• 대한기계학회논문집B
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• 제39권1호
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• pp.61-69
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• 2015

본 논문은 수직 오리피스 이젝터의 혼합유동 및 산소전달 특성에 대한 실험적 연구를 목적으로 한다. 실험장치는 전동 모터-펌프, 오리피스 이젝터, 순환 수조, 공기압축기, 고속 카메라 시스템 그리고 제어 및 측정기기로 구성하였다. 측정된 구동유체 및 유입공기의 유량을 이용하여 유량비를 도출하였다. 이적터에서 분출된 혼합유동의 가시화를 통해 정성적 거동을 고찰하였으며, 용존산소 농도를 측정하여 총괄 산소전달계수를 도출하였다. 구동유체의 유량이 일정하고 압축기의 공기압이 높아지면 유량비와 산소전달계수는 증가하며, 압축기의 공기압이 일정하고 구동유체의 유량이 증가하면 유량비는 감소하지만 산소전달계수는 증가하였다. 기포의 크기에 따른 체류시간 및 확산도와 수직 혼합유동의 도달거리는 2 상의 접촉면적과 시간에 크게 영향을 미치기 때문에 산소전달율의 중요한 변수임을 유추할 수 있다.

• 대한기계학회논문집B
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• 제39권1호
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• pp.37-43
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• 2015

현열 뿐만 아니라 잠열을 이용하는 증발냉각은 배기열 회수에 매우 유용하게 사용될 수 있다. 본 연구의 목적은 증발냉각을 이용한 배기열 회수장치의 성능을 실험적으로 규명하는 것이다. 성능실험장치는 플라스틱 열교환기, 물 분무 노즐, 공기유동용 홴, 물 순환용 펌프, 수조, 온도 습도 유량 측정 센서 등으로 구성되었다. 증발이 없는 현열 회수에서의 유용도와 증발을 수반하는 전열 회수에서의 유용도를 여러가지 작동조건에서 측정하여 비교하였다. 현열냉각과 증발냉각의 유용도는 공기의 유량이 증가함에 따라 감소하고, 대향류에서의 유용도가 평행류에서의 유용도 보다 휠씬 높다. 증발냉각의 경우 물 유량이 증가함에 따라 유용도는 증가하고, 평행류가 대향류보다 물 유량에 더 민감함을 알 수 있다.

• Journal of Chest Surgery
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• 제12권1호
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• pp.33-42
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• 1979

The present study reports 41 cases of congenital and acquired heart diseases, who received open heart surgery under extracorporeal circulation [ECC] by Sarns Heart-Lung-Machine [HLM] at the Department of Thoracic and Cardiovascular Surgery, Hanyang University Hospital during the` period between July 1975 and February 1979. The priming of pump oxygenator was carried out by the hemodilution method using Hartman`s solution, whole blood, and fresh human plasma. The rate of hemodilution was in the average of 50.8 ml/kg. ECC was performed at the average perfusion flow rate of 85.0 ml/kg/min [2.43 L./ kg/2] and at moderate hypothermia. In the total cardiopulmonary bypass, arterial pressure ranged between 55 mmHg and 90 mmHg, but generally maintaining over 70 mmHg. Patient age ranged between 2 and 54 year old, in congenital heart diseases, between 2 and 28, in acquired heart diseases, between 17 and 54 Sex ratio of male to female was 20:21. The cases include a case of pulmonary valvular stenosis, 4 cases of atrial septal defect, 9 cases of ventricular septal defect, 9 cases of tetralogy of Fallot, 5 cases of pentalogy of Fallot, 3 cases of atypical multiple anomalies 7 cases of mitral stenosis or insufficiency, a case of myxoma in left atrium, and a case of ruptured aneurysm of Valsalva`s sinus. The surgical managements were 16 valvulotomy for pulmonary valvular stenosis, 2 Teflon patch graft closure and 5 simple suture closure of atrial septal defect, 16 Teflon patch graft closure and 5 simple suture closure of ventricular septal defect, 12 pericardial patch graft for infundibular stenosis of right ventricle, one anastomosis between left superior vena cava and right atrium, 2 open mitral commissurotomy, 5 mitral valve replacement using Starr-Edward`s ball valve, porcine xenograft by Hancock, by Carpentier-Edward, or Angell-Shiley, one removal of left atrial myxoma, and a repair of ruptured aneurysm of Valsalva`s sinus. Four [9.7%] out 41 cases expired postoperatively and the rest of 37 cases survived with satisfactory results. The causes of death were one coronary embolism in tetralogy of Fallot, 2 postoperative lower cardiac output in atypical multiple anomalies, and one right heart failure in large: ventricular septal defect with pulmonary hypertension.

• Journal of Chest Surgery
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• 제10권2호
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• pp.268-273
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• 1977

During the period from March, 1963, to November, 1977, forty-eight patients with secundum type atrial septal defects have undergone surgical repair using cardiopulmonary bypass with a pump oxygenator at the Seoul National University Hospital. Twenty-six [55 percent] of the patients were females and Twenty-two [45 percent] were males. The patients varied in age from 3 years to 51 years. We have divided secundum defects into three types. These are: 1] the high defect; 2] Ovale type defect; and 3] low defect including the defect in the area of the coronary sinus. An ovale type defect was present in forty-one cases [85 percent]. Partial anomalous pulmonary venous connections were present in two patients in the high defect group. All of the forty-eight patients had had right heart catheterization before operation. The pulmonary to systemic flow ratio [Qp/Qs] was determined in our 38 patients. The Qp/Qs was less than 1.5/1 in only five of the 38 patients. Among the 33 patients with moderate and severe left-to-right shunts [Qp/Qs 1.6-3.5/1], the systolic pulmonary artery pressures. ranged from 30 to 80 mm Hg. Large left-to-right shunts [Qp/Qs>3.6/1] were present in 13 patients. The postoperative complications occurred in 13 patients [27. 1 percent]. Postoperative wound infections were the most frequent complications being present in 6 patients [12.5%]. Forty-six of the patients with secundum atrial septal defects survived surgical repair of their defects. Thus the hospital mortality of surgery was 4.2 percent. The causes of death in the early postoperative period were: 1] low cardiac output syndrome related to severe pulmonary hypertension in one case; and 2] postoperative several bleeding in one case.

• International Journal of Vascular Biomedical Engineering
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• 제2권2호
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• pp.27-32
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• 2004

The objective of the present study is to visualize the steady and pulsatile flow fields in a branching model by using a high-resolution PIV system. A bifurcated flow system was built for the experiments in the steady and pulsatile flows. Harvard pulsatile pump was used to generate the pulsatile velocity waveforms. Conifer powder as the tracing particles was added to water to visualize the flow fields. CCD cameras($1K{\times}1K$(high resolution camera) and $640{\times}480$(low resolution camera)) captured two consecutive particle images at once for the image processing of several cross sections on the flow system. The range validation method and the area interpolation method were used to obtain the final velocity vectors with high accuracy. The results of the image processing clearly showed the recirculation zones and the formation of the paired secondary flows from the distal to the apex of the branch flow in the bifurcated model. The results also indicated that the particle velocities at the inner wall moved faster than the velocities at the outer wall due to the inertial force effects and the helical motions generated in the branch flows as the flow proceeded toward the outer wall. Even though the PIV images from the high resolution camera were closer to the simulation results than the images from the low resolution camera at some locations, both results of the PIV experiments from the two cameras generally agreed quite well with the results from the computer simulations. Therefore, instead of using the expensive stereoscopic PIV or 3D PIV system, the three-dimensional flow fields in a bifurcated model could be easily and exactly investigated by this study.

• 한국전자통신학회논문지
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• 제10권5호
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• pp.615-622
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• 2015

반도체 제조기술의 발달로 고효율 및 고휘도의 LED가 개발됨에 따라 재래식 조명들로부터 LED를 이용한 조명으로 조명산업이 이동하는 추세이다. LED 조명등은 에너지 효율이 재래식 조명보다 뛰어나지만 많은 열이 발생한다는 단점이 있다. 특히 대형 LED 조명등에서는 이러한 발열문제가 심각한 실정으로, LED에 의한 메탈기판의 열은 납땜 부분을 열화시켜 조명등의 수명을 단축시키는 주된 원인이 된다. 따라서 대형 조명등을 개발하기 위해서는 이러한 열 문제를 해결하는 것이 매우 중요하다. 본 연구에서는 대형 LED 조명등에서 열문제를 해결하기 위한 방법을 제시하였고, 제시한 방식으로 1200W급 LED 조명등을 개발하였다. 본 연구에서 이용한 방법은 LED 조명등에 워터재킷을 설치하여 냉각수를 채웠으며, 소형의 수중펌프를 이용하여 냉각수를 순환시키는 방법을 이용하였다.

• 대한기계학회논문집B
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• 제39권8호
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• pp.645-651
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• 2015

본 논문은 중앙구동 이젝터의 유량비에 미치는 설계변수의 영향에 대한 연구를 목적으로 한다. 중앙구동 이젝터의 설계변수는 구동노즐 출구 단면적 및 거리비, 디퓨저 출구 단면적비로 설정하였다. 실험장치는 가변노즐 이젝터, 전동 모터-펌프, 구동유체 저장수조, 제어판넬 그리고 고속 카메라 시스템으로 구성하였다. 유량비는 실험변수에 따라 측정되는 유입 공기량과 구동유체인 물의 유량을 이용하여 도출하였다. 유량비는 구동노즐 거리비와 혼합관 길이비가 커지면 증가하는 반면에, 구동노즐 면적비와 디퓨저 출구 면적비가 커지면 감소하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제25권1호
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• pp.55-62
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• 2002

Aneurysm-mimicking findings were frequently visualized due to hemodynamical causes of dephasing effects around area of A-com artery during magnetic resonance angiography(MRA) and these kind of phenomena have not been clearly known yet. We investigated the hemodynamical patterns of dephasing effect around area of the A-com artery that might be a cause of false intracranial aneurysms on MRA. For experimental study, We used hand-made silicon phantoms of the asymmetric A-com artery as like a bifurcation configuration. In a closed circulatory system with UHDC computer driven cardiac pump system. MRA and fast digital subfraction angiography(DSA) involved the use of these phantoms. Flow patterns were evaluated with axial and coronal imaging of MRA(2D-TOF, 3D-TOF) and DSA of Phantoms constructed from an automated closed-type circulatory system filled with glycerol solution [circulation fluid(glycerol:water = 1:1.4)]. These findings were then compared with those obtained from computational fluid dynamic(CFD) for inter-experimental correlation study. Imaging findings of MRA, DSA and CFD on inflow zone according to the following: a) MRA demonstrated high signal intensity zone as inflow zone on silicon phantom; b) Patterns of DSA were well matched with MRA on trajectory of inflow zone; and c) CFD were well matched with MRA on the pattern of main flow. Imaging findings of MRA. DSA and CFD on turbulent flow zone according to the following: a) MRA demonstrated hyposignal intensity zone at shoulder and axillar zone of main inflow; b) DSA delineated prominent vortex flow at the same area. The hemodynamical causes of signal defect, which could Induce the false aneurysm on MRA, turned out to be dephasing effects at axilla area of bifurcation from turbulent flow as the results of MRA, DSA and CFD.

• 한국수소및신에너지학회논문집
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• 제26권4호
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• pp.324-330
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• 2015

The electrolyte flow rates of vanadium redox flow battery play very important role in terms of ion transfer to electrolyte, kinetics and pump efficiency in system. In this paper a vanadium redox flow battery single cell was tested to suggest the optimization criteria of electrolyte flow rates on the efficiencies. The compared electrolyte circulation flow rates in this experimental work were 15, 30 and 45 mL/min. The charge/discharge characteristics of the flow rate of 30 mL/min was the best out of all flow rates in terms of charging and discharging time. The current efficiencies, voltage efficiencies and energy efficiencies at the flow rate of 30 mL/min were the best. The IR losses obtained at thd current density of $40mA/cm^2$, at the flow rates of 15, 30 and 45 mL/min were 0.085 V, 0.042 V and 0.115 V, respectively. The charge efficiencies at the current density of $40mA/cm^2$ were 96.42%, 96.45% and 96.29% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. The voltge efficiencies at the current density of $40mA/cm^2$ were 77.34%, 80.62% and 76.10% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. Finally, the energy efficiencies at the current density of $40mA/cm^2$ were 74.57%, 77.76% and 73.27% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. The optimum flow rates of electrolytes were 20 mL/min in most of operating variables of vanadium redox flow battery.

• Journal of Biosystems Engineering
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• 제31권3호
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• pp.161-167
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• 2006

The purpose of this study is to find the optimal conditions of PCM slurry manufacturing equipment for saving the marketing cost and keeping the original quality of products. In addition, the characteristics of the movable container for shipping or distributing products is analysed. The major results are as follows. 1. PCM thermal storage system is designed with the conditions of temperature($-5{\sim}10^{\circ}C$), cold chain time(30 minutes), and one time usage(50 liter). This system includes tank, freezer, circulating pump, cycle type heat exchanger, swelling tank, equipment of supplying PCM supplying unit includes cold tank, cycle type heat exchanger, suction unit and control equipments, etc. 2. After ability test of PCM thermal storage system, it shows that the required freezing time of PCM thermal storage system is less than one of the previous system. The reason is that churn (top and bottom) and compulsion circulation are occurred simultaneously and unit cooler type method is better than chiller type method. 3. By the experiment of transportation latent heat container, it is decided that the best container is $K_1$ with latent heat temperature($0{\sim}5^{\circ}C$) and density(0.15%). However, for $K_l\;and\;K_2$, it is necessary more studies on latent heat thermal conditions and conditions of making method.