• 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.

• Journal of Energy Engineering
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• v.13 no.1
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• pp.51-59
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• 2004

The NSSS (Nuclear Steam Supply System) thermal-hydraulic programs adopted in the domestic full-scope power plant simulators were provided in early 1980s by foreign vendors. Because of limited compulsational capability at that time, they usually used very simplified physical models for a real-time simulation of NSSS thermal-hydraulic transients, which entails inaccurate results and, thus, the possibility of so-called "negative training", especially for complicated two-phase flows in the reactor coolant system. In resolve the problem, KEPRI developed a realistic NSSS T/H program ARTS which was based on the RETRAN-3D code for the improvement of the Nuclear Power Plant full-scope simulator. The ARTS (based on the RETRAN-3D code) guarantees the real-time calculations of almost all transients and ensures the robustness of simulations. However, there is some possibility of failing to calculate in the case of large break loss of coolant accident (LBLOCA) and low-pressure low-flow transient. In this case, the backup calculation system cover automatically the ARTS. The backup calculation system was expected to provide substantially more accurate predictions in the analysis of the system transients involving LBLOCA. The results were reasonable in terms of accuracy, real-time simulation, robustness and education of operators, complying with FSAR and the AMSI/ANS-3.5-1998 simulator software performance criteria.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.473-480
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• 2011

The proton exchange membrane (PEM) fuel cell system is critically dependent on the humidity, which should be properly maintained over the entire operating range. A membrane humidifier is used for the water management in the PEMFC because of the membrane humidifier's reliable performance and zero parasitic power loss. In the PEMFC system, the membrane humidifier is required to provide appropriate humidity for the design point of the fuel cell. Although the performance of the fuel cell depends on the performance of the humidifier, few studies have provided a systematic analysis of the humidifier. We carry out an experimental analysis of the membrane humidifier using a vapor condensation bottle. The dry air pressure, water flow temperature, and air flow rate were chosen as the operating parameters. The results show that the time constant for the dynamic response of the membrane humidifier is relatively short, but additional analysis should be carried out.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.419-426
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• 2012

A transient, three-dimensional, two-phase flow analysis code, CUPID, has been developed in KAERI. In this work, we performed a preliminary analysis using the CUPID code to investigate the thermal-hydraulic behavior of the moderator in the Calandria vessel of a CANDU reactor. At first, we validated the CUPID code using the three experiments that were performed at Stern Laboratories Inc. To avoid the complexity to generate computational mesh around the Calandria tube bundles, a porous media approach was applied for the region. The pressure drop in the porous media zone was modeled by an empirical correlation. The results of the calculations showed that the CUPID code can predict the mixed flow pattern of forced and natural convection inside the Calandria vessel very well. Thereafter, the analysis was extended to a two-phase flow condition. Also, the local maximum temperature in the Calandria vessel was plotted as a function of the injection flow rate, which may be utilized to predict the local subcooling margin.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.393-399
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• 2017

In a reciprocating compressor, the piston and connecting rod are important parts. Excess mechanical stress on these parts may cause damage, and broken parts are expensive and difficult to replace. Therefore, it is necessary to analyze the mechanical stress affecting durability and longevity. The main purpose of this study was to identify locations of maximum stress on pistons and connecting rods. Based on dynamic calculation of the working process of a specific air compressor, an analysis of piston and connecting rod performance has been completed. A three-dimensional model for the air compressor's pistons and connecting rods was built separately, and FEM analysis of these components was carried out using a numerical method. The pistons were loaded by pressure which was changed according to crankshaft angle without thermal boundary conditions. The simulation results were used to predict and estimate stress concentration as well as the value of this stress on pistons and connecting rods. The maximum equivalent stress calculated are over 190 MPa on pistons and 123 MPa on connecting rods at crank angle $135^{\circ}$ and $225^{\circ}$ but these are under tensile yield strength. Besides, the calculated safety factors of connecting rods and pistons is higher than 1. Moreover, the results obtained can be used to provide manufacturers with references to optimize the design of pistons and connecting rods for reciprocating compressors.

• The Korean Journal of Pharmacology
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• v.24 no.1
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• pp.135-145
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• 1988

Dopamine when given icv induces antidiuresis along with transient natriuretic tendency, and it has been suggested that both subtypes of central dopamine receptors may influence renal function differentially. This study was undertaken to delineate the role of central $D_2$ receptors employing domperidone (DOM), a selective $D_2$ antagonist. DOM icv elicited antidiuresis and antinatriuresis in doses ranging from 15 to $135{\mu}g/kg$. GFR and RPF as well as sodium excretion decreased. Systemic blood pressure increased slightly. Intravenous DOM did not elicit significant changes in sodium excretion. Denervation of the kidney abolished the hemodynamic change induced by icv DOM, but sodium excretion decreased on both innervated and denervated kidneys. No diuretic tendency was uncovered by the denervation. Dopamine, $150{\mu}g/kg$ icv, produced antidiuresis along with decreases in hemodynamics. These effects were not affected by DOM-pretreatment, and no natriuretic tendency was unveiled. Bromocriptine, a $D_2$ receptor agonist, $200{\mu}g/kg$ icv, elicited marked diuresis and natriuresis, which were completely abolished by DOM-pretreatment. Apomorphine, another prototype of $D_2$ agonist, $150{\mu}g/kg$ icv, produced diuresis and natrituresis with increases in renal hemdoynamics, followed by decreases in all parameters. DOM-pretreatment did not affect the renal hemodynamic effects, wherease the increases in urine flow and sodium excretion were markedly reduced by DOM, Present study suggests that central $200{\mu}g/kg$ receptors mediate natriuretic and diuretic influence to the kidney, possibly through mediation of natriuretic humoral factor, and provide further evidence supporting the hypothesis that central $200{\mu}g/kg$ receptors mediate antidiuretic influence via nerve pathway, whereas natriuresis are brought about through mediation of central $200{\mu}g/kg$ receptors.

• Tuberculosis and Respiratory Diseases
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• v.81 no.4
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• pp.319-329
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• 2018

Background: Bronchoalveolar lavage (BAL) is a necessary procedure for diagnosis of various lung diseases. High-flow nasal cannula (HFNC) oxygen delivery was recently introduced. This study aimed to investigate the safety and effectiveness of HFNC oxygen supply during BAL procedure in patients with acute respiratory failure (ARF). Methods: Patients who underwent BAL while using HFNC at a partial pressure of oxygen in arterial blood/fraction of inspired oxygen ($PaO_2/FiO_2$; PF) ratio of 300 or below among patients who had been admitted from March 2013 to May 2017 were retrospectively investigated. Results: Thirty-three BAL procedures were confirmed. Their baseline PF ratio was $166.1{\pm}46.7$. $FiO_2$ values before, during, and after BAL were $0.45{\pm}0.12$, $0.74{\pm}0.19$, and $0.57{\pm}0.14$, respectively. Flow (L/min) values before, during, and after BAL were $26.5{\pm}20.3$, $49.0{\pm}7.2$, and $40.8{\pm}14.2$, respectively. Both $FiO_2$ and flow during and after the procedure were significantly different from those before the procedure (both p<0.001). Oxygen saturation levels before, during, and after BAL measured by pulse oximeter were $94.8{\pm}2.9$, $94.6{\pm}3.5$, and $95.2{\pm}2.8%$, respectively. There were no significant differences in oxygen saturation among the three groups. Complications of BAL procedure included transient hypoxemia, hypotension, and fever. However, there was no endotracheal intubation within 24 hours. Baseline PF ratio in "without HFNC" group was significantly higher than that in "with HFNC" group. There were no differences in complications between the two groups. Conclusion: The use of HFNC during BAL procedure in ARF patients was effective and safe. However, there were no significant differences in oxygen saturation level and complications comparing "without HFNC" group in mild ARF. More studies are needed for moderate to severe ARF patients.

• Journal of Yeungnam Medical Science
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• v.10 no.2
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• pp.423-431
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• 1993

To eveluate the risk factors which are related to recurrence of ischemic stroke, we selected subjects who were admitted to YNUH due to recurrent stroke and compared their risk factors with non-recurred group who suffered from single ischemic stroke. In the subjects, 55 of them are men and 22 were women and in the non-recurred groups, 84 of them were men and 40 were women, Subject's age ranged from 29 to 85 years(Mean 62, 5years), and non-recurred group's age ranged from 27 to 90 years(Mean 60, 7years), Peak incidence of ischemic stroke is in the 7th decade in both groups. Age and sex are not, statistically significant for recurrence of ischemic stroke. The patient's history of diabetes mellitus, myocardial infarction, atrial fibrillation, transient attack and type or site of ischemic stroke had no significant effect statistically on the recurrent ischemic stroke. However, when the patient had previous history of hypertension or systolic blood pressure more than 160mmHg and diastolic more than 95mmHg, there was substantial difference(P<0.05) between the two group in the recurrence of ischemic stroke. According to the above results, hypertension is most likely significant risk factor of the recurrence of ischemic stroke within 2years after initial one. Therefore, adequate treatment of the hypertension is important for the prevention of ischemic stroke. Further study is required for searching other risk factors.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.141-149
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• 2014

In the present study, pure RHO zeolite was hydrothermally synthesized by using 18-crown-6 ether as a structure directing agent(SDA), and the small gases adsorption was investigated. Synthesized RHO zeolite was a cube shape particle of which average edge length was around $1.2{\mu}m$ and composed of primary crystallites having a diameter of around 100 to 200 nm. RHO zeolite structure was stable under 3h calcination at $600^{\circ}C$. Water adsorption data announced that RHO zeolite has a specific surface area of 483.32 m2/g and its micropore diameter was about 4 A. Gas adsorption was studied in the pressure range of 50 to 500 kPa for $CO_2$, $N_2$, $O_2$ and $H_2$. It was evident that RHO zeolite showed a strong $CO_2$ adsorption behavior. Especially, RHO zeolite showed a transient $CO_2$ adsorption behavior. The 3h $CO_2$ up-take at 50 kPa and 500 kPa was 1.283 and 3.357 mmol/g, respectively. The $CO_2/H_2$ selectivity was around 16 at 500 kPa. Compared with gas adsorption data for some representative microporous adsorbents, it was certain that RHO zeolite is a beneficial adsorbent for $CO_2/H_2$ separation.

• Archives of Plastic Surgery
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• v.39 no.5
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• pp.540-545
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• 2012

Background Patients have anxiety and fear of complications due to general anesthesia. Through new instruments and local anesthetic drugs, a variety of anesthetic methods have been introduced. These methods keep hospital costs down and save time for patients. In particular, the target-controlled infusion (TCI) system maintains a relatively accurate level of plasma concentration, so the depth of anesthesia can be adjusted more easily. We conducted this study to examine whether intravenous anesthesia using the TCI system with propofol and remifentanil would be an effective method of anesthesia in breast augmentation. Methods This study recruited 100 patients who underwent breast augmentation surgery from February to August 2011. Intravenous anesthesia was performed with 10 mg/mL propofol and 50 ${\mu}g/mL$ remifentanil simultaneously administered using two separate modules of a continuous computer-assisted TCI system. The average target concentration was set at 2 ${\mu}g/mL$ and 2 ng/mL for propofol and remifentanil, respectively, and titrated against clinical effect and vital signs. Oxygen saturation, electrocardiography, and respiratory status were continuously measured during surgery. Blood pressure was measured at 5-minute intervals. Information collected includes total duration of surgery, dose of drugs administered during surgery, memory about surgery, and side effects. Results Intraoperatively, there was transient hypotension in two cases and hypoxia in three cases. However, there were no serious complications due to anesthesia such as respiratory difficulty, deep vein thrombosis, or malignant hypertension, for which an endotracheal intubation or reversal agent would have been needed. All the patients were discharged on the day of surgery and able to ambulate normally. Conclusions Our results indicate that anesthetic methods, where the TCI of propofol and remifentanil is used, might replace general anesthesia with endotracheal intubation in breast augmentation surgery.