• Journal of the Korean Society of Safety
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• v.39 no.1
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• pp.1-8
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• 2024

Commercial gas stoves feed primary air to the burner and burn the fuel-air mixture in a partially premixed combustion. This mechanism produces carbon monoxide during combustion. In this study, design parameters of a commercial gas stove were optimized by considering the carbon monoxide emission. Gas consumption rate, carbon monoxide emission, and water boiling temperature as a heating performance were determined. Carbon monoxide emission was measured using a Korean Industrial Standards standard collector. Water boiling temperature was measured by first soaking the pot in water for approximately 10 min and then heating the pot filled with water. A thermocouple was installed inside the pot. Carbon monoxide increased as the nozzle diameter was increased and the burner-pot height was decreased. This result was due to the insufficient mixing between the fuel and air. Heating performance was enhanced when the nozzle diameter was increased and the burner-pot height was decreased. However, the heating performance deteriorated when the nozzle diameter was 1.8 mm and the burner-pot height was reduced to 50 mm. This phenomenon was due to the formation of a flame on the side of the pot. A merit factor was defined to find the optimal design parameters to satisfy gas consumption rate, carbon monoxide emission, and heating performance. Optimal design values were established to be a nozzle diameter of 1.5 mm and a burner-pot height of 60 mm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.459-465
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• 2013

In the manufacturing process of steel plates, materials at high temperatures above $800^{\circ}C$ are rapidly cooled by using a circular impinging water jet to determine their strength and toughness. In this study, the basic heat and fluid flow is solved by using the existing numerical model for boiling heat transfer. Actually, steel undergoes a phase change from austenite to ferrite or bainite during the cooling process. The phase change induces changes in its thermal properties. Instead of directly solving the phase change and the material cooling together, we solve the heat transfer only by applying the thermal properties that vary with temperature, which is already known from other studies. The effects of the changes in the thermal properties on the cooling of steel and the necessity of calculating the phase change are discussed.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.493-501
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• 1994

An experimental study has been peformed on the pool-boiling critical heat flux (CHF) phenomenon on downward -facing plates. The CHF for inclinations of -90$^{\circ}$(horizontally downward position), -88$^{\circ}$, -86$^{\circ}$, -84$^{\circ}$, -60$^{\circ}$ and -40$^{\circ}$ were measured using plate-type test sections of 20mm 200mm and 25mm 200mm in a pool of saturated water under atmospheric pressure. The measured CHF was lower for the wider test section and decreased as its orientation approached to the horizontally downward position. The lower CHF can be attributable to the increased difficulty for the bubbles in escaping from the heater surface. When compared with the previous works, the overall trends were similar; however, a transition angle, at which the decrease rate in the CHF was changed, was observed in the vicinity of -80$^{\circ}$.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4329-4337
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• 2022

Jet impinging device is designed for decay heat removal on horizontal fuel rods in a low temperature heating reactor. An experimental system with a fuel rod simulator is established and experiments are performed to evaluate water film covering capacity, within 0.0287-0.0444 kg/ms mass flow rate, 0-164.1 kW/m² heating flux and 13.8-91.4℃ feeding water temperature. An effective method to obtain the film coverage rate by infrared equipment is proposed. Water film flowing patterns are recoded and the film coverage rates at different circumference angles are measured. It is found the film coverage rate decreases with heating flux during single-phase convection, while increases after onset of nucleate boiling. Besides, film coverage rate is found affected by Marangoni effect and film accelerating effect, and surface wetting is significantly facilitated by bubble behavior. Based on the observed phenomenon and physical mechanism, dry-out depth and initial dry-out rate are proposed to evaluate film covering potential on a heating surface. A model to predict film coverage rate is proposed based on the data. The findings would have reliable guide and important implications for further evaluation and design of decay heat removal system of new reactors, and could be helpful for passive containment cooling research.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.1-8
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• 2018

The 23 wt% polyvinylidene fluoride (PVDF)/15 wt% polyurethane (PU) fibers were electrospun using the conjugated nozzle at a flow rate of 1.0 mL/h and an electric field of 1 kV/cm. The formation of ${\beta}$ crystal phase in the PVDF and the PVDF/PU fibers was confirmed by Fourier transform infrared spectroscopy. After electrospinning, the asspun fibers were immersed in a boiling water and then dried at $100^{\circ}C$ in a convection oven to make a crimp phenomenon. The crimps with a diameter of $2.0{\pm}0.08{\mu}m$ were observed for the PVDF/PU fibers after hydrothermal treatment without sacrificing the extent of ${\beta}$ crystal phase. All the PU, PVDF and PVDF/PU fibers exhibited average cell viability of more than 98 %. The cell proliferation results suggested that L-929 cells adhered well to the PU, PVDF and PVDF/PU fibers and proliferated continuously with increasing time, indicating that the PVDF/PU fibers are highly applicable to the biomedical applications.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.3
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• pp.8-14
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• 2011

The clogging of the flow area at the tube support plates(TSPs), especially at the upper TSPs results in the water level oscillation of a steam generator during normal operation. A reduction of the TSP flow area causes to increase in pressure drop within the two-phase flow zone, which destabilizes the boiling flow through the tube bundle. This phenomenon was occasionally observed at a few domestic and foreign nuclear power plants. One of the methods for defining the flow area clogging is visual inspection, which is the most effective inspection method. The results of the visual inspection for TSPs' flow area are clogging images on TSPs' quartrefoil lobes. These images are complexly distorted due to lens aberration and external factors like the distance to a subject and angle etc. In this work, we developed the analysis algorithm for clogging image of the TSP flow area of steam generators. For this purpose, we designed an image verification device applicable to the camera employed in the field for visual inspection and then, we demonstrated the validity of image analysis algorithm by using this device and commercial autoCAD program.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2094-2099
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• 2004

An experimental study on heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with the increase of the system pressure For a fixed inlet mass flux and subcooling, the CHF falls sharply at about 3.8 MPa and shows a trend toward converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall because the CHF occurred at remarkably low power levels. In the pressure reduction transient experiments, as soon as the pressure passed through the critical pressure, the wall temperatures rise rapidly up to a very high value due to the occurrence of the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, then tends to decrease gradually.

• Nuclear Engineering and Technology
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• v.36 no.5
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• pp.403-414
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• 2004

An experimental study of heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) tests, and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with increase of the system pressure for fixed inlet mass flux and subcooling. The CHF falls sharply at about 3.8 MPa and shows a trend towards converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall, because the CHF occurs at remarkably low power levels. In the pressure reduction transients, as soon as the pressure passes below the critical pressure from the supercritical pressure, the wall temperatures rise rapidly up to very high values due to the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, and then tends to decrease gradually.

• Membrane Journal
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• v.20 no.2
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• pp.135-141
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• 2010

Various asymmetric Polysulfone membranes were prepared for a MBR process. Ether-typed alcohols (co-solvent) were added into a dope solution in order to control the pore size of membrane, whose effect on water permeability were investigated. Pore size of the prepared membranes were more affected by molecular-structure of co-solvent than by boiling point of theirs. With the increasing order of methoxy ($CH_3$-O-) < secondary propanol ($-CH_2$-CH(OH)$-CH_3$) < ethoxy ($CH_3-CH_2$-O-), water permeability of the prepared membrane increased. The phenomenon might attribute to the difference of molecularly steric hinderance of co-solvent (eg, Methoxy propanol, Ethoxy ethanol, Methoxy ethanol) in dope solution during the phase inversion. By the addition of ether typed alcohol into a dope solution, the pore size of MF (microfiltration) could be controlled. Also, Membrane prepared was applied to a MBR process and the system was stably operated for 2 months.

• The Journal of Internal Korean Medicine
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• v.18 no.2
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• pp.268-295
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• 1997

Sweating is natural phenomenon necessary for the regulation of an individual's body-temperature. The secretion of sweat is mediated by a portion of our vegetative nervous system(the sympathetic nervous system). In some people, this system is working at a very high activity level, far higher than needed to keep a constant temperature. This condition is referred to as hyperhidrosis. Especially excessive sweating of the hands and the feet is palmoplantar hyperhidrosis or volar hyperhidrosis. This is by far the most distressing condition. It was founded that the first important cause of this was emotional factor. The hands are much more exposed in social and prefessional activities than any other part of our body. Many individuals with palmoplantar hyperhidrosis are limited in their choice of proffession, because unable to manipulate materials sensitive to humidity or reluctant to shake hands; some patients arrive to the point to avoid social contact. The occidental medical treatments for palmoplantar hyperhidrosis include application of topical agents(chemical antiperspirants such as aluminum chloride), iontophoresis(treatment with electrical current), or surgery(thoracic sympathectomy). It was reported that the most effective treatment was thoracic sympathectomy. So this study was started to find the easy and effective oriental medical treatments against the occidental medical treatments through the oriental medical literature. The occidental medical idea for palmoplantar hyperhidrosis is only limited in neurologic system, so surgery is the best treatment. But the oriental medical idea for palmoplantar hyperhidrosis is much wider, so the oriental medical causes and treatments for this are able to be veriety. And the oriental medical teatment is freely in treating the patients of palmoplantar hyperhidrosis, because entire idea including pulse, facial color, mental condition, constitution and other symptom exists in the oriental medicine. The results of a bibliographic study of causes and treatments for palmoplantar are as follows; 1. The main causes of pa1moplantar hyperhidrosis are heat in the stomach, damp-heat in the spleen and the stomach, insufficiency of the spleen-qi and the stomach-qi, deficiency of the spleen-yin and the stomach-yin, and the others are the stomach-cold syndrome, stasis of blood and dyspepsia in the stomach, disorder of the liver-qi, deficiency of the heart-yin and the kidney-yin, deficiency of the heart-yang and the kidney-yang, stagnated heat in the liver and the spleen, the lung channel-heat etc. 2. The main methods of medical treatments for palmoplantar hyperhidrosis are clearing out the stomach-heat, eliminating dampness and heat in the spleen and the stomach, invigorating the spleen-qi and the stomach-qi, reinforcing the spleen-yin and the stomach-yin, warming the stomach, relaxing the liver and alleviating of mental depression and tonifying the heart and the kidney etc. 3. The main prescriptions of palmoplantar hyperhidrosis are Taesihotang, Palmultang-kakam, Samyeongbaechusan, Chongbisan, Sasammaekmundongtang, the others are Leejungtang, Hwangkikonjungtang, Seungkitang, Boyumtang, Baekhotang, Chongsimyonjayum, Moyrosan, etc. 4. Local medicine for external use are liquid after boiling alum in water for about 1 or 2 hours, liquid after boiling alum and pueraria root in water and liquid after boiling stragalus root, pueraria root, ledebouriella root and schizonepeta in water, etc. 5. The methods of acupuncture therapy include invigorating Bokyru, Yumkuk and purgating Hapkouk, or invigorating Bokyru, Kihae and purgating Hapkouk, or steadying Hapkouk, Nokung.