• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.6
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• pp.751-758
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• 2015

Noise prediction for HVAC(Heating, Ventilating and Air Conditioning) systems are normally performed by empirical method suggested by NEBB(National Environmental Balancing Bureau, 1994). However, the method is not suitable for large ducts in ships. In this paper, computational analysis methods are used to develop a noise prediction method for the large ducts in ships. To develop regression formula of attenuation of sound pressure level in large ducts, Boundary Element Method(BEM) is used. BEM and Computational Fluid Dynamics(CFD) are applied to the analysis of flow-induced noise in ducts with stiffeners inside. Loud noise above 100 dB can be generated in some cases. Breakout noises of large ducts are also analyzed by using BEM and Finite Element Method(FEM). The acoustic pressure level shows about 10-15dB difference between inside and outside of the duct. Utilizing the results of this study, it is expected that shipyard planners can predict noise of the HVAC system for ships.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.126-127
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• 2014

• Journal of KSNVE
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• v.10 no.5
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• pp.892-897
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• 2000

In this paper, experimental methods to find acoustic characteristics of acoustically treated air-conditioning duct system are proposed. Existing methods to analyze acoustic properties of duct with absorbent material have dilemma which has to assume the wave in duct to be a plane wave. Under this assumption. applicable frequency limitation makes accurate analysis of practical air-conditioning system impossible. In order to analyze the properties of in-lined treated absorbent with high degree of accuracy, in this experiments the range of exciting frequency of sound source is broadband, which means that source speaker excited higher mode of in-duct sound field. Also, to define the relations of air cavity to the acoustic characteristics, acoustic experiments on ducts with air cavity of different depth are operated. In conclusion, air-cavity makes the absorbing ability of duct improved in low frequency range. Due to the interactions between the air cavity depth and the depth of absorbents, according to depth of cavity, the magnitude of absorption coefficients vs frequencies in specific range is changed. In lower frequency range, the absorption of sound energy by air cavity is more dominant than by absorbent itself, in higher range, the inversion is true.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.130-135
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• 2002

Bypass air conditioning systems are divided into three types; outdoor air bypass, mixed air bypass and return air bypass system. Among bypass air conditioning systems, a return air bypass system is more effective than other two systems because it doesn't induce unconditioned outdoor air into conditioned room. The numerical study on the bypass air conditioning system shows this system can maintain indoor RH(Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. A simulator was built to compare results of a numerical experiment and those of a simulator experiment. The results of the simulator experiment was nearly same as those of the numerical experiment; when a design sensible load (the ratio of sensible load to total sensible load) was 70 percent (at this time, RSHF=0.7), indoor relative humidity (in case of both numerical experiments and simulator experiments) was maintained below 60% specified by ASHRAE STANDARD 62-1999. The bypass air conditioning system is expected to be applied to many buildings where the Percentage of latent loads or air change tate is high.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.3
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• pp.116-121
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• 2021

A lot of research is being done to develop a high-efficiency heat pump to save energy, and research to reduce or eliminate the phenomenon of frost occurring in the outdoor unit coil is also being conducted at the same time. A curved constant temperature chamber was constructed that can be tested under the same conditions as in the natural state so that the research can be conducted in which frost does not occur on the outdoor unit of the heat pump regardless of the season. Simulations were performed to verity whether such a curved constant temperature chamber has feasibility as an experimental device. For CFD conditions, the length of the straight duct in front of the outdoor unit located in the duct-type constant temperature chamber was 1, 5, 10 and 15 times the diameter of the duct. As a result, it was found that a straight space must be secured 10 times the diameter of the duct.

• The Journal of the Acoustical Society of Korea
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• v.12 no.2E
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• pp.88-95
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• 1993

공조덕트계에 소음 챔버를 설치하여 발생되는 음향투과손실을 유한요소법에 의하여 산출하는 방법을 검토하였다. 여기서는 음장내의 네트음향인텐시티를 입사파와 반사파의 인텐시티로 분리하므로서 투과손실의 산출을 가능하게 하였다. 산출방법의 타당성을 검증하기 위하여 형상과 내부흡음조건이 다른 소음챔버를 대상으로 수치해석과 모형실험을 실시한 결과, 양자는 잘 일치하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1055-1062
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• 2011

The purpose of this study is to develop the shape of photocatalyst-coated module for improve the IAQ, which is installed at inside of ductwork and detachable. Including 3 column types(square, circle, diamond) and 2 fin types(diamond and square), totally 5 types are previously declared for numerical analysis and comparison, 5 types are. As the results of numerical analysis, almost the velocity varied at the range of ${\pm}0.3m$ from the module, except the Type A-3(diamond column type) which is affected to ${\pm}0.4m$ range and shows the biggest velocity differences. Among the 5 types, the diamond fin type(Type B-1) is analyzed as the most stable in velocity. And the results of local pressure drop show that the difference of pressure coefficient of Type B-1 is computed as 0.59, and that of Type A-3 is 2.44. Meanwhile, from the effect analysis of the number of module, the flow conflict happens and the pressure difference between before and after the module increases if there are over 3 modules inserted.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.29-34
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• 2006

Although the importance of good conservation of historic sites including ancient royal tombs is well aware, still not much attention has been paid for the facilities and systems to preserve those historic sites, which includes precious artifacts as wall paints and carved works, etc. Even the level of general understanding about the environment of the underground space of tombs is not satisfactory. In Korea, researchers have recently begun addressing the importance of maintaining proper environment for underground space as of ancient tombs and are making efforts to develop suitable HVAC(heating, ventilating and air-conditioning) systems for them. In this study, an HVAC system for a tomb ($D{\times}W{\times}H=1.3m{\times}3.0m{\times}1.2m$) was installed to maintain suitable indoor conditions for conservation of tomb. The temperature and humidity inside the tomb were measured to represent the performance of the installed duct-type HVAC system. Vibration levels due to the installed an HVAC system are alive investigated experimentally. According to the measured data, the level of vibration inside the present model tomb with the duct-type unit showed significantly lower values than the case with the indoor unit inside.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.121-122
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• 2008

본 논문에서는 2차 경로의 추정을 통하여 안정성이 강화된 능동소음 제어 시스템을 제안한다. LMS 알고리즘은 구조가 단순하고 계산량이 적은 장전이 있지만, 광대역 소음원에 적용할 경우 수렴 성능이 좋지 않은 단점이 있으며, 2차 경로 및 소음원 입력의 파워가 시변 할 경우 적응 알고리즘의 안정성이 약화되는 문제점이 발생한다. 본 논문에서는 지속적으로 누적 오차를 추적하여 일정 값 이상으로 증가하면 자동적으로 2차 경로 전달함수를 새로 추정하는 자동오프라인 추정 기법을 제안하였다. 공조용 덕트에 광대역 소음을 적용하여 제안된 능동소음제어 시스템을 실험을 수행한 결과 우수한 특성을 얻었다.

• 월간 기계설비
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• s.167
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• pp.16-19
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• 2004

관악구 신림동에 위치한 관악우체국 청사 개축 기계설비공사는 정보통신부 조달사무소로부터 분리발주로 수주된 현장이다. 미작산업(주)(대표 배태석)와 (주)광운기전(대표 이광수)이 기계설비공사를 공동도급으로 시공하고 있으며 미작산업이 51%, 광운기전이 49%의 공사를 맡고 있는데 기계실 및 공조배관, 덕트. 위생배관 등 주요 공사는 광운기전이, 정화조, 자동제어, TAB, 연도 등 주로 외주제작은 미작산업이 시공하고 있다. 원래는 광운기전과 일성공업이 공동으로 수주받았으나 일성공업이 부도나는 바람에 일성공업의 보증업체인 미작산업으로 대체된 것이다. 공사금액은 13억9천 5백만원으로 지난 2003년 10월에 시작하여 오는 2006년 1월까지 완공예정이었으나 공사의 빠른 진행으로 6개월여를 앞당겨 오는 2005년 6월경 완공 예정이다.