• Architectural research
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• v.22 no.1
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• pp.13-21
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• 2020

The purpose of this study was to evaluate the variation in building energy predictions caused by simulation settings related to building envelop thickness. The study assessed the ceiling depth impact on skylight energy performance through OpenStudio integrated Radiance and EnergyPlus simulation programs. A ceiling as deep as 1.5 to 3m was analyzed for skylight to roof ratios from 1% to 25%. The results indicated that the building ceiling depth negatively affected the capability of skylights to significantly reduce building energy consumption. Through a parametric analysis, the study concluded that 8%, 9%, 10% and 11% skylight to roof ratio were optimal in terms of total building energy consumption for a ceiling depth of 1.5m, 2m, 2.5m and 3m, respectively. In addition, the results showed that the usually recommended 5% skylight to roof ratio was only efficient when no ceiling depth was included in the simulation model. Furthermore, the study indicated that the building energy saved by the optimal skylight of each ceiling depth decreased as the ceiling depth deepened. The highest total building energy reduction was 9%, 7%, 5% and 3% for a ceiling depth of 1.5m, 2m, 2.5m and 3m, respectively. This study induced that the solar heat gains and daylight visible transmittance by ceiling depth were crucial in the predictions of skylight energy performance and should not be neglected through building simulation simplifications as it is commonly done in most simulation programs' settings.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.601-607
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• 2023

Pyrolysis oil (C5-C20) produced using plastic non-oxidative pyrolysis technology produces naphtha oil (C5-C10) through a separation process, and naphtha oil produces hydrogen through a reforming reaction to secure economic efficiency and social and environmental benefits. In this study, waste plastic pyrolysis oil was subjected to a steam reforming reaction on a commercialized catalyst of 46-3Q And it was found that the 46-3Q catalyst reformed the pyrolysis oil to produce hydrogen. Therefore, an experiment was performed to increase hydrogen yield and minimize the byproduct of ethylene. The reaction experiment was performed using actual waste plastic oil (C8-C11) with temperature, steam/carbon ratio (S/C) ratio, and space velocity as variables. We studied reaction conditions that can maximize hydrogen yield and minimize ethylene byproducts.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.5
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• pp.847-852
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• 2004

The wind turbine blade is the equipment converted wind into electric energy. The effect of the blade has influence of the output power and efficiency of wind turbine. The design of blade is considered of lift-to-drag ratio. structure. a condition of process of manufacture and stable maximum lift coefficient, etc. This study is used the simplified method for design of the aerodynamic blade and aerodynamic analysis used blade element method This Process is programed by delphi-language. The Program has any input values such as tip speed ratio blade length. hub length. a section of shape and max lift-to-drag ratio. The Program displays chord length and twist angle by input value and analyzes performance of the blade.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.3-9
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• 1999

The vortex tube is a simple device which splits a compressed gas stream into a cold stream and a hot stream without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. In this study, the insulation effect of surface on the efficiency of vortex tube was performed experimentally. The experiment is carried out for nozzle area ratio of 0.194, diameter ratio of cold end orifice of 0.6 and input pressure ranging from 0.2Mpa to 0.5Mpa. The purpose of this study is focused on the effect of surface insulation of vortex tube with the variation of cold air mass flow ratio. The results indicate that the temperature difference of cold and hot air are higher about 12% and 30% than that of not insulated vortex tube respectively. Furthermore, for the insulated vortex tube, the similarity relation for the prediction of cold end temperature as the function of cold air mass flow ratio and input pressure is obtained.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.464-473
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• 1996

Two-month feeding experiment was conducted to investigate the optimum dietary protein level and energy to protein ratio in fat cod (Hexagrammos otakii Jordan et STARKS). The fish averaging 29 g were fed with one of the isocaloric diets containing 30, 40, 50 or $60\%$ of protein, or with one of the isoproteic diets containing 9, 10, 11 or 12 of available energy/protein (E/P) ratio. Weight gain and feed efficiency increased significantly with dietary protein level up to $50\%$, then decreased with $60\%$ protein diet (P<0.05). Daily protein intake increased significantly with dietary protein level, whereas protein efficiency ratio decreased with dietary protein level (P<0.05). Second order polynomial regression analyses of percent weight gain and daily protein intake may indicate that the adequate dietary protein level is $45\%$ and daily protein requirement per 100g fish is 1.5g for maximal growth. Weight gain, feed efficiency and protein efficiency from fish led the diet containing 12 of E/P ratio were significantly higher than those from fish fed the other diets (P<0.05). Daily feed or protein intake from fish fed the diet containing 12 of E/P ratio was significantly lower than those from fish fed the other diets (P<0.05). Daily lipid intake increased significantly with dietary E/P ratio (P<0.05).

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.201-207
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• 2004

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contact considered by the researchers to play a important role for DAF performance. It is hard to make up conceptual model through simple mass balance for estimating collision efficiency in the contact zone because coupled behavior of the solid-liquid-gas phase in DAF system is 90 complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, the standard $k-{\varepsilon}$ mode I(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widely accepted and the coefficients for the model are well established. Particle-bubble collision efficiency was calculated using predicted turbulent energy dissipation rate and gas volume fraction. As the result of this study, the authors concluded that bubble size and recycle ratio play important role for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreement with measured removal efficiency in the contact zone. Also, simulation results indicated that collision efficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collision efficiency according to the decrease of the bubble size.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.4
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• pp.56-64
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• 2000

The design of filters for pattern recognition that have optimal trade-off for the criteria of noise robustness, peak sharpness and Homer efficiency, when input scene noise is spatially disjoint (nonoverlapping) with the target, are presented Three different criteria, ie, signal-to-noise ratio, peak-to-output energy ratio and light efficiency are used to design the filter. Computer simulation is made for the various types of noise and parameters to illustrate filter performance for optical pattern recognition. When we compare the new trade-off filter with the original optimal trade-off filter, the performance of trade-off filter for nonoverlapping background is better than that of trade-off filter for overlapping background.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.389-396
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• 1994

It is very important to clarify the ignition and flame propagation processes of methanol fuel in the Spark-ignition engine. High speed Schlieren photography and pressure trace analyses were used to study on combustion characteristics of methanol fuel in a constant volume chamber. Methanol-air mixtures equivalence rations from lean limit to 1.4 were ignited at initial pressure (0.1, 0.3, 0.5 MPa), temperature (313 343, 373 K) and ignition energy (40, 180 mJ). As the result of this study, we verified the characteristics such as ignition delay, effective thermal efficiency, flame propagation velocity, lean limit, ignitability and combustion duration. Obatained results are as follows. (1) The time to 10% reach of maximum pressure was 40-50% of the total combustion duration for this experimental condition hardly affected by equivalence ratio. (2) The Effective thermal efficiency, as calculated from maximum pressure was the highest when the mixture was slightly lean $({\phi} 0.8-0.9)$ and maximum pressure was the highest when the mixiture was slightly rich $({\phi} 1.2-1.2).$

• International Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.25-29
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• 2016

This paper highlights the performance of an impulse turbine which is a part of turbopump in a liquid rocket first stage engine. The turbopump, currently under development at Korea Aerospace Research Institute, has an impulse type turbine with 12 nozzles and a single rotor. The impulse turbine can archive high specific power with the low gas flow rates. The supersonic impulse turbine with a single rotor can make a simple structure. High-pressure gases are converted into the dynamic energy with flows through the 12 nozzles and drive the rotor to make the power for the pumps. The turbine test was performed in the high-pressured turbine test facility with air gas instead of burned gas. A hydraulic dynamometer was used to absorb the power from the turbine and control the rotational speed and torque. The test points were at several pressure ratios with 7 different rotational speeds. Results showed the efficiency was highest at the design pressure ratio. The efficiency was insensitive to the pressure ratio variation than the rotational speed. It was a typical characteristic in an impulse turbine.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.1
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• pp.11-18
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• 2018

A high efficiency integrated reforming system for improving the efficiency of the 5 kW PEMFC system used as the back up power of building was studied. The separated reforming system consisted of three parts - A steam reformer with two stage concentric circular shape, a heat exchanger type steam generator and a CO shift reactor. Temperature and steam carbon ratio (SCR) were control variables during operation. The operating conditions were optimized based on the thermal efficiency of the steam reformer as reformate gas composition changes at different temperature. In experiments, water was fully vaporized in the steam generator up to SCR 3.5 and the maximum thermal efficiency was achieved at the operating temperature around $700^{\circ}C$ in the steam reforming reactor. With the results of the separated reforming system research, we improved the shape of high efficiency integrated reformer. The performance evaluation of the integrated reformer was based on optimized operating conditions in SCR 3.5. As a result, the developed integrated reforming system maintained an efficiency of 76% and constant performance over 3,000 hours.