• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 2000년도 춘계 학술발표회 논문집
• /
• pp.181-188
• /
• 2000

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2007년도 동계학술발표대회 논문집
• /
• pp.546-551
• /
• 2007

The present study numerically investigated the tube geometry and arrangement on the performance of a high temperature generator (HTG) of the double effect LiBr-water absorption system. FLUENT, as a commercial code, was used to estimate the thermal performance of the HTG. Key parameters were the spacing raito of circular and flattened tubes, the pitch ratio of the rib on the flattened tube, and total heat transfer area of the HTG. Temperature and velocity profiles around the tubes of the HTG were calculated to estimate the thermal performance of the HTG. When the spacing ratio of circular and flattened tube is 1.11 and 0.73, the exhaust gas temperature is $185^{\circ}C$ without rib. The exhaust gas temperature when applied the rib in flattened tubes was lower by $24^{\circ}C$ than that without the rib. Rib can reduce the HTG volume by 7%.

• 에너지공학
• /
• 제14권2호
• /
• pp.98-104
• /
• 2005

Pannier-arrangement condensers are usually adopted in the turbine generator units of combined cycle power plants. Optimization of operating performance and economy is an important goal, which requires accurate understanding of flow and heat transfer effects in the condenser. The tube bundle arrangement and steam flow behaviors of pannier-arrangement condensers are very different from those of common condensers. The physical model for existing numerical simulation program of condenser is refined by constructing the correlations for flow resistance and condensation heat exchange coefficient in which the influences of steam flow direction are considered according to available experimental data. The adaptability of the developed physical model and simulation program of pannier-arrangement condenser is verified with available experimental data.

• 에너지공학
• /
• 제14권4호
• /
• pp.241-247
• /
• 2005

3열 정렬형 관군 배열에서 3열의 'common flow up'과 'common flow down' 형상의 와류발생기를 부착하여 와류발생기에 의한 열전달 촉진과 압력강하를 비교하였다 선행 연구자들이 제안한 'common flow down' 형상의 와류발생기는 와류발생기가 없는 휜-관군에 비해 열전달 촉진은 $10\%{\~}25\%$ 향상되었고, 압력강하는 $20\%{\~}35\%$ 증가하였다. 'common flow up' 형상의 와류발생기의 경우 후연 수평거리(${\Delta}y$)를 변화시키면서 평가하였다. 와류발생기는 삼각형과 사각형 형상을 적용하였다. 후연 수평거리(${\Delta}y$)가 5mm이고 삼각형의 'common flow up' 형상의 와류발생기가 정렬형 관군에서 설치될 때 Reynolds수(유로 높이의 배를 기준으로)가 $300{\~}2700$ 범위에서 열전달촉진은 10까지 향상하였고, 동시에 압력강하는 $8\%{\~}15\%$ 감소하였다. 삼각형 와류발생기가 부착된 휜-관군의 성능이 상대적으로 작은 압력강하 때문에 사각형 와류발생기가 부착된 휜-관군의 성능보다 좋게 나타났다.

• 한국태양에너지학회 논문집
• /
• 제25권1호
• /
• pp.35-44
• /
• 2005

The absorbing rate of solar irradiation on the surface of an absorbing tube in a glass evacuated solar collector is numerically investigated. Four different shapes of the absorbing tubes are considered, and the absorbed solar irradiation on the surface is calculated for several distances between the absorbing tubes and the incidence angle of solar beam radiation. From the calculation, it is known that the absorbing rate of solar irradiation on the tube surfaces depends upon the shape and the arrangement of absorbing tube and the incidence angle.

• Journal of Korean Neurosurgical Society
• /
• 제63권3호
• /
• pp.327-337
• /
• 2020

Junctional neurulation represents the most recent adjunct to the well-known sequential embryological processes of primary and secondary neurulation. While its exact molecular processes, occurring at the end of primary and the beginning of secondary neurulation, are still being actively investigated, its pathological counterpart -junctional neural tube defect (JNTD)- had been described in 2017 based on three patients whose well-formed secondary neural tube, the conus, is widely separated from its corresponding primary neural tube and functionally disconnected from corticospinal control from above. Several other cases conforming to this bizarre neural tube arrangement have since appeared in the literature, reinforcing the validity of this entity. The cardinal clinical, neuroimaging, and electrophysiological features of JNTD, and the hypothesis of its embryogenetic mechanism, form part of this review.

• 대한기계학회논문집
• /
• 제19권1호
• /
• pp.212-218
• /
• 1995

Turbulent flow and heat transfer characteristics around staggered tube bundles were studied using a non-orthogonal boundary fitted coordinate system and the low Reynolds .kappa. - .epsilon. turbulence model suggested by Lam and Bremhorst. The predicted flow characteristics for two tube pitches and tube arrangement showed good agreement with the experimental data except the strongly curved region. The predicted Nusselt number was compared with measurements obtained in the staggered rough bundles and it revealed the similar trend to measurements, but the location of the maximum and minimum heat transfer differed somewhat from the measurements.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권5호
• /
• pp.76-81
• /
• 1996

In this paper, a calculation method for fin efficiency of continuous fin is introduced. The continuous fin of in-line and staggered arrangement was divided into many sectors and fin efficiencies of each sectors were calculated by assuming that each sectors be the circular fins. To get the converged fin efficiency which is averaged by the each areas, the number of sectors was increased. The results were compared with equivalnet method by varying the aspect ratios in both cases of in-line and staggered tube arrangement and showed some differences of fin efficiencies.

• 대한기계학회논문집B
• /
• 제25권12호
• /
• pp.1748-1755
• /
• 2001

The shell and tube heat exchangers were introduced to apply to a big capacity condenser and a high pressure feed water heater for power plant in the beginning of 1990s. Design and manufacturing technology fur shell and tube heat exchangers have been developed until now. But it is very difficult to calculate the expected performance characteristics of the shell and tube heat exchanger, because there are many design parameters to be considered according to internal structure and the shell side heat transfer mechanism complicately related to the design parameters. Design parameters to be considered in the design stage of shell and tube heat exchanger are shell and tube side fluids, flow rate, inlet and outlet temperature, physical properties, type of heat exchanger, outer diameter, thickness, length of tube, tube arrangement, tube pitch, permissive pressure loss on both sides, type of baffle plate, baffle cutting ratio. The propose of study is an analysis TEMA(Tubular Exchanger Manufacturers Association) E shell and tube heat exchanger performance with changing a number of baffles(3, 5, 7, 9, 11) and tubes(16, 20) and determined optimal baffle spacing.

• 설비공학논문집
• /
• 제15권12호
• /
• pp.1078-1087
• /
• 2003

Kimchi refrigerator is a household electric appliance developed with the wholly domestic technology for maturing and keeping kimchi. However, the principle of keeping is not yet revealed obviously. This numerical study has been conducted to investigate the flow and heat transfer characteristics in a kimchi refrigerator. The effects of arrangement variation of a evaporation tube are examined. Also, the heat transfer characteristics through the insulation material are discussed in detail. The flow and temperature field was simulated using the commercial code of CFX-5.3. A natural convection flow is formed through about 5/6 region from the bottom within the keeping space and accordingly, the 90% region of kimchi containers satisfies the temperature requirement with 0$\pm$0.5$^{\circ}C$. The stagnant flow exists in the upper 1/6 region of the keeping space and accordingly, the stratified high temperature distributions appear in the upper region of kimchi containers. The upward shift of the start location of a evaporation tube improves the temperature concentration toward $0^{\circ}C$ but the pitch variation is of no effect. The heat fluxes on the insulation surfaces show two-dimensional distributions with being higher toward the center. Through the variation of insulation thickness, 3.5% saving of insulation material is obtained under the same heat transfer rate.