• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.2
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• pp.94-100
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• 2013

A convergent-divergent nozzle or venturi nozzle has been used to accelerate the wind speed at its throat. The wind speed at the throat is inversely proportional to its area according to the continuity equation. In this numerical study, an airflow phenomena in the venturi system placed at a vertical structure was investigated to understand the vortex effect occurred at the rear-side of the vertical structure on the air speed increment at the throat of the venturi system. For this study, a venturi system sized by $20(m){\times}20(m){\times}6(m)$ was modelled and the area ratio(AR) of the model venturi was 2.86. To see the vortex effect on the air flow acceleration in the venturi throat, two different boundary conditions was defined From the study, it was found that the pressure coefficient(CP) of the venturi system with the vortex formed at the exit of the venturi was about 2.5times of the CP of the venturi system without the vortex effect. The velocity increment rate of the venturi system with the vortex was 61% but 9.5% only at the venturi system without the vortex. Conclusively, it can be said that the venturi system installed in a vertical structure has very positive effect on the flow acceleration at its throat due to the vortex formed at the rear-side of the vertical structure.

• International Journal of Advanced Culture Technology
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• v.10 no.3
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• pp.295-306
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• 2022

The NOx removal performance of the SCR process depends on various factors such as catalytic factors (catalyst composition, shape, space velocity, etc.), temperature and flow rate distribution of the exhaust gas. Among them, the uniformity of the flow flowing into the catalyst bed plays the most important role. In this study, the flow characteristics in the SCR reactor in the design stage were simulated using a three-dimensional numerical analysis technique to confirm the uniformity of the airflow. Due to the limitation of the installation space, the shape of the inlet duct was compared with the two types of inlet duct shape because there were many curved sections of the inlet duct and the duct size margin was not large. The effect of inlet duct shape, guide vane or mixer installation, and venturi shape change on SCR reactor internal flow, airflow uniformity, and space utilization rate of ammonia concentration were studied. It was found that the uniformity of the airflow reaching the catalyst layer was greatly improved when an inlet duct with a shape that could suppress drift was applied and guide vanes were installed in the curved part of the inlet duct to properly distribute the process gas. In addition, the space utilization rate was greatly improved when the duct at the rear of the nozzle was applied as a venturi type rather than a mixer for uniform distribution of ammonia gas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.9
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• pp.699-703
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• 2012

The performance of the typical VAV dampers; blade type, venturi type and blade-orifice type, for the circular duct, is obtained by measuring the volume flow rate as a function of the opening degree. The performance features are discussed by comparing the volume flow rate of each damper. It is shown that the blade-orifice type damper, recently developed, is excellent in its linearity of the performance and that it is worse than the blade type but much better than the venturi type in its flow resistance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.543-548
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• 2011

New concept of wind energy conversion system is proposed to increase the energy density at a given working space. The quality of wind for wind power generation is depend on its direction and speed. However, the quality is not good on land because wind direction is changeable all the time and the speed as well. The most popularly operated wind turbine system is an axial-flow free turbine. But its conversion efficiency is less than 30% and even less than 20% considering the operating time. In this research, a cross-flow type wind turbine system is proposed with a convergent-divergent duct system to accelerate the low speed wind at the inlet of the wind turbine. Inlet guide vane is also introduced to the wind turbine system to have continuous power generation under the change of wind direction. In here, the availability of wind energy generation is evaluated with the change of the size of the inlet guide vane and the optimum geometry of the turbine impeller blade was found for the innovative wind power generation system.

• Journal of the Korean Solar Energy Society
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• v.32 no.6
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• pp.76-84
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• 2012

This study conducted experiments to measure air currents in an experimental building according to external conditions, types of induction ducts, and types of internal sockets by applying an external induction duct comprised of inducing openings and lines and induction units to the kitchen and bathroom vents at the rooftop of a super high-rise apartment building in order to help to improve the venting performance. The study also proposed the optimization of the external induction-style kitchen and bathroom vents capable of wind power generation. (1) As for air current distribution according to vent velocity changes, it increased the venting performance of the kitchen and bathroom by 1.0m/s at vent velocity of 2.0m/s or higher and allowed for wind power generation. (2)As for air current distribution according to external velocity changes, it increased the venting performance of the kitchen and bathroom by 1.2m/s at external velocity of 2.0m/s or higher and allowed for wind power generation. (3)As for air current distribution according to wind direction changes($0{\sim}180^{\circ}$), it was favorable for higher vent velocity when the angle between the external induction duct direction and prevailing wind direction was within ${\pm}30^{\circ}$. (4)As for air current distribution according to induction duct type, the[M1] type combining the inducing openings and lines with the induction units recorded the highest improvement effects in the kitchen and bathroom venting performance by increasing vent velocity by 46%. (5)As for air current distribution according to the changing types of internal sockets where the main ducts of the kitchen and bathroom are connected to the external induction ducts, the venturi tube type[Sv] increased vent velocity by 66% based on the smoothest external inflow.