• 한국산학기술학회논문지
• /
• 제1권2호
• /
• pp.9-14
• /
• 2000

건물의 에너지 효율과 절약을 위해 최근 주목을 많이 받고 있는 가변 풍량 유닛(VAV)에 대해 실제적인 적용을 위한 적분기를 가진 상태 궤환 제어기를 연구한다. 디지털 제어기에 적합하도록 제어기를 개발하게 되며, 디지털 제어기는 결과적으로 대상으로 하는 실내 공간의 온도와 급기 유량으로부터 VAV 유닛 댐퍼의 개도를 조절한다. 설정 온도의 변화와 외부 온도의 변화등의 조건에 대해 모의 실험이 수행되었으며, 단순화된 대상 실내 공간과 댐퍼 구동기의 모델링이 고려되어 제어기의 이득 파라미터와 시스템의 동특성과의 관계를 고찰한다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2001년도 제34회 추계학술대회 개최
• /
• pp.19-26
• /
• 2001

The wear characteristic of Zircaloy-4 tube, which is used for a cladding of light water reactor fuel rod, is investigated experimentally. The experiment is conducted with contacting the crossed tube specimens in air as well as in water at room temperature with various combination of contact normal force and sliding distance of reciprocating motion. The contour and the volume of each wear are examined to study the effect of contact condition and environment on wear. As a result, it is found that the wear volume in the water environment is larger than that in the air for all the contact (i.e., force and sliding distance) conditions. However, the wear depth is greater in air than in water if the contact normal force and the sliding distance are larger. These are explained by the ease of detachment of wear particles from the contact surface. On the other hand, workrate model is applied with the contact shear force range measured by our wear tester. Investigated is the correlation between the workrate and the wear volume increase rate of the present experiment. The parabolic curve is found to fit well for the present wear data.

• 한국자동차공학회논문집
• /
• 제23권4호
• /
• pp.428-435
• /
• 2015

This paper presents the experimental study of cabin thermal comfort using a cold storage heat exchanger in a vehicle air-conditioning system. Recent vehicle-applied ISG functions for fuel economy and emission, but when vehicles stop, compressors in the air-conditioning system stop, and the cabin temperature sharply increases, making passengers feel thermal discomfort. This study conducts thermal comfort evaluation in the vehicle, which is applied to a cold storage system for the climate control wind tunnel test and the vehicle fleet road test with various airflow volume rates and ambient temperatures blowing to the cold storage heat exchanger. The experimental results, in the cold storage system, air discharge temperature is $3.1-4.2^{\circ}C$ lower than current air-conditioning system when the compressor stops and provides cold air for at least 38 extra seconds. In addition, the blowing airflow volume to the cold storage heat exchanger with various ambient temperature was examined for the control logic of the cold storage system, and in the results, the airflow volume rate is dominant over the outside temperature. For this study, a cold storage system is economically useful to keep the cabin at a thermally comfortable level during the short period when the engine stops in ISG vehicles.

• 설비공학논문집
• /
• 제24권12호
• /
• pp.875-880
• /
• 2012

The field of the large volume heat exchanger for wasted heat recovery ventilation system is being expanded enormously seeing as the fact that the quantity of reducing energies are huge due to the large volume heat exchanger for wasted heat recovery system at large buildings and factories, which consume large amount of energies while it has been arising huge amount of losses in Korea because of the lack of technology. To develop large volume waste heat recovery heat exchanger, rotor type heat exchanger was simulated for the surface corrugation. Based on the simulation results produced $30,000m^3/h$ grade waste heat recovery, heat exchanger was performed for the actual experiment. In addition, performance tests exceed the capacity of a large waste heat recovery heat exchanger performance test methods proposed.

• 한국농공학회논문집
• /
• 제61권4호
• /
• pp.55-61
• /
• 2019

Motor pumps cannot be used in those areas where electricity is not accessible such as remote rural areas in many African countries. Hydraulic ram pump is one of the solutions for supplying water for irrigation or domestic uses. The hydraulic ram pumps are working based on the water hammer effect for pumping without external power or electricity. This study was conducted to investigate the effect of air chamber volume and operation parameters on the performance of the hydraulic ram pump which was assembled with common plumbing parts. The experimental results showed the volume of the air chamber did not affect the performance such as discharge rate and head. When drive heights were 1.7 and 2.35 m, the maximum discharge heads were up to 7 m and 10 m, respectively. When the air chamber volume was 1 L, discharge rates were 0.23 and 2.12 L/min under the drive heights of 1.7 and 2.35 m, respectively. The average energy efficiency of the hydraulic ram pump assembled in this study was about 60% for all the experimental conditions.

• 한국농공학회지
• /
• 제36권4호
• /
• pp.87-94
• /
• 1994

The aim of the work descrihed in this paper is to study a characteristics of an unsaturated soil for the different matric suctions. To this end, a series of suction controlled isotropic and triaxial compression tests is conducted on silty sands. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. Total volume change, air and water volume changes are measured by the device made for the experiment. The specimens are compacted using a half of Proctor compaction energy and with the water contents of 5% drier than the optimum moisture contents. Isotropic compression and triaxial compression tests are conducted on the specimen at each equilibrium state of matric suction. From test results, volume changes and deviator stresses are analyzed at each state and their relationships are formulated.

• 한국대기환경학회:학술대회논문집
• /
• 한국대기환경학회 2000년도 춘계학술대회 논문집
• /
• pp.129-133
• /
• 2000

환경대기중 입자상물질의 검사방법은 환경부고시 97-98호(97. 11. 5)에 의거 고용량공기포집법(high volume air sampler), 저용량공기포집법(low volume ai sampler), 광산란법 및 광투과법 그리고 $\beta$흡수법 등으로 되어 있다. 이중 고용량공기포집법, 저용량공기포집법, $\beta$흡수법등은 중량법의 범주에 드는 측정법으로 되어 있다. 이들 방법 중 먼지채취전후의 무게를 직접 칭량하여 분석하는 고용량공기포집법은 총부유먼지의 측정법으로, 저용량공기포집법은 $PM_{10}$의 분석에 이용되는 것이며 $PM_{10}$ 고용량공기포집기($PM_{10}$ high volume air sampler) 또는 $PM_{10}$ 분석에 이용될 수 있다. (중략)

• 한국자동차공학회논문집
• /
• 제4권3호
• /
• pp.156-167
• /
• 1996

The present work is a continuation of our previous study to investigate the effects of parameters such as equivalence ratio, hydrogen supplement rate and initial pressure on combustion characteristics in a disk-shaped constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The flames in near stoichiometric mixture of methane-air are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed to an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate. Also, flame is sluggishly propagated at increased initial pressure in combustion chamber. Volume fraction of burned gas and flame radius as the combustion characteristics are increased by increasing the hydrogen supplement rate, especially at the combustion middle period, but then are slowly increased by increasing the initial pressure.

• 한국항공우주학회지
• /
• 제47권12호
• /
• pp.881-889
• /
• 2019

가스터빈 이차 유로의 프리스월 시스템은 터빈의 효율을 높이고 소재의 수명을 연장하기 위해 설치되는 냉각 장치이다. 본 연구에서는 프리스월 시스템의 설계점을 기준으로 가스터빈 외기 온도와 터빈 부하 변화에 따른 탈설계점 분석을 수행하였다. 탈설계점에서 내부 유동의 특성을 분석하기 위하여 유량계수와 단열계수를 비교하였다. 터빈 부하 증가에 따라 시스템 내부 냉각 공기의 체적 유량이 증가하였고, 단열계수 또한 20% 터빈 부하와 비교하여 100% 터빈 부하에서 30.46% 상승하였다. 외기 온도가 증가할수록 질량 유량과 냉각 공기의 밀도는 감소하였지만 체적 유량은 상승하였으며, 결과적으로 프리스월 시스템 내부의 냉각 성능은 향상되었다. 프리스월 시스템 출구에서 -20℃ 외기 온도와 비교하여 55℃ 외기 온도의 단열계수는 14.82% 향상되었다.

• 반도체디스플레이기술학회지
• /
• 제20권4호
• /
• pp.89-95
• /
• 2021

As the influence of fine dust on society spreads gradually, the public's interest in indoor air is increasingly rising. Air-purifying plants are drawing keen attention due to their natural purifying function enabled by plant physiology. However, as their fine dust reduction mechanism is limited to adsorption only, vegetation bio-filters that optimize purification effects through integration with air-conditioning systems is rising as an alternative. In accordance with the relevant standard test methods, this study looked into the fine dust reduction assessment method by air-conditioning airflow volume that can be used for the industrial spread of vegetation bio-filters. In the case of PM₁₀ at 300 ㎍/m³, it was in the order of EG-B(3,500CMH, 29 min.) < EG-A (2,500CMH, 37 min.) < CG(0CMH, 64 min.) for reaching the maintenance level (100 ㎍/m³) of publicly used facilities. For reaching the WHO Guideline(50 ㎍/m³) requirement, it was in the order of EG-B (51 min.) < EG-A (160 min.) < CG (170 min.). In the case of PM_2.5, it was in the order of EG-B (26 min.) < EG-A (33 min.) < CG (57 min.) for reaching the maintenance level (50 ㎍/m³) of publicly used facilities. It was in the order of EG-B (48 min) < EG-A (140 min) < CG (158 min) for reaching the WHO Guideline (25 ㎍/m³) requirement. The findings from the analysis showed that fine dust can be reduced most efficiently when the system is operated at 3,500CMH level. The limitation of this study is that due to the absence of a way of assessing the stress of plants in vegetation bio-filters, generating optimal air-conditioning air flow of the relevant system and economics analysis against the existing facility-type air purification system have been clarified, which should be explored further though follow-up studies.