• Title/Summary/Keyword: Natural convection heat transfer

Search Result 449, Processing Time 0.027 seconds

EFFECT OF PARTITION AND SPECIES DIFFUSIVITY ON DOUBLE DIFFUSIVE CONVECTION OF WATER NEAR DENSITY MAXIMUM

  • Sivasankaran, S.;Kandaswamy, P.
    • Journal of the Korean Society for Industrial and Applied Mathematics
    • /
    • v.11 no.1
    • /
    • pp.71-83
    • /
    • 2007
  • The double diffusive convection of cold water in the vicinity of its density maximum in a rectangular partitioned enclosure of aspect ratio 5 with isothermal side walls and insulated top and bottom is studied numerically. A thin partition is attached to the hot wall. The species diffusivity of the fluid is assumed to vary linearly with concentration. The governing equations are solved by finite difference scheme. The effects of position and height of the partition, variable species diffusivity and enclosure width are analyzed for various hot wall temperatures. It has been found that adding partition on the hot wall reduces the heat transfer. The density inversion of the water has a great influence on the natural convection. When increasing species diffusivity parameter heat and mass transfer rate is decreased.

  • PDF

Two-Dimensional Benard Natural Convection with a Rectangular Body (사각 물체가 존재하는 2차원 Benard 자연 대류)

  • Yoon, Kyung-Soo;Ha, Man-Yeong;Yoon, Hyun-Sik
    • Proceedings of the KSME Conference
    • /
    • 2000.04b
    • /
    • pp.282-289
    • /
    • 2000
  • Direct numerical solution for flow and heat transfer for Benard convection with a body is obtained using an accurate and efficient Fourier-Chebyshev collocation and multi-domain method. The flow and temperature fields are obtained fur different Rayleigh numbers and thermal boundary conditions of body. The body has adiabatic and constant temperature conditions. The existence of a body gives different flow and heat transfer fields in the system, compared to pure Benard convection. The flow and temperature fields are also affected by the thermal boundary condition of a body.

  • PDF

Buoyant Convection in a Cylinder with Azimuthally-varying Sidewall Temperature (방위각방향 온도변화를 가지는 실린더 내의 부력 유동)

  • Chung, K.H.;Hyun, J.M.;Song, T.H.
    • Proceedings of the KSME Conference
    • /
    • 2000.04b
    • /
    • pp.45-50
    • /
    • 2000
  • A numerical investigation is made of three-dimensional buoyant convection of a Boussinesq-fluid in a vertical cylinder. The top and bottom endwalls are thermally insulated. Flow is driven by the substantial azimuthal variations in thermal boundary conditions. Comprehensive numerical solutions to the Navier-Stokes equations are obtained. The representative Rayleigh number is large, thus, the overall flow pattern is of boundary layer-type. Three-dimensional (low characteristics are described. Specially, the global flow and the heat transfer features are delineated when the severity of azimuthal variation of sidewall temperature n, is intensified. Temperature and velocity fields on the meridional planes and the planes of constant height are presented. The global flow weakens as n becomes large. The pattern of the local Nusselt number on the surface of cylinder is similar regardless of n. The convective gain in heat transfer activities is reduced as n increases.

  • PDF

A Study on the Effects of Fin Length on Natural Convection Heat Transfer from a Inclined Flat Plate (경사평판에서의 핀길이가 자연대류 열전달에 미치는 영향에 관한 연구)

  • 천대희
    • Fire Science and Engineering
    • /
    • v.12 no.1
    • /
    • pp.3-8
    • /
    • 1998
  • This study has been conducted experimentally on the effects of natural convection heat transfer characteristics for inclined flat plate with vertical fin in air. The effects of various fin length, flat plate inclined angle and Grashof number are mainly investigated The experimented results are as follows: The mean heat transfer coefficient increase according to the decrease of H/S in the various fin lengh. The mean heat transfer coefficient at H/S-0.5, 1.0, 1.5 for Gr=2.11$\times$103. $\theta$=00 increase by 107%, 43%, 15% than H/S=2.0. The mean heat transfer coefficient decrease with the increase of $\theta$ the inclined angles. The mean heat transfer coefficient at Gr=2.97$\times$103 is constant, at $\theta$= 00 for H/S=0.5 decrease by 33% than $\theta$=90$^{\circ}$. The mean heat transfer coefficient increase as Grashof as Grashof number increase. The mean heat transfer coefficient at Gr=2.31$\times$103, Gr=2.61$\times$103, Gr=2.97$\times$103 for H/S=1.0, $\theta$=0$^{\circ}$increase by 9%, 16%, 28% than Gr=2.11$\times$103.

  • PDF

Influence of the Entrance and Exit Lengths on the Natural Convection Heat Transfer of a Cylinder in a Duct (도관내 원형관의 자연대류 열전달에서 입구 및 출구 길이 효과)

  • Lim, Chul-Kyu;Chung, Bum-Jin
    • Journal of Energy Engineering
    • /
    • v.21 no.1
    • /
    • pp.18-25
    • /
    • 2012
  • This work investigated the influence of the chimney dimensions(exit and entrance length, and diameter) on the heat transfer of a vertical cylinder in a duct. The measured mass transfer rates for the natural convection of vertical cylinder in a duct were presented for Prandlt number 2,094, Rayleigh number in the range of $4.55{\times}10^9$, $5.79{\times}10^{10}$, and $1.69{\times}10^{11}$. Experiments were performed using a copper sulfate electroplating system to simulate heat transfer based upon the analogy concept. The diameter of the duct was varied from 0.06 m to 0.14 m, and the heights from 0.30 m to 1.10 m. Nusselt numbers measured at open channel condition agreed well with the existing laminar heat transfer correlations for vertical plate developed by Le Fevre. The increase of the exit length enhanced the heat transfer up to a certain duct height but further increase does not affects the heat transfer. The heat transfer decreased with increasing the entrance length up to a certain duct height and was constant at further increase. The Nusselt number decreased with increasing the diameter of duct, until Nusselt number becomes similar to that at open channel beyond a certain diameter.

Numerical study on the thermal behavior of a natural convection hybrid fin heat sink (자연대류상의 하이브리드 휜 히트싱크의 열특성에 대한 수치적 연구)

  • Kim, Kyoung Joon
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.37 no.1
    • /
    • pp.35-39
    • /
    • 2013
  • This paper reports numerical study results with respect to the thermal behavior of a natural convection cooled hybrid fin heat sink (HFH). The HFH consists of hybrid fins, hollow pin fins integrated with plate fins. The thermal performance of the HFH was numerically investigated by employing a commercial CFD software package and compared with that of the pin fin heat sink (PFH). Numerical study has found that array-based and mass-based heat transfer coefficients of the HFH are 12% and 37% greater than those of the PFH, respectively. Extended surface area and lighter weight may explain the better thermal performance of the HFH than the PFH.

Natural Cconvection in a Vertical Channel with Thermal Blocks (장방형 발열체가 부착된 채널에서 자연대류 연구)

  • 최용문;박경암
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.17 no.2
    • /
    • pp.438-444
    • /
    • 1993
  • The circuit board of an electronic equipment were simulated with a vertical channel which had thermal blocks protruded from one of the channel walls. A rought front plate was made of a circuit board attached with short wires to simulate the back side of a printed circuit board. Natural convection experiments were carried out to study the effects of channel space and rough front plate and to find the suitable characteristic value after the fourth row. The effect of a rough front plate was negligble. There were negligible effects of the channel space on the first and second heaters. Heat transfer coefficients after the third row decreased as the channel space decreased. Heat transfer coefficients were almost constant for larger than 20 mm channel space. A characteristic length was suggested to non-dimensionalize Nu and Ra numbers in a vertical channel with protruded heaters. A correlation was obtained using the new characteristic lengths.

A study on velocity measurements of natural convection flows using multiple pulsed particle image analysis (다중노출 입자영상해석을 통한 자연대류 유속측정에 관한 연구)

  • Han, H.T.;Kim, Y.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.9 no.3
    • /
    • pp.268-275
    • /
    • 1997
  • Using the film-based particle image velocimetry, natural convective flows have been measured quantitatively in a rectangular enclosure with a heater located on the bottom surface. The success rate of the present interrogation method has been obtained as a function of the number of particle pairs and the distance between the particle pairs. The influence of the diffraction halo at the center have been effectively eliminated by rotating-subtracting the original Fourier-transformed image. By utilizing the coded multiple pulsed illumination with two different time intervals, the minimum measurable velocity have been improved. The results of the velocity distributions and the heat transfer correlations have been obtained for different locations of heater in the enclosure.

  • PDF

Analytical Modeling of Natural Convection in a Tall Rectangular Enclosure with Multiple Disconnected Partitions

  • Bae, Youngmin;Kim, Seong Hoon;Seo, Jae-Kwang;Kim, Young In
    • Nuclear Engineering and Technology
    • /
    • v.48 no.4
    • /
    • pp.925-931
    • /
    • 2016
  • In this study, laminar natural circulation and heat transfer in a tall rectangular enclosure with disconnected vertical partitions inside were investigated. Analytical expressions were developed to predict the circulation flow rate and the average Nusselt number in a partially partitioned enclosure with isothermal side walls at different temperatures and insulated top and bottom walls. The proposed formulas are then validated against numerical results for modified Rayleigh numbers of up to $10^6$. The impacts of the governing parameters are also examined along with a discussion of the heat transfer regimes.

A performance comparison of heat sink using FEM in the natural convection (자연대류에서 유한요소법을 이용한 히트싱크의 성능비교)

  • Lee, Min;Lee, Chun-Kyu
    • Design & Manufacturing
    • /
    • v.12 no.1
    • /
    • pp.31-35
    • /
    • 2018
  • The peltier thermoelectric module are used to cool the heat generated by electronic equipment. In order to increase the efficiency of the peltier thermoelectric module, the heat must be released to the outside. A heat sink is used to discharge such heat to the outside. in this paper, two types of heat sinks with internal tunnels were designed. And the heating and cooling performance of the heat sink with internal tunnel structure was compared and analyzed through ANSYS. The heat sink of the A type had better heat transfer than the heat sink of the B type. Which is about 70% improved.