• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.21-26
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• 2005

We performed the numerical analysis on the characteristics of indoor air quality and local supply index with a variation of supply · exhaust airflow rate. We analyzed the local supply index and carbon dioxide concentration at the room and breathing zone with respect to the variation of the supply · exhaust airflow rate. From the numerical results, we found that local supply index was affected but carbon dioxide concentration was hardly affected by the variation of the airflow rate in the room. And we also knew that carbon dioxide concentration was raised in despite of the increment of the supply airflow rate in the breathing zone. After this study it is necessary to analyze the local exhaust index when we evaluate the state of the ventilation in the room.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.351-357
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• 2009

This study was conducted to verify the simulation model through the drying test, and investigate effect of factors, such as temperature of drying air, airflow rate, and velocity of the airflow, on the drying. The low temperature drying simulation model was developed based on the circulation dry simulation model presented by Keum et al. (1987), and by modifying low temperature thin layer drying model, equilibrium moisture content model, latent heat of vaporization model, and crack ratio prediction model. The heat pump and experimental dryer with a capacity of 150kg were used for the test. The RMSE between the predicted and measured value was 0.27% (drying temperature), 0.15% (crack ratio), and 2.08% (relative humidity), so the relevance of the model was verified. In addition, the effect of drying temperature, airflow rate, and velocity of the airflow on the drying was examined. The experimental results showed that the crack ratio at drying temperature of $25{\sim}40^{\circ}C$ was allowable. Moreover, at below $30^{\circ}C$, variation of the crack ratio was slight, but drying time was delayed. Given these results, the drying temperature of over $30^{\circ}C$ was effective. As the airflow rate increased, required energy dramatically increased. Whereas drying rate slowly increased, so loss of drying efficiency was caused. Considering these results, the dryer needed to be designed and adjusted to lower than $30\;m^3/min{\cdot}ton$. As velocity of the airflow increased, required drying energy increased when the velocity of the airflow was over $5\;m^3$/hr, while crack ratio and drying rate showed little variation.

• Journal of Environmental Science International
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• v.21 no.10
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• pp.1181-1186
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• 2012

We studied the ozone concentrations generated by low-temperature dielectric barrier discharge plasma reactor after adding air and phytoplankton to control the ozone concentrations in seawater. We also examined the numbers of bacteria and Vibrio spp. after treatment using the plasma reactor. As the airflow rate was increased, more ozone was removed. Although marked variation in the ozone decrease was observed with and without airflow, the rate of ozone removal did not increase proportionately with the airflow rates. The ozone concentration decreased with increasing organic matter and time. The amount of organic matter seems to be an important factor decreasing the dissolved ozone concentration in liquid. The ozone concentration was 0.07, 0.32, 1.28, and 2.3 mg/L when operating the plasma reactor for 30, 60, 180, and 300 s, respectively; i.e., the ozone concentration increased with the reactor operating time. The initial numbers of bacteria and Vibrio spp. were 800 and 480 CFU/mL, respectively. After operating the plasma reactor at a flow rate of 6 L/min for 30 s, no bacteria or Vibrio spp. were detected. The disinfection effect of this plasma reactor seems to be superior to that of a conventional ozone generator.

• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.71-76
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• 2010

According to recent changes in industry for semiconductor devices, a low-temperature treatment has become a necessity. These changes relate to size refinement and the development of new materials. While variation in cooling efficiency does not affect the yield when using a high-temperature treatment, uniform cooling efficiency is necessary avoid "inconsistencies/bends" in low temperature treatments. However it is difficult to increase temperature stabilization in low temperature treatments. In this paper, using CFD (Computer Fluid Dynamics), we analyze and manipulate the design and input of the low-temperature system to attempt to control for temperature variations within the quartz tube, of which airflow appears to be a predominant factor. This simulation includes variable inputs such as airflow rate, head pressure, and design manipulations in the S.C.U. (Super Cooling Unit).

• Tunnel and Underground Space
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• v.28 no.6
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• pp.609-619
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• 2018

This study was carried out at a local limestone mine to analyze the ventilation efficiency of the shaft equipped with a main fan. The results show that its ventilation efficiency is clearly verified for the natural as well as the mechanical ventilation. The airflow rate of $11.7m^3/s$ was induced by the natural ventilation force and the maximum quantity is almost same as the airflow rate estimated by monitoring the average temperatures in the upcast and downcast air columns. Meanwhile, the airflow rate exhausted by the main fan through the shaft was $20.3{\sim}24.8m^3/s$; variation of the quantity was caused by the upward shift of the mine ventilation characteristic curve due to the frequent movement of the equipment. This indicates efforts are required to reduce the ventilation resistance and raise the quantity supplied by the main fan. The turbulent diffusion coefficients along the 1912 m long airway from the portal to the shaft bottom was estimated to be $15m^2/s$ and $18m^2/s$. Since these higher coefficients imply that contaminants will be dispersed at a faster velocity than the airflow, prompt exhaust method should be planned for the effective air quality control. The ventilation shaft and main fan are definitely what local limestone mines inevitably need for better working environment and sustainable development.

• Particle and aerosol research
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• v.14 no.4
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• pp.181-189
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• 2018

In this study, the risk rates of different contamination sources of the contaminant in a minienvironment were analyzed through Computational Fluid Dynamics (CFD) simulation. The airflow pattern characteristics can only predict the qualitative variation of contaminant concentration, but cannot evaluate the quantitative variations in the risk rate of sources. From the results, the ambient contamination sources mainly affect wafers in the Front Opening Unified Pod (FOUP), whereas the internal contamination sources mainly affect wafers laid on the robot arm in the minienvironment. And the purging plenum system is very useful in protecting the wafers in the FOUP from contaminants transferred from the Fan Filter Unit (FFU). However, this system is unable to protect the wafers on the robot arm from internal contaminants and the wafers in the FOUP from sources of the interface between the FOUP and the minienvironment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.463-469
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• 2009

We performed the experimental study on the control of suspended dust in a cement packaging process for various ventilation systems. To effectively remove the dust generated in the cement packaging process, three different kinds of ventilation system, such as local exhaust ventilation, electrostatic scrubber, and local air supply system, were adopted. Dust concentrations in the packaging process were measured with the variation of the airflow rate of the ventilation systems and then their ventilation performance were evaluated. From the results, we knew that the ventilation performance was the best when the local exhaust ventilation and the electrostatic scrubber were simultaneously operated in the packaging process. In the electrostatic scrubber system, the effect of the airflow rate on the indoor dust removal efficiency was negligible so hat he system ust be operated at $2,700m^3/h$ for saving power consumption.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.163-172
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• 2012

As more diesel engines have been employed in underground limestone mines with large cross section, underground space environment is worsened by diesel exhausts and heat flow. This paper aims for the ultimate goal to optimize the work place environment through assuring the optimal required ventilation rate based on the analysis of the airflow, diesel exhaust gas concentrations and the effects of mechanization and deepening working face on temperature and humidity. Due to the insufficient capacity of the main exhaust fan and poor airway management, stagnant airflows were observed at various locations, while the flow direction was reversed instantly with passing diesel equipment and the flow reversal was also made by the seasonal variation of the outside surface weather. During the loading operation, CO concentration measurements were found to be frequently higher than the threshold limit of 50 ppm, and most of the $NO_2$ measurements during drilling and loading operations shows even more serious levels surpassing the permissible limit of 3 ppm. The actual ventilation quantity was considerably less than the required quantity estimated by the mine health and safety law, and this shortage problem was less serious in colder winter showing more effectiveness of the natural ventilation.

• Tuberculosis and Respiratory Diseases
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• v.52 no.4
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• pp.346-354
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• 2002

Background : Dyspnea and a limitation in exercise performance are important cause of disability in patients with chronic obstructive pulmonary disease(COPD). A depleted nutritional state is a common problem in patients with a severe degree of chronic airflow limitation. This study was carried out to assess the factors determining the maximum exercise capacity in patients with COPD. Methods : The resting pulmonary function, nutritional status, and maximum exercise performance was assessed in 83 stable patients with moderate to severe COPD. The nutritional status was evaluated by bioelectrical impedance analysis. Maximum exercise performance was evaluated by maximum oxygen uptake($VO_2max$). Results : Among the 83 patients, 59% were characterized by nutritional depletion. In the depleted group, a significantly lower peak expiratory flow rate(p<0.05), Kco(p<0.01) and maximum inspiratory pressure(p<0.05), but a significantly higher airway resistance(p<0.05) was observed. The maximum oxygen uptake and the peak oxygen pulse were lower in the depleted group. The $VO_2max$ correlated with some of the measures of the body composition : fat-free mass(FFM), fat mass(FM), body mass index(BMI), intracellular water index(ICW index), and pulmonary function : forced vital capacity(FVC), forced inspiratory vital capacity(FIVC), diffusion capacity(DLCO) : or maximum respiratory pressure : maximum inspiratory pressure(PImax), maximum expiratory pressure(PEmax). Stepwise regression analysis demonstrated that the FFM, DLCO and FIVC accounted for 68.8% of the variation in the $VO_2max$. Conclusion : The depletion of the FFM is significant factor for predicting the maximum exercise performance in patients with moderate to severe COPD.