• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.12
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• pp.1722-1728
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• 2002

Most researches regarding emulsified fuel were in the areas of emulsifier, emulsified fuel manufacturing and emulsified fuel droplet combustion, but there were little papers published regarding emulsified fuel combustion and boiler efficiency in an industrial boiler. The main purpose of this study is to clarify whether improvements in the boiler efficiency and the reduction of pollutants such as CO, NOx, SOx and smoke exist or not when emulsified fuels are combusted in the commercial boiler. Main experimental parameters were water content in heavy oil , excess $O_2$, and boiler load. The fuels used in this experiment were 0.5 B-C, and 5 kinds of 0.5 B-C/water emulsified fuels. The combustion characteristics of heavy oil and its emulsions with water were investigated in an industrial boiler. The combustion stability was monitored and exhaust gases such as CO, NOx, SOx and smoke were measured with excess $O_2$ and combustion load. In case of emulsified fuel combustion, flame stability was poor and boiler efficiency was lowered by 1.6~5.7%, but emission levels of CO and smoke were improved.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1229-1237
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• 2003

The production of hydrogen fuel depends basically on the water electrolysis. The ultrasonic effects the decrease of the overpotential in a water electrolysis. A study on the overpotential which activates the hydrogen production is the core to elevate the hydrogen production efficiency on the principle. A pressure sensor system by a new idea is developed and applied. Solutions are 4 kinds of KOH concentration such as 0%, 10%, 20%, and 30%. Two frequency bands of the ultrasonic transducer are 28kHz and 2MHz. The directions of ultrasonic forcing are the vertical direction and the horizontal direction. The temperatures are two states, i.e., no constant and constant. Experiments are carried out sequentially in order in three cases of no ultrasonic forcing, ultrasonic forcing, and ultrasonic discontinution. In results, it is clarified that the ultrasonic effects the decrease of overpotential to elevate the efficiency of hydrogen production.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1635-1646
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• 1998

The present study investigated the effects of geometric parameters considered on the performance of an automotive scroll compressor by assuming ideal, semi-real and real gases for R-134a. The geometric parameters were center thickness of scroll, height of scroll and the size of discharge port. Fourth-order Runge-Kutta method was applied to solve the thermodynamic equations, leaking rate equation and the equation of motion of discharge valve for ideal, semi-real, and real gases. The volumetric and adiabatic efficiencies for semi-real and real gases differed little, but those for ideal gas differed by 18% and 25% compared with those for real gas at 2,000rpm. The volumetric efficiency changed little as the design angle of scroll (${\gamma}$) changed, but the adiabatic efficiency at ${\gamma}$ of $34^{\circ}$ was higher by 2.4% than that of $147^{\circ}$ for 2,000rpm. The volumetric and adiabatic efficiencies at scroll height of 29.8mm were higher by 1.7% and 2.8% than those of 65.8mm. The volumetric efficiency changed little as the size of discharge port changed, but the adiabatic efficiency increased a little as the size of discharge port decreased.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.90-98
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• 2005

HMT is a type of continuously variable transmission which has split power flow path characteristics with gear train and hydro static unit. The benefit of improved fuel economy and high power capacity enables it to be a promising application fur large vehicles. This paper presents the analysis results including velocity, static torque, transmission efficiency and dynamic model of the HMT that is developed for city buses. The speeds or gear shafts, the static clutch torque and split power ratio for each mode are detailed here. From the analysis of HMT transmission efficiency considering the power loss in meshed gear and hydraulic unit, we can conclude that minimization of hydraulic power is necessary for improved fuel economy design. Also, the dynamic simulation result for mode shift characteristics shows that little shift shock is observed because of the synchronized rotation speed in clutch.

• Journal of the Korean Solar Energy Society
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• v.31 no.1
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• pp.15-22
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• 2011

It is a great interest to convert more energy in the heat source into the power and to improve the efficiency of power generating processes. Since the efficiency of power generating processes becomes poorer as the temperature of the source decreases, to use an ammonia-water mixture instead of water as working fluid is a possible way to improve the efficiency of the system. In this work performance of ammonia-water regenerative Rankine cycle is investigated for the purpose of extracting maximum power from low-temperature waste heat in the form of sensible energy. Special attention is paid to the effect of system parameters such as mass fraction of ammonia and turbine inlet pressure on the characteristics of system. Results show that the power output increases with the mass fraction of ammonia in the mixture, however workable range of the mass fraction becomes narrower as turbine inlet pressure increases and is able to reach 16.5kW per unit mass flow rate of source air at $180^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.159-166
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• 2007

Mixing between two or more reagents is one of important processes in biochemical microfluidics. In efficient micromixer design, it is essential to analyze flow pattern and evaluate mixing efficiency with good precision. In this work, mixing efficiency for Y-channel micromixer is measured by fluorescence intensity using LIF(Laser Induced Fluorescence) Confocal Microscope. The Y-channel micromixers are fabricated with polydimethylsiloxane(PDMS) and those are bonded to glass plate through Plasma bonding. Nile Blue A is injected into the micromixer as a fluorescence dye for measuring of fluorescence intensity by He/Ne laser. For visualization of the flow pattern, dynamic image capturing is carried out using CAM scope. For the comparison with computer simulation, modified SIMPLE algorithm for incompressible flow equation is solved for the same geometry as in the experiment. Throughout the experiments and computer simulation, accurate mixing efficiency evaluation process for a PDMS Y-channel micromixer is established.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.4
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• pp.490-495
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• 2007

This research aims to examine accuracy and efficiency of the first four moments corresponding to mean, standard deviation, skewness, and kurtosis, which are estimated by a function approximation moment method (FAMM). In FAMM, the moments are estimated from an approximating quadratic function of a system response function. The function approximation is performed on a specially selected experimental region for accuracy, and the number of function evaluations is taken equal to that of the unknown coefficients for efficiency. For this purpose, three error-minimizing conditions are utilized and corresponding canonical experimental regions constructed accordingly. An interpolation function is then obtained using a D-optimal design and then the first four moments of it are obtained as the estimates for the system response function. In order to verify accuracy and efficiency of FAMM, several non-linear examples are considered including a polynomial of order 4, an exponential function, and a rational function. The moments calculated from various coefficients of variation show very good accuracy and efficiency in comparison with those from analytic integration or the Monte Carlo simulation and the experimental design technique proposed by Taguchi and updated by D'Errico and Zaino.

• Solar Energy
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• v.17 no.4
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• pp.57-66
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• 1997

The performance of gas-fired boilers were experimentally investigated. The heat exchanger used for the experiments consisted of circular tube with longitudinal fins for the gas side and a spiral coil for the water side. The burner was located at the top of the heat exchanger, and the burned gas flowed down to the exit. The experiments carried out for different water flow rates, the heat capacities of the boiler and the number of baffle. The thermal efficiency of the upward flow was higher than that of the downward flow of the water in the heat exchanger. As the boiler capacity increased, the thermal efficiency decreased. As the number of the baffles increase, the thermal efficiency increased and the increasing rate of the efficiency decreased. The gas-side overall heat transfer coefficient was independent of the flow rate of the water. The effect of the number of the baffles on the heat transfer coefficient was greater than that of the boiler capacity.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.264-268
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• 2007

The filtration performance of micron-sized metal fibrous filter was improved by synthesizing carbon nanotubes grown on the surface of metal fibers. The carbon nanotubes are grown with bush-like nanostructures covered around the micron-fibers or web-like nanostructures crossing between the fibers at different synthetic conditions. Filtration efficiency of CNT-metal-filter was measured and compared with the efficiency of the raw metal filter without CNTs. The developed CNT-metal-filter has higher filtration efficiency without significant difference in pressure drop compared with the conventional metal filter, which is because the carbon nanotubes function as the trap of pollutant nanoparticles.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.78-88
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• 2007

In the present study a detailed examination of various porous media models for predicting filtration efficiency and pressure drop of diesel particulate filter (DPF), such as sphere-in-cell and constricted tube models, are attempted. In order for demonstrating their validities of correct estimation on permeability, geometry of property configurations common in commercial cordierite DPFs are correlated to the porous media flow models, and validations of predicted filtration efficiencies due to the use of different unit collectors are made with experiments. The result shows that the porosity, pore size and permeability of cordierite DPF can be successfully correlated by Kuwabara flow field with correction factor of 0.6. The unit collector efficiency predicted by sphere-in-cell model agrees very well with measurements in accumulation mode, whereas that by constricted tube model with significant prediction error.