• Title/Summary/Keyword: Air duct

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Improving the Distribution of Temperature by a Double Air Duct in the Air-Heated Plastic Greenhouse (시설내 온도분포 균일화를 위한 온풍난방기용 2중 덕트개발)

  • 김태영;김기덕;조일환;남은영;남윤일;우영회;문보흠
    • Journal of Bio-Environment Control
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    • v.13 no.3
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    • pp.162-166
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    • 2004
  • Air temperature variation along the length of the air duct in an air-heated plastic greenhouse was large, 13 ~ 15$^{\circ}C$ between the front and the rear side of a greenhouse. To reduce this temperature variation, a new PE-film air duct having a small duct inside a large duct (double duct) was developed. This double duct was consisted of an inner duct with air outlets at a 0.15 m interval and an outer duct with air outlets at a 2.5 m interval. Diameters of the air outlet holes were 7, 15, and 35 cm from the front to the end of the inner duct film, while identical 10 cm holes were used on the outer duct film. As a result, air temperature was $46^{\circ}C$ at the beginning side and $47^{\circ}C$ at the ending side, while the conventional single duct had $53^{\circ}C$ at the beginning point and $38^{\circ}C$ at the ending point with a variation of $15^{\circ}C$. Height of a cucumber crop grown in a greenhouse with the new double air duct system was 65.5 cm, 14% increase as compared to that in a greenhouse with a conventional air duct system. Total fruit yield per l0a greenhouse in a greenhouse with the new double air duct system was 4,616 kg, which was 17% greater than that in a greenhouse with a conventional air duct system. Amount of heating oil consumption during March 3 to April 24, 2002 was 3,233 L per l0a greenhouse with the new double air duct system, which was 13% less than that with a conventional air duct system.

A Study for the Design of the Air-Conditioning Duct of Korean High Speed Train (한국형 고속전철의 에어컨 덕트 설계를 위한 연구)

  • 이승민;박철희;이우식
    • Proceedings of the KSR Conference
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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.

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Performance Evaluation of Multidrop Chamber Ventilation System in Apartment (공동주택 적용을 위한 다분기챔버 환기 시스템의 성능평가에 관한 연구)

  • Kim, Sung Soo;Sohn, Jang yeul
    • KIEAE Journal
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    • v.9 no.4
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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.

Analysis of loop duct system by extended T-method (확장 T-method에 의한 환상식 덕트시스템 해석)

  • 이승철;문종선;이재헌
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.4
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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.

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Numerical study on the flow characteristics in Air-conditioner duct of EMU (전동차 공조기 덕트 내의 유동특성에 관한 수치해석적 연구)

  • Kim Seung-Tech;Kim Sung-Jong;Park Geun-Soo;Park Hyung-Soon
    • Proceedings of the KSR Conference
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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.

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Improvement of Maldistributed Air Velocity in the Vane Wheel of a Bowl Type Pulverizer (바울형 미분기 베인휠에서의 유속 불균일 개선에 관한 연구)

  • Park, Deok-Bae;Hur, Jin-Huek;Moon, Seung-Jae
    • Plant Journal
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    • v.6 no.2
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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.

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Study on the Vinyl House Heating by Warm Air (농업용 비닐하우스의 온풍난방에 관한 기초적 연구)

  • 조진구;이근후
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.19 no.3
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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.

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Numerical Analysis of the Development of an Air Conditioning Duct for Marine and Oil Drilling Ships (해양 시추선용 공조덕트 개발에 대한 수치해석)

  • Yi, Chung-Seob;Chin, Do-Hun
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.16 no.2
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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.

A Survey for the Air Treatment System according to the Position of HVAC and the Feature of Air Duct Structure in the Train (철도 차량의 HVAC 위치에 따른 공기조화 시스템 및 Air Duct 구조의 특성에 관한 고찰)

  • Jung, Hwa-Sic;Park, Jae-Hong;Yeom, Gyu-Hak
    • Proceedings of the KSR Conference
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    • pp.1330-1335
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    • 2007
  • The HVAC and the air duct is to make optimal indoor environment. By the HVAC position, method and the air duct construction, the important elements can affect on cooling performance, passengers' convenience, and energy efficiency. According to this, there are features, such as the indoor temperature distribution, cooling performance, velocity distribution from diffuser, tend to be come out variously. Also, comparing and analysing temperature distribution, cooling performance, air velocity, noise based on the real practical vehicle tests, it shows features in detail. Besides, it can lead to make design the system of HVAC & air duct effectively.

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A Study on the Absorption Characteristics of Absorbents in Duct System with the Air Cavity (공기층을 갖는 공조덕트 구조물에서 흡음재의 흡음특성에 관한 연구)

  • 김찬묵;김도연;방극호
    • 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.

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