• Title/Summary/Keyword: Air flow control

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Development of Dissolved Air Flotation Technology from 1st Generation to the Newest or 3rd One (Very Thick Microbubble Bed) with High Flowrates DAF in Turbulent Flow Conditions (차세대 고효율 용존공기 부상공정(High Rate DAF)의 개발)

  • Kiuru, H.J.
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.2
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    • pp.228-234
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    • 2004
  • Dissolved air flotation (DAF), in which suspended solids are removed from water by means of micro-size air bubbles raising slowly up in water and lifting solids from water (smaller than those) attached onto the micro-bubbles as well as those (larger than solids) being attached on these, have been used in water and wastewater since 1920s. The dissolved air flotation technology was originally based on the laminar flow conditions prevailing in water to be treated, but the latest development in that technology has led now to a situation, in which the flow conditions may also be turbulent ones in the modem dissolved air flotation units. Despite of that, the flotation phenomenon used in this unit operation for removal suspended solids from water or wastewater is still the same.

Comparative Part Load Performance Analysis of Gas Turbine Power Generation Systems Considering Exhaust Heat Utilization (배열 이용도를 고려한 가스터빈 발전시스템의 부분부하 성능 비교분석)

  • Kim, T.S.
    • The KSFM Journal of Fluid Machinery
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    • v.6 no.3 s.20
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    • pp.28-35
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    • 2003
  • This paper presents analysis results for the effect of power control strategies on the part load performance of gas turbine based power generation systems utilizing exhaust heat of the gas turbine such as combined cycle power plants and regenerative gas turbines. For the combined cycle, part load efficiency variations were compared among different single shaft gas turbines representing various technology levels. Power control strategies considered were fuel only control and IGV control. It has been observed that gas turbines with higher design performances exhibit superior part load performances. Improvement of part load efficiency of the combined cycle by adopting air flow modulation was analyzed and it was concluded that since the average combined cycle performance is affected by the range of IGV control as well as its temperature control principle, a control strategy appropriate for the load characteristics of the individual plant should be adopted. For the regenerative gas turbine, it is likewise concluded that maintaining exhaust temperature as high as possible by air flow rate modulation is required to increase part load efficiency.

A Method to Reduce Flow Depth of a Plate Heat Exchanger without a Loss of Heat Transfer Performance (판형 열교환기의 열전달성능 손실 없이 유동방향 길이를 축소하는 방법)

  • Song Gwi-Eun;Lee Dae-Young
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.2
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    • pp.129-136
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    • 2006
  • Optimal design of an air-to-liquid finned plate heat exchanger is considered theoretically in this study. Based on existing correlations for the pressure loss and the heat transfer in channel flows, the optimal configuration of the plate heat exchanger including the optimal plate pitch and the optimal fin pitch is obtained to maximize the heat transfer within the limit of the pressure drop for a given flow depth of the plate heat exchanger. It is found that the optimal fin pitch is about one ninth of the optimal plate pitch. In the optimal configuration, the flow and thermal condition in the channels is just at the boundary between the laminar developing and laminar fully developed states. It is also found when reducing the flow depth of plate heat exchangers for compactness, the heat transfer performance can be maintained exactly the same if the geometric parameters such as the plate thickness, plate pitch, fin thickness, and fin pitch are reduced proportional to the square root of the flow depth as long as the flow keeps laminar within the heat exchangers.

A Study on the Individual Room Control of Radiant Floor Heating System in Apartment Buildings (공동주택에서 바닥복사 난방시스템의 실별 제어에 관한 연구)

  • 김오봉;이미경;김광우;여명석
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.5
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    • pp.421-429
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    • 2004
  • In Korea, the radiant heating system has been widely used as a residential heating method, which has been modernized to use hot water running into the tubes embedded in the floor structure. According to the recent improvement of living standard of residential buildings, the requirement of the thermal comfort and energy saving in heating system has been raised. Until now, the radiant floor heating system has been controlled by room thermostat installed in the living room, but for better thermal comfort, an individual room control method is adopted as an alternative. Therefore, it is necessary to evaluate the control performance between the current control method and the individual room control method. In this study, the control performance between the two systems is evaluated through the field experiment. And the control performances of room air temperature and energy performances are analyzed through the simulation using TRNSYS. Firstly, the simulations are performed in the various outdoor conditions and the flow rates and the simulation results are analyzed for the control performances. Also, to evaluate the energy performance, the simulations are performed under the operating conditions in which the set-point of the room air temperature is fixed or changed according to the schedule of occupancy, and the simulation results are analyzed between the two methods.

The refrigerant flow noise from the A/C distribute pipe line shapes (A/C 실내기 배관 형상에 따른 냉매 유동 소음 특성에 관한 연구)

  • Bae, Seong-Won;Huh, Deok;Oh, Sai-Kee;Chung, Baek-Young;Oh, Il-Kwon
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.371-375
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    • 2009
  • The distribution control of refrigerant flow is one of the basic technique to enhance system efficiency. However, if engineers forget to control the refrigerant flow speed in all operation range, refrigerant flow mal distribution becomes a noise source. The refrigerant flow noise should be checked and controlled at the lowest air flow mode which is the most silent mode and frequently used in night time.

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Implementation of Fuzzy Logic Control for Air Conditioning Systems

  • Mongkolwongrojn, M.;Sarawit, V.
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.1264-1267
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    • 2005
  • Fuzzy logic control has been widely applied for handling the system which has uncertainty or high robust system. Since the dynamic behaviors of the systems contain complexity and uncertainty in its parameters, several fuzzy logic controllers have been implemented to control room temperature in the field of air conditioning system. In this paper, the fuzzy logic control has been developed to control both in door temperature and humidity in the air conditioning systems. The manipulating variables are speed of compressor, heater and supply air flow rate. The microcomputer was used to interface with in system. The experimental results show the superior of multivaiable fuzzy logic control to keep room temperature and humidity in air conditioning system for the best comfortable.

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