• Title/Summary/Keyword: Characteristics of Cold Air Flow

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Cooling Characteristics at Hot Side of the Thermoelectric Module for an Air Conditioner (열전모듈을 이용한 에어컨의 방열부 냉각특성에 대한 연구)

  • 김서영;강병하;장혁재;김석현
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.3
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    • pp.214-220
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    • 2002
  • A small air conditioner using thermoelectric module has been designed and built. Three types of cooling methods, such as air cooling, closed-loop water cooling, and evaporative cooling, for hot side of thermoelectric module have been investigated. Among three types of cooling method, the evaporative cooling method is seen to be the most effective to achieve the steady state operation of a thermoelectric air conditioner The system performance with evaporative cooling method are also studied in detail for several oprating parameters, such as input power to the thermoelectric module, water or air flow rate at the hot side, and air flow rate at the cold side. The results obtained indicate that the cooling capacity of a system is increased with an increase in the input power to the thermoelectric module while the system COP is decreased. It is also found that the optimal air flow rate as well as water flow rate at the hot side is needed for the best system performance at a liven operating condition. Both the system COP and cooling capacity are increased as the air flow rate at cold side is increased.

Study on Atomization Characteristics of Shear Coaxial Injectors (전단동축형 분사기들의 미립화 특성에 대한 연구)

  • Ahn, Jonghyeon;Lee, Keunseok;Ahn, Kyubok
    • Journal of ILASS-Korea
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    • v.26 no.1
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    • pp.9-17
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    • 2021
  • Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

A Study on the Spray and Combustion Characteristics of Gasoline Direct Injector (가솔린 직분식 인젝터의 분무 및 연소특성에 관한 연구)

  • 신민규;박종호;유철호;이내현;최규훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.5
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    • pp.114-122
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    • 1997
  • Nowadays, gasoline direct injection engines are being commercialized by virtue of improvement in control technology of spray, flow, air fuel ratio. The stratified charge type has the advantage of improving lean limit. The homogeneous type has the advantage of reducing engine-out hydrocabon emissions in the first 30 seconds after a cold start, in addition, improving transient air fuel ratio control. The vaporization and mixing if injected fuel with air has to e completed in a short time and the fuel film in cylinder and on piston has to be minimized. So, the flow and injection should be well controlled. This paper surveyed the spray characteristics of gasoline direct injection by using laser equipment and the combustion characteristics of the single cylinder engine using homogeneousas-mixture type gasoline direct injection.

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Experimental Investigation for the Characteristics of Energy Separation of a Vortex Tube at Various Inlet and outlet Pressure Conditions (입.출구의 압력조건에 따른 보텍스 튜브의 에너지분리 특성에 관한 실험적 고찰)

  • 유갑종;김정수;최인수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.11
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    • pp.1149-1155
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    • 2001
  • The experimental investigation on energy separation in a vortex tube has been carried out to sow the effect of inlet and outlet pressures with various working fluids(air,$O_2,\;and\; CO_2$). Those outlet pressure means cold outlet and hot outlet pressure which were set equally. The results showed that the total enthalpy variation became a maximum when the mass flow rate at the cold outlet was a half of the total mass flow rate in the vortex tube (y=0.5). The total enthalpy variation was quite affected by the pressure difference between the inlet and outlet of vortex tube when the ratio of the inlet pressure to the cold outlet pressure remained constant. Although specific enthalpy differences between the inlet and the outlet (both cold and hot outlet) did not noticeably vary with the pressure difference, the specific enthalpy difference between the inlet and cold outlet was dominantly affected by physical properties of working gases.

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Characteristics of Cooling Temperature of Cold Water Pipes Buried in the Wall of a Small Mobile Modular House (소형 이동식 모듈주택의 벽면에 냉수배관 매설에 의한 냉방온도 특성)

  • Cho, Dong-Hyun
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.3
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    • pp.110-117
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    • 2022
  • A chiller cooler absorbs the thermal energy of water to generate cold water and supplies the generated cold water to a cold water pipe buried in the wall of a small mobile modular house to greatly increase the cooling area. An attempt was made to reduce the required cooling time significantly. A small chiller cooler suitable for the cooling load of a small mobile modular house with an area less than 3.3 m2 was employed. When cooling is done during summer using a chiller cooler installed outdoors, heat absorption energy loss occurs in the cold water pipe owing to the high temperature. To address this, a study was conducted to reduce the endothermic energy loss significantly. As the mass flow rate of the cold water flowing inside the cold water pipe increased, the temperature decrease gradient of the cold water increased. From the start of the cooling operation, the air temperature of the small mobile modular house decreased linearly in proportion to the operation time. Furthermore, the temperature of the air inside the small mobile modular house decreased in proportion to the increase in the flow of water inside the cold water pipe.

Analysis of the Cold Air Flow in Suwon for the Application of Urban Wind Corridor (도시 바람길 활용을 위한 수원시 찬공기 유동 분석)

  • CHA, Jae-Gyu;CHOI, Tae-Young;KANG, Da-In;JUNG, Eung-Ho
    • Journal of the Korean Association of Geographic Information Studies
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    • v.22 no.4
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    • pp.24-38
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    • 2019
  • Due to the dramatic spatial changes caused by industrialization, environmental problems such as air pollution and urban heat island phenomenon, etc. are occurring in cities. In this case, the wind corridor, which is a passage through which fresh and cool air generated in forests outside cities move to the downtown, can be used as a spatial planning method for improving urban environmental problems. Cold air is determined by the characteristics of the flow depending on the topography and land use of cities, and based on this, the medium- and long-term plan should be established. Therefore, this study analyzed the flow of cold air at night through the KLAM_21 model in Suwon-si, Gyeonggi-do, to prepare the basic data required to apply the wind corridors. As a result, it turned out that cold air of Suwon-si was mainly generated from Gwanggyo Mountain that is a large mountain area in the north, and flowed into the urbanization promotion area, and about three hours after sunset, cold air flowed into the downtown. By district, the depth, wind speed, and direction of the cold air layer were formed differently according to the characteristics of the topography and land use. In the areas where large forests were adjacent, the flow of cold air was active. There are three main wind corridors where cold air flows to the downtown of Suwon-si, all of which are formed around rivers. Especially, if the connection between rivers and the surrounding green areas is high, the effect of wind corridors is found to be significant. In order to utilize the wind corridors of Suwon-si, based on the results of this study, it is necessary to make climate maps through actual survey and complex analysis of cold air flow and establish mid-to-long-term plans for the conservation and expansion of major wind corridors.

A Numerical Study on Low Noise Refrigerator Fans (저소음 냉장고용 팬의 운동 해석)

  • Kim, Wook;Jeon, Wan-Ho;Jung, Yong-Gyu;Kim, Chang-Joon
    • 유체기계공업학회:학술대회논문집
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    • 2003.12a
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    • pp.489-495
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    • 2003
  • A high performance and low noise refrigerator fan has been developed in order to satisfy the customer's high quality needs, that is, luxury, big size and low noise. In this study, the characteristics of a new developed fan and a current fan was calculated and compared by using numerical simulation. Rotation of a fan makes cold air circulation inside a refrigerator. A numerical simulation of air flow shows distribution and local flow regime of a cold air flow circulation, and revealed a cause of low noise as well. Optimization of a duct shape also decreased noise level.

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An Experimental Study on the Characteristics of Temperature Separation for the Formal Change of Counterflow Type Vortex Tube (대향류형 보텍스 튜브에서의 형상 변화에 따른 온도 분리에 관한 실험적 연구(I))

  • 황승식;전운학;김종철;이희상
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.1
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    • pp.84-93
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    • 2001
  • The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial temperature distribution and the radial temperature distribution in internal space of a tube. From the study, following conclusive remarks can be made. Average flow rate that flows into a tube is in proportion to square root of inlet pressure. As inlet pressure increases axial and radial temperature distribution in the inner space of vortex-tube increase. As mass flow rate ratio change, separation point moves.

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An Experimental Study on the Characteristics of Temperature Distribution in Internal Space of a Tube for the Formal Change of Counterflow Type Vortex Tube (대향류형 보텍스 튜브의 노즐형상 변화011 따른 튜브 내부의 온도분포에 관한 실험적 연구)

  • 황승식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.4
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    • pp.69-76
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    • 2002
  • The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial and the radial temperature distribution in internal spare of a tube. From the study, fellowing conclusive remarks 7an be made. First, As the number of nozzles increase, separation point move into the hot exit. Second, When we use guide vane type nozzle, the axial temperature distribution constant over the 0.75 of air mass flow rate radio. Third, When we use Spiral type nozzle, axial and radial temperature distribution in the inner space is higher than another nozzle. Fourth, Axial and radial temperature distribution in the inner space vortex-tube is determined by separation point. And separation point is moved by changing of air mass flow rate ratio. At last, A heating apparatus is possible far vortex-tube to use.

Secondary Air Injection Effect on Cold Flow in a Laboratory-scale Circulating Fluidized Bed Combustor (실험실 규모 순환유동층 연소로에서 2차공기 주입이 냉간유동에 미치는 영향)

  • Jang, S.D.;La, S.H.;Hwang, J.H.;Kang, K.T.
    • 한국연소학회:학술대회논문집
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    • 2000.12a
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    • pp.217-228
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    • 2000
  • Circulating Fluidized Bed Combustor(CFBC) has been used for the incineration of waste sewage sludge and for the power generation. In this study hydrodynamic characteristics of two phase flow have been studied in a riser section of CFBC. A lab-scale riser is designed and SiC (Geldart type B) is used for solid particles. Experiments are performed by controlling the fluidization parameters including superficial velocity and secondary air to primary air ratio for determination of solid holdup profiles in the riser. Superficial velocities of each fluidization regime are well agreed with results predicted by a theoretical model. The results show that the axial solid holdup distributions calculated by measuring differential static pressures in the riser are found to show a basic profile described by a simple exponential function. Our flow regime during experiments mainly belongs to fast fluidization regime for particle size of 300${\mu}m$. As the SA/PA ratio increases, solid holdup in the lower dense region of the riser increases.

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