• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.23-29
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• 2003

Transonic two-phase flow of Saturated humid air, in which relative humidity is 100%, with various condensation processes around thin airfoils is investigated. The study uses an extended transonic small-disturbance(TSD) model of Rusak and Lee [11, 12] which includes effects of heat addition to the flow due to condensation. Two possible limit types of condensation processes are considered. In the nonequilibrium and homogeneous process, the condensate mass fraction is calculated according to classical nucleation and droplet growth rate models. In the equilibrium process, the condensate mass fraction is calculated by assuming an isentropic process. The flow and condensation equations are solved numerical1y by iterative computations. Results under same upstream conditions describe the flow structure, field of condensate, and pressure distribution on airfoil's surfaces. It is found that flow characteristics, such as position and strength of shock waves and airfoil’s pressure distribution, are different for the two condensation processes. Yet, in each case, heat addition as a result of condensation causes significant changes in flow behavior and affects the aerodynamic performance of airfoils.

• Journal of Energy Engineering
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• v.9 no.4
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• pp.334-341
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• 2000

회전 히트파이프의 열 전달 특성은 내부 관벽에 형성되는 응축 액막 두께와 증발부로 귀한되는 응축액의 유동율에 의해 결정된다. 본 연구는 축 방향으로 그루브(groove)를 갖는 회전 히트파이프의 열 전달 성능에 대한 실험 연구로써, 그루브에 의한 효과를 파악하기 위해 2종류의 히트파이프를 제작하고 작동성은 시험을 수행하였다. 회전 히트파이프가 작동시, 원심력에 의해 그루브로 응축액의 유동을 촉진시키며, 따라서 응축부 벽면에 형성되는 액막 두께가 얇게 된다. 응축부에 그루브를 갖는 히트파이프의 열전달 계수는 풀 유동에서 2000~4000W/$m^2$$^{0}$ C, 환상 유동 영역에서 1500~2500W/$m^2$$^{0}$ C로써, 전체 원형단면을 갖는 히트파이프와 비교하여 약 1.5배 정도의 열저달 향상을 볼 수 있었으며, 열전달 한계는 약 40% 정도 향상되는 것으로 나타났다.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.577-583
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• 1998

직접 접촉에 의한 응축 열전달은 혼합증기의 레이놀즈수, 비응축 가스(공기)의 질량비, 액막의 레이놀즈수, 그리고 액막의 과냉 정도에 따라 영향을 받게 된다. 이러한 변수들의 영향을 고찰하기 위하여 본 연구에서는 수평면으로부터 87˚ 기울어진 수직 사각 덕트에서 직접 접촉 응축 열전달 실험을 수행하였다. 위의 각 실험 변수에 따른 평균 열전달 대수의 변화를 고찰하였으며, 실험결과로부터 혼합증기 레이놀즈수, 비웅축 가스의 질량비, 액막 레이놀즈수, 그리고 제이콥수를 변수로 하여 직접 접촉 응축 열전달에 대한 평균 누셀트수에 대한 실험 상관식을 도출하였다. 혼합증기의 직접 접측 웅축 열전달에 대한 평균 열전달 계수는 비응축 가스의 질량비가 증가할수록 현저히 증가함을 보였으며, 액막의 과법 정도가 증가할수록 평균 열전달 계수는 감소하였다. 그리고 혼합증기의 레이놀즈수가 30,000 이상의 템위에서는 액막 레이놀즈수의 변화에 따라 평균 열전달 계수의 변화가 거의 없었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1069-1078
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• 2013

Recently, condensation heat exchangers have been studied for applications to the passive cooling systems of nuclear plants. To design vertical-type condensation heat exchangers in secondary passive cooling systems, TSCON (Thermal Sizing of CONdenser), a thermal sizing program for a condensation heat exchanger, was developed at KAERI (Korea Atomic Energy Research Institute). In this study, the existing condensation heat transfer correlation of TSCON was evaluated using 1,157 collected experimental data points from the heat exchanger of a secondary passive cooling system for the case of pure steam condensation. The investigation showed that the Shah correlation, published in 2009, provided the most satisfactory results for the heat transfer coefficient with a mean absolute error of 34.8%. It is suggested that the Shah correlation is appropriate for designing a condensation heat exchanger in TSCON.

• Nuclear Engineering and Technology
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• v.17 no.1
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• pp.45-52
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• 1985

A two inverted U-tubes condenser was constructed from transparent materials to study the heat removal capability of steam generators under filmwise reflux condensation mode. Essentially, two sets of experiments were performed: (1) the first dealt with the reflux condensation length, and (2) the second dealt with the flooding points with and without the presence of a noncondensible gas in the steam flow, and the effect of the flooding time. In addition, experimental results are compared with the predictions of analytical models.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.298-308
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• 1999

Experimental study on characteristics of direct contact condensation of steam discharged into a sub-cooled water pool has been performed using five different sizes of horizontal nozzle over a wide range of steam mass fluxes and pool temperatures. Steam condensation phenomena have been observed visually and by taking pictures of steam jets using a high speed video camera. Two different steam jet shapes such as ellipsoidal shape and conical shape were typically observed for a stable steam jet, depending on the steam mass flux and pool temperature. The steam jet expansion ratio and the steam jet length as well as the condensation heat transfer coefficients were determined. The effect of steam mass flux, pool temperature, and nozzle diameter on these parameters were also discussed. Empirical correlations for the steam jet lengths and the condensation heat transfer coefficients as a function of steam mass flux and condensation driving potential were established. The axial and radial temperature distributions in steam jet and in surrounding water were measured. The effect of steam mass flux, pool temperature, and nozzle diameter were also discussed. The condensation regime map, which consists of six regimes such as chugging, transient chugging, condensation oscillation, stable condensation, bubble condensation oscillation, and intermittent oscillation condensation, were established. In addition, the dynamic pressures at the pool wall were measured. The close relation of dynamic pressure and steam condensation mode, which is also dependent on steam mass flux and pool temperature, was found.

• Transactions of the KSME C: Technology and Education
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• v.2 no.1
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• pp.47-55
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• 2014

A new concept of an Eco-friendly desalination method is introduced in this study. The main idea of the desalination method of seawater is the condensation of the vaporized seawater by solar heat energy on the surface of seashore. The wind turbine blade plays a role of heat exchanger condensing the vaporized water in the air. In this analytical study, the availability of the proposed desalination system was studied. First, an analytical condensation theory of the vaporized water in air was arranged and the parametric study was conducted to estimate the amount of freshwater produced from the system with the change of the temperature difference between the humid air and turbine blade, and the relative humidity in air, and wind speed. From the analytical calculation, 2,927(ton/year) of freshwater was produced at the vertical-type wind turbine (Diameter=4m, Height=3m) as the relative humidity is 100%, the temperature difference between the impeller blade and the humid air is $40^{\circ}C$ and the wind speed is 10m/s.

• Journal of Energy Engineering
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• v.25 no.2
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• pp.1-20
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• 2016

A condensation heat transfer model is very important for the safety analysis of nuclear power plants. Especially, condensation under the presence of noncondensable gases (NCGs) is an important issue in nuclear safety because the presence of even a small quantity of NCGs in the vapor largely reduces the condensation rate. In this study, the condensation heat transfer model of the severe accident analysis code MELCOR 1.8.6 has been assessed using a set of condensation experiments performed under the thermal-hydraulic conditions similar to those inside a containment during design-basis accidents or severe accidents. Experiment conditions are categorized into 4 types according to the shape of the condensation surface: vertical flat plates, outer surface of vertical pipes, inner surface of vertical pipes, the inner surface of horizontal pipes. The results of the calculations show that the MELCOR code generally under-predicts the condensation heat transfer except the condensation on inner surface of vertical pipes.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.269-275
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• 2004

콘덴싱보일러는 배기가스중의 수증기를 콘덴싱방식이라는 열교환 기술을 통해 2개의 열교환기에서 응축시키면서 생기는 응축잠열을 보일러에 더하여 줌으로써 기존보일러 대비 15 $^{\sim}$ 20% 이상 열효율이 높이는 첨단기술이 사용된 보일러로 콘덴싱보일러의 개발현황, 에너지 절감 효과 그리고 환경친화적 효과를 소개하고자 합니다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.28 no.5
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• pp.389-395
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• 1999

냉동공조설비, 발전설비, 화학플랜트설비 등에 사용되는 응축기는 주로 증기가 관의 외부에서 응축을 하고 냉각수가 관 내부로 흐르는 쉘-튜브(shell and tube)형 태를 취하고 있다. 초기투자비용 및 운전비용을 줄이기 위해서는 응축기의 열교환 성능을 향상시키는 일이 필수적이며 이를 위해 코팅 표면(coated surfaces), 거친 표면(rough surfaces), 코일 튜브(coiled tubes), 선회 흐름장치(swirl flow), 전열면적을 넓힌 낮은 핀관과 3차원 형상을 갖는 열전달 촉진관의 사용이 제시되고 있다.