• 동력기계공학회지
• /
• 제4권2호
• /
• pp.11-16
• /
• 2000

Simultaneous quantitative measurements are made of the velocity fields for two-dimensional natural convection in a rectangular enclosure using PIV(Particle Image Velocimetry). The experiments are performed at a Prandtl number of 6.62, an aspect ratio of 1.0, Rayleigh numbers from $1.294{\times}10^6\;to\;3.8841{\times}10^6$, and angles of inclination of $0^{\circ},\;30^{\circ}\;and\;60^{\circ}$ inside a $30mm{\times}30mm{\times}8mm$ cavity made of an acrylic glass 10mm, with two isothermal copper walls kept at a prescribed temperature. The experimental results agreed very well with the numerical results. It was found that the flow consisted of a large double convection cell at angle of inclination of $60^{\circ}$.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2004년도 추계학술대회 논문집
• /
• pp.104-107
• /
• 2004

Most of the previous studies on natural convection were based on the numerical analysis, and some experimental studies considered the classic case of thermal convection. In this study, an adiabatic square body was located at the center of an enclosure between the bottom hot and top cold walls. And the measurement of the detailed temperature fields was conducted by the method of two-color Laser Induced Fluorescence using a Nd:Yag laser. As a result, heat transfer characteristics of natural convection with an adiabatic body was estimated as a function of time over a range of Rayleigh numbers.

• 대한기계학회논문집
• /
• 제16권11호
• /
• pp.2181-2188
• /
• 1992

본 연구에서는 크기가 45˚인 부채형 공간내의 자연대류 열전달 특성을 고찰 하기 위하여 간격비, 경사각 그리고 Rayleigh 수를 변수로 하여 유한 차분법으로 수치 해석 하고, 대료적인 간격비 L/r$_{i}$=1.6에서 Ra=2.51*$10^{4}$ 및 Pr=0.71일때, Machzehnder 간섭계를 사용하여 실험 하였으며, 수치해석과 실험결과를 비교하였다.

• 한국해양공학회지
• /
• 제10권4호
• /
• pp.109-117
• /
• 1996

The numerical and experimental studies on the mixed convection of a rectangular enclosure for indoor air control has been studied numerically using the finite volume method and experimentally with holographic interferometry and Laser apparatus. The parameters studied here are Pr= 0.71, $30{\leq}Re{\leq}600$, $700{\leq}Gr{\leq}100000$ and the positions of an outlet. The results show streamlines, isothrems, velocity distributions and photograph of holographic interferometry and streamlines. It is found that the minimum cell occurs at Re=100, Gr=10000. The mean Nusselt numbers can be expressed by the correlation equation $Nu=C{\cdot}Gr^a$ $Re^b.$ The comparison of numerical and experimental results shows a good agreement.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 제39회 하계학술대회
• /
• pp.641-642
• /
• 2008

본 논문에서는 정열계 해석을 위해 짧은 해석 시간을 가지는 열전달 문제의 해석 기법에 대하여 제시한다. 특히, 열전달의 주요쟁점인 혼합 경계조건을 띄는 대류 문제의 열전달 계수 산정에 대하여 해석적 방법(analytic method)을 이용하여 구한 뒤, 수치해석적 방법(numerical method)인 유한요소법(F.E.M)으로 해석한다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.322-327
• /
• 2000

Natural convection heat transfer in an enclosure with an opening in the right vertical wall and a heat source at the bottom surface is investigated using a holographic interferometric technique. The effects of the opening length, divider length attached to the top wall, and heater temperature on the temperature distribution are examined. The openging length as well as the divider length greatly affects the degree of inflow and outflow of air. With a small opening, the opening doesn't affect much the upward warm air flow resulting in the symmetric temperature distribution. On the other hand, with the increase of the opening length, the inward cold flow moves the upward flow to the left direction. With the increase of the divider length, temperature in the lower region of enclosure becomes higher for the small opening and lower for the large opening.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.109-114
• /
• 2003

The physical model considered here is a horizontal layer of fluid heated below and cooled above with a periodic array of evenly spaced square cylinders placed at the center of the layer, whose aspect ratio here varies from unity to twelve. Periodic boundary condition is employed along the horizontal direction to allow for lateral freedom for the convection cells. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral multi-domain methodology for a given Rayleigh numbers of $10^{6}$.

• 에너지공학
• /
• 제10권3호
• /
• pp.266-271
• /
• 2001

투과 흐름이 있는 수평 다공질 유체층에서 부력에 의하여 발생하는 자연대류 현상을 선형 안정성 이론을 사용하여 해석하였다. 다공질 층에서의 유동 특성을 나타내기 위하여 Dacrcy 법칙을 사용하였다. 선형 안정성 해석 결과를 근거로 자연대류 발생점 근처에서 비선형 해석을 하여 열전달 상관관계를 얻었다. 해석 결과 투과 흐름의 세기가 커짐에 따라 계는 점점 안정해 지고, Darcy-Rayleigh수의 변화에 따른 Nusselt수의 변화는 감소하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1177-1182
• /
• 2004

The physical model considered here is a horizontal layer of fluid heated below and cooldabove with a heat-generating conducting body placed at the center of the layer. The body genrates a constant amount of heat as initial condition. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for various of Rayleigh number from $10^3$ to $10^6$. Multi-domain Technique is used to handle heat-generating conducting body. The results for the case of heat-generating body are also compared to those of adaibatic body.

• 설비공학논문집
• /
• 제13권12호
• /
• pp.1230-1235
• /
• 2001

The laminar convection heat transfer in a ventilated space with various horizontal partitions was studied numerically and experimentally. The experimental results by holographic interferometer showed good agreements with the numerical results. For the numerical study, the governing equations were solved by using a finite volume method for $46.6\leqRe\leq1332,\;1460\leqGr\leql1585$, Pr=0.71 and the variations of partition lengths. The isotherms and velocity vectors have been represented for various parameters. As the length of partition increases, the convection heat transfer decreases. Based on the numerical data, a correlation was obtained for the dimensionless mean Nusselt number in terms of $Gr/Re^2$. In the region of $Gr/Re^2$<1, the mean Nusselt number was very small, but in the region of $Gr/Re^2\geq1$, the mean Nusselt number was constant.