• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2261-2266
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• 2007

In this study, the numerical analysis to estimate condensation heat and mass transfer of the condenser was carried out using the PMA (porous medium approach). In the PMA, the details of tube bundle in the condenser are replaced by the porous medium, and the flow resistance term is added in the momentum equation. In this regard, the PMA is quite helpful for the study of tube bundle in the large condenser. The pressure loss through tube bundle can be compensated by viscous and inertial momentum sink terms, which was validated numerically. Value of the pressure drop was compared to that of Butterworth correlation. Three dimensional analysis of condensation for McAllister condenser with the PMA was conducted using Fluent 6.2 and UDFs (use-defined functions). The result of condensation rate was analogous to previous results (experimental and numerical data).

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.509-518
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• 2005

Liquid film thickness in laminar film condensation for flow over a flat plate generally is so thin that both fluid acceleration and thermal convection within the liquid film can be neglected. An integral solution method is proposed to solve the conjugate problems of laminar film condensation and heat conduction in a solid wall. It is found that approximate solutions of the governing equations involve four physical parameters to describe the conjugate heat transfer problem for laminar film condensation. It is shown that the effects of interfacial shear. mass transfer and local heat transfer are strongly dependent on the thermo-physical properties of the working fluids and the Jacob number.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.368-373
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• 1996

A simple set of the transition criterion of the condensation regimes and the heat transfer coefficients on the direct contact condensation of the core makeup tank is developed, and implemented in RELAP5/MOD3.1 The condensation regimes are divided into two regimes: supply limit and condensation limit. In mode]ing the transition criterion between two regimes, a large-eddy model developed by Theofanous is used, and the empirical coefficient of the present large-eddy model is close to that of the large-eddy model. It turns out that the modified code better predicts the experimental data, especially the injection flow rate and the water level trend than the original code does.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.59-68
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• 2020

ECCMIX component was introduced in RELAP5/MOD3 for calculating the interfacial condensation. Compared to other existing components in RELAP5, user experience of ECCMIX component is restricted to developmental assessment applications. To evaluate the capability of the ECCMIX component, ECCS experiment was conducted which included single-phase and two-phase thermal mixing. The experiment was carried out with test sections containing a main pipe (70 mm inner diameter) and a branch pipe (21 mm inner diameter) under the atmospheric pressure. The steam mass flow in the main pipe ranged from 0 to 0.0347 kg/s, and the subcooled water mass flow in the branch pipe ranged from 0.0278 to 0.1389 kg/s. The comparison of the experimental data with the calculation results illuminated that although the ECCMIX component was more difficult to converge than Branch component, it was a more appropriate manner to simulate interfacial condensation under two-phase thermal mixing circumstance, while the two components had no differences under single-phase circumstance.

• 설비공학논문집
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• 제14권8호
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• pp.656-663
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• 2002

Flow condensation heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A were measured on horizontal plain and microfin tubes. The experimental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water/glycol loop. The test section in the refrigerant loop was made of both a plain and a microfin copper tube of 9.52 mm outside diameter and 1.0 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. Tests were performed at a fixed refrigerant saturation temperature of $40^{\circ}C$ with mass fluxes of 100, 200, and 300 kg/$m^2s$. Test results showed that at similar mass flux the flow condensation HTCs of R134a were similar to those of R22 for both plain and microfin tubes. On the other hand, HTCs of R407C were lower than those of R22 by 11~l5% and 23~53% for plain and microfin tubes respectively. And HTCs of R410A were similar to those of R22 for a plain tube but lower than those of R22 by 10~21% for a microfin tube. In general, HTCs of a microfin tube were 2.0~3.0 times higher than those of a plain tube.

• 한국항공우주학회지
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• 제35권3호
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• pp.248-252
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• 2007

본 연구는 공급계 관에서 극저온 연료의 일부가 기화될 경우에 로켓엔진이 지속적으로 작동될 수 있는지의 여부를 묻는 문제와 관련되어 있다. 유동장 내에 증기가 발생하는 것을 모사하는 실험의 결과분석으로 관내의 압력조건에서 극저온 유체의 온도가 포화온도보다 낮을 경우 발생된 증기가 완전히 응축될 수 있다는 것을 확인하였다. 극저온 유체의 정상유동에서 비평형 응축영역을 계산하기 위한 경험관계식을 무차원형태로 구하였고, 이 경험관계식이 실제적으로 활용 될 수 있는 분야를 제시하였다.

• 설비공학논문집
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• 제3권3호
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• pp.153-160
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• 1991

Heat transfer characteristics of a direct contact heat exchanger utilizing sieve trays and spray nozzles for steam condensation for the purpose of combining with a LNG evaporator have been investigated with various cooling water flow rates and different vacuum pressures within the heat exchanger for the purpose of steam condensation. Temperature profiles and the volumetric overall heat transfer coefficients in a direct contact heat exchanger have been obtained for comparisons. The results show that the temperature differences between cooling water and steam along the direct contact heat exchanger height are rapidly decreasing and the volumetric overall heat transfer coefficients of the exchanger improves greatly as the inside vacuum pressure increases. The values of the overall heat transfer coefficients at P=-680mmHg have been increased significantly compared with at atmospheric pressure. At given pressure conditions, it is found that the values of average volumetric overall heat transfer coefficients for the sieve tray are found to be approximately 10% higher than those of the spray nozzle.

• 대한기계학회논문집B
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• 제21권2호
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• pp.329-340
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• 1997

A passive control of interaction of condensation shock wave / boundary layer for reducing the strength of condensation shock was conducted experimentally in a 2.5 * 8 cm$^{2}$ indraft type supersonic wind tunnel. The effects of following factors on passive control were investigated: 1) the thickness of porous wall, 2) the diameter of porous hole, and 3) the orientation of porous hole. On the other hand, the location of nonequilibrium condensation region and condensation shock wave was controlled by regulation of the stagnation conditions. Surface static pressure measurements as well as Schlieren observations of the flow field were obtained, and their effects were compared with the results the cases of without passive control. It was found that thinner porous wall, smaller porous hole and FFH orientation for the same cavity size and porosity of 12% are more favourable than the cases of its opposite.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1725-1734
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• 1996

Experimental condensation and evaporation heat transfer coefficients were measured in a horizontal smooth tube and a horizontal micro-finned tube with HFC-134a. The test sections are straight, horizontal tubes with have a 9.52mm outside diameter and about 5000mm long. The micro-finned tube had 60 fins with a height of 0.12mm and a spiral angle of 25.deg.. The condensation test section was a double-pipe type with counter flow configuration. The evaporation test section employed an electic heating method. Enhancement factors which is defined as a ratio of the heat transfer coefficient for micro-finned tube to that for smooth tube, varied from 1.3 to 1.6(mass flux:110~190kg/m$^{2}$s) for condensation and 1.2 to 1.5 (mass flux:70~160kg/m$^{2}$s) for evaporation. The experimental data of condensation and evaporation heat transfer coefficients were compared to several empirical correlations. Based on these comparisons, modified correlations of the condensation and evaporation heat transfer coefficient for both smooth and micro-finned tubes were proposed.

• 에너지공학
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• 제12권2호
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• pp.74-83
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• 2003

APR1400과 같은 차세대 원자력발전소에서는 원자로 안전성을 증진시키기 위하여 SDVS와 같은 계통을 도입하고 있다. 완전급수상실사고와 같은 경우는 POSRV가 개방되어 수조내 Sparger를 통하여 증기가 방출·응축되게 된다 증기가 응축함에 있어서 설계에서 고려해야 될 사항은 하중과 수조 혼합이며 증기제트 응축의 물리적 현상 이해를 통하여 적절한 대처를 마련할 수 있다. 수조내 Sparger를 통하여 분사되는 증기 응축에 대하여 하중과 수조 혼합 검토에 도움이 될 수 있도록 증기제트 응축의 물리적 현상 이해에 대한 검토와 평가를 수행하였다.