• 한국산학기술학회논문지
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• 제11권1호
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• pp.55-60
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• 2010

고압의 가스를 이용하여 고온 가스와 저온 가스를 분리하거나 입자상 물질의 분리에 사용 할 수 있는 장치인 볼텍스 튜브의 에너지 분리 특성을 적용하여 자동차의 EGR Cooler 대체장치의 기본 설계 자료를 구축하기 위하여 실험을 수행하였다. 설계를 위한 기초 자료를 확보하기 위하여, 볼텍스 튜브의 입구 압력, 저온출구 및 고온출구압력 변화에 따른 에너지 분리 특성을 분석하였다. 공급압력이 상승할수록 에너지 분리 효과가 상승하였으며, 최고온도는 저온유량비가 약 0.85 에서, 최저온도는 저온유량비가 약 0.35 에서 발생하였다. 볼텍스 튜브의 고온측 출구온도는 고온측 및 저온측 출구압력에 영향을 받으며, 저온측 출구온도는 출구압력 변화에 독립적인 온도변화 특성을 나타내었다. 본 연구의 결과는 자동차의 EGR Cooler 대체장치의 기본 설계 자료로 응용될 수 있을 것이다.

• Nuclear Engineering and Technology
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• 제27권5호
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• pp.775-783
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• 1995

CANDU원자로에서 압력관의 건전성을 향상시키기 위한 방안으로 압력관의 두께를 증가시키는 방법과 압력관 제조공정에서 초기수소농도를 줄이는 방법이 연구중에 있다. 본 연구에서는 압력관 두께증가가 가동중 압력관의 안전여유도에 미치는 영향과 새로운 압력관의 낮은 수소농도가 파손의 주원인인 DHC에 미치는 영향에 대해 연구하였다. 가동중 압력관에 날카로운 결함이 발생할 경우 5.2mm두꺼운 압력관은 안전여유도 관점에서 현행 2mm 압력 관에 비해 25% 증가효과를 보이는 것으로 나타났다. LBB평가에서도 두꺼운 압력관은 DHC 발생에 필요한 초기균열 길이 (a), 중수누설 감지 시점에서의 균열길이 (Lp), 중수누설후 압력관 파단까지의 허용시간(t)등에서 많은 이점이 있는 것으로 평가되었으며, 또한 LOCA시 압력관 파단관점에서도 유익한 것으로 나타났다. 여러가지 다른 두께 및 다른 초기수소농도를 갖는 압력관을 대상으로 20년 가동후의 총 누적 수소량을 계산한 결과, 5ppm의 초기 수소량을 갖고 두께가 5.2 mm인 압력관이 가장 우수한 저항성을 보였다. 결함 성장평가에 있어서 초기에 낮은 수소량을 갖는 압력관은 20년 가동후에도 수소화물의 석출이 일어나는 TSS 도달 온도가 낮게 유지되며 냉각시 균열성장량도 매우 적은 것으로 나타났다.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.235-241
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• 2002

The process of energy separation in a low pressure vortex tube with air as a working medium is studied In detail. Experimental data of the temperature of the cold and hot air leaving the vortex tube are presented. The variation of the maximum wall temperature along the inner surface of the vortex tube and the temperature distribution in the vortex tube provides useful information about the location of the stagnation point of the flow field at the axis of the vortex tube. In this study Outer tube is used for the application of Diesel engine exhaust. The hot gas flow is fumed 180° and passes the outside of the vortex tube a second time heating it. From this geometric setup of a vortex tube the effects of energy separation and the prediction of the ignition of Diesel Soot is presented by experimental data.

• 한국추진공학회지
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• 제15권6호
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• pp.47-55
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• 2011

본 논문에서는 매니폴드 내의 튜브 라운드 적용에 따른 고온 고압 튜브형 열교환기에서의 압력강하와 열성능을 분석하기위해 전산해석을 수행하였다. 튜브형 열교환기에서의 압력강하와 열성능은 튜브라운드의 위치에 많은 영향을 받는다. 튜브 라운드에 따른 연구는 튜브 입구, 튜브 출구, 그리고 튜브 양쪽 세 가지 위치에 따라 수행하였다. 본 연구에서, 튜브 양쪽에 라운드를 적용한 경우에는 가장 낮은 압력강하와 감소된 열전달을 보였지만 튜브 출구에 라운드를 적용한 경우에는 압력강하와 열전달 모두 기본형상에 비하여 좋은 특성을 보였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.353-358
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• 2005

The heat transfer and pressure drop of supercritical $CO_2$ cooled in a helically coiled tube was investigated experimentally. The experiments were conducted without oil in the refrigerant loop. The experimental apparatus of the refrigerant loop consist of receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section is a helically coiled tube in tube counter flow heat exchanger with $CO_2$ flowed inside the inner tube and coolant( water) flowed along the outside annular passage, It was made of it copper tube with the inner diameter of 4.55[mm]. the outer diameter of 6.35 [mm] and length of 10000 [mm]. The refrigerant mass fluxes were $200^{\sim}600$ [kg/m2s] and the inlet pressure of gas cooler varied from 7.5 [MPa] to 10.0 [MPa]. The main results are summarized as follows : The heat transfer coefficient of supercritical $CO_2$ increases, as the cooling pressure of gas cooler decreases. And the heat transfer coefficient increases with the increase of the refrigerant mass flux. The pressure drop decreases in increase of the gas cooler pressure and increases with increase the refrigerant mass flux.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.93-96
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• 2012

The spontaneous ignition mechanism of high pressure hydrogen gas released into tube is well-deduced from previous studies. However, those results have a limit because the studies have been conducted at low burst pressure of about 10 MPa. In this study, the process or ignition feature are investigated with higher burst pressure of up to 30 MPa through numerical analysis. The results show that the trend of ignition became to be different with a burst pressure. While two reaction regions is important to initiate the ignition when burst pressure is about 10 MPa, the reaction of the core region does not play a role in ignition inside the tube when a burst pressure is above 20 MPa.

• 설비공학논문집
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• 제27권2호
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• pp.63-68
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• 2015

The fin and tube type heat exchangers widely used in air conditioners have been developed to improve on the heat transfer performance and compactness. This study presents the new type of tube for the heat exchanger to improve the heat transfer performance by increasing the heat transfer area per unit volume in the air-conditioner heat exchanger. The new type tube can be used for mechanical expansion facility, due to the two-port copper tube. Numerical calculation shows that the heat exchanger using the two-port copper tube outperforms the conventional heat-exchanger using a circular copper tube, in terms of the increased heat transfer coefficient and higher pressure drop. The calculation results were experimentally validated and are in agreement with the experimental results. Compared to the heat exchanger using a conventional circular tube, the heat exchanger with a two-port tube increased the heat transfer coefficient up to 21%, and the pressure dropped up to 16%.

• Journal of Advanced Marine Engineering and Technology
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• 제30권4호
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• pp.463-473
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• 2006

The effect of tube diameter on heat and mass transfer characteristics of absorber in absorption chiller/heater using LiBr solution as a working fluid has been investigated by both of numerical and experimental study to develop a high performance and compact absorber. The diameter of the heat exchanger tube inside absorber was changed from 15.88mm to 12.70mm and 9.52mm. In numerical study a model of vapor pressure drop inside tube absorber based on a commercial 20RT absorption chiller/heater was performed. The effect of tube diameter, longitudinal pitch, vapor Reynolds number, longitudinal pitch to diameter ratio on vapor pressure drop across the heat exchanger tube banks inside absorber have been investigated and found that vapor pressure drop decreases as tube diameter increases, longitudinal pitch increases, vapor Reynolds number decreases and longitudinal pitch to diameter ratio increases. In experimental study, a system includes a tube absorber, a generator, solution distribution system and cooling water system was set up. The experimental results shown that the overall heat transfer coefficient, mass transfer coefficient. Nusselt number and Sherwood number increase as solution flow rate increases. In both of study cases, the heat and mass transfer performance increases as tube diameter decreases. Among three different tube diameters the smallest tube diameter 9.52mm has highest heat and mass transfer performance.

• 설비공학논문집
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• 제21권4호
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• pp.215-221
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• 2009

The objectives of this paper are to measure the heat transfer and pressure drop of the heat transfer tube for an evaporator of absorption system applications. Five types of heat transfer tubes with different shape and heat transfer area are tested in the present experiment. Heat transfer and pressure drop performance of heat transfer tubes are measured in various operating conditions, and compared each other. The results show that the heat transfer coefficient of thermoexcel notch tube increases about 79.6% and 45.3% at the film Reynolds number 69.7 compared with that of bare tube and low fin tube, respectively. The thermoexcel notch tube is show the best performance considering pressure drop and heat transfer coefficient.

• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.947-957
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• 2003

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle. In order to complete the integrity evaluation of pressure tube, expert knowledge, iterative calculation procedures and a lot of input data are required. More over, results of integrity assessment may be different according to the evaluation method. For this reason, an integrity evaluation system, which provides efficient way of evaluation with the help of attached database, was developed. The present system was built on the basis of 3D FEM results, ASME Sec. XI, and Fitness For Service Guidelines for CANDU pressure tubes issued by the AECL (Atomic Energy Canada Limited). The present system also covers the delayed hydride cracking and the blister evaluation, which are the characteristics of pressure tube integrity evaluation. In order to verify the present system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.