• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.2
• /
• pp.251-259
• /
• 2000

The ionic wind formed in a nonuniform electric field has been recognized to have a significant effect on particle collection in an electrostatic precipitator(ESP). Under normal operating conditions the effect of ionic wind is not pronounced. However, as the flow velocity becomes smaller, the ionic wind becomes pronounced and induces secondary flow, which has a significant influence on the flow field and the particle collecting efficiency. In this paper, experiments for investigating the effect of secondary flow on collection efficiencies were carried out by changing the flow velocities in 0.2-0.7m/s and the applied voltages in 9-11kV/cm. The particle size distributions and concentrations are measured by DMA and CNC. To analyze the experimental results, numerical analysis of electric filed in ESP was carried out. It shows that particle collection is influenced by two independent dimensionless numbers, $Re_{ehd}\;and\;Re_{flow}$ not by $N_{ehd}$ alone. When $Re_{flow}$, decreases for constant $Re_{ehd}$, the secondary flow prohibits the particle collection. But when $Re_{ehd}$ increases for constant $Re_{flow}$, it enhances the particle collection by driving the particles into the collection region.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.9
• /
• pp.2223-2236
• /
• 1995

0The fields of turbomachinery and electrical generators provide many examples of flow through rotating internal passages. At the practicing Reynolds number, most of the flow motion is three dimensional and highly turbulent. The proper understanding for the characteristics of these turbulent flow is necessary for the design of thermo-fluid machinery of a good efficiency. The flow characteristics in the rotating duct with curvature are very complex in practice due to the curvature and rotational effect of the duct. The understanding of the effect of the curvature on the structure and rotational effect of the duct. The understanding of the effect of the curvature on the structure of turbulence in the curved passage and the characteristics of the flow in a rotating radial straight channel have been well studied separately by many workers. But the combined effects of curvature and rotation on the flow have not been well understood inspite of the importance of the phenomena in the practical design process. In this study, the characteristics of a developing turbulent flow in a square sectioned 90.deg. bend rotating at a constant angular velocity are measured by using hot-wire anemometer to seize the rotational effects on the flow characteristics. As the results of this study, centrifugal forces associated with the curvature of the bend and Coriolis forces and centripetal forces associated with the rotational affect directly both the mean motion and the turbulent fluctuations.

• Journal of Mechanical Science and Technology
• /
• v.17 no.12
• /
• pp.2010-2018
• /
• 2003

Although continuous casting process has highly developed, there still remain many problems to be considered. Specifically, two vortex flows resulting from impingement against narrow walls make a flow field unstable in a mold, and it is directly related to internal and external defects of steel products. To cope with this instability, EMBR (Electromagnetic Brake Ruler) technique has been lately studied for the stability of molten steel flow, and it is revealed that molten steel flow in a mold can be controlled with applied magnetic field. However, it is still difficult to clarify flow pattern in an EMBR caster due to complex correlations among variables such as geometric factors, casting conditions, and the place and the intensity of charged magnetic field. In the present study, flow field in a mold is focused with different conditions of electromagnetic effect. To accurately analyze the case, three dimensional low Reynolds turbulent model and appropriate boundary conditions are chosen. To evaluate the electromagnetic effect in molten steel flow, dimensionless numbers are employed. The results show that the location and the intensity of the applied magnetic field significantly influence the flow pattern. Both impingement and internal flow pattern are changed remarkably with the change of the location of applied magnetic field. It turns out that an insufficient magnetic force yields adverse effect like channeling, and rather lowers the quality of steel product.

• Journal of the korean Society of Automotive Engineers
• /
• v.4 no.3
• /
• pp.24-39
• /
• 1982

It has already been known that quenching effect is influenced greatly by stirring and changing coolant's temperature on quenching. But according to the past investigations its effect has not been taken into consideration quantitatively in the cooling process. The purpose of this study is that the influence of flow rate and temperature on the quenching effect of cooling water as quenching medium is quantitatively examined by using the open channel. The stream of water in this study is turbulent flow. The temperature of the specimen made of pure copper is measured by CA thermocouple in the vicinity of the surface and recorded by an automatic recorder during the quenching process in city water. The results obtained are as follows; 1. The quenching effect of cooling water generally increases with Reynolds Number(characteristic length; specimen diameter)as shown in the experimental formula; but at the realm of Reynolds Number from 1.2 * 10$^{4}$ to 9.2 * 10$^{4}$, the increasing rate of quenching effect shows little increase. 2. The increasing rate of quenching effect was increased under the flow rate of 221 cm/sec. On the other hand, it was decreased below this flow rate. 3. The quenching effect was influenced by the water temperature and the flow rate. But it was rather dependent upon the former than the latter. 4. Although the quenching effect appeared loosely in the water temperature of 50.deg. C, it was shown that the quenching effect increased in the low flow rate of 31 cm/sec. comparing with the still water. 5. It is desirable to design the quenching system to be over 1.2 * 10$^{4}$ in Reynolds Number or over, 3000$cm^{-1}$ / in V/v in order to increase the quenching effect of the system using open channel.annel.

• The KSFM Journal of Fluid Machinery
• /
• v.6 no.4 s.21
• /
• pp.29-37
• /
• 2003

This study was undertaken to verify the effect of flow coefficient when a globe control valve was attached by different type of fitting. The valve flow coefficient is usually determined by measuring the flow rate and the pressure drop with the connection of straight pipe through the valve. The effect of different fitting that is mounted on the downstream of the valve is studied. Four types of fittings and three distances between the valve and a downstream fitting are compared parametrically to investigate the effect on the flow coefficient of it. Measured flow coefficient and numerically predicted value by using computational fluid dynamics were compared in detail. It is concluded that the flow coefficient is reduced if the fitting is attached after a valve, but the effect of different type of fitting is not crucial.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.4
• /
• pp.45-51
• /
• 2008

The purpose of this study is to examine the effect of nozzle shape on the performance and internal flow of a cross-flow hydro turbine. CFD analysis for three kinds of nozzle shape is conducted to simulate the effect of nozzle shape. The results reveal that relatively narrow nozzle width is effective to increase the turbine efficiency and output power. Almost output power is achieved at Stage 1. Therefore, optimum design of the nozzle shape is necessary to improve the turbine performance. Recirculation flow in the runner passage decreases the turbine efficiency and output power because the flow make hydraulic loss and collision loss in the region. Air should be put into the runner passage and the recirculating flow should be suppressed by the air layer in the runner.

• Journal of Chest Surgery
• /
• v.17 no.1
• /
• pp.101-109
• /
• 1984

The influences of acute respiratory and metabolic acid-base disturbances on the carotid, renal and coronary blood flow were measured in dogs. Respiratory acidosis was induced by artificial respiration with 8% CO2 -02 gas mixture and respiratory alkalosis was induced by hyperventilation under the control of respirator. Metabolic acidosis and metabolic alkalosis were induced by intravenous infusion of 0.3N hydrochloric acid and 0.6M sodium bicarbonate solution. To observe the effect of hyperkalemia, isotonic potassium chloride solution was infused. CVI electromagnetic flowmeter probes were placed on the left common carotid artery, left renal artery and left circumflex coronary artery. Each flow was recorded on polygraph. 1. The carotid blood flow showed rapid showed rapid and marked increase in acute respiratory acidosis. Even in the cases when arterial blood pressure was lowered during the state of respiratory acidosis, carotid blood flow increased. By the infusion of hydrochloric acid, carotid blood flow increased slowly and returned to the previous label after discontinuation of the infusion. Carotid blood flow also increased by the infusion of large amount of sodium bicarbonate, but it might be the combined effect of expansion of extracellular fluid and compensatory elevation of carbon dioxide tension. 2.The renal blood flow remained unchanged during the acute acid-base disturbances, suggesting effective autoregulation. Renal blood flow, however, increased very slowly when the infusion of potassium chloride continued for a long period. 3.Although less marked than the carotid blood flow, the coronary blood flow increased in the acute respiratory and metabolic acidosis. In asphyxiated condition, coronary blood flow increased most markedly and this might be the combined effect of hypoxia, hypercapnea, and lowering of pH. In summary, the carotid blowflow showed more marked change in the acute respiratory and metabolic acidosis than the renal and coronary blood flow. Respiratory and metabolic components of acid-base disturbances may influence the local blood flow concomitantly, there being more differences in the individual responses, but respiratory component manifested more rapid and marked effect than metabolic component.

• Journal of Korean Academy of Nursing
• /
• v.52 no.3
• /
• pp.278-290
• /
• 2022

Purpose: This study aimed to identify the mediating effect of learning flow and the moderated mediation effect of digital literacy on the effect of the learning presence of non-face-to-face class experience in nursing students on academic achievement. Methods: Participants were 272 nursing students from six universities in two different cities. A self-report questionnaire was used to measure learning presence, learning flow, digital literacy, and academic achievement. Analysis was performed using SPSS 26.0 and SPSS PROCESS Macro (4.0). Results: The mediating effect of learning flow on the effect of learning presence on academic achievement was 0.42, and the moderated mediation index of digital literacy was 0.17. Learning flow showed a mediating effect on the relationship between learning presence and academic achievement. Digital literacy had a moderated mediation effect on the relationship between learning presence and academic achievement that was mediated by learning flow. Conclusion: The intensity of the mediating effect of nursing students' learning presence on academic achievement through learning flow increases as the level of digital literacy increases. These results suggest that educational programs considering the level of learning presence, learning flow, and digital literacy are required to promote the academic achievement of nursing college students.

• International Journal of Fluid Machinery and Systems
• /
• v.1 no.1
• /
• pp.101-108
• /
• 2008

The effect of Reynolds number on the performance of a regenerative pump was examined in a low Reynolds number range in experiment. The head of the regenerative pump increased at low flow rates and decreased at high flow rates as the Reynolds number decreased. The computation of the internal flow was made to clarify the cause of the Reynolds number effect. At low flow rates, the head is decreased with increasing the Reynolds number due to the decrease of the shear force exerted by the impeller caused by the increase of leakage and hence local flow rate. At higher flow rates, the head is increased with increasing the Reynolds number with decreased loss at the inlet and outlet as well as the decreased shear stress on the casing wall.

• Journal of Korean Dental Hygiene Science
• /
• v.4 no.2
• /
• pp.31-41
• /
• 2021

Background: To investigate the mediating effect of learning flow in the relationship between blended learning achievement and learning satisfaction in dental hygiene students, and to identify whether face-to-face studies should be substituted with non-face-to-face studies. Methods: Total 134 dental hygiene students, who underwent blended learning in the dental hygiene class during the first semester of 2021, were recruited. The research tools were blended learning achievement, learning flow, and learning satisfaction, comprising 15 questions in total. Mediation regression analysis was used to analyze the mediating effect of learning flow in the relationship between learning achievement and learning satisfaction, and that between each variable. Results: Learning flow and learning satisfaction (r=0.490, p<0.001) were positively interrelated, and the interrelation between variables was statistically significant. Class environment had the biggest effect as a subfactor of class achievement, and it appeared to have an effect on class attitude and learning motive. The effect of learning flow on learning satisfaction was statistically significant. Learning flow was partially mediated by both blended learning achievement and learning satisfaction. Learning flow was directly related to blended learning satisfaction and learning achievement. Conclusion: The results showed the possible use of blended learning in dental hygiene theory and practical subjects.