• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.2
• /
• pp.52-60
• /
• 2002

Line heating is a forming process which makes the curved surface with the residual strain created by applying heat source of high temperature to steel plate. in order to control the residual strain, it is necessary to understand not only conductive heat transfer between heat source and steel plate, but also temperature distribution of steel plate. In this paper we attempted to analyze is temperature distribution of steel plate by simplifying a line heating process to collision-effusive flux of high temperature and high velocity, and conductive heat transfer phenomenon. To analyze this, combustion in the torch is simplified to collision effusive phenomenon before analyzing turbulent heat flux. The distribution of temperature field between the torch and steel plate is computed through turbulent heat flux analysis, and the convective heat transfer coefficient between effusive flux and steel plate is calculated using approximate empirical Nusselt formula. The velocity of heat flux into steel plate is computed using the temperature distribution and convective heat transfer coefficient, and temperature field in the steel plate is obtained through conductive heat transfer analysis in which the traction is induced by velocity of heat flux. In this study, Finite Element Method is used to accomplish turbulent heat flux analysis and conductive heat transfer analysis. FEA results are compared with empirical data to verify results.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.05a
• /
• pp.635-638
• /
• 2000

The propose of study analyze a TEMA(Tubular Exchanger Manufacturers Association) E shell and tube heat exchanger performance with 3, 5, 7, 9, 11 baffles and 16, 20 tubes. In this investigate measured a variation of the heat exchanger cooling capacity change within each number of baffle and tube number and determined optimal number of baffle. designs for industry applications are optimized using the analysis of test results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.59-60
• /
• 2017

Combustion instability of gas turbine is performed by adopting dynamic mode decomposition (DMD). The unstable frequencies are calculated and compared with FFT results. The damping coefficient derived from the DMD technique and FFT results were compared and analyzed. OH radical is measured by experimental work and fluctuation field is extracted and FTF was calculated at various points with DMD. The gains of FTF are changed depending on the extraction position of the heat release fluctuation field.

• Applied Chemistry for Engineering
• /
• v.19 no.3
• /
• pp.338-344
• /
• 2008

The improvement of energy conservation is mandatory to decrease consumption of fossil fuels and to minimize negative impacts on the environment which originates from large cooling and heating demand. The absorption heat pump technology has a large potential for energy-saving in this respect. Absorption heat pump is a means to upgrade waste heat without the addition of extra thermal energy. The higher performance of absorber is of great importance for absorption heat pump cycle. In this study, in order to improve the performance of absorber, the absorber of tangential feed of a liquid phase with spiral tube has been investigated using methanol-glycerine as a working fluid. The spiral tube and tangential feeding generate the turbulence into the liquid flow while increasing the mass and heat transfer coefficients. The simultaneous heat and mass transfer were found to take place in a liquid turbulent film in the absorber with the spiral tube during the process of gas absorption. By calculating mass and heat transfer coefficients by measurement of the concentration and the temperature of each position in the absorber, the entrance was found to be more effective in enhancing mass and heat transfer.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.12
• /
• pp.1079-1088
• /
• 2015

Parallelism and performance enhancement of calculating view factors in KSDS developed by KARI is introduced in this paper. View factor is an essential parameters of radiation thermal analysis for a spacecraft, and the amount of computation of them is not negligible. Especially, independent integration of view factors at each position of the orbit because the relative displace between solar panel and main body of a satellite varies with the position on the orbit. This paper introduces a range of parallelism of computing view factor and their performance, detection of obstructions by spatial search algorithm based on KD-Tree, and the reduction of the calculation of view factors of a satellite with relative motion between solar panel and main body, called updating fractional view factor matrix, for satellite thermal analysis.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.4
• /
• pp.395-404
• /
• 2013

In this study, R-410A evaporation heat transfer tests were conducted in flattened tubes made from 5-mm round tubes. The test range covered a saturation temperature of $15^{\circ}C$, heat flux of $5{\sim}15kW/m^2K$, and mass flux of $200-400kg/m^2s$. The results showed that both the condensation heat transfer coefficient and the pressure drop increased as the aspect ratio increased, with a pronounced increase for an aspect ratio of 4. A comparison of the flattened tube data with existing correlations revealed that the heat transfer coefficients were reasonably predicted by the Shah correlation, and the pressure drops were reasonably predicted by the Jung and Radermacher correlation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.12
• /
• pp.1111-1119
• /
• 2010

In this study, condensation heat transfer coefficients of R-410A were obtained in flattened tubes made from round tubes with an inner diameter of 5.0 mm. The saturation temperature was $45^{\circ}C$; the heat flux, 10 kW/$m^2K$; the mass flux, 100-400 kg/$m^2s$; and the quality, 0.2-0.8. The results showed that the effect of the aspect ratio on the condensation heat transfer coefficient depended on the flow pattern. For annular flow, the heat transfer coefficient increased as the aspect ratio increased. For stratified flow, however, the reverse was true: the pressure drop increased as the aspect ratio increased. Existing correlations adequately predicted the heat transfer coefficients and pressure drops of the flattened tubes.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.1
• /
• pp.9-15
• /
• 2013

The effective use and management of energy resources has been issued to solve the global warming problem and petrolium price increase. To improve the energy efficiency of a heat exchanger, a new countermeasure is required and the heat transfer research of nano-fluids as a new working fluid is needed. This study was carried out with increasing the Reynolds number and the vol% of nano-fluids in the inlet temperature of $25^{\circ}C$ and $50^{\circ}C$. As the result, the higher the entrance temperature is, the higher the convective heat transfer coefficient is.

• Journal of Advanced Marine Engineering and Technology
• /
• v.17 no.1
• /
• pp.45-54
• /
• 1993

동심 이중관내에서 사각돌출형 조도요소에 의한 비대칭 난류유동과 열 전달특성을, 열전달과 마찰계수에 미치는 조도의 합성효과를 조사하기 위해, 연구하였다. 이론해석에서는 한쪽면에 거칠기가 있는 평행평판의 유동에 대한 수정 플란틀 혼합길이(mixing length)이론의 난류모델을 속도분포와 마찰계수를 구하는데 사용하였다. 최대속도지점에서 안쪽과 바깥쪽의 두 속도형상들은 힘의 평형에 의해 매치(match) 시켰다. 그리고나서, 온도 분포와 열전달 계수를 계산하였다. 속도형상과 마찰계수들의 해석결과는 실험과 매우 잘 일치하였다. 마찰계수와 Nusselt number에 미치는 조도비, 조도에 대한 피치비, 그리고 반경비등과 같은 여러 변수들의 효과들을 조사하였다. 본 연구는 일정 임의의 조도 요소들이 전체적 효율 측면에서 볼 때 유리하게 열전달을 향상시킨다는 것을 증명하였다.

• Plant Journal
• /
• v.15 no.1
• /
• pp.25-30
• /
• 2019

In this study, by varying flow patterns, which is one of the hydraulic factors of FAC, a strategy to reduce pipe wall thinning by mass transfer has been investigated. A similarity between heat transfer and mass transfer was verified via theoretical analysis, and local convective heat transfer coefficients were analyzed using a commercial numerical analysis program. When ribs were installed inside and outside of the internal surface in the straight section of the pipe, the maximum local heat transfer coefficient was shown to decrease substantially by up to 24.9% compared to the basic flow depending on the position and shape of ribs. If a guide vein was inserted in the pipe elbow, the maximum local heat transfer coefficient decreased by up to 26.7% compared to the basic flow depending on the internal surface area of the pipe by the guide vein.