• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.391-392
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• 2021

해마다 실내 냉방기 냉매누설 문제가 고질적으로 반복되며 소비자들의 피해도 커져가고 있다. 특히 제조사와 설치 업체가 다른 경우 냉매 누수의 원인이 제품인지, 설치하자인지 책임소재를 두고 갈등을 빚는 경우가 빈번하다. 이에 더 이상 소비자들의 피해를 막기 위해 냉매누설 검출 방안 마련이 필요해 보인다. 본 연구에서는 실내 냉방기 설치 후 냉매누설 검출을 위한 별도의 하드웨어 장치 추가 없이 냉방기의 운영을 위해 설치된 센서들의 값을 이용하여 냉매누설의 유무를 판단할 수 있는 방안을 제안하는 것을 목적으로 한다. 데이터 분석을 위하여 제조사의 제품 출하 전 현장 테스트 단계에서 측정한 온도값, 전류값, 습도값을 취합하여 데이터 셋을 구축하였다. 이때 자동화된 머신러닝(AutoML)을 이용하여 데이터의 80%를 훈련 데이터로 20%를 테스트 데이터로 사용하여 냉매량 80%는 1, 그 이하는 0으로 훈련시켰다. 구축한 데이터 셋을 이용하여 훈련시킨 결과 99% 정확도로 냉매누설 검출을 분별할 수 있었다. 또한 냉매누설과 관련성이 높은 중요 특징 4개를 추출할 수 있었다. 본 연구를 통하여 별도의 하드웨어 장치 추가 없이 소프트웨어적인 접근 방법으로 문제를 해결할 수 있는 feasibility를 확인할 수 있었다.

• Korean Journal of Construction Engineering and Management
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• v.10 no.4
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• pp.111-118
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• 2009

This study is to analyze the performance of SWH(Solar Water Heating) and GSHP(Ground Source Heat Pump) systems by evaluating their energy efficiency and LCC(Life Cycle Cost) as being applied to the OO hall as a selected building in the Army. The OO hall, used as bathrooms, dining rooms, accommodations and offices, has reinforced concrete structure system with three floors above the ground and one underground, and its total floor area is approximately 2,917$m^2$. Two energy simulations are conducted to predict the yearly cooling and heating energy of the selected building: One is for analysis of an air-conditioning energy consumption using the e-Quest program, and another is for two new-renewable energy facilities as a water heating source using the RETScreen. The installed capacity of two new-renewable energy facilities is determined according to the 5% level of total standard construction cost. As a briefly result, SWH system is more energy-effective than GSHP system. Considering the break-even point, it is expected that SWH can take only 3 years 11 months to pay for itself in savings while the investment of GSHP can be recovered in more than 16 years 6 months.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.592-597
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• 2013

The heat generated at the motor and inverter inside the electric compressor of inverter built-in type is mainly cooled by refrigerant and generally, there is not a thermal problem. However, the close relation of heat transfer from the motor and inverter parts to the compression part affects on compressor efficiency. Also, according to the surrounding environment and system operation condition, the increased temperature of the motor and inverter can affect the power density of the motor system, and especially, the inverter may be prevented to operate by the temperature limits. In this study, we performed thermo-flow analysis of electric compressor motor system, and investigated the heat dissipation enhancement of the motor and inverter. The motor part in the operation region of the electric compressor was generally maintained at low temperature and the inverter part at high compressor speed was lower temperature than the temperature limit of $85^{\circ}C$. However, the case of the inverter at low speed harsh condition was in excess of $10^{\circ}C$. Therefore, in order to solve the thermal problem, the heat reduction technology of the motor and inverter is essential as well as the improvement of flow path in the compressor.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.197-201
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• 2017

Most fishing vessels use an ice cooling system to manage and store captured fish. However, it is difficult to maintain an adequate temperature and salt concentration as well as operating time limitations in ice cooling systems. The purpose of this study is to investigate the heat transfer characteristics of flooded-type evaporators for a seawater cooling system to maintain proper seawater temperature in a fish tank. Experiments were conducted to investigate the heat transfer characteristics by changing the seawater temperature, flow rate, and saturation temperature of the refrigerant. It was confirmed that the heat transfer coefficient of an aluminum-brass tube was approximately 10% higher than that of a copper-nickel tube at the same heat flux. Furthermore, it was confirmed that applying the aluminum-brass tube to the heat transfer tube of a seawater heat exchanger was effective in terms of heat transfer. A comparison of the overall heat transfer coefficient of a single-tube heat exchanger and the flooded-type multi-tube heat exchanger for an 18-kW cooling system showed that the heat transfer coefficient of the single-tube heat exchanger was 25% higher under the same conditions. These results are considered to be important data for designing a flooded-type multi-tube heat exchanger.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1996.05a
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• pp.91-115
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• 1996

In the recent years, protected horticultural facilities have been modernized and glasshouses are also propagating in Korea, even most vegetables production are conducted in the traditional plastic houses covered with, for example, PVC film for just temperature keeping. It would limit the productivity and competitivity of the vegetable production industry without automatization and high quality year round production. A plant factory, aimed to produce vegetables in the limited areas, was initiated in Christensen farm, Denmark in 1957, and widely propagated in some developed countries. As it has the automatized system which enables to keep optimized environment conditions, it will be the best facility for high quality products as well as year round planned production. However, we have not even started the plant factory production. Since the plant factory is requiring lots of resources, besides plant cultivation technologies, such as environment control, automatic engineering and robotics, our approach to the development of plant factories should be minded on Practical Plant Factories considering our current farming practices and least capital needs rather than blindly employing the advanced technologies from developed countries. Thus, Korean plant factory development can be initiated with year round leaf vegetables production in NFT or DFT cultivation system instead of the moval bed system, in which aerial environment factors such as light, temperature, humidity and CO$_2$ concentration and root environment ones such as solution concentration, temperature, pH and water soluble oxygen shall be automatically controlled. And the seeding, seedling and transplanting operations shall be accomplished in the house entrance, and the harvesting and grading opreations shall be conducted in the house exit. For practical plant factories, environment control technologies including artificial light source, illumination and air conditioning, automatic management for nutrient solution and automatic production line of moval bed system, transplanting and harvest should be developed along with researches on the cost reduction of factory building construction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1220-1228
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• 2012

This study was carried out in order to offer medical service in good quality by enhancing dental hygienists' job satisfaction and to arrange basic data necessary for individual development and health promotion in dental hygienists through grasping the job stress level and job satisfaction of being experienced by dental hygienists, and the correlation. The self-administered questionnaire was surveyed and collected from August 1-12 of 2011 targeting 210 dental hygienists of general hospitals, dental hospitals, and dental clinics nationwide(Seoul, Gyeonggi, Daegu, Pohang).The analysis was made on 205 people. The collected data was analyzed by using SPSS WIN 15.0 program. As a result, out of job stress, the average was indicated to be the highest with 2.71 in 'job demand.' As a result of examining about sphere-based relationship between health perception level and job stress related to building in dental hygienists, the central nervous system manifestation showed statistically significant positive correlation with physical environment(r=.281, p<.001), job demand(r=.281, p<.001), relational conflict(r=.163, p<.05), organizational system(r=.166, p<.05), compensation inappropriateness(r=.267, p<.001), and job stress(r=.311, p<.001). Overall, the building-related health perception level showed statistically significant correlation with physical environment(r=.259, p<.001), job demand(r=.311, p<.001), relational conflict(r=.172, p<.05), organizational system(r=.158, p<.05), compensation inappropriateness(r=.197, p<.01), and job stress(r=.275, p<.001). They need to improve their quality of life and life and mental health by developing proper air conditioning system and using one in their work place. if so, they could contribute to better quality of oral cavity service for everyone.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.197-205
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• 2010

Recently abrupt climate changes have been occurred in global and regional scales and $CO_2$ reduction technologies became an important solution for global warming. As a method of the solution shallow underground thermal energy storage (UTES) has been applied as a reliable technology in most countries developing renewable energy. The geothermal energy system using thermal source of soil, rock, and ground water in aquifer or cavern located in shallow ground is designed based on the concept of thermal energy recovery and storage. UTES technology of Korea is in early stage and consistent researches are demanded to develop environmental friendly, economical and efficient UTES systems. Aquifers in Korea are suitable for various type of ground water source heat pump system. However due to poor understanding and regulations on various UTES high efficient geothermal systems have not been developed. Therefore simple closed U-tube type geothermal heat pump systems account for more than 90% of the total geothermal system installation in Korea. To prevent becoming wide-spread of inefficient systems, UTES systems considering to the hydrogeothemal properties of the ground should be developed and installed. Also international collaboration is necessary, and continuous UTES researches can improve the efficiency of shallow geothermal systems.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.118-118
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• 2017

지구 온난화에 따른 환경변화로 인하여 최근 10년('02~'11)간 여름의 일수는 4일, 겨울 일수는 16일 각각 증가하였다. 현재 육계사 내의 고밀도 밀집사육으로 인하여 고온스트레스로 하절기 육계의 폐사율이 증가하고 있는 실정이다. 2016년 폭염으로 닭 406.1천수, 오리 15.7천수, 메추리 70천수, 돼지 8천수가 폐사하였다. 이에 혹서기 가축이 약430만수가 폐사하였으며 피해 보상금액 128억원 소요되었다. 본 연구에서는 하절기 고온스트레스 경감과 폐사율 저감을 위해 계사 냉난방 공조와 냉온 음용수 급수를 병행할 수 있는 고효율 환경 개선 시스템을 개발하여 고온스트레스 저감 및 생산성 향상에 목적이 있다. 계사 냉난방 공조 및 냉온음용수 급수 병행 시스템 설계요인을 분석하고 냉난방 공조부하, 냉온수 생산 부하를 고려한 시스템 용량 산정하고 히트펌프, 축열조, 냉난방 및 냉온수 분배장치 등 구성요소로서 공조 및 냉온음용수 급수시스템을 설치하였다. 시스템 용량은 공기-물 히트펌프(10kW,1대), 축열조(10톤), 음용수조(2톤), 열교환기(열교환량,5만kcal/h), 물순환펌프(250W,2대) 및 팬코일유닛(1만kcal/h,4대)으로 시스템 모니터링 및 제어 시스템 개발하여 계사 내 환경, 시스템 성능에 대한 실시간 모니터링을 통하여 저장하였다. 조사항목으로 위치별 온습도, 체중, 사료섭취량, 페사율 등을 조사 분석하였다. 연구결과 계사의 내부온도는 시험구에서는 평균 $25.3^{\circ}C$를 나타내었고 대조구에서는 평균 $28.1^{\circ}C$로서 $2.8^{\circ}C$ 높게 나타났으나 상대습도는 시험구 76.2%, 대조구 75.0%로 큰 차이가 없었다. 냉수급여에 따른 계사 높이별 내부온도는 상하의 온도차가 $4.5^{\circ}C$로 크게 차이가 났다. 육계의 음수량은 혹서기 냉수를 급여한 시험구에서 일일 23.2L, 대조구에서는 21.5L를 섭취하였다. 일일 사료섭취량은 냉수를 급여한 시험구에서 937g, 대조구에서는 725g을 섭취하였다. 사료섭취량은 냉수를 급여한 시험구가 212g 많이 섭취하였으며 사료요구율은 시험구는 1.86, 대조구는 1.91로서 시험구가 낮게 나타났다. 체중은 냉수를 급여한 시험구가 359g 많았으며 증체량은 냉수를 급여한 시험구에서 495g, 대조구에서는 392g으로 나타났다. 폐사율은 냉수를 급여한 시험구에서 84%가 폐사율을 줄일 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.761-772
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• 2015

Microfin tubes having an outside diameter (O.D.) of 7.0 mm are widely used in residential air conditioning systems and heat pumps. It is known that the mass fluxes for air conditioners and heat pumps under partial load conditions are several tens of $kg/m^2s$. However, literature surveys reveal that previous investigations were limited to mass flux over $100kg/m^2s$. In this study, we conduct R-410A evaporation heat-transfer tests at low mass fluxes ($50-250kg/m^2s$) using a 7.0 mm O.D. microfin tube. During the test, the saturation temperature was maintained at $8^{\circ}C$, and the heat flux was maintained at $4.0kW/m^2$. For comparison purposes, we also test a smooth tube with a 7.0 mm O.D. The results showed that the heat-transfer enhancement factor of the microfin tube increased as the mass flux decreased up to $150kg/m^2s$, which decreased as the mass flux further decreased. The reason for this was attributed to the change of the flow pattern from an annular flow to a stratified flow. Within the test range, the frictional pressure drops of the microfin tube were approximately the same as those of the smooth tube. We then compare experimental data obtained with the predictions obtained for the existing correlations.

• Journal of Conservation Science
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• v.35 no.2
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• pp.99-115
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• 2019

The Royal Tombs at Songsanri is one of the most important historic site for ancient historical study in Korean Peninsula. Since the excavation of the tombs, continuous exposure to the outside environment and the negative effects of the artificial air conditioning system have caused significant threats to the thermal environment stability of the tombs. Unlike the outside temperature that shows significant differences according to seasonal changes, the burial chamber of the tombs had a relatively stable temperature range of 11.4 to $22.2^{\circ}C$ throughout the year, and the standard deviation of temperature was within 3.5. It was revealed that major factors affecting the microclimate of the tombs were inflow of outdoor air, wind direction and speed, and all of them had closely related to airtightness of the tombs. The solar radiation was in inverse proportion to the thickness of burial mounds, and thus Royal Tomb of King Muryeong, which has the thickest burial mound, was least affected by solar radiation. Especially, microclimate of the tombs caused to the highest influence with artificial environmental changes due to access by people, which varied in proportion to the number of accessed people and time of stay. Currently, the inside of the tombs are sealed and always in saturated condition, it is very vulnerable to dew condensation. As a result of analyzing the possibility of condensation in each tomb, all the tomb No. 5, tomb No. 6 and Royal Tomb of King Muryeong had condensation most of the time throughout the year. It is required to make a proper conservation environment for the Royal Tombs at Songsanri.