다관원통형 열교환기의 성능평가 방법 개발에 관한 연구

원세열(Won Se Youl),윤은섭,이한희(Lee Han Hee),Park Young Sheop 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

As the operation time of heat exchangers is increased, the thermal performance of them is gradually decreased because of tube plugging in terms of fouling generated by water-borne deposits which is known to reduce the thermal efficiencies. Currently, thermal performance management of heat exchangers is more importantly presented. In nuclear power plants, the thermal performance evaluation has been analyzing in some safety related heat exchangers only. The performance evaluation method for shell and tube heat exchanger is required to improve the present method of performance criterion and film heat transfer coefficient calculation. This paper describes the developed thermal performance evaluation method for shell and tube heat exchangers and presents the result of performance evaluation applied for a regenerative heat exchanger in a nuclear power plant.

표면조도를 가지는 오목한 면에 충돌하는 원형제트에 의한 열전달 측정

이대희,원세열,이준식,Lee, Dae Hee,Won, Se Youl,Lee, Joon Sik 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.6

The local Nusselt numbers have been measured for a round turbulent jet impinging on the concave surface with and without rib. Liquid crystal/transient method was used to determine the Nusselt number distributions along the surface. The temperature on the surface was measured using liquid crystal and a digital color image processing system. The experiments were made for the jet Reynolds number (Re) 23,000, the dimensionless nozzle-to-surface distance (L/d) from 4 to 10, the dimensionless surface curvature (d/D) 0.056, and the rib type (height ($d_1$) 0.2 cm, pitch (p) from 1.2 to 3.2 cm). It was founded that only when $L/d{\geq}6$, the average Nusselt numbers on the concave surface with rib are higher than those without rib, mainly due to an increase in the turbulent intensity caused by the effect of rib attached to the wall surface. It was realized that the rib attached to the concave surface may no longer enhance the heat transfer rate or even lowers it depending on the rib type and flow conditions. In addition, the results by the steady-state method using the gold-film Intrex were in good agreement with those by the transient shroud method.

완전 발달된 원형 충돌제트의 노즐 직경이 열전달에 미치는 영향

이대희,원세열,이영민,조헌노,Lee, Dae-Hee,Won, Se-Youl,Lee, Young-Min,Cho, Heon-No 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.4

The effect of nozzle diameter on the local Nusselt number distributions has been investigated for an axisymmetric turbulent jet impinging on the flat plate surface. The flow at the nozzle exit has a fully developed velocity profile. A uniform heat flux boundary condition at the plate surface was created using gold film Intrex. Liquid Crystal was used to measure the plate surface temperature. The experiments were made for the jet Reynolds number (Re) 23,000, the dimensionless nozzle to surface distance (L/d) from 2 to 14, and the nozzle diameter (d) from 1.36 to 3.40 cm. The results show that the Nusselt number at and near the stagnation point increase with an increasing value of the nozzle diameter.

격납건물 냉방수계통에서의 이상유동/수격 영향 평가

신혜영(Hye-Young SHIN),원세열(Se-Youl WON),이경수(Kyoung-Soo LEE),이진용(Jin-Yong LEE),이거형(Keo-Hyoung LEE) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

Some technical issues addressed in Generic Letter 96-06 by the U.S. NRC are related to the possibilities of two-phase flow and water-hammer phenomena which were not considered in the stage of design at a cooling water system to support containment fan coolers for cooling the high pressure and high temperature containment atmosphere during the design basis accidents such as a loss of coolant accident or a main steam line break accident accompanied by a loss of off-site power. The evaluations on the occurrence possibilities and effects of the phenomena of two phase flow and water-hammer at a chilled water system to support containment fan cooler in a nuclear power plant were performed in a view of containment structural integrity under the scenario of design basis accidents accompanied by loss of off-site power considering emergency operation procedures.

노즐 직경이 충돌제트에 의하여 열전달에 미치는 영향

이대희,원세열,이영민,조헌노 인제대학교 1999 仁濟論叢 Vol.14 No.3

본 연구는 축대칭 난류원형제트가 평판에 충돌하는 경우에 노즐직경이 국소 Nusselt 수 분포에 미치는 영향을 연구하였다. 노즐출구에서의 유동은 완전 발달된 속도형상을 지니고 있다. 그리고, 금박막이 된 Intrex를 사용하여 평판에는 등열유속 경계조건을 형성시켰다 또한, 액정은 평판의 벽면온도를 측정하기 위하여 사용하였다. 실험시 Reynolds 수는 Re=23,000으로 고정하였으며, 노즐과 평판사이의 거리는 L/d=2~14 까지, 노즐 직경은 d=1.36, 2.16, 3.40으로 변화시켰다. 실험결과 정체점과 정체점 영역에서의 Nusselt 수는 노즐 직경이 증가함에 따라 증가함을 알았다. The effect of nozzle diameter on the local Nusselt number distributions has been investigated for an axisymmetric turbulent jet impinging on the flat Plate surface. The flow at the nozzle exit has a fully developed velocity profile. A uniform heat flux boundary condition at the plate surface was created using gold film Intrex. Liquid Crystal was used to measure the plate surface temperature. The experiments were made for the jet Reynolds number (Re) 23,000, the dimensionless nozzle to surface distance (L/d) from 2 to 14., and the nozzle diameter (d) from 1.36 to 3.40 cm. The results show that the Nusselt number at and near the stagnation point increase with an increasing value of the nozzle diameter.

The effect of swirl on heat transfer in a circular impinging jet

Lee, Dae Hee,Won, Se Youl 인제대학교 1998 仁濟論叢 Vol.14 No.2

본 연구는 와류원형 충돌제트가 평판에 미치는 국소 Nusselt 수를 측정하였다. 와류는 특별히 제작된 베인타입의 와류발생기를 통하여 형성되며, 와류발생기는 노즐 안쪽에 위치해 있다. 평판에서 등열 유속경계조건은 금박막필름을 이용하여 형성되었고, 평판의 온도는 액정과 디지털 영상처리 시스템을 이용하여 측정하였다. 제트의 레이놀즈 수는 Re = 23,000 으로 유지시켰다. 또한, 와류 수는 S = 0 에서 0.77 까지 변화시켰고, 노즐과 평판사이의 거리는 L/d = 2 에서 10 까지 변화시켰다. 그리고, 와류가 Nusselt 수 분포에 비치는 영향은 비슷한 유동현상을 가지는 비 와류 충돌제트의 실험결과와 비교함으로써 연구되었다. The local Nusselt numbers from a flat surface to a swirling round impinging jet have been measured. The swirling air jet was created by a specially designed vane-type swirl generator which was inserted inside the pipe nozzle. The uniform heat flux boundary condition at the plate surface was created using gold film Intrex. The plate surface temperature was measured using liquid crystal and a digital image processing system. The jet Reynolds number (based on the mean nozzle exit velocity in the non-swirling jet case) was kept at Re = 23,000. The swirl number was varied from S = 0 to 0.77 and the nozzle-to-surface distance ranged from L/d = 2 to 10. The effect of swirl number on the Nusselt number distribution was investigated by comparing to data for a non-swirled impinging jet with similar flow configurations.

각-관 열교환기의 냉각능력 향상에 관한 연구

이대희,조헌노,원세열,이영민 인제대학교 1999 仁濟論叢 Vol.14 No.3

본 연구에서는 변압기 냉각용 각-관(Shell and Tube) 열교환기의 성능을 실험적으로 테스트하여 열교환기의 냉각능력을 향상시키는 기술을 개발하고자 하였다. 예열수조 2개를 항온조와 함께 사용함으로써 열교환기 입구에서와 온수의 초기온도를 60℃로 유지하고, cooling tower를 이용하여 입구에서 냉각수 온도를 20℃로 유지하였다. 냉각수 유량변화(5ℓ/min, 10ℓ/min, 15ℓ/min)에 따른 baffle의 형태(Single-segmental baffle, Double-segmental baffle, Disk & Doughnut baffle, Helical baffle)와 baffle의 개수(7개에서 5개) 및 tube의 개수(26개에서 18개)를 변화시켰을 때 열교환기의 냉각능력을 각각 실험하였다. 온수와 냉각수의 입ㆍ출구에서의 온도변화를 측정하기 위하여 Thermocouple을 온수와 냉각수 관의 입ㆍ출구에 하나씩 설치하였다. 실험결과 Disk & Doughnut, Helical baffle, Double-segmental baffle의 열전달률이 Single-segmental baffle보다 5.3%, 5.5%, 11.8% 높고, Double-segmental baffle의 경우 Tube 수의 감소율이 35%일 때 열전달률의 감소율은 14.3%임을 알 수 있었고, baffle의 수가 5개에서 7개로 증가했을 때 열전달률이 12.1% 증가함을 알았다. An experimental study to enhance the cooling capacity of the shell and tube type heat exchanger has been carried out. The initial temperature of hot water in the heat exchanger is maintained at 60℃, using two preheating water baths and one constant temperature water bath, while the coolant temperature is maintained at 20℃ by way of the cooling tower. For the coolant rates of 5 ℓ/min, 10 ℓ/min, 15 ℓ/min, the experiments to determine the heat exchanger cooling capacity have been performed using the various types of baffle(Single- segmental baffle, Double-segmental baffle, Disk & Doughnut baffle, Helical baffle), the number of baffles(from 7 to 5) and number of tubes(from 26 to 18). Thermocouples are installed in the inlet and outlet of hot-water and coolant tube to measure the temperature difference. It was found that the heat transfer rates for Disk & Doughnut baffle, Helical baffle, Double-segmental baffle are 5.3%, 5.5%, 11.8% higher than the Single-segmental baffle, respectively. When the number of tube is reduce by 35%, the 14.3% decrease in the heat transfer rate occurs, while when the number of baffle increases from 5 to 7, the 12% increase in the heat transfer rate occurs.

The Development Liquid Crystal Calibration Technique Using Neural Networks with Median Filtering

Lee, Dae-Hee,Boo, Kwang-Suk,Chung, Jae-Hun,Won, Se-Youl,Kim, Yun-Taek 인제대학교 1999 仁濟論叢 Vol.14 No.3

본 연구는 Neural networks와 median filtering을 사용함으로써 새로운 액정 교정기술을 개발하였고, 열전달 측정에 본 액정교정 기술을 응용하였다. 새로운 액정측정 기술의 확실성을 입증하기 위하여, 평판에 축대칭 충돌제트를 충돌시킬때 국소 Nusselt 수를 측정하였고, 같은 조건하에서 Hue 온도교정 기술에 의한 결과와 비교하였다. Neural networks는 온도와 R, G, B 값들 간에 비선형 관계를 예측할 수 있기 때문에 Neural network와 median filtering 교장기술은 실험에서 Hue 온도교정 기술보다 더 넓은 칼라구간을 사용할 수 있으며 실험시간면에서 현저한 감소의 결과를 가져올 수 있다. This study has developed a new liquid crystal calibration technique using Neural networks and median filtering and applied this technique to heat transfer measurements. To verify the validity of this new measurement technique, the local Nusselt numbers on a flat plate surface subjected to an axisymmetric impinging jet were measured and compared to the results by the conventional Hue-temperature calibration technique under the same conditions. Because Neural networks predict the non-linear relations between temperatures and corresponding R, G, B values, Neural networks-median filtering calibration technique can utilize a much wider color band in the experiment than the Hue-temperature calibration technique, resulting in the significant reduction in the experimental time.