• Title/Summary/Keyword: 분무냉각

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Study on Minimum Heat Flux Point in Spray Cooling of Hot Plate (고온 강판의 분무냉각에 있어서 MHF 점에 관한 연구)

  • Kim, Yeung-Chan
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.175-180
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    • 2001
  • In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about $900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the experimental results show that the velocity of wetting front increases with the increase of the droplet flow rate.

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A Study on the Spray Cooling Characteristics according to the Angle of Hot Heat Transfer Surface (고온 열전달면의 각도에 따른 분무냉각 특성에 관한 연구)

  • Yoon, D.H.;Oh, C.;Yoon, S.H.
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.3
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    • pp.320-327
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    • 2002
  • An experimental study of heat transfer from hot flat surface to water sprays was conducted in high temperature region. Heat transfer measurements for hot flat surface were made by 4 sheathed C-A thermocouples. Droplets volume flux were also measured-independently at a position in spray field. The test conditions included variations in droplets volume flux, subcooling of cooling water of $1.565\times10^{-3} to 14.089\times10^{-3}m^3/m^2s and 80 to $20^{\circ}C$ respectively. The effects of inclination angle on heat transfer were investigated and changes in inclination angle of hot flat surface affected heat transfer coefficients of high temperature region.

Cooling Effect of a Heated Porous Plate by Droplets Impingement - A Preliminary Study (가열 상태의 다공성 판에 충돌하는 액적의 냉각 성능에 대한 기초 연구)

  • Ryu, S.U.;Kim, W.S.;Lee, S.Y.
    • Journal of ILASS-Korea
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    • v.14 no.1
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    • pp.20-27
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    • 2009
  • In the present work, effects of spray characteristics (droplet size and velocity) on the temperature variation of a heated porous plate (Melamine foam) have been investigated through a series of experiments. Based on the measured data, time required to cool down the hot porous material turned out to be shorten by doing with the smaller droplet size and/or smaller impinging velocity. In particular, the droplet size effect is more prominent than the impinging velocity. The cooling performance in the porous material is directly proportional to the penetration velocity.

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An Experimental Study on Ultrasonic Spray Cooling of Heat Pipe Condenser (히트파이프 응축부의 초음파 분무냉각에 관한 실험적 연구)

  • 김영찬;한양호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.1
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    • pp.77-83
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    • 2004
  • In this study, the spray cooling heat transfer and working characteristics of the screen wick heat pipe with ultrasonic spray cooling system in condenser were experimentally investigated. The heat pipe was made of copper tube 300 mm long with inner diameter of 11.1 mm. The evaporator and condenser lengths of heat pipe were 40, 200 mm and the wick structure consists of two layer of 100 mesh copper screen. The experimental results show that the ultrasonic spray cooling increases the heat transfer rate on the condenser surface, and the total thermal resistance of heat pipe system decreases remarkably. A comparison is made for the two working fluids, water and ethanol. The surface temperature of the ethanol tube in evaporator section becomes higher than that of the water tube. Thus, the experimental result shows that water is more useful than ethanol as the working fluid because of increasing the operational limit within this experimental conditions.

Study on Correlation of Droplet Flow Rate and Film Boiling Heat Transfer in Spray Cooling (액적 유량과 분무냉각 막비등 열전달의 상관관계에 관한 연구)

  • Yun, Seung-Min;Kim, Yeung-Chan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.4
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    • pp.335-340
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    • 2007
  • A new correlation between the Nusselt number based on modified heat transfer coefficient and Reynold number based on droplet-flow-rate was developed for the experimental data. The modified heat transfer coefficient was defined as ratio of wall heat flux to droplet subcooling. In the previous reports, the local heat flux of spray cooling in the film boiling region was experimentally investigated for the water spray region of $D_{max} = 0.0007{\sim}0.03m^3/(m^2s)$ . In the region near the stagnation point of spray flow, a new heat transfer correlation is recommended which shows good predictions for the water spray region of $D_x{\le}0.01m^3/(m^2s)$.

Study on Minimum Heat Flux Point in Spray Cooling of Hot Plate (고온 평판의 분무냉각에 있어서 MHF점에 관한 연구)

  • 김영찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.10
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    • pp.974-981
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    • 2001
  • In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about$ 900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the velocity of wetting front increases with the increase of the droplet flow rate.

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Measurements of Heat Transfer Distribution in Spray Cooling of Hot Steel Plate . (분무냉각에 의한 강판 열처리과정에 있어서 열전달분포의 측정)

  • 김영찬;유갑종;서태원
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.10
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    • pp.886-893
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    • 2000
  • A good understanding of the heat transfer distribution is very important to suppress the deformation of steel products. In this study, the local heat transfer coefficients are experimentally investigated to understand the heat transfer distribution of thick steel plates with even flat spray nozzle. The steel slabs are cooled down from the initial temperature of about $1000^{\circ}C$ , and the local heat transfer coefficients and surface temperatures are calculated from the measured temperature-time history. The results show that the local heat transfer coefficients of spray cooling are dominated by the local droplet flow rate, and in proportion to becoming more distant from the center of heat transfer surface, the local heat transfer coefficients decrease with the decrease of the local droplet flow rate.

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Study on Film Boiling Heat Transfer of Spray Cooling in Dilute Spray Region (희박 분무영역에서의 분무냉각 막 비등 열전달에 관한 연구)

  • Kim Yeung Chan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.2 s.233
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    • pp.279-286
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    • 2005
  • This study presents experimental results on the heat transfer coefficients in the film boiling region of spray cooling for actual metallurgical process. In this study, the heat flux distributions of a two dimensional dilute spray impinging on a hot plate were experimentally investigated. A stainless steel block was cooled down from intial temperature of about $800^{\circ}C$ by twin fluid (air-water) flat spray. It was found from the experimental results that the heat transfer area was classified into the stagnation region and wall-flow region. In the stagnation region, the experimental data of local heat transfer coefficient was closely correlated with the local droplet-flow-rate supplied from the spray nozzle directly. Thus, the local heat transfer coefficients are in good agreement with the predicted values from the correlations proposed by our previous study. In wall-flow region, however, remarkable differences are observed between experimental data and predicted values because the number of rebound droplets increase with increasing the distance from the stagnation point.

Study on Film Boiling Heat Transfer of Spray Cooling in Air-Water Full Cone Spray System (물-공기 원추형 분무시스템에 있어서 분무냉각 막비등 열전달에 관한 연구)

  • Kim, Yeung-Chan;Yun, Seung-Min
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.12 s.255
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    • pp.1236-1242
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    • 2006
  • The local heat flux of spray cooling in the film boiling region were experimentally investigated for the spray region of $D_{max}$ = $0.005{\sim}0.03m^3/(m^2s)$. A twin-fluid full cone spray nozzle was employed for the experiment and the distributions of droplet flow rates were obtained for air-water full cone sprays. A stainless steel block was cooled down from initial temperature of about $800^{\circ}C$ by full cone spray. In the region near the stagnation point, it was found that the experimental data are in good agreement with the results predicted from the correlations between the local heat transfer and the local droplet flow rate proposed in the previous report. However, it was found that the experimental data of $D_r$ > $0.01m^3/(m^2s)$ are a little smaller than the results predicted from the correlations.

Design of Film-cooling Ring of The Engine Using Green Propellant And Thermal Analysis (친환경 추진제를 사용하는 액체로켓엔진의 막냉각링 설계 및 열해석)

  • Kim, Jung-Hoon;Lee, Jae-Won;Lee, Yang-Suk;Ko, Young-Sung;Kim, Yoo;Kim, Sun-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.119-122
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    • 2009
  • The purpose of this study is to design of film-cooling ring for the small thrust rocket engine using green propellants(Hydrogen peroxide and kerosene). Cold flow test was carried out to measure the mass flow rate and atomizing characteristic. Required mass flow rate was obtained from thermal analysis of the engine, and measured flow rate 42.25g/s was in the range of permissible coolant flow rate. With the same mass flow rate, cooling ring with more hole and high velocity shows better spray pattern. The result of thermal analysis, cooling ring has enough cooling performance.

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