• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.74-77
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• 2002

The channel of the superconducting Flux Flow Transistor has been fabricated with plasma etching method using ICP. The ICP conditions were 700 W of ICP power, 150 W of rf chuck power, 5 mTorr of the pressure in chamber and 1:1 of Ar : Cl$_2$, respectively. The channel etched by plasma gas showed superconducting characteristics of over 77 K and superior surface morphology. The critical current of SFFT was altered by varying the external applied current. As the external applied current increased from 0 to 12 mA, the critical current decreased from 28 to 22 mA. Then the obtained r$\sub$m/ values were smaller than 0.1Ω at a bias current of 40 mA. The current gain was about 0.5. Output resistance was below 0.2 Ω.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.921-930
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• 2001

A new theoretical critical heat flux (CHF) model was developed for the forced convective flow boiling at high pressure, high mass velocity, and low quality. The present model for an intermittent vapor blanket was basically derived from the sublayer dryout theory without including any empirical constant. The vapor blanket velocity was estimated by an axial force balance, and the thickness of vapor blanket was determined by a radial force balance for the Marangoni force and lift force. Based on the comparison of the predicted CHF with the experimental data taken from previous studies, the present CHF model showed satisfactory results with reasonable accuracy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.10
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• pp.704-709
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• 2010

The effect of oil on flow boiling of R-123 in a plain tube bundles was experimentally investigated for a range of quality and heat flux. It is shown that the heat transfer coefficient decreased as the oil concentration increased. Comparison with the previous pool boiling data reveals that the reduction of heat transfer coefficient by oil is more pronounced in pool boiling, and the difference increased with the increase of oil concentration and heat flux. Within the experimental range, the variation of mass flux or quality has negligible effect on the heat transfer coefficient.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.424-428
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• 2003

The channel of a superconducting flux flow transistor has been fabricated with plasma etching method using a inductively coupled plasma etching. The ICP conditions then were ICP Power of 450 W, rf chuck power of 150 W, the pressure in chamber of 5 mTorr, and Ar : Cl$_2$=1:1. Especially, over the 5 mTorr, the superconducting thin films were not etched. The channel etched by plasma gas showed the critical temperature over 85 K. The critical current of the SFFT was altered by varying the external applied current. As the external applied current increased from 0 to 12 mA, the critical current decreased from 28 to 22 mA. Then the obtained trans-resistance value was smaller than 0.1 $\Omega$ at a bias current of 40 mA.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.335-346
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• 2013

The Critical Heat Flux (CHF) of water with dispersed alumina nanoparticles was measured for the geometry and flow conditions relevant to the In-Vessel Retention (IVR) situation which can occur during core melting sequences in certain advanced Light Water Reactors (LWRs). CHF measurements were conducted in a flow boiling loop featuring a test section designed to be thermal-hydraulically similar to the vessel/insulation gap in the Westinghouse AP1000 plant. The effects of orientation angle, pressure, mass flux, fluid type, boiling time, surface material, and surface state were investigated. Results for water-based nanofluids with alumina nanoparticles (0.001% by volume) on stainless steel surface indicate an average 70% CHF enhancement with a range of 17% to 108% depending on the specific flow conditions expected for IVR. Experiments also indicate that only about thirty minutes of boiling time (which drives nanoparticle deposition) are needed to obtain substantial CHF enhancement with nanofluids.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2839-2846
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• 2021

In this study, experiments of downward-facing flow boiling were conducted to investigate material effects on CHF. Experiments were conducted using aluminum, copper, and carbon steel. It was found that different materials had different CHFs. Aluminum has the biggest CHF while copper has the lowest CHF for each mass flux. After experiment, surface wettability increased and surface became rougher, which was probably due to the oxidation process during nucleate boiling. The CHF difference is likely to be related to the surface wettability, roughness and thermal effusivity, which influences the bubble behavior and in turn affects CHF. Further studies are needed to determine which factor is dominant.

• Environmental Engineering Research
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• v.24 no.2
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• pp.347-353
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• 2019

Although membrane distillation (MD) has great promise for desalination of saline water sources, it is crucial to improve its thermal efficiency to reduce the operating cost. Accordingly, this study intended to examine the thermal energy efficiency of MD modules in a pilot scale system. Two different modules of hollow fiber membranes were compared in direct contact MD mode. One of them was made of polypropylene with the effective membrane area of $2.6m^2$ and the other was made of polyvinylidene fluoride with the effective membrane area of $7.6m^2$. The influence of operation parameters, including the temperatures of feed and distillate, feed flow rate, and distillate flow rate on the flux, recovery, and performance ratio (PR), was investigated. Results showed that the two MD membranes showed different flux and PR values even under similar conditions. Moreover, both flow rate and temperature difference between feed and distillate significantly affect the PR values. These results suggest that the operating conditions for MD should be determined by considering the module properties.

• Clean Technology
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• v.5 no.2
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• pp.25-35
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• 1999

Behavior of permeate flux decline was examined through the hollow fiber membrane in ultrafiltration system for Si colloidal solution. Flux decline with time was due to the growth of Si cake deposited on the membrane surface and the pore blocking by Si particles for the hollow fiber membrane. At the pseudo steady state of operation, the permeate flux of dead-end flow was 60 % to that of the cross flow. The ratio of permeate flux to the pure water flux, $J/J_w$, decreased with increasing the trans-membrane pressure, from 64.2 % for $0.5kg_f/cm^2$ to 45.7 % for $2.0kg_f/cm^2$. When the feed flow rate was 3 L/min, the pore blocking model was dominant at the initial period of filtration and was followed by the cake filtration model. And with increasing the feed flow rate from 1 L/min to 3 L/min, $R_c$ was $1.79{\times}10^{12}{\sim}2.34{\times}10^{12}m^{-1}$ which was the about 40 % decreased value to that of the 1 L/min while $R_p$ was not changed and was $1.71{\times}10^{12}m^{-1}$ approximately.

• Journal of computational fluids engineering
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• v.15 no.1
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• pp.31-36
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• 2010

In the present study, computations for flow fields inside the CDI unit cells with electrodes and spacers have been made to evaluate their performance. Three types of unit cells that include a planar type, a serpentine channel type, and a spiral wound type were considered and their flow characteristics were compared. From the computational results, it is found that the serpentine channel type has a large flow resistance and can not guarantee the outflow flux for industrial applications. On the other hand, the planar type can sustain a large enough outflow flux but it's efficiency is low for the electrode-use because of the non-uniform velocity distribution inside the cell and dead zones in every corner. Finally, The spiral wound type has not only a large outflow flux as much as the planar type has, but also a high efficiency for the electrode-use because of uniform velocity distribution. From this comparison, we can expect that the spiral wound type of CDI unit cell would have a high performance deionization capability.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1031-1036
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• 2009

This study is intended to identify how quick disconnect coupling which connects with refrigerant piping of air-conditioner using R-22 refrigerant has effect on characteristics of flux. in the case where the air-conditioner installs utilizes quick disconnect coupling, COP has an effect on the quantity of cooling load because of changing flow rate and physical properties of refrigerant which flow into an entrance of expansion valve from coupling. Variation of flow rate can be regulated by changing expansion-contraction angle; $\alpha$ of an entrance and an exit of coupling. In this study, quick disconnect coupling is presented flow of coupling by using FLUENT as heat flow program. To have an effect on the expansion entrance valve, and by changing expansion-contraction angle; $\alpha$ of an entrance and an exit