• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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• pp.322-327
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• 2020

In this work, a study for the reduction of the electric power consumption has been estimated in main air compressors in the air separation unit through cryogenic distillation columns with PRO/II with PROVISION V10.2 at AVEVA company. Both required LNG mass flow rate and cold heat contained in 1 ton of LNG were also predicted using Peng-Robinson equation of state with Twu's new alpha function. Through this work, we concluded that 32.33-48.69% of electric power could be saved by using LNG cold heat.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.692-699
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• 1999

The vortex tube is a sample device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. The phenomena of energy separation through the vortex tube were investigated experimentally, to see the effects of the number of nozzle holes on the energy separation. The experiment was carried out with the number of nozzle holes from 1 to 10 by varying inlet pressure and cold mass fraction. The experimental results were indicated that the effective number of nozzle holes for the best cooling performance was found as 4. Also, to find effective use in a given operation conditions, the temperature difference of cold air and the cooling capacity of vortex tube was compared. The result is that cooling capacity was more important than temperature difference of cold air.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1053-1058
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• 2008

Porous medium was considered in the present study for the heat transfer enhancement. This was attributed to its high surface area to volume ratio as well as intensive flow mixing by tortuous flow passages. But when the air or water flow through in the porous medium, it is occurred the pressure drop between inlet and outlet. So in the present study investigated simulation result about the pressure drop in the porous medium before apply to heat exchanger. In this simulation, the thickness of the solid inside the porous medium region was varied 0.2 mm to 0.4 mm. And then the simulation result were compared the pressure drop in the same unit cell ($0.5\;mm{\times}0.5\;mm{\times}0.5\;mm$). To make the analysis model, it was assumed the 14-sided tetrakaidecahedron cell which has long been considered the optimal packing cell first proposed by the Lord Kelvin in 1887. And then the simulation is carried out using by STAR-CCM+ which is commercial software. The simulation result can be showed quantified pressure drop by solid effect in the porous medium.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.46-52
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• 2010

In this paper, emission analysis during cold start period of CVS-75 mode in LPG vehicle was performed to find out proper operating conditions of SAI(Secondary Air Injection) system. In order to meet SULEV target, the simulated emission system had a SAI system as well as a MCC(Manifold Catalytic Converter) and a UCC(Under body Catalytic Converter). Using commercial 1-D code AMESIM, in which 7 step global surface chemical reactions of Langmuir-Hinshelwood type were adopted, transient emission analysis in the exhaust system during cold start period of CVS-75 mode were carried out to figure out the effects of flow rate, duration of supply air on HC, CO, NO emission.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.489-495
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• 2003

A high performance and low noise refrigerator fan has been developed in order to satisfy the customer's high quality needs, that is, luxury, big size and low noise. In this study, the characteristics of a new developed fan and a current fan was calculated and compared by using numerical simulation. Rotation of a fan makes cold air circulation inside a refrigerator. A numerical simulation of air flow shows distribution and local flow regime of a cold air flow circulation, and revealed a cause of low noise as well. Optimization of a duct shape also decreased noise level.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.9-17
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• 2021

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

• Journal of the Korean Institute of Landscape Architecture
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• v.44 no.5
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• pp.103-115
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• 2016

This study aims to analyze the properties of cold air production and its flow of Nakdong-Jeongmaek(mountain ranges), and to suggest management strategies for Nakdong-Jeongmaek in order to enhance the green air conditioning functions of Jeongmaek. For this purpose, three study sites including Gudeoksan Mountain and the vicinity in Busan, Goheonsan Mountain and the vicinity in Ulsan, and Unjusan Mountain and the vicinity in Pohang were selected. The results found that cold air flow and its height of the three study sites were analyzed based on topographic properties and land use. Management strategies for preserving and enhancing their temperature reduction functions were suggested. The cold air produced in the vicinity of Gudeoksan was not fully developed and spread because of the high-density development at the border of Jeongmaek. Since high pressures of development are expected at the border, high conservation policies are required. In the vicinity of Goheonsan, where the agricultural complex and industrial park are located, cold air flows well throughout the entire study site thanks to fully developed cold air in the wide, flat valley. Hence, plans to maintain the current cold air flow are required, and conservation plans to mitigate future developments are also needed in the flat valley. The cold air in Unjusan and the vicinity with its complex and narrow mountain valleys gradually develops into valley bottoms. In order to take advantage of the terrain, the valley near the cold air production areas are preserved. In particular, special plans are required to prevent damage to the cold air layer near Youngcheonho Lake, where the highest height of cold air was recorded due to the closed and lower terrain feature. This study could support the establishment of systematic management plans of Nakdong-Jeongmaek to preserve and enhance its green air conditioning functions.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.217-228
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• 2000

Circulating Fluidized Bed Combustor(CFBC) has been used for the incineration of waste sewage sludge and for the power generation. In this study hydrodynamic characteristics of two phase flow have been studied in a riser section of CFBC. A lab-scale riser is designed and SiC (Geldart type B) is used for solid particles. Experiments are performed by controlling the fluidization parameters including superficial velocity and secondary air to primary air ratio for determination of solid holdup profiles in the riser. Superficial velocities of each fluidization regime are well agreed with results predicted by a theoretical model. The results show that the axial solid holdup distributions calculated by measuring differential static pressures in the riser are found to show a basic profile described by a simple exponential function. Our flow regime during experiments mainly belongs to fast fluidization regime for particle size of 300${\mu}m$. As the SA/PA ratio increases, solid holdup in the lower dense region of the riser increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.69-76
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• 2002

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial and the radial temperature distribution in internal spare of a tube. From the study, fellowing conclusive remarks 7an be made. First, As the number of nozzles increase, separation point move into the hot exit. Second, When we use guide vane type nozzle, the axial temperature distribution constant over the 0.75 of air mass flow rate radio. Third, When we use Spiral type nozzle, axial and radial temperature distribution in the inner space is higher than another nozzle. Fourth, Axial and radial temperature distribution in the inner space vortex-tube is determined by separation point. And separation point is moved by changing of air mass flow rate ratio. At last, A heating apparatus is possible far vortex-tube to use.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.84-93
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• 2001

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial temperature distribution and the radial temperature distribution in internal space of a tube. From the study, following conclusive remarks can be made. Average flow rate that flows into a tube is in proportion to square root of inlet pressure. As inlet pressure increases axial and radial temperature distribution in the inner space of vortex-tube increase. As mass flow rate ratio change, separation point moves.