• 생물환경조절학회지
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• 제13권3호
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• pp.162-166
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• 2004

동절기 시설내 온도분포를 균일하게 하기 위하여 온풍난방기용 이중덕트를 개발하고자 본 연구를 수행한 결과 관행 온풍덕트의 각 지점간 토출구 송풍온도 차이가 13 ～ $14^{\circ}C$인데 비하여 개선형 덕트인 이중덕트의 토출구 송풍온도 차이가 3 ～ $4^{\circ}C$로 나타나 각 지점간의 온도 불균형이 크게 개선되었으며 이중덕트의 각지점간의 생육정도도 관행덕트에 비해 크게 향상 된 것으로 나타났다. 수량에 있어서도 관행덕트를 사용한 재배시설에서 10a당 3,924kg에 비하여 이중덕트를 사용한 재배가 4,616kg으로 약 17%가 증수되었다. 그리고 반촉성 재배기간 동안 난방에 소요된 연료소모량은 관행덕트가 3,724ι/10a인데 비하여 이중덕트가 3,233ι 13%의 연료절감효과가 있다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.479-486
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• 1999

The noises generated from the air-conditioning duct are known to strongly affect the indoor-noises of high speed trains. The acoustic characteristics of an air-conditioning duct should depend on the geometry and shape of the duct. The structural material for Korean high speed train is supposed to be changed from Steel, which was used for TGV, to Aluminum in order to reduce the total train weight. Accordingly, the shape and layout of the air-conditioning duct of Korean high speed train will be different from that of TGV. Thus, this paper introduces a analytical method to predict the noise attenuation through the air-conditioning duct, based on the ISO 7235. In this method, the whole duct is divided into several pieces and the noise attenuations predicted for each duct piece are integrated to get the noise attenuation for the whole duct system. The validity of the method introduced herein is discussed through some numerical tests.

• KIEAE Journal
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• 제9권4호
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• pp.17-22
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• 2009

It is common to design the duct branches where to supply the required air flow for individual room in residential apartment house. However it is difficult to adjust the air volume adequately in small air duct branches in residential ventilation system. The purpose of this study is to figure out the performance of Multidrop chamber coupling system for the residential ventilation system. The experiments were designed to simulate apartment of $84m^2$ and established multidrop chamber duct and general duct on the ceiling of the apartment. Distribution performance of air supply rate were evaluated in this experiments. As a result, distribution performance of air supply rate in the general duct is different from designed air supply rate by about 35% ~ 50% and about 10% in the multidrop chamber system. In additional the sound insulation performance of the multidrop chamber system decreased about 20% compared with general duct system. Therefore, the multidrop chamber system is considered to satisfy proper air supply rate of each room and to improve the sound insulation performance in apartment Houses.

• 설비공학논문집
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• 제10권4호
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• pp.389-397
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• 1998

A loop duct system is often found in a VAV-HVAC(variable air volume heating, ventilating and air conditioning) design. It is known that the simple T-method is not be applicable to the loop duct system and cannot be used to calculate the flow rate and the pressure drop at each duct section of the loop duct system. In this paper, the extended T-method has been developed and it is found to be applicable to the loop duct system to which the simple T-method cannot be applied. The validity of the extended T-method has been verified by using to solve for a simple, ideal loop duct system for which there exists analytical solution. In addition, the extended T-method is employed to compute the loop duct system of a real building with an area of 380$m^2$. The results show that the computed flow rate at the exit differs from the designed flow rate by a range of -13.6~43.5 %. Consequently, three design factors must be adjusted in order that the flow rate may be balanced. These include the duct sizes, in terms of their lengths and diameters, the sub-duct locations and the positioning of damper which is found upstream of the exit duct.

• 설비공학논문집
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• 제13권3호
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• pp.160-166
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• 2001

A numerical analysis has been performed for natural convection in an air conditioner duct system. The governing equations were solved a finite volume method using a SIMPLE algorithm. In the calculation mode of duct, the room temperature was preserved at $25.0^{\circ}C$ and duct wall temperature had a temperature of 15, 20.0, 22.5, 23.75, 26.25, 27.5 30 and $35^{\circ}C$. The results of velocity vectors and contours have been represented for various parameters. Based on the numerical data, the relationships between temperature difference and flow rate into room was represented. In the case of $T_\gamma>T_\omega$, the equation for temperature difference and flow rate was $Q=0.0285\triangleT^0.4005$, and in the case of $T_\gamma>T_\omega$, the equation was $Q=0.0099\triangleT^0.4752$. The duct system has an important relation to room temperature and duct wall temperature.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.345-350
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• 2003

The inside of EMU is supplied with the cooling air from air-conditioner and the fresh air from exterior through the air-conditioner duct which is one of the air conditioning system. The shape of air-conditioner duct is a major factor in determining the air-conditioning efficiency, thermal comfort and energy efficiency. Therefore, this study is to understand the flow characteristics in the air-conditioner duct by three dimensional numerical simulation. The air-conditioner duct was calculated for the design volume flow rate, $2,726\;m^3/h/unit$. From the result of calculation and measurement, the velocity at diffuser outlet presented good agreement in general. [n this present study, the calculation was also performed for three volume flow rate(1,800, 2,200, 3,000 $m^3/h/unit$) and total pressure characteristic curve with volume flow rate was presented.

• 플랜트 저널
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• 제6권2호
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• pp.62-69
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• 2010

The stability of coal pulverizer in the 800 MW coal-fired plants is vital to maintain their performance. Thus, this study analyzed the uneven abrasion of the deflector and coal spillage due to the air velocity maldistribution in the vane wheel of a bowl-type pulverizer as it is a possible cause for problems of facility using pulverized coal. In addition, air flow in the underbowl of a bowl-type pulverizer was studied to check air velocity maldistribution in the vane wheel using numerical method. In an attempt to correct the maldistribution of air velocity, air flow of the modified duct vane was studied as enlarging the length of the duct vanes installed at the air inlet duct of the pulverizer and increasing the angle of inclination. It was found that modified duct vane make the velocity distribution at the vane wheel uniform. formed by the duct vanes installed at the air inlet duct of the pulverizer and swirling flow is the major factor in making the velocity distribution of vane wheel exit uniform. This can prevent the uneven abrasion of the deflector, which is one of the components inside the pulverizer and coal spillage.

• 한국농공학회지
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• 제19권3호
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• pp.4483-4491
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• 1977

The results obtained are as follows; 1. The variation of the temperature in a vinyl house without heating system is similar to that of air temperature in a day. The difference of maximum temperature and minimum one in a day is 27$^{\circ}C$ which is two times greater than the daily difference of air temperature. 2. When the length of the duct is increased, the high temperature zone is built up in the direction of warm air discharge from the duct, and the low temperature zone is built up in the opposite direction of warm air discharge. But, in case of the duct length is short (0.05 L), the temperature distrubution in a vinyl house become uniform. It is concluded that the shorter length of the duct, the better the distribution of the temperature in a vinyl house is. 3. When the duct is installed at high position, the high temperature zone is built up in the upper zone of the vinyl house and the low temperature zone is built up in the lower zone. And when the position of the duct is low, the rate of temperature variation along the vertical direction become high, and the direct contact of warm air with the plant in the house is occured. It is concluded that the duct should be installed at the position of slightly higher than the plant height. 4. When the fuel consumption rate is fixed at the 101/hr, the lowest temperature warming rate in the vinyl house is 5$^{\circ}C$ without regard to the air temperature.

• 한국기계가공학회지
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• 제16권2호
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• pp.50-55
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• 2017

This study is about the distributions of flow in an air conditioning duct used for marine and oil drilling ships. Three-dimensional steady state turbulence was assumed as a governing equation for describing the flow in the air conditioning duct in this study. We compared the flow field with the pressure distribution according to the inlet velocity for two types of air conditioning duct, and stress and safe factors were simulated using ANSYS W/B. The result of fluid analysis showed an increased pressure drop in the duct according to the inlet velocity. Furthermore, secondary flow and complicated flow characteristics occurred at the bellows zone.

• 소음진동
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• 제10권5호
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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.