• Title/Summary/Keyword: Heat Transfer Block

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Conjugate Heat Transfer in a Vertical Channel with Protrunding Heat Source (돌출된 열원이 부착된 수직 채널내 복합열전달)

  • Kim, Ui-Gwang;Baek, Byeong-Jun;Jo, Byeong-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.2
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    • pp.741-751
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    • 1996
  • The coupled conduction and convection heat transfer from the protruding heat source in a vertical channel is numerically investigated. Conjugate solution of the two-dimensional energy equation is obtained for the incompressible air flow over the rectangular block with local heat source. It was found that several recirculation zones and separation bubble near the block were related to Re and Gr. And the results show that fractions of the heat transfer through each of the block face, maximum temperature of the block and the relative effect of each parameter on the maximum temperature and heat transfer.

Heat Transfer from a Porous Heat Sink by Air Jet Impingement (충돌공기제트에서의 다공성 방열기의 열전달 특성)

  • 백진욱;김서영;강병하
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.2
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    • pp.73-79
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    • 2001
  • Experiment were carried out to investigate the heat transfer characteristics of an aluminum foam block as a porous heat sink on a heat source by a vertical air jet impingement that can be applied for electronics cooling. The performance of the aluminum foam heat sink was evaluated by the convective heat transfer coefficient on the heat source. At a fixed porosity, pore density ($\beta$) of the foam and Reynolds number Re were varied in the range of $\beta$a=10, 20, 40 PPI(Pore Per Inch) and $850\leqRe\leq25000$. A nozzle diameter and the nozzle-to-plate spacing were also varied. It was found that the convective heat transfer was enhanced by the aluminum foam heat sink with lower pore density due to relatively intensified flow through the foam block. The aluminum foam block with much reduced weight shows slightly better performance with larger Nusselt number, compared with the convectional heat sink.

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Analysis of the thermal behaviors of the cylinder block of a small gasoline engine (소형 가솔린 기관의 실린더 블록에 대한 열적 거동 해석)

  • 김병탁;박진무
    • Journal of the korean Society of Automotive Engineers
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    • v.15 no.3
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    • pp.55-67
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    • 1993
  • In this study, the thermal behavior characteristics of the cylinder block of a small 3-cylinder, 4-stroke gasoline engine were analyzed, using the 3-dimensional finite element method. Before numerical analyses were conducted, the performance test and the heat transfer experiment of the engine were carried out in order to prepare the input data for the computations. Engine cycle simulation was performed to obtain the heat transfer coefficient and the temperature of the gas and the mean heat transfer coefficient of coolant. Temperature fields as a result of steady-state heat transfer were obtained and compared with experimental results measured at specific points of the inner and the outer walls of the cylinder block. The thermal stress and deformation characteristics resulting from the nonuniform temperature distributions of the block were investigated. The effects of the thermal behaviors of the cylinder block on the engine operations and the unfavourable aspects of excessive thermal loading were examined on the basis of the calculated results.

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Heat Transfer Characteristics of Radiation-Mixed Convection in a Three-Dimensional PCB Channel (3차원 PCB 채널내에서의 복사-혼합대류 열전달 특성)

  • Lee, J.H.;Park, K.W.;Pak, H.Y.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.4
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    • pp.561-575
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    • 1996
  • The interaction of turbulent mixed convection and surface radiation in a three-dimensional channel with the heated blocks is analyzed numerically. Two blocks are maintained at high temperature and the other bottom and horizontal walls are insulated. S-4 method is employed to calculate the effect of the radiative heat transfer. The low Reynolds number k-$\varepsilon$ model proposed by Launder and Sharma is used to estimate the turbulent influence on the heat transfer enhancement. From above modeling, the effects of various channel specifications on the flow and heat transfer characteristics are investigated. The variables used for the present study are Reynolds number, block spacing, the channel height spacing for block and the emissivity. Average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number, emissivity and dimensionless geometric parameters. For the range of conditions in this study, average Nusselt numbers along the block surfaces are strongly influenced by the Reynolds numbers and channel height spacing for block but weakly influenced by the block spacing and the emissivity of the adiabatic walls.

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Heat transfer characteristics of multiple slot jets at the surface of protruding heated blocks (돌출 발열블록 표면에서의 배열 충돌제트에 의한 열전달 특성)

  • Chung, In-Kee;Park, Si-Woo;Hong, Sung-Ho
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.274-279
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    • 2001
  • An experimental investigation of heat transfer characteristics at the surface of two-dimensional protruding heated blocks using confined impinging multiple slot jets has been performed. The effects of jet-to-jet distances(S=16B, 24B), dimensionless nozzle-to-block distances(H/B=2, 6) and jet Reynolds numbers(Re=2000, 3900, 5800, 7800) on the local and average heat transfer coefficients have been examined with five isothermally heated blocks at streamwise block spacing(p/w=1). To clarify local heat transfer characteristics, naphthalene sublimation technique was used. From the results, it was found that the local and average heat transfer of heated blocks increases with decreasing jet-to-jet distance and increasing jet Reynolds number. Measurements of local heat transfer coefficients have given an indication of the nature of the interaction between jets and of the uniformity of heat transfer obtainable with various arrangements. In the case of S/B=16, H/B=6 and Re=7800, maximum average Nusselt number of overall blocks was obtained.

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Cooling Characteristics of a Parallel Channel with Protruding Heat Sources Using Convection and Conduction Heat Transfer (돌출된 열원이 있는 채널에서 대류와 전도열전달을 이용한 냉각특성)

  • 손영석;신지영
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.11
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    • pp.923-930
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    • 2002
  • Cooling characteristics of a parallel channel with protruding heat sources using convection and conduction heat transfer are studied numerically. A two-dimensional model has been developed for numerical prediction of transient, compressible, viscous, laminar flow, and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve the problem. The assembly consists of two channels formed by two covers and one printed circuit board which has three uniform heat source blocks. Six different cooling methods are considered to find out the most efficient cooling method in a given geometry and heat sources. The velocity and temperature fields of cooling medium, the temperature distribution along the block surface, and the maximum temperature in each block are obtained. The results are compared to examine the cooling characteristics of the different cooling methods.

Transient cooling experiments with a cooper block in a subcooled flow boiling system (과냉비등류에 있어서 동블록을 이용한 과도적 냉각실험)

  • 정대인;김경근;김명환
    • Journal of Advanced Marine Engineering and Technology
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    • v.11 no.1
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    • pp.72-79
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    • 1987
  • When the wall temperature is very high, a stable vapor film covers the heat transfer surface. The vapor film creates a strong thermal resistance when heat is transferred to the liquid though it. This phenomenon, called "film boiling" is very important in the heat treatment of metals, the design of cryogenic heat exchangers, and the emergency cooling of nuclear reactors. In the practical engineering problems of the transient cooling process of a high temperature wall, the wall temperature history, the variation of the heat transfer coefficients, and the wall superheat at the rewetting points, are the main areas of concern. These three areas are influenced in a complex fashion such factors as the initial wall temperature, the physical properties of both the wall and the coolant, the fluid temperature, and the flow state. Therefore many kinds of specialized experiments are necessary in the creation of precise thermal design. The object of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The block was 240 mm high and 79 mm O.D.. The coolant flowed throuogh the center of a 10 mm diameter channel in the copper block. In the copper block, three sheathed thermocouples were placed in a line perpendicular to the flow. These thermocouples were used to take measurements of the temperature histories of the copper block.

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A Study on Combined Heat Transfer in a Enclosure with a Block (밀폐공간내의 피가열체 존재시 복합열전달에 관한 연구)

  • Hong, Seong-Kook;Ryou, Hong-Sun;Hong, Ki-Bae;Chae, Soo
    • Journal of the Korean Society of Safety
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    • v.15 no.1
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    • pp.19-27
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    • 2000
  • This paper numerically deals with combined heat transfer in a enclosure with a block. The block affected by hot wall is located centrally in the enclosure with a radiating gray gas. The discrete ordinate method(DOM) was used for solving the radiative transfer equation. Both laminar and turbulent cases were investigated for various Rayleigh number and standard k-$\varepsilon$ model was adopted to turbulent case. The effects of optical thickness, wall emissivity and fluid-solid thermal conductivity ratio are investigated on the flow and temperature fields. This study shows that as the wall emissivity decreases, the temperature distribution gradually becomes uniform and the heat transfer is reduced in enclosure. It is expected that this study can help to design the energy system related to the combined heat transfer and operate it safely.

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An Experimental Study on Heat Transfer Characteristics of Arrangement Chips by Swirl Jet Impingement (선회충돌제트에 의한 배열 칩의 열전달 특성에 관한 실험적 연구)

  • 최재욱;전영우;정인기;박시우
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.4
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    • pp.624-631
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    • 2004
  • The experimental study on heat transfer characteristics of protruding heated block array as conducted to investigate and to compare the performance of impinging single circular jet in fully developed tube with a twisted tape as a swirl generator. The effects of jet Reynolds number(Re=8700, 13800, 20000. 26500), dimensionless jet-to-block distance(H/d=1. 3, 5. 7) and swirl number(S=0.11, 0.23, 0.30) of the swirl jet on the average Nusselt number for each block and all blocks have been examined. Measurements of heat transfer rate on block surfaces were used naphthalene sublimation technique. Mean velocity and turbulence intensity of the jet along the axis were measured. Potential core length of the jet was 5 times of nozzle diameter because it was fully developed and initially turbulent. With the twisted tape in the nozzle, heat transfer coefficients were higher than those without the twisted tape. which are mainly caused with increasing the jet Reynolds number and swirl number.

Study on the Jet Impingement Heat Transfer Characteristics at Protruding heated Blocks (돌출 발열블록표면에서의 충돌분류 열전달 특성에 관한 연구)

  • Jeong, In-Gi;Park, Si-U;Park, Su-Cheol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.12
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    • pp.1670-1677
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    • 2000
  • An experimental investigation on heat transfer characteristics of two-dimensional heated blocks using a confined impinging slot jet has been performed. The effect of jet Reynolds number(Re=3900, 5800, 9700), streamwise block spacing(p/w=0.5, 1, 1.5) and dimensionless nozzle to block distance(H/B=1, 2, 4, 6) have been examined with five isothermally heated blocks. With the measurement of jet mean velocity and turbulence intensity distributions at nozzle exit, initially turbulent regimes, are classified. To clarify local heat transfer characteristics, naphthalene sublimation technique as used. The maximum Nusselt number at the stagnation point for the jet Reynolds number is occurred at H/B=4. Besides, the local and a average heat transfer of heated blocks increase with decreasing streamwise block spacing and increasing jet Reynolds number.