by active systems. However, they use fossil fuel, and ultimately greenhouse effect is urged. Thus, we proposed BIPV system functioned as solar collector which can substitute active system. As an fundamental stage, heat balance equation in steady-state by Fortran was used not only, in winter for pre-heating effect and electric power capacity during the day, but also in summer, for the latter during the day and sky radiation effect during the night. Especially, we should have considered shading on PV by IES Suncast, since even a little bit of it makes the efficiency too low for the PV modules to work. As a result, in summer day, the PV panel should be tiled in 70 degrees to gain the most electric power. Moreover, we could verify that this model makes higher temperature and heat flux under 0.02 m/s. On the other hand, the PV had the high efficiency with high velocity because of cooling effect behind the PV. Therefore, we should regard the air current distribution later on.