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Yong Hun Lee

Bio: Yong Hun Lee is an academic researcher from Gyeongsang National University. The author has contributed to research in topics: Gas compressor & Vaporizer. The author has an hindex of 4, co-authored 14 publications receiving 131 citations.

Papers
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Journal ArticleDOI
01 Jun 2010-Energy
TL;DR: In this paper, the authors conducted a computational fluid dynamics (CFD) investigation into the flow structure inside a steam ejector and found that the ejector with a converging duct angle of 1° has the best performance.

83 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared the characteristics of the finned type 4fin75le and finned 8 fin50le air-heating vaporizers, and showed that the 4 fin75le vaporizer has better performance than the 8 fin 50le.
Abstract: Air-heating vaporizers are usually used to regasify LNG at satellite areas because of the small demand for natural gas there. The common type of air heating vaporizer which exists in the market is the longitudinally finned type with 8 fins, 50mm fin length and 2mm fin thickness. To contribute in developing an efficient air-heating vaporizer, experiment on finned type air-heating vaporizer using 8 fins, 50mm fin length with 2mm fin thickness (8fin50le)-which exist in the market-and 4 fins, 75mm fin length with 2mm fin thickness (4fin75le), which is proposed, were conducted. Then, both types of vaporizers are compared. The experiments were conducted in one hour by varying the ambient condition and the length of the vaporizer. The ambient air was controlled so that it has the same condition (same temperature, humidity and air velocity) with air condition in every season available and the length was varied 4000mm, 6000mm and 8000mm for each type of vaporizer. Additional experiment with longer duration, i.e., 4 hours and in a single room condition was conducted to validate the previous result. In this experiment, the main aspects in analyzing the characteristics of the air heating vaporizer are the inlet-outlet enthalpy difference and the outlet temperature of the working fluid. LN2 is used to substitute LNG for safety reasons. The results show that the characteristics of the finned type 4fin75le vaporizer are comparable to the finned type 8fin50le vaporizer.

24 citations

Journal ArticleDOI
TL;DR: In this paper, a longitudinally finned vertical pipe was used to represent the air-heating vaporizer in the CFD model, and Nitrogen gas was used as the working fluid inside the vertical pipe, and it was made to flow upward.
Abstract: In this study, CFD analysis of air-heating vaporizers was conducted. A longitudinally finned vertical pipe was used to represent the air-heating vaporizer in the CFD model. Nitrogen gas was used as the working fluid inside the vertical pipe, and it was made to flow upward. Ambient air, which was the heat source, was assumed to contain no water vapor. To validate the CFD results, the convective heat transfer coefficients inside the pipe, hi-c, derived from the CFD results were first compared with the heat transfer coefficients inside the pipe, hi-p, which were derived from the Perkins correlation. Second, the convection heat transfer coefficients outside the pipe, ho-c, derived from the CFD results were compared with the convection heat transfer coefficients, ho-a, which were derived from an analytical solution of the energy equation. Third, the CFD results of both the ambient-air flow pattern and temperature were observed to determine whether they were their reasonability. It was found that all validations showed good results. Subsequently, the heat transfer coefficients for natural convection outside the pipe, ho-c, were used to determine the Nusselt number outside the pipe, Nuo.. This was then correlated with the Rayleigh number, Ra. The results show that Ra and Nuo have a proportional relationship in the range of 2.7414×1012 ≤ Ra ≤ 2.8263×1013. Based on this result, a relation for the Nusselt number outside the pipe, Nuo, was proposed.

23 citations

Journal ArticleDOI
TL;DR: In this article, the influence of operating pressures and ejector geometries on the flow structure and the performance of a steam ejector was investigated and the best performance was obtained by the ejector with converging duct angle of 1°.
Abstract: A thermo vapor compressor is simply a steam ejector employed in a multi effect desalination process. A greater understanding of flow phenomena inside an ejector plays an important role in its performance improvement. In this paper, CFD investigation has been carried out to study the flow structure inside a steam ejector. This research revealed the influence of operating pressures and ejector geometries on the flow structure and the performance of a steam ejector. The CFD results were verified with available experimental data. The angle of the converging duct as the geometry parameter was varied as 0°, 0.5°, 1°, 2°, 3.5° and 4.5°. The best performance was obtained by the ejector with converging duct angle of 1°.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the optimum solidification conditions were shown for crucible rotation for Czochralski (CZ) silicon melt flow and the solidification regions were classified with crystal rotation and crucible rotations.
Abstract: Silicon crystallization is very important in many industrial processes, and it is desirable that maker should have a low cost manufacturing and high efficiency for producing semiconductors. One semiconductor process is the Czochralski (CZ) silicon melt flow and this CZ process has an excellent manufacturing feature and is utilized for silicon solidification. But CZ silicon melt flow is very complicated and this defect can be erased by the numerical analysis of the melt flow. In this paper, the optimum solidification conditions were shown for crucible rotation. This is because the solidification conditions depend on crucible rotation under the cooling process and the solidification conditions were investigated on heat generation rate on crucible wall and rotation by using numerical analysis. For the numerical validations, we verified with experimental data and showed good agreement with current numerical results. The solidification regions are classified with crystal rotation and crucible rotation. For the heat generation rate, qw, the optimum heat generation rate was estimated for 20 W/cm2 and when crystal rotation and crucible rotation is 5 rpm, the maximum solidification length can be obtained and has a stable solidification.

5 citations


Cited by
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Journal ArticleDOI
TL;DR: The objective of this work is to provide a literature survey on the research attempts made in the field of ejector refrigeration systems and the studies made on the ejector as a component.

202 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of the primary nozzle geometries on the performance of an ejector used in the steam jet refrigeration cycle was investigated numerically using the commercial CFD package, FLUENT 6.3.

158 citations

Journal ArticleDOI
TL;DR: In this article, computational fluid dynamics (CFD) method is employed to investigate the effects of the mixing chamber geometries on the performance of steam ejectors used for multi-effect distillation systems.

86 citations

Journal ArticleDOI
06 Mar 2019
TL;DR: A review of the main developments in ejectors over the last few years can be found in this article, where the main findings and trends in the area of heat-driven ejectors and ejector-based machines using low boiling point working fluids are summarized.
Abstract: Ejectors used in refrigeration systems as entrainment and compression components or expanders, alone or in combination with other equipment devices, have gained renewed interest from the scientific community as a means of low temperature heat recovery and more efficient energy use. This paper summarizes the main findings and trends, in the area of heat-driven ejectors and ejector-based machines, using low boiling point working fluids, which were reported in the literature for a number of promising applications. An overall view of such systems is provided by discussing the ejector physics principles, as well as a review of the main developments in ejectors over the last few years. Recent achievements on thermally activated ejectors for single-phase compressible fluids are the main focus in this part of the review. Aspects related to their design, operation, theoretical and experimental approaches employed, analysis of the complex interacting phenomena taking place within the device, and performance are highlighted. Conventional and improved ejector refrigeration cycles are discussed. Some cycles of interest employing ejectors alone or boosted combinations are presented and their potential applications are indicated.

70 citations

Journal ArticleDOI
TL;DR: The grid generation issues found in the 3D simulation of two-phase flow in a pipe using Computational Fluid Dynamics (CFD) are discussed in this paper, showing that there is a strong dependency of the flow behaviour on the mesh employed.
Abstract: The grid generation issues found in the 3D simulation of two-phase flow in a pipe using Computational Fluid Dynamics (CFD) are discussed in this paper. Special attention is given to the effect of the element type and structure of the mesh. The simulations were carried out using the commercial software package STAR-CCM+, which is designed for numerical simulation of continuum mechanics problems. The model consisted of a cylindrical vertical pipe. Different mesh structures were employed in the computational domain. The condition of two-phase flow was simulated with the Volume of Fluid (VOF) model, taking into consideration turbulence effects using the k-e model. The results showed that there is a strong dependency of the flow behaviour on the mesh employed. The best result was obtained with the grid known as butterfly grid, while the cylindrical mesh produced misleading results. The simulation was validated against experimental results.

68 citations