• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.1-7
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• 2004

The polyethylene pipe can use semi-permanent because of the high corrosion resistance with chemical stability. In addition to, there is the merit that is an easy to establish and to maintain. However, as the reason that it is simply degraded when the polyethylene pipe was exposed to the outside, mainly it is used to lay under the ground with low-pressure gas transportation pipe. In this study, the nondestructive evaluation method was used to maintain the integrity of the polyethylene pipe. We simulated the various defects on the polyethylene pipes, and then the AE signal occurred according to the impact test of steel ball was evaluated by the acoustic emission method. From the results, the waveform and dominant frequency could be distinguishing from the defect shapes of polyethylene pipe. Especially, in the case of notch defect, the AE signals occur different by the angle and depth of the notch.

• Journal of the Korean Institute of Gas
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• v.11 no.3
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• pp.44-48
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• 2007

The cooling heat transfer characteristics of supercritical $CO_2$ in a helical coil gas cooler on the change of coil diameters are experimentally investigated. The main components of the refrigerant loop are a receiver, a variable speed pump, a mass flow-meter, a pre-heater and a helical coil gas cooler (test section). The test sections are made of a copper tube which the inner diameter is 4.55 mm and the helical coil diameters are done of 26.75 mm and 41.35 mm. The mass fluxes of refrigerant are varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler are 7.5 to 10.0 (MPa). A gas cooler with helical coil diameter of 26.75 mm has larger heat transfer coefficient than that of 41.35 mm. Also, when compared with experimental data and published correlations avaliable, most of correlations are under-predicted, but Pitla published correlations avaliable, most of correlations are under-predicted, but Pitla et al.'s correlation shows a relatively good coincidence with the experimental data except the region of pseudo critical temperature.

• Journal of the Korean Institute of Gas
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• v.11 no.3
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• pp.1-6
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• 2007

The heat transfer coefficient and pressure drop during gas cooling process of $CO_2$ (R-744) in inclined helical coil copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube, which is specified as the inner diameter of 4.55 mm. The refrigerant mass fluxes were varied from 200 to $600kg/m^2s$ and the inlet pressures of gas cooler were done 7.5 to 10.0 (MPa). The heat transfer coefficients of $CO_2$ in the inclined helical coil tubes increase with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows relatively good coincidence with those predicted by Ito's correlation developed for single-phase in a helical coil tube. The local heat transfer coefficient of $CO_2$ is well coincident with the correlation by Pitla et al. However, at the region near pseudo-critical temperature, the experiments indicate higher values than the Pitla et al. correlation.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.43-49
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• 2008

The evaporation heat transfer coefficient and pressure drop of R-22 and R-407C in horizontal copper tubes were investigated experimentally. The main components of therefrigerant loop are a receiver, a compressor, a mass flow meter, a condenser and a double pipe type evaporator (test section). The test section consists of a smooth copper tube of 4.3 mm and 6.4 mm inner diameter. The refrigerant mass fluxes were varied from 100 to $300[kg/m^2s]$ and the saturation temperature of evaporator were 5 [$^{\circ}C$]. The evaporation heat transfer coefficients of R-22 and R-407C rise with the increase in mass flux and vapor quality. The evaporation heat transfer coefficient of R-22 for inner diameter tube of 4.3 mm and 6.4 mm is about $7.3{\sim}47.1%$ and $5.68{\sim}46.6%$ higher than that of R-407C, respectively.

• Archives of Plastic Surgery
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• v.37 no.6
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• pp.827-830
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• 2010

Purpose: Congenital spinal dermal sinus tract is a rare lesion connecting skin to deeper structures including neural tissue. It results from the failure of the neuroectoderm to separate from the cutaneous ectoderm in the third to fifth week of gestation. The common locations are the lumbosacral and occipital regions. Sometimes it extends to spinal canal. In this paper we report a case of congenital spinal dermal sinus tract in the coccyx. Methods: A 21-month-old male child born after an uncomplicated full-term pregnancy was admitted to our institute with a midline dermal sinus and a cartilaginous protrusion in the coccygeal region. There were no signs of infection. Neurologic examination showed no functional deficit in both lower limbs. He was treated with complete excision of the tract and an underlying accessory cartilage. Results: The spinal dermal sinus tract was extended from the skin to the coccyx. The stalk was loosely attached to the accessory cartilage of coccyx. At that point, it was dissected from the accessory cartilage and resected. The accessory cartilage was also resected at the bone and cartilage junction. During the follow-up period of 6 months, the wound healed well without any complication nor recurrence. Conclusion: Congenital spinal dermal sinus tract is known as a form of spinal dysraphism. In order to prevent complications, timely surgical intervention including complete resection of sinus tract with correction of associated abnormalities is of utmost importance.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.36 no.3
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• pp.137-148
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• 2018

Li Yu's Xian Qing Ou Ji was written during the late Ming and early Qing Dynasty when material culture flourished due to the development of the commercial economy. Xian Qing Ou Ji is considered a retrospective work that reflects the rich material society at that time. This study focuses on his gardening theories through the interpretation and analysis of these two texts of 'Jushibu(居室部)' and 'Zhongzhibu(種植部)' in Xian Qing Ou Ji. The results are summarized as follows. First, he explained the method of garden configuration and orientation according to the topography utilizing the theory of 'suiting one's measures to local conditions(因地制宜)'. He emphasized the detailed understanding of topography as the starting point for all the gardening theories. It stated that he tried to adjust the height of the terrain artificially to create an ideal form of 'anterior high and posterior low(前低後高)'. The successful arrangement of houses, pavilions, rockery and waterways et al. was able to be achieved because of his accurate understanding of topography. Second, 'borrowing scenery(取景在借)' means 'borrowing the outside scenery to the inside'. He applied this theory by 'viewing in motion(動觀)' and 'viewing in repose(靜觀)'. 'Viewing in motion' is seen as a positive methodology for landscape enjoyment. For example, the view through a window changes with movements of the boat, and it can portray thousands of landscape paintings which can be seen through the windows. In the case of 'viewing in repose', the window is regarded as a means of attracting outside garden views to the inside. Third, he emphasized 'the firmness of objects(制體宜堅)', where the design of windows and railings must be considered ahead of others. Fourth, he interpreted the contents of 'the pursuit of novelty(創異標新)'. This generalizes the characteristics of his gardening theory. The contents included 'hall wall(廳壁)', 'variable sun visor(活?)', 'hanging boards and couplets(聯?)' and 'method of supporting vines with bamboo screen(竹屛扶植法)'.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4721-4726
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• 2010

The performance characteristics of water-chilling heat pump using CO2 for the control of inverter frequency was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter flow type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4m length. The experimental results summarize as the following: for constant inlet temperature of evaporator and gas cooler, as mass flow rate, compression ratio and discharge pressure increases with the inverter frequency. And heating capacity and compressor work increases, but coefficient of performance(COP) decreases with the inverter frequency of compressor. As inlet temperature of secondary fluid in the evaporator increases from $15^{\circ}C$ to $25^{\circ}C$, compression ratio and compressor work decreases, but mass flow rate, heating capacity and COP increases with the inverter frequency of compressor. The above tendency is similar with performance variation with respect to the variation of inverter frequency in the conventional vapor compression refrigeration cycle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.545-551
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• 2011

Recently, demands for generating high quality tap waters are increasing with high concern of water pollution and corrosion of water pipelines. For the reasons, developing water quality stabilization technique in water purification system is sought rather than replacing to a new pipelines. In this study, high-purity liquid lime($Ca(OH)_2$) was introduced for a water quality stabilization technique in water purification process and simulated water distribution system of pilot-scale size was applied to evaluate anti-corrosion control effect. The effect of anti-corrosion control was calculated in terms of LSI(Langelier Saturation Index) In conclusion, the result of pilot plant showed improvement of corrosiveness by liquid lime($Ca(OH)_2$) with reduction of released iron(Fe). Application of anti-corrosion control technique to the mild steel coupon and the copper coupon were effective by indicating 35.4, 44.5% of improvements. Besides, sample pipes which were treated with liquid lime had formated more thicker layer of corrosion product inside of pipes. As a result, the process of injecting water stabilizer can greatly contribute to the high quality of tap water.

• Solar Energy
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• v.18 no.2
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• pp.145-152
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• 1998

In this experimental study, for obtaining the data to be used in the increased recover rate of waste heat from the recirculated sand, the furan foundry sand were used as the fluidized particle in the fluidized bed in which the smooth, spiral and finned tubes($Do={\varphi}12.7$) were horizontally installed and used as the heat-transfer tubes. The heat transfer experiments were performed in the conditions of water Reynolds number of inside tubes in the range of 4,000 to 18,000 and particle Reynolds number of outside tube in the range of 0.8 to 7.5. The heat-transfer coefficients(ho) increase as the higher inside temperature of the fluidized bed and the maximum heat-transfer coefficients can be obtained in the range of 3.5 to 5.5 of particle Reynolds number in the all tubes. The maximum Nu numbers of smooth, spiral and finned tubes are figured as about 1:1.5:3 in order even if the ratios show little different as the temperatures of bed.

• Fire Science and Engineering
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• v.34 no.4
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• pp.69-77
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• 2020

With the recent enlargement and complication of buildings, damage caused by the incidents of fires breaking out are escalating. Consequently, the use of sprinkler facilities is increasing among water-based fire extinguishing systems. Piping materials used in fire prevention systems include carbon steel (for general or pressure pipeline), CPVC, copper, and stainless-steel. Among these, the steel and CPVC pipes, which are commonly employed in fire prevention, were considered for testing the reliability of the water-based systems. This analysis was performed using the PIPENET software to perform hydraulic calculations in order to examine the flow and pressure at the terminal head when the corrosion coefficient was applied; this coefficient was applied considering the aging of pipes. Assuming a uniform pipe diameter in the steel pipes, the rated flow in the pump installed on the first floor of the basement was reduced by over 10% after 20 years had passed (C value of 90); moreover, the reduction in pressure and flow at its terminal head exceeded 30% and 16.5%, respectively. The results indicate that it is difficult to ensure the reliability of these fire prevention facilities. Furthermore, according to our estimation, considering 30 years had passed (C value of 80), the rated flow of the pump was reduced by over 15%, and the corresponding reduction in pressure and flow at its terminal head exceeded 42% and 24%, respectively.