• 에너지공학
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• 제24권2호
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• pp.103-109
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• 2015

배열회수 보일러는 입구 확관 덕트와 전열관군으로 이루어져 있는데 전열관군에서 열전달 효율을 향상하기 위해서는 전열관군 전에서 배기가스 유동이 균일하게 되어야 한다. 본 연구에서는 전열관군 전의 배열회수 보일러 입구 덕트에서 유동 특성을 살펴보았고 전열관군의 열전달 메커니즘을 지금까지 다른 연구들에서 적용하였던 일정한 열전달 량으로 한 경우와 전열관군 배관의 내부와 외부의 대류열전달을 고려한 열전달 메커니즘을 적용한 경우의 해석에서 온도 분포를 비교하여 배열회수 보일러의 전열관군에서 실제 현상에 보다 적합한 열전달 메커니즘을 정립하는 것을 목적으로 하였다. 본 연구를 통하여 전열관군 배관의 내부와 외부의 대류열전달을 고려한 열전달 메커니즘을 적용한 해석이 일정한 열전달 량을 적용한 경우보다 온도 분포가 타당한 결과를 도출하였고 이렇게 적용한 경우는 배열회수 보일러 탈질설비 전단에서 온도 분포가 설계 기준 ${\pm}10^{\circ}C$에 만족함을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.61-66
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• 2003

Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator.

• 한국전산유체공학회지
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• 제17권3호
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• pp.39-44
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• 2012

In this study, a longitudinal pitch effect on in-line tube bank heat transfer has been analyzed numerically. To verify the accuracy of the solver model and boundary conditions, global Nusselt number(Nu) and pressure drop across the 2 row tube bank are compared with the existing experimental correlations under 500 ~ 2,000 Reynolds number(Re) range. By changing transverse pitch($S_T$) or longitudinal pitch($S_L$) separately in tube bank, we're trying to identify the each effect on heat transfer. We found that the effect of transverse pitch can be accounted for Reynolds number evaluated with maximum velocity($V_{max}$) at the smallest flow area similar to most existing correlations. Variation of the longitudinal pitch($S_L$) has a greater impact on the heat transfer compared to the transverse pitch($S_T$). Overall Nusselt number increases with larger longitudinal pitch($S_L$), however individual Nusselt number of the tube row has significant difference after the first row.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.185-190
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• 2007

For the successful design of heat exchangers, it is very important to understand local heat transfer characteristics on the circular cylinder of the cross flow heat exchangers. In this study, the heat exchanger using screen is developed to enhance heat transfer. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients in the heat exchanger. The experiments are performed for single circular tube, in-line array tube bank with and without heat transfer promoter. Local Nusselt numbers of single circular tube and tube bank with heat transfer promoter are investigated and compared to those of without heat transfer promoter.

• 대한기계학회논문집
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• 제15권1호
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• pp.218-228
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• 1991

Since heat exchangers are composed of bank of tubes, the knowledge on the flow and heat transfer characteristics of the tube bank are required for the optimum design and selection of heat exchangers. In this paper, the turbulent flow fields and heat transfers normal to a staggered tube bank are solved numerically employing K-.epsilon. 2 equation turbulence model and non-orthogonal coordinate transformation for the treatment of curved surface of tubes. Predicted mean Nusselt numbers of tube bank agree reasonably well with Grimision's correlation

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.837-841
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• 2001

Almost all power plant boiler has temperature distribution nonuniformity problem in heat transfer tube flow path. It can cause hot spot damage of superheated or reheated heat transfer section and reduce maintenance schedule when nonuniformity is severe. There are two solutions for improvement temperature nonuniformity. one is change of gas flow distribution of gas path and the other is contorl steam flow in tube bank. Of course, first method is very difficulty to apply but second method is'nt. In this paper, control steam flow is used to solve temperature nonuniformity of power plant boiler.

• 설비공학논문집
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• 제12권8호
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• pp.745-754
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• 2000

An experimental study has been carried out in order to investigate the heat storage characteristics for a latent heat storage tank with horizontal shell and tube type. The heat storage tank consists of cylindrical capsules with a staggered tube bank. The effects of flow rates and initial temperature differences on the melting time and heat storage rates are examined. It is found that the melting time decreases with increase of the flow rates and initial temperature differences. Results also show that the time-averaged overall heat transfer coefficients increase in proportion to the increase of flow rates and initial temperature differences.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.131-139
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• 1999

An experimental study was conducted to investigate the fouling effects of geothermal water scale deposited onto a heating surface upon its forced convection heat transfer characteristics. Scales deposited onto the heating surfaces of heat exchangers seriously reduce the heat transfer perfor-mance and also increase the hydrodynamic drag. Accordingly fouling is an important problem in the design and operation of heat exchangers. The cylinders were settled in tandem with equal dis-tance between neighbouring cylinders and only the test cylinder was heated under the condition of constant heat flux. The Reynolds number was varied from 13000310 through 50003100. It is found that the heat transfer of the in-line tube banks greatly varies with the fouling of geothermal water scale especially its scale height. Further the local and average Nusselt numbers strongly depend upon the cylinder spacing and the Reynolds number.

• 대한기계학회논문집B
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• 제24권1호
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• pp.50-59
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• 2000

An experimental study has been carried out in order to investigate the heat storage characteristics for a latent heat storage tank with horizontal shell and tube type. The heat exchanger consisted of horizontal cylindrical capsules with a staggered tube bank layout. Based on the obtained data, the effects of flow rate and inlet fluid temperature on the melting time and heat storage rates were examined. It is found that the melting time decreased with increase of the flow rate and the inlet temperature. Results also show that at the initial stage of heat transfer the heat storage rate represents the maximum value and rapidly decreases.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.528-533
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• 2007

A finned tube type heat transfer module has been proposed for a multi-burner water tube boiler. Fins change their geometry along the streamwise direction to maximize the performance, which makes it difficult to apply conventional bulk analysis. The design program has been improved by updating data for every row of tubes along the flow. A numerical simulation has been also performed to evaluate the effect of inlet conditions and validated with experiment. The heat transfer of the first row has been underpredicted by the conventional Zhukauskas correlation, where the acceleration of the flow due to the blockage is not fully inflected. The fin tip temperature is also underpredicted by Bessel solution, because of the interaction with neighboring fins.