• Journal of Powder Materials
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• v.13 no.4 s.57
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• pp.263-268
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• 2006

In this study, the colloidal stability and sedimentation behavior of crystalline $TiO_2$ particles (300nm) in various organic solvents have been investigated by means of a backscattered light flux profile (Turbiscan). The backscattered light flux profiles revealed that the $TiO_2$ nanoparticles were readily sedimented in water, methyl alcohol, and ethyl alcohol due to a flocculation-induced particle growth, while a particle coalescence and a sedimentation of the $TiO_2$ nanoparticles were hardly observed in isopropyl alcohol. The migration velocities of the $TiO_2$ particle were measured as around 6.15/min, 12.53 m/min, 6.51m/min, and 0.18m/min for water, methyl alcohol, ethyl alcohol, and isopropyl alcohol, respectively, showing a remarkably slow migration of the $TiO_2$ particles in isopropyl alcohol.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.25-30
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• 1999

An experimental investigation was conducted to explore the effects of air mass flux on the combustion efficiency and particle size distributions in a solid fuel ramjet using a fuel grain highly loaded with boron carbide. Particle distributions were measured at the grain exit and at the nozz1e entrance using a Malvern 2600 HSD. Combustion efficiency increased with decreasing air mass flux. In general, the particle distribution was trimodal or quadrimodal with node peaks at approximately 4, 15, and 25$\mu\textrm{m}$ and possibly one at less than 2$\mu\textrm{m}$. The larger particles were the result of surface agglomeration, primarily within the recirculation region. Higher inlet air temperature produced higher combustion efficiencies, apparently the result of enhanced combustion of the larger boron carbide particles that burn in a diffusion controlled regime.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.125-130
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• 2006

The characteristics of boiling heat transfer and critical heat flux (CHF) behavior of nano-fluids were studied by using various sized silver and alumina nanoparticles. The diameter of nanoparticles was from 2 nm to 250 nm for silver and from 20nm to 40nm for alumina. Pool boiling characteristics and CHF enhancement of nano-fluids with different sized nanoparticles were compared with those of pure water and each nano-fluids. The experiment was performed at atmospheric pressure and the temperature of the pool was maintained constantly by using a flat immersed heater. The concentration of nano-fluids was uniform in all experiments as 0.01g/liter. The results showed that the measured boiling curves were shifted to the right. It demonstrated that the occurrence of nucleate boiling regime in nano-fluids retarded, compared with that of pure water. Also, in nano-fluids, the boiling curves showed that CHF of nano-fluids is significantly enhanced and represented the effect of particle size on boiling characteristics.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.825-832
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• 1988

An experiment was performed to study the heat pipe phenomenon of porous media heated above at one-dimensional steady state for the range of heat flux, 300 W/ $m^{2}$ ~ 2000w/ $m^{2}$. Glass beads, sand, and copper particles were used as porous media and distilled water was used as a working fluid. Result of experiment shows that the length of the two-phase zone increases with the decreasing particle size for the same heat flux. At relatively lower heat flux the length of the two-phase zone increases with the increasing heat flux, which contradicts the result of earlier work. However, its length remains nearly constant when the heat flux increases above a certain value. The length of the two-phase zone is proportional to the product of the heat flux by the hydrostatic capillary height under the limited value on heat flux, that is, $l_{t}$ = A(q. $l_{cap}$)+B, q.leg.1/A(C+B/ $l_{cap}$) where A is 1.7*10$^{-4}$ $m^{2}$/w, B is 1.9*10$^{-2}$ m, and C is 0.43 for copper particles and 0.31 for glass beads and sand.d.d.d.

• Membrane and Water Treatment
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• v.12 no.2
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• pp.65-73
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• 2021

Sponge ball cleaning can generate an abrasion effect, which leads to an attractive increasing in both permeate flux and membrane rejection. The aim of this study was to investigate the influence of the daily sponge ball cleaning (SBC) on the performance of different UF cross-flow membrane modules integrated with a bioreactor. Two 1"-membrane modules and one 1/2"-membrane module were tested. The parameters measured and controlled are temperature, pH, viscosity, particle size, dissolved organic carbon (DOC), total suspended solids (TSS), and permeate flux. The permeate flux could be improved by 60%, for some modules, after 11 days of daily sponge ball cleaning at a transmembrane pressure of 350 kPa and a flow velocity of 4 m/s. Rejection values of all tested modules were improved by 10%. The highest permeate flux of 195 L/㎡.h was achieved using a 1"-membrane module with the aid of its negatively charged membrane material and the daily sponge ball cleaning. In addition, the enhancement in the permeate flux caused by daily sponge ball cleaning improved the energy specific demand for all tested modules. The negatively charged membrane showed the lowest energy specific demand of 1.31 kWh/㎥ in combination with the highest flux, which is a very competitive result.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.83-83
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• 2004

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.121-131
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• 2001

An investigation of the sensitivity depletion laws for rhodium SPNDs was performed to reduce the uncertainty of the sensitivity depletion laws used in Combustion Engineering (CE) reactors and to develop calculational tools that provide the sensitivity depletion laws to interpret the signal of the newly designed rhodium SPND into the local neutron flux. The calculational tools developed in this work are computer programs for a time-dependent neutron flux distribution in the rhodium emitter during depletion and for a time-dependent beta escape probability that a beta particle generated in the emitter escapes into the collector. These programs provide the sensitivity depletion laws and show the reduction of the uncertainty by about 1 % compared to that of the method employed by CE in interpreting the signal into the local neutron flux. A reduction in the uncertainty by 1 % in interpreting the signal into the local neutron flux reduces the uncertainty tv about 1 % in interpreting the signal into the local power and lengthens the lifetime of the rhodium SPND by about 10% or more.

• Membrane Journal
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• v.13 no.2
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• pp.88-100
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• 2003

A change of filtrate flux in Taylor vortex flow filtration was investigated experimentally by rotating speed of inner cellulose ester membrane cylinder (average pore size: 1.2 ${\mu}m$), slurry concentration, and particle size. The filtrate flux was a direct proportion relation with TMP, but an inverse relation with resistances. A change of cake resistance with time was examined by rotating speed, slurry concentration, and particle size. Initial resistance increased dramatically as raising slurry concentration, and the pseudo-steady state was maintained at high resistance value. However, times to reach the pseudo-steady state did not depend on slurry concentration. The resistance was larger as smaller particle size, because possibility of pore blocking inside membrane could be higher and shear effect should be lower as smaller particle size. A model equation suggested in this study was composed of particle deposition and removal terms, and could confirm well experimental data using average values of experimental coefficients.

• 한국초전도학회:학술대회논문집
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• v.11
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• pp.67-67
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• 2001

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.317-322
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• 2017

When the heat flux on the heating surface following changing heat condition in the boiling heat transfer system exceeds critical heat flux, the critical heat flux phenomenon is going over to immediately the film boiling area and then it is occurred the physical destruction phenomenon of various heat transfer systems. In order to maximize the safe operation and performance of the heat transfer system, it is essential to improve the CHF(Critical Heat Flux) of the system. Therefore, we have analysis the effect of improving CHF and characteristics of heat transfer following the nanoparticle coating thickness. As the results, copper nanocoating time are increased to CHF, and in case of nano-coatings are increased spray-deposited coating times more than in the fure water; copper nanopowder is increased up to 6.40%. The boiling heat transfer coefficients of the pure water are increased up to 5.79% respectively. Also, the contact angle is decreased and surface roughness is increased when nano-coating time is increasingly going up.