• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.624-629
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• 2008

The problem was derived from a simple process in solar water heating system. In a new designed electro less separated system we involved a kind of bubble pump. Beside experiment analysis, numerical simulation of the core of bubble pump is also very important. In this paper we investigated the motion of bubbles in vertical tube in two dimensions. The heat and mass transfer was simulated. The result of numerical simulation give a significant help of optimize design of bubble pump.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.3
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• pp.158-166
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• 2005

The present study investigated experimentally and numerically the enhancement of absorption performance due to the waviness of falling film in the vertical absorber tube. The momentum, energy and mass diffusion equations were utilized to find out temperature and concentration profiles at both the interfaces of liquid solution and refrigerant vapor and the wall. Flow visualization was performed to find out the wetting characteristics of the falling film. The maximum heat transfer coefficient was obtained for the wavy flow using spring as an insert device through both numerical and experimental studies. Based on the numerical and experimental results, the maximum absorption rate was found for the wavy-flow using spring as the insert device. The differences between experimental and analytical results ranged from $5.0\;to\;25\%\;when\;Re_j>100$.

• Journal of ILASS-Korea
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• v.19 no.2
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• pp.82-87
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• 2014

Nanofluids are that metallic or nonmetallic nanometer-sized particles are dispersed in liquid. They can be used in various fields to increase the heat transfer rate because the thermal conductivity of nanofluids can be increased significantly. Nanofluids may be used as a good alternative of coolants in spray cooling. This study conducted experiments to compare the characteristics of sprays between water and nanofluid sprays. The radial distributions of droplet velocities and diameters of water, 0.2% wt.(weight), and 0.5% wt. $Al_2O_3$ nanofluids at the pressure of 0.2 and 0.3 MPa were measured by laser doppler instruments. The radial distributions of droplet diameters and velocities at two axial positions with water and 0.2% wt. nanofluid sprays didn't show much difference. A big difference, however, was observed between 0.5% wt. nanofluid and water sprays. With the increase of the mass of nano-particles, the average droplet diameters were increased and the average droplet velocities were decreased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.7
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• pp.556-562
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• 2006

The objectives of this paper are to analyze simultaneous heat and mass transfer performance for a plate type bubble absorber with binary nanofluids numerically and to investigate the effects of binary nanofluids and surfactants on the size of the bubble absorber. The effective absorption ratio represents the effect of binary nanofluids and surfactants on the absorption performance. The kinds and concentrations of nano-particles and surfactants are considered as the key parameters. The results show that the addition of surfactants can reduce the size of absorber up to 74.4%, the application of binary nanofluids does the size up to 63.6%. Combination of binary nanofluids and surfactants can reduce the size of absorber up to 77.4%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.6
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• pp.984-989
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• 1995

The concentration-efficiencyh of blue dextran solution in the progressive freeze-concentration was related to the freezing conditions such as the freezing speed and the stirring speed in the solution phase. From the theoreticla balance equation of heat and mass transfer at freezing front, the relationship between the freezing conditions and the ice structure at freezing front was drived. A high freeze-concentration efficiency was obtained under the operating conditions represented by a low speed of freezing and a high speed of stirring. The operating conditions were related to a smooth solid-liquid interface and these results were well explained by the theoretical equation. Effect of the solute component size on the concentration efficiency in the progressive freezeconcentration was also tested. The concentration efficiency of latex particles showed a lower value than that of blue dextran, however, its difference was insignificant.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.173-175
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• 2015

We simulate the particle bed motions with combustion and reduction in steel making rotary kilns. The particle bed motions are simulated by a Lagrangian approach called Discrete Phase Model (DPM). To reduce the number of tracking particles, the Coarse Grain Model (CGM) was applied. The model for particle motions showed good agreements with experimental results. In addition to the particle motion, the combustion and reduction simulation was performed. The combustion and reduction simulation can consider heat, mass and momentum transfer between the gas phase and particle beds.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.4
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• pp.47-61
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• 1983

In this paper the simulation of a thermodynamic power cycle for a 4-stroke, single-cylinder, spark-ignition engine was studied. In this simulation the cylinder volume was restricted to two zones, a burnt and an unburnt zone, and the convective heat transfer from cylinder contents to surroundings was considered. The chemical species in burnt gas considered was 12 species including H$_{2}$O, H$_{2}$, OH, H, N$_{2}$, NO, N, CO$_{2}$, CO, $O_{2}$, O and Ar. Using this model, computer program for compression, ignition and expansion processes was composed and pressure, temperature and composition of cylinder gas at each crank angle were computed. The composition of CO$_{2}$, CO, $O_{2}$ in the burnt gas when exhaust valve opens, the maximum temperature, the maximum flame speed and the combustion duration were also computed as a function of equivalence ratio. The relation between burnt mass fraction and burnt volume fraction was also computed.

• Membrane Journal
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• v.7 no.2
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• pp.57-64
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• 1997

Membrane Distillation(MD) is reviewed as an application to new separation technology. Hydrophobic membrane which has been used to microfiltration is feasible material for MD process. MD has perfect selectivity under moderate temperature and is promised to simplify typical water treatment process. The principle of MD separation is phase transition by vapor-liquid interface at the pore of membrane surface. Feed and permeate temperature, composition, membrane wetting, heat and mass transfer phenomena affect the selectivity and flux of MD.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.477-484
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• 2005

Model fer the dynamic simulation of dynamic behaviors of a solid oxide fuel cell (SOFC) is provided. This model is based upon (1) coupled mass and heat transfer characteristics and (2) important chemical reactions such as electrochemical and reforming reactions in high temperature fuel cells such as SOFC. It is found that the thermal inertia of solid materials in SOFC plays an important role to the dynamic behavior of cell temperature. Dynamic characteristics of cell voltage, power, and chemical compositions with different levels of load change are investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1096-1105
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• 1996

A theoretical model of the frost formation has been presented to investigate the characteristics of the growth of frost layer by considering molecular diffusion of water vapor and heat generation caused by sublimation of water vapor in the frost layer. The present model was compared with existing experimental data as well as a previous model. The difference between the present model and existing experimental data was found to be about 6 percent. An analysis for the behavior of frost formation using present model shows a good agreement with the trend for a number of experimentally observed features. The present analysis can also provide the physical understanding on the phenomena of the frost formation.