• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.175-183
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• 2002

Flow Condensation heat transfer coefficients (HTCs) of Rl2, R22, R32, Rl23, Rl25, R134a, R142b were measured experimentally on a horizontal plain tube. The experi- mental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water-glycol loop. The test section in a refrigerant loop was made of a copper tube of 8.8 mm inner diameter and 1000 mm length respectively. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. All tests were performed at a filed refrigerant saturation temperature of 4$0^{\circ}C$ with mass fluxes of 100, 200, 300 kg/$m^2$s. The experimental result showed that flow condensation HTCs increase as the quality, mass flux, and latent heat of condensation increase. At the same mass flux, the HTCs of R32 and R142b were higher than those of R22 by 35~45% and 7~14% respectively while HTCs of R134a and Rl23 were similar to those of R22. On the other hand, HTCs of Rl25 and Rl2 were lower than those of R22 by 28 ~30% and 15 ~25% respectively Finally, a new correlation for flow condensation HTCs was developed by modifying Dobson and Chato's correlation with the latent heat of condensation considered. The correlaton showed an average deviation of 13.1% for all pure fluids data indicating an excellent agreement.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1347-1357
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• 2005

Effects of combustor-level high free-stream turbulence on the blade-surface heat/mass transfer have been investigated in the three-dimensional flow region near the endwall within a high-turning turbine rotor cascade passage. Free-stream turbulence intensity and integral length scale in the high turbulence case are 14.7 percents and 80 mm, respectively. The result shows that there is no considerable discrepancy in the blade heat/mass transfer near the endwall between the low and high turbulence cases. As departing from the endwall, however, the deviation between the two cases becomes larger, particularly in the region where flow separation and re-attachment occur. Under the high turbulence, flow disturbances such as boundary-layer separation and re-attachment seem to be suppressed, which makes the blade heat/mass transfer more uniform. Moreover, there are some evidences that endwall vortices tend to be weakened under the high turbulence.

• Journal of Computational Design and Engineering
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• v.3 no.3
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• pp.198-214
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• 2016

Oval substrates are widely used in automobiles to reduce the exhaust emissions in Diesel oxidation Catalyst of CI engine. Because of constraints in space and packaging Oval substrate is preferred rather than round substrate. Obtaining the flow uniformity is very challenging in oval substrate comparing with round substrate. In this present work attempts are made to optimize the inlet cone design to achieve the optimal flow uniformity with the help of CATIA V5 which is 3D design tool and CFX which is 3D CFD tool. Initially length of inlet cone and mass flow rate of exhaust stream are analysed to understand the effects of flow uniformity and pressure drop. Then short straight cones and angled cones are designed. Angled cones have been designed by two methodologies. First methodology is rotating flow inlet plane along the substrate in shorter or longer axis. Second method is shifting the flow inlet plane along the longer axis. Large improvement in flow uniformity is observed when the flow inlet plane is shifted along the direction of longer axis by 10, 20 and 30 mm away from geometrical centre. When the inlet plane is rotated again based on 30 mm shifted geometry, significant improvement at rotation angle of $20^{\circ}$ is observed. The flow uniformity is optimum when second shift is performed based on second rotation. This present work shows that for an oval substrate flow, uniformity index can be optimized when inlet cone is angled by rotation of flow inlet plane along axis of substrate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.881-887
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• 2014

This paper presents numerical study on flow and heat transfer characteristics in micro-gap plate heat exchanger. In particular, we investigate the effect of flow inertia on the flow distribution from single main channel to multiple parallel micro-gaps. The flow regime of the main channel is varied from laminar regime (Reynolds number of 100) to turbulent regime (Reynolds number of 10000) by changing the flow rate, and non-uniformity of the flow distribution and temperature field is evaluated quantitatively based on the standard deviation. The flow distribution is found to be significantly affected by not only the header design but also the flow rate of the main channel. It is also observed that the non-uniformity of the temperature field has its maximum at the intermediate flow regime.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.179-185
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• 2014

Average temperature and temperature uniformity in a battery cell are the important criteria of the thermal management of the battery pack for hybrid electric vehicles and electric vehicles (HEVs and EVs) because high power with large size cell is used for the battery pack. Thus, liquid cooling system is generally applied for the HEV/EV battery pack. The liquid cooling system is made of multiple cooling plates with coolant flow paths. The cooling plates are inserted between the battery cells to reject the heat from batteries to coolant. In this study, the cooling plate with U-shaped coolant flow paths is considered to evaluate the effects of coolant flow condition on the cooling performance of the system. The counter flow and parallel flow set up is compared and the effect of flow rate is evaluated using CFD tool (FLUENT). The number of counter-flows and flow rate are changed and the effect on the cooling performance including average temperature, differential temperature, and standard deviation of temperature are investigated. The results show that the parallel flow has better cooling performance compared with counter flow and it is also found that the coolant flow rate should be chosen with the consideration of trade-off between the cooling performance and pressure drop.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.387-392
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• 2020

This paper proposes a flow-rate control system for industrial valves. Industrial valves are used in piping systems to control the flow rate and pressure. In general, valves used in pipelines are classified into globe valves, butterfly valves, and ball valves according to the shape. Motor, hydraulic, and pneumatic systems are used for operating valves. The flow meter should measure the flow rate when configuring the flow-rate control system. On the other hand, because the flow rate of the valve can be expressed by flow coefficient, a control scheme is proposed using the pressure deviation, which measures at the front and rear of the valve. The transfer function for the valve, according to the control input, was estimated using the signal compression method. Based on the induced transfer function, the disturbance observer was designed to improve the command following the performance of the valve stem. The performance of the proposed control method is compared with the flow-rate control result using the flow meter used.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.249-257
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• 2017

Filtering the data for travel time records obtained from DSRC probes is essential for a better estimation of the link travel time. This study addresses the major deficiency in the performance of TRANSGUIDE in removing anomalous data. This algorithm is unable to handle unstable traffic flow conditions for certain time intervals, where fluctuations are observed. In this regard, this study proposes an algorithm that is capable of overcoming the weaknesses of TRANSGUIDE. If TRANSGUIDE fails to validate sufficient number of observations inside one time interval, another process specifies a new validity range based on the median absolute deviation (MAD), a common statistical approach. The proposed algorithm suggests the parameters, ${\alpha}$ and ${\beta}$, to consider the maximum allowed outlier within a one-time interval to respond to certain traffic flow conditions. The parameter estimation relies on historical data because it needs to be updated frequently. To test the proposed algorithm, the DSRC probe travel time data were collected from a multilane highway road section. Calibration of the model was performed by statistical data analysis through using cumulative relative frequency. The qualitative evaluation shows satisfactory performance. The proposed model overcomes the deficiency associated with the rapid change in travel time.

• Journal of Korean Society of Transportation
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• v.34 no.6
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• pp.499-509
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• 2016

The pedestrian traffic flow has more complicated microscopic features than vehicular traffic flow. Without any designated lanes or any guidance, pedestrians naturally move and change their routes in two dimensional domain with ease. Thus the assessment of pedestrian comfort level should be considering the microscopic features of pedestrian flow. This study is aimed at developing pedestrian comfort criteria based upon pedestrian flow simulation model. This study suggests three criteria to determine pedestrian comfort level; the deviation of route, the acceleration of walk, and the number of collision. Each criterion, which can address the unique walking patterns of pedestrian flow, is represented as each different function with respect to traffic flow rate. The criteria can be the additional indicators to determine the level of service of pedestrian flow together with traffic flow rate and walking speed.

• Ocean and Polar Research
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• v.25 no.2
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• pp.201-211
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• 2003

Bottom simulating reflectors (BSR), representing the base of the gas hydrate stability field, are widespread on the South Shetland continental margin (SSM), Antarctic Peninsula. With the phase diagram fur the gas hydrate stability field, heat flow can be derived from the BSR depth beneath the seafloor determined on multichannel seismic profiles. The heat flow values in the study area range from $50mW/m^2$ to $85mW/m^2$, averaging to $65mW/m^2$. Small deviation from the average heat flow values suggests that heat flow regime of the study area is relatively stable. The landward decrease of heat flow from the South Shetland Trench to the continental shelf would be attributed to the landward thickening of the accretionary prism and the upward advection of heat associated with fluid expulsion. The continental slope 1500m to 3000m deep, where BSRs are most distinguished in the SSM, shows relatively large variation of heat flow possibly due to complex tectonic activities in the study area. The local high heat flow anomalies observed along the slope may be caused by heat transport mechanisms along a NW-SE trending large-scale fault.

• Journal of The Korean Society of Integrative Medicine
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• v.4 no.1
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• pp.65-72
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• 2016

Purpose : This study was carried out to find out the relationship between emotion intelligence, learning flow and career stress of nursing students and influence factors for career stress. Methods : This study targeted 197 university students in their freshman-senior year attending College of Nursing located in P Metropolitan City. For collected data, real numbers and percentage, mean and standard deviation and multiple regression analysis were carried out by using PASW 21.0 program and the correlation between emotion intelligence, learning flow and career stress was analyzed with Pearson's correlation coefficients. Results : Emotional self-awareness(M=3.80, SD =.71), clear goals(M=3.39, SD=.90) and school environment stress(M=2.97, SD=.96) were found to be high in the degree of emotion intelligence, learning flow and career stress of the subjects. The relationship between emotion intelligence and learning flow showed a positive correlation(r=.489, p<.01) in the correlation between emotion intelligence, learning flow, career stress and emotion intelligence showed a negative correlation with career stress(r=-.204, p<.01). Emotion intelligence and learning flow show that career stress is predicted significantly (${\beta}$ =-.15, p < .01) and explained a career stress variate as 18%(F = 24.5, p < .01). Conclusion : Emotion intelligence of nursing students was found to be very influential on the degree of learning flow or career stress. Based on the results of this study, replication studies on emotion intelligence and career stress are needed and the development of intervention programs to increase emotion intelligence is needed.