• Title/Summary/Keyword: Cooling

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Cooling Characteristics of Fruits and Vegetables for Pressure Cooling (차압통풍 예냉 청과물의 냉각특성)

  • 윤홍선;박경규
    • Food Science and Preservation
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    • v.4 no.3
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    • pp.237-243
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    • 1997
  • Numerous variables affect product cooling rate of pressure cooling system for fruits and vegetables. These include carton vent area, initial and desired final product temperature, flow rate and temperature of the cooling air, product size, shape and thermal properties and product configuration(whether in bulk or packed in shipping cartons). This study was carried out to determine the influence of each of these variables as they affect cooling time. The opening ratio and number of the vent hole were recomended as 4∼10% and 2∼4ea., respectively, for a minimum alt flow resistance and for a uniform air flow pattern. In the cooling experiment for tomatoes and mandarins, optimum air flow rate was 0.04 m3/min.kg in terms of energy saving. The cooling air temperature should be about 2$^{\circ}C$ less than the desired final product temperature for reducing cooling time.

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Cooling Simulation for Fixed-Bed of Rough Rice (벼 퇴적층 냉각 시뮬레이션)

  • 김동철;김의웅;금동혁
    • Journal of Biosystems Engineering
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    • v.24 no.1
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    • pp.31-40
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    • 1999
  • The objective of this study were to develop a cooling simulation model for fixed-bed of rough rice and to analyze the factors affecting cooling time of rough rice. A computer simulation model based on equilibrium conditions between grain and air was developed to predict temperature and moisture content changes during cooling of rough rice. the result of t-test showed that there were no significant differences between predicted and measured temperature changes on significance model agreed well with measured values. This cooling simulation model was applied to analyze the effect of some factors, such as air flow rate, cooling air temperature and humidity, initial grain temperature and moisture content, and bed depth, on cooling time of rough rice. Cooling rate increased with increase of air flow rate and bed depth whereas it decreased with increase of cooling air temperature and humidity and initial grain temperature. Among these factors, the most important factor was air flow rate. Specific air flow rate of 0.35㎥/min㎥ was required for cooling rough rice in 24 hours.

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Analysis of Flow and Heat Transfer in Swirl Chamber for Cooling in Hot Section (고온부 냉각을 위한 스월챔버내의 유동 및 열전달 해석)

  • Lee K. Y.;Kim H. M.;Han Y. M.;Lee S. Y.
    • Journal of computational fluids engineering
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    • v.7 no.3
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    • pp.9-16
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    • 2002
  • Most of modem aerospace gas turbines must be operated at a gas temperature which is several hundreds of degrees higher than the melting temperatures of the materials used in their construction. Complicated cooling schemes need to be employed in the combustor walls and in the high pressure turbine stages. Internal passages are cast or machined into the hot sections of aero-gas turbine engines and air from the compressor is used for cooling. In many cases, the cooling system is engineered to utilize jets of high velocity air, which impinge on the internal surfaces of the components. They are categorized as 'Impinging Cooling Method' and 'Vortex Cooling Method'. Specially, research of new cooling system(Vortex Cooling Method) that overcomes inefficiency of film cooling and limitation of space. The focus of new cooling system that improves greatly cooling efficiency using less amount of cooling air on surface heat transfer elevation. Therefore, in this study, a numerical analysis has been peformed for characteristics of flow and heat transfer in the swirl chamber and compared with the flow measurements by LDV. Especially, for understanding high heat transfer efficiency in the vicinity of wall, we considered flow structure, vortex mechanism and heat transfer characteristics with variation of the Reynolds number.

Cooling Characteristics of a Hot Steel Plate by a Circular Impinging Liquid Jet (원형수직 충돌 수분류에 의한 고온강판의 냉각특성 연구)

  • 오승묵;이상준
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.6
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    • pp.1150-1155
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    • 1992
  • The cooling characteristics of a hot steel plate by a laminar impinging water bar were investigated experimentally. The dynamic parameters investigated were nozzle height L between nozzle and the hot plate, flow rate Q, and initial cooling temperature. Because the boiling phenomena on a hot steel plate are unsteady and change discontinuously, it is difficult to analyze the cooling characteristics directly. In this study the cooling efficiency was estimated by using the temperature decay rates and expansion speed of the water cooling zone. Temperature in the water cooling zone decreased rapidly and the radius of the water cooling zone expanded nearly in proportion to square root of the cooling time. With increasing initial temperature of a hot steel plate, the cooling efficiency became descendent. The cooling curve in the case of L/D = 30 showed the largest temperature decay rate and excellent cooling performance.

Studies on the Performance Evaluation of Downsized High-efficiency Cooling Module (높이 축소형 고효율 냉각모듈의 성능 평가에 관한 연구)

  • Jung, Jung-Hun;Shin, Yoon-Hyuk;Park, Sung-Wook;Jeong, Sun-An;Kim, Sung-Chul
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.6
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    • pp.61-67
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    • 2011
  • The cooling module needs enough space (or distance) from hood to absorb the energy from any pedestrian collision. Downsized cooling module for pedestrian protection is important to reduce the severity of pedestrian injury. When a vehicle collision happens, the downsized cooling module is required to reduce the risk of injury to the upper legs of adults and the heads of children. In this study, the performance of cooling module to cool the engine was investigated under 25% height reduction. The heat dissipation and pressure drop characteristics have been experimentally studied with the variation of coolant flow rate, air inlet velocity and A/C operation ON/OFF for the downsized cooling module. The results indicated that the cooling performance was about 94% level compared to that of the conventional cooling module. Therefore, we checked that the cooling module had good performance, and expected that the cooling module could meet the same cooling performance as conventional cooling module through optimization of components efficiency.

Cryogenic cooling system for HTS cable

  • Yoshida, Shigeru
    • Progress in Superconductivity and Cryogenics
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    • v.19 no.2
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    • pp.1-8
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    • 2017
  • Recently, Research and development activity of HTS (High Temperature Superconducting) power application is very progressive worldwide. Especially, HTS cable system and HTSFCL (HTS Fault current limiter) system are proceeding to practical stages. In such system and equipment, cryogenic cooling system, which makes HTS equipment cooled lower than critical temperature, is one of crucial components. In this article, cryogenic cooling system for HTS application, mainly cable, is reviewed. Cryogenic cooling system can be categorized into conduction cooling system and immersion cooling system. In practical HTS power application area, immersion cooling system with sub-cooled liquid nitrogen is preferred. The immersion cooling system is besides grouped into open cycle system and closed cycle system. Turbo-Brayton refrigerator is a key component for closed cycle system. Those two cooling systems are focused in this article. And, each design and component of the cooling system is explained.

Evaluation of Design Parameters for Optimizing the Cooling Channel in Hot Press Bending Process (핫 프레스 벤딩 공정에서 냉각회로 최적화를 위한 공정변수의 평가)

  • Nam, Ki-Ju;Choi, Hong-Seok;Ko, Dae-Cheol;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.11
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    • pp.1267-1273
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    • 2009
  • Hot press forming can produce high-strength components by rapidly cooling between closed punch and die after hot forming using quenchable boron steel austenized in a furnace. In the hot press forming process, the cooling rate is influenced by the size, position and arrangement of the cooling channel and the file condition of cooling water in the die. Also, mechanical properties of the final components and operation time are related to cooling rate. Therefore, the design of optimized cooling channel is one of the most important works. In this paper, the effect of position and size of the cooling channel on the cooling rate was investigated by using design of experiment and FE analysis in hot press bending process. Therefore the optimum cooling channel ratio was presented in the HPB.

Prediction of Tool Life on Cooling System in Warm Forging (온간 단조에서의 냉각방법에 따른 금형 수명 예측)

  • 이현석
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2000.04a
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    • pp.67-70
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    • 2000
  • The tool life is not long enough under sever forming condition in warm forging. The tool life is affected by wear heat fatigue plastic deformation and so on. Especially wear is one of the most serious factors for tool life. To increase tool life we should consider various factors like processing design die design die materials lubrication and cooling system This study design to obtain the steady state temperature of die by FEM analysis under several conditions of cooling. There are four cooling conditions in this study no cooling internal cooling external cooling and both internal and external cooling. With above obtained temperatures tool life is predicted using Archard's model that is considered softening of die. The effect of internal cooling system is better than that of externally cooled die. To predict the die life the steady state temperature is calculated by using mean temperature of die. Considering only wear the die life much longer as the cooling effect is bigger. The more accurate die life will be predicted if we consider heat crack as well as wear.

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A Study on the Thermal Environmental Analysis and the Application of Radiant Floor Cooling in Apartment Building (공중주택의 열환경분석과 바닥복사냉방의 적용에 관한 연구)

  • 김용이;김광우
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.6
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    • pp.541-548
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    • 2001
  • The objective of this study is to analyze the possibilities and considerations for the application of the radiant floor cooling system by analyzing the problems of a conventional cooling system through field tests and thermal performance simulations of the radiant floor cooling in an apartment building. The results are as follows. (1) Problems of he conventional cooling system with PAC()packaged air conditioner)'s include draft, local discomfort, and excessive electrical peak demand. (2) According to the measurement during the cooling and intermediate seasons, the floor surface temperatures which are experienced at the time of cooling with PAC\`s and during intermediate season are similar to the temperatures for radiant floor cooling. (3) The radiant floor cooling system is applicable to apartment buildings during the cooling season, especially on hot and clear days.

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Measurement of the Film Cooling Effectiveness on a Flat Plate using Pressure Sensitive Paint

  • Park, S.D.;Lee, K.S.;Kwak, J.S.;Cha, B.J.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.53-58
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    • 2008
  • Film cooling effectiveness on a flat plate was measured with pressure sensitive paint. The pressure sensitive paint(PSP) changes the intensity of its emissive light with pressure and the characteristic was used in film cooling effectiveness measurement. The film coolants were air and nitrogen, and by comparing the intensity of PSP coated surface with each coolant, the film cooling effectiveness was calculated. Three blowing ratio of 0.5, 1, and 2 were tested with two mainstream turbulence intensities. Results clearly showed the effect of blowing ratio and mainstream turbulence intensity. As the blowing ratio increases, the film cooling effectiveness was decreased near the film cooling holes. However, the film cooling effectiveness far downstream from the injection hole was higher for higher blowing ratio. As the mainstream turbulence intensity increased, the film cooling effectiveness was decreased at far downstream from the injection hole.

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