• Title/Summary/Keyword: Heat convection

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Computational Simulation of Heat flow phenomena in Newly Designed Heat Sinks (뉴 디자인된 히트싱크의 열 유동 현상 컴퓨터 시뮬레이션)

  • Lim Song Chul;Choi Jong Un;Kang Kae Myung
    • Korean Journal of Materials Research
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    • v.14 no.11
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    • pp.775-779
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    • 2004
  • For improvement of heat dissipation performance, heat analysis is conducted on the newly designed heat sinks under two convection conditions by using computational fluid dynamics(CFD). Three types of heat sink, plate, wave and top vented wave, are used, and convection conditions are the variations of gravity direction at natural convection and of fan location at forced convection. The results of analysis showed that the heat resistances of top vented wave heat sink were $0.17^{\circ}C$/W(forced convection) and $0.48^{\circ}C$/W(natural convection). In the case of natural convection, gravity direction affected heat flow change, and protection against heat performance was superior in case of z-axis gravity direction. Under the forced convection, all the heat sinks revealed superior thermal characteristics in the fan position of z-axis rather than y-axis. In this study, it was observed that the top vented wave type heat sink showed the best ability of heat radiation comparing with the others.

An Experimental Study on the Thermal Resistance Characteristics for Various Types of Heat Sinks (다양한 형상의 Heat Sink 열저항 특성에 관한 실험적 연구)

  • 김종하;윤재호;이창식
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.8
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    • pp.676-682
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    • 2002
  • This paper has been made to investigate the thermal performance characteristics for the several types of heat sinks such as extruded heat sink, aluminum foam heat sink, layered heat sink. The various types heat sinks are prepared and tested for natural convection as well as forced convection. The experimental results for natural convection are compared to those for three types of heat sink so that the appropriate heat sink can be designed or chosen according to the heating conditions. The overall heat transfer performances for layered heat sink, extruded heat sink and aluminum foam heat sink are almost comparable to those under natural convection and forced convection. The forced convection of layered heat sink become 1.2 times as high as those of extruded heat sink, and the forced convection of extruded heat sink become 1.2 times as high as those of aluminum foam heat sink. This study shows that bar height, bar distance and number of bar for layered heat sink are important parameters, which have a serious influence on thermal performance for layered heat sinks.

Numerical investigation of natural convection heat loss in solar receiver for dish concentrating system (접시형 태양열 집광시스템용 흡수기의 자연대류 열손실 수치해석 연구)

  • Kang, Myeong-Cheol;Kang, Yong-Heack;Kim, Jong-Kyu;Kim, Jin-Soo;Yoo, Seong-Yeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.680-683
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    • 2007
  • In dish concentrating system, natural convection heat loss occurs in cavity receiver. Heat loss mechanisms of conduction, convection, and radiation can reduce the system efficiency. To obtain the high efficiency, the receiver is to absorb the maximum of solar energy and transfer to the working fluid with maximum of heat losses. The convection heat loss is an important factor to determine the system performance. Numerical analysis of the convection heat loss of receiver was carried out for varing inclinaton angle from 0$^{\cdot}$ to 70$^{\cdot}$ with temperature range from 400$^{\cdot}C$ to 600$^{\cdot}C$ using the commercial software package, Fluent 6.0. The result of numerical analysis was comparable with convection heat loss model of solar receiver.

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Topological Optimization of Heat Dissipating Structure with Forced Convection (강제 대류를 통한 열소산 구조물의 위상최적화)

  • Yoon, Gil-Ho
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.408-409
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    • 2008
  • This paper presents a new development for topology optimization of heat-dissipating structure with forced convection. To cool down electric devices or machines, two types of convection models have been widely used: Natural convection model with a large Archimedes number and Forced convection with a small Archimedes number. Nowadays, many engineering application areas such as electrochemical conversion device or fuel cell devices adopt the forced convection to transfer generated heat. Therefore, to our knowledge, it becomes an important issue to design flow channels inside which generated heat transfer. Thus, this paper studies optimal topological designs considering fluid-heat interaction. To consider the effect of the advection in the heat transfer problem, the incompressible Navier-stokes equation is solved. This paper numerically studies the coupling phenomena and presents optimal channel design considering forced convection.

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A Study on the Heat Sink with internal structure using Peltier Module In the Natural and Forced Convection (자연대류와 강제대류에서 펠티에 소자를 이용한 내부터널 구조를 가지는 히트싱크에 관한 연구)

  • Lee, Min;Kim, Tae-Wan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.7
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    • pp.4072-4080
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    • 2014
  • The Peltier Module has been used to dissipate the heat from electronic devices and electronic components. In this module, a heat sink is used to release the operating heat into the air outside. This study addressed the heat transfer characteristics for a heat sink with an inner tunnel. Under forced and natural convection conditions, the heat transfer characteristics were different. Therefore, the cooling and heating performances were studied for the heat sink, which has an inner tunnel. The heat transfer conditions were also evaluated by performing an experimental test, which investigated the heat transfer characteristics related to the variance in time and temperature distribution. Experiments on the heat transfer characteristics of the heat sink were conducted based on the forced and natural convection and temperature distribution changes. In the cooling experiment, the A- and B-shaped cooling pin heat sinks decreased the temperature of the forced convection than the temperature of natural convection. In the forced and natural convection, the A- and B-shaped decreased to a minimum of $-15^{\circ}C$. Under the forced and natural convection conditions, A- and B-shaped cooling pin heat sinks decreased the temperature when the voltage was increased. In the heating experiment, the A- and B-shaped cooling pin heat sinks increased the temperature of the forced convection than the temperature of natural convection. In forced convection, when the voltage was $15^{\circ}C$, the temperature of the A-shaped cooling pin heat sink increased to $150^{\circ}C$, and the temperature of the B-shaped cooling pin heat sink increased to $145^{\circ}C$. Under forced and natural convection conditions, the A- and B-shaped cooling pin heat sinks showed an increase in temperature with increasing voltage.

Conjugated heat transfer on convection heat transfer from a circular tube in cross flow (원관 주위의 대류 열전달에 대한 복합 열전달)

  • 이승홍;이억수;정은행
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.5
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    • pp.523-534
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    • 1998
  • The convection heat transfer on horizontal circular tube is studied as a conjugated heat transfer problem. With uniform heat generation in a cylindrical heater placed in a cross flow boundary condition, heat flow that is conducted along the wall of the heater creates a non-isothermal surface temperature and non-uniform heat flux distribution. In the present investigation, the effects of circumferential wall heat conduction on convection heat transfer are investigated for the case of forced convection around horizontal circular tube in cross flow of air and water. Non-dimensional conjugation parameter $ K^*$ which can be deduced from the governing energy differential equation should be used to express the effect of circumferential wall heat conduction. Two-dimensional temperature distribution$ T({\gamma,\theta})$ is presented. The influence of circumferential wall heat conduction is demonstrated on graph of local Nusselt number.

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A study on the Analysis of Combustion Gas and its Flow Induced by Fire in an Enclosure (밀폐공간내 화재에 의해 생성된 연소가스 분석 및 유동에 관한 연구)

  • 추병길;조성곤
    • Journal of the Korean Society of Safety
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    • v.12 no.1
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    • pp.77-93
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    • 1997
  • The natural convection and combined heat transfer induced by fire in a rectangular enclosure is numerically studied. The model for this numerical analysis is partially opened, it is divided by a vertical baffle projecting from ceiling. The solution procedure Includes the standard k- $\varepsilon$ model for turbulent flow and the discrete ordinates method (DOM ) is used for the calculation of radiative heat transfer equation. In this study, numerical simulation on the combined naturnal convection and radiation is carried out in a partial enclosure filled with absorbed-emitted gray media, but is not considered scattering problem. The velocity vectors, streamlines, and isothermal lines are compared the results of pure convection with those of the combined convection-radiation, the combined heat transfer. Comparing the results of pure convection with those of the combined convection-radiation, the combined heat transfer analysis shows the stronger circulation than those of the pure convection. Three different locations of heat source are considered to observe the effect of heat source location on the heat transfer phenomena. As the results, the circulation and the heat transfer In the left region from heating block are much more influenced than those in the right region. It is also founded that the radiation effect cannot be neglected in analyzing the building in fire.

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Convection Heat-Transfer Characteristics of Ondol-Heated Room (온돌난방공간(溫突暖房空間)의 내표면(內表面) 대류열전달특성(對流熱傳達特性)에 관(關)한 연구(硏究))

  • Sohn, J.Y.;Ahn, B.W.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.5
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    • pp.376-385
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    • 1991
  • The purpose of this paper is to propose basic data on convection heat-transfer coefficients in Ondol-heated room. Surface temperatures and several temperatures around each inside surface of wall, floor and ceiling composed of heating room are measured vertically in Ondol-heated model rooms, and the vertical temperature profiles could be expressed by nonlinear equation models. Also, the convection heat transfer phenomena are analysed from the nonlinear equation models. In the results, the convection heat-transfer coefficients of Ondol heated space are suggested by the term of temperature difference between each wall surface and room air temperature and by the relationship between Nusselt number and Rayleigh number of dimensionless numbers.

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Convection Heat Transfer Coefficient of a Meat Cube in a Continuous Flow Sterilizing System

  • Hong, Ji-Hyang;Han, Young-Joe;Chung, Jong-Hoon
    • Food Science and Biotechnology
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    • v.14 no.3
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    • pp.328-333
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    • 2005
  • Finite difference model and dynamic thermal property evaluation system were developed to estimate convection heat transfer coefficient by modeling temperature-time profile of beef cube in continuous flow sterilizing system. As input parameters of the model, specific heat and thermal conductivity values of beef frankfurter meat were independently measured from 20 to $80^{\circ}C$. Convection heat transfer coefficient was estimated by comparing simulated and measured temperature-time profiles. Actual temperature-time profiles of meat cube were measured at flow rates of 15, 30, and 45 L/min and viscosities from 0 to 15 cp, and mean values of convection heat transfer coefficients ranged from 792 to $2107\;W/m^2{\cdot}K$. Convection heat transfer coefficient increased with increase in flow rate and decreased as viscosity increased.

Forced Convection Heat Transfer from an Inner Surface of a Two-Dimensional Rectangular Cavity (이차원 사각형 공동 내부에서의 강제 대류 열전달)

  • Seo, T.B.;Han, K.Y.;Kange, Y.H.
    • Journal of the Korean Solar Energy Society
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    • v.22 no.4
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    • pp.77-84
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    • 2002
  • In order to investigate forced convection heat transfer due to the wind from the inner surface of a cavity receiver for a parabolic dish type solar energy collecting system, a two-dimensional rectangular cavity receiver is prepared and installed in a wind tunnel. The convection heat transfer coefficient of the inner surface of the receiver is dependent on the direction and the velocity of the wind. The attack angle of the cavity and the air velocity in the tunnel are controlled in a wide range so that the effects of the attack angle and the wind velocity on the heat transfer coefficient can be studied. The skirt is installed at the aperture of the cavity in order to reduce convective heat loss. The effects of the length and the installation angle of the skirt on convection heat transfer of the cavity are tested. It is found that convection heat loss can be significantly reduced by installing the skirt. Also, it is known that heat transfer from the cavity can be minimized if the angle of the skirt is $90^{\circ}$ to the outer surface of the cavity.