• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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• pp.293-301
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• 2020

This paper describes a numerical study on the improvement of performance of the 2 vane pump impellers. The design of these impellers was optimized using a commercial computation fluid dynamics code and design of experiments. Geometric design variables were defined by the impeller blade angle distribution. The objective functions were defined as the total head, total efficiency and solid material size of the impellers. The importance of the geometric design variables was analyzed using 2^k factorial designs. The interaction between the total head, total efficiency and solid material size, according to the impeller blade angle distribution, is discussed by analyzing the 2^k factorial design results.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.143-151
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• 2015

Recently, tidal current energy conversion is a promising way to harness the power of tides in order to meet the growing demands of energy utilization. A new concept of tidal current energy conversion device, named Vane Tidal Turbine (VTT), is introduced in this study. VTT has several special features that are potentially more advantageous than the conventional tidal turbines, such as propeller type tidal turbines. The purpose of this study on VTT is to analyze the possibility of extracting the hydrokinetic energy of tidal current and converting it into electricity, and evaluate the performance of turbines for various numbers of blades (six, eight and twelve) using Computational Fluid Dynamics (CFD). At various tip-speed ratios (TSR), the six-bladed turbine obtains the highest power and torque coefficients, power efficiency is up to 28% at TSR = 1.89. Otherwise, the twelve blade design captures the smallest portion of available tidal current energy at all TSRs. However, by adding more blades, torque extracted from the rotor shaft of twelve-bladed turbine is more uniform due to the less interrupted generation of force for a period of time (one revolution).

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.632-635
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• 2009

Nowadays renewable energy has undergone major development, however most renewable energy resources still have demerit which is under the influence of environmental factors that can not be set up the power plants or can not be generated the rated power. To wander from the point of environmental instability, the present paper looks at the tidal current energy which can supply regular electric power. It has an important merit which is more predictable than others, however the place which can be set up is limited and the turbine system must be optimized. The development of the optimized rotor blades design is urgent to obtain regular electric power using the tidal current energy. Therefore, the paper expands on this idea and presents a conceptual design of 100kW horizontal axis rotor blade for the tidal current turbine using blade element momentum (BEM) analysis. The compatibility of horizontal axis tidal turbine (HATT) is verified using a commercial computational fluid dynamics (CFD) code, ANSYS-CFX. This paper presents results of the numerical analysis, such as pressure, streak line and the performance curves with torque data for the inflow of the horizontal axis tidal current turbine (HATT).

• Journal of the Korean Solar Energy Society
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• v.29 no.4
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• pp.58-64
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• 2009

This aim of the study is to demonstrate the effect of a photovoltaic module installed on a small wind-photovoltaic hybrid generation system. Computational fluid dynamics(CFD) is used to interpret the velocity field around the photovoltaic module and the blade areas of a wind turbine. According to the simulation results, it is obvious that x_velocity and y_velocity varies very significantly with time near the photovoltaic module. This would lead to an increase of periodic wind load caused by flow separation at the edge of the photovoltaic module. This study discusses the flow characteristics in term of velocity and frequency analysis. Moreover we suggest a distance between a photovoltaic module and a wind turbine to avoid partially the negative effect caused by the photovoltaic module.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3618-3624
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• 2012

Photodissociation dynamics of propiolic acid ($HC{\equiv}C-COOH$) at 212 nm in the gas phase was investigated by measuring rotationally resolved laser-induced fluorescence spectra of OH ($^2{\Pi}$) radicals exclusively produced in the ground electronic state. From the spectra, internal energies of OH and total translational energy of products were determined. The electronic transition at 212 nm responsible for OH dissociation was assigned as the ${\pi}_{C{\equiv}C}{\rightarrow}{\pi}^*{_{C=O}}$ transition by time-dependent density functional theory calculations. Potential energy surfaces of both the ground and electronically excited states were obtained employing quantum chemical calculations. It was suggested that the dissociation of OH from propiolic acid excited at 212 nm should take place along the $S_1/T_1$ potential energy surfaces after internal conversion and/or intersystem crossing from the initially populated $S_2$ state based upon the potential energy calculations and model calculations for energy partitioning of the available energy among products.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.541-549
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• 2022

This study investigates anti-icing design by conjugate heat transfer analysis in lab-scale printed circuit heat exchanger (PCHE) for supply of cryogenic high pressure liquid hydrogen. The conjugate heat transfer analysis by using computational dynamics (CFD) provided various temperature distributions at important locations in PCHE heat exchanger and predicted the possibility of freezing in hot channel. And, the effect of inlet temperature of glycol water was analyzed in order to resolve the freezing problem in PCHE.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.24-24
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• 2011

• Journal of Photoscience
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• v.9 no.2
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• pp.78-81
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• 2002

Fluorescence rise and decay curves of carotenoids were measured in solutions and in pigment protein complexes with a femtosecond time-resolved fluorescence spectroscopy. For linear carotenoids, the S$_2$ lifetimes showed the maximum value around n = 9-10. The conjugation of a keto-carbonyl group shortened the S$_2$lifetime and prolonged the S$_1$lifetime. The excitation relaxation dynamics within carotenoids and the excitation energy transfer kinetics from carotenoids to chlorophylls are discussed as a function of molecular structure of carotenoids.

• Coupled systems mechanics
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• v.7 no.5
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• pp.611-626
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• 2018

We theoretically consider a possible influence of periodic oceanic tides on non-periodic changes in the dynamics of the Earth and Moon over a long time scale. A particular emphasis will be placed on the contribution from rotating tidal waves, which rotate along the inner edge of an oceanic basin surrounded by topographic boundary. We formulate the angular momentum and the mechanical energy of the rotating tidal wave in terms of celestial parameters with regard to the Earth and Moon. The obtained formula are used to discuss how the energy dissipation in the rotating tidal wave should be relevant to the secular variation in the Earth's spin rotation and the Earth-Moon distance. We also discuss the applicability of the formula to general oceanic binary planets subject to tidal coupling.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.34-41
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• 2005

An experimental study of molecular motions on a liquid-vapor interface is limited due to micro-scale characteristics of a system with an angstrom or a nanometer size Therefore, in recent, many studies for micro-scale systems have been conducted by a computer simulation because it is free from experimental limitations. In this study, through the molecular dynamic (MD) method. molecular behavior was clarified on a liquid-vapor interface and a criterion to distinguish between liquid and vapor was suggested by a potential energy and the number of neighboring molecules. At an interface. the potential energy of a molecule was increased but the number of neighboring molecules was decreased when the molecule moved into a vapor region from a liquid region, and vice versa.