• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.363-369
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• 2007

Probably the most significant heat transfer in the cryogenic liquid hydrogen storage tank from the atmosphere may occur through its support system. In this paper the efficient support system for the cryogenic storage vessel was newly developed and analysed. The support system was composed of a spherical ball as a supporter to reduce the contact area. which is located between two supporting SUS tubes inserted SUS and PTFE blocks. Numerical analyses for temperature distribution, and the thermal stress and strain of the support system were performed by the commercial codes FLUENT and ANSYS. The heat transfer rate of the supporter was evaluated by the thermal boundary potential method which can consider the variation of thermal conductivity with temperature. The results showed that the heat transfer rate through the developed supporter compared with the common SUS tube supporter was significantly reduced. The thermal stress and strain were obtained well below the limited values. It was found that the developed supporter can be one of the most efficient support systems for cryogenic liquid storage vessel.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2296-2302
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• 2005

This study is focused on the comparison of heat transfer performance of two thermosyphons having 60 straight and helical internal grooves. Distilled water has been used as working fluid. Liquid fill charge ratio defined by the ratio of working fluid volume to total internal volume of thermosyphon, the inclination angle and operating temperature were used as experimental parameters. The heat flux and heat transfer coefficient are estimated from experimental results. The conclusions of this study may be summarized as follows; Liquid fill charge ratio, inclination angle and geometric shape of grooves were very important factors for the operation of thermosyphon. The optimum liquid fill charge ratio for the best heat flux were $30\%$. The heat transfer performance of helically grooved tube was higher than that of straight grooved tube in low inclination angle (less than $30^{\circ}$), but the results were opposite in high inclination angle (more than $30^{\circ}$). As far as optimum inclination angle concerns, range of $25^{\circ}\~30^{\circ}$ for a helically grooved tube and about $40^{\circ}$ for a straight grooved tube are suggested angles for the best results.

• Korean Journal of Hazardous Materials
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• v.6 no.2
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• pp.95-104
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• 2018

Gas-liquid bubble column reactors are extensively used in industrial processes. A detailed knowledge of bubble size distribution is needed for determining the mass transfer in gas-liquid film. Experimental data on bubble size distribution and liquid-side mass transfer coefficient($k_L$) were used to calculate the estimated time to saturation in bubble column reactor. Also, the gas flux was evaluated to the liquid-side mass transfer coefficient($k_L$) and solubility data for hydrogen sulfide($H_2S$) and chlorine($Cl_2$) absorption into water. Simulation results show that $H_2S$ absorption time to 50 % of saturation concentrations are 611 sec and 1,329 sec when bubble diameters are 0.5 mm and 4.5 mm, while absorbing 1 % $H_2S$ gas. In case of $Cl_2$, absorption time range 657 to 1,400 sec when bubble size range 0.5 mm to 4.5 mm, while absorbing 1 % $Cl_2$ gas. Calculated simulation results can be used in the design of emergency relief bubble reactors.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.25-30
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• 2000

In present paper, mass transfer over a flat plate with film condensation including noncondesable gas is analyzed with the help of similarity methods. Couette flow was assumed in liquid film and boundary-layer approximation was used in the ambient flow. Governing equations were transformed into the ordinary differential equtions by the similarity methods. Runge-Kutta and shooting method were used in order to fine the effect of mass transfer on the velocity and concentrations at the liquid-vapor interface.

• Journal of the Korean Society of Safety
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• v.9 no.3
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• pp.67-73
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• 1994

The gas holdup and volumeteric liquid phase mass transfer coefficient with the variation of the concentration of CMC aqueous solution, gas velocity, diameter and area of the draught tube were investigated. As the results of the experiments, the gas holdup and volumetric liquid phase mass transfer coefficient decreased with decreasing the concentration of CMC aqueous solution, increased with increasing the gas velocity and increased with increasing the circulated area ratio of the draught tube.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.961-962
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• 2008

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.10
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• pp.1327-1339
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• 1999

Characteristics of two-phase flow and heat transfer were numerically investigated in a submerged gas Injection system. Effects of both the gas flow rate and bubble size were investigated. In addition, heat transfer characteristic and effects of heat transfer were investigated when temperature of the injected gas was different from that of the liquid. The Eulerian approach was used for the formulation of both the continuous and the dispersed phases. The turbulence in the liquid phase was modeled by the use of the standard $k-{\varepsilon}$ turbulence model. The interphase friction and heat transfer coefficient were calculated by means of correlations available in the literature. The turbulent dispersion of the phases was modeled by introducing a "dispersion Prandtl number". The plume region and the axial velocities are increased with increases in the gas flow rate and with decreases in the bubble diameter. The turbulent flow field grows stronger with the increases in the gas flow rate and with the decreases in the bubble diameter. In case that the heat transfer between the liquid and the gas is considered, the axial and the radial velocities are decreased in comparison with the case that there is no temperature difference between the liquid and the gas when the temperature of the injected gas is higher than the mean liquid temperature. The results in the present research are of interest in the design and the operation of a wide variety of material and chemical processes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.303-311
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• 2011

This study presents a new idea of liquid desiccant dehumidifier with extended surface to improve the compactness. Extended surface is inserted between vertical cooling tubes, and the liquid desiccant flows down along the tube walls and the extended surface as well. Though the extended surface contributes to the increase in the mass transfer area, the effect tends to be limited because less conductive non-metallic materials need to be applied due to the high corrosiveness of liquid desiccant. To analyze the effects of the extended surface insertion, mathematical modelling and numerical integration are performed for the heat and mass transfer in the liquid desiccant dehumidifier. The results show that, though the liquid desiccant on the extended surface is heated due to the moisture absorption, the temperature can be maintained by periodic mixing at the contact points between the tube and the extended surface with the liquid desiccant stream from the tube side at a relatively low temperature. This implies the absorption heat from the extended surface side can be removed effectively by mixing, which leads to a substantial improvement of the dehumidification in the liquid desiccant dehumidifier with extended surface. When the interval of the extended surface, $p_e/L$, is less than 0.1, the dehumidification is shown to increase by more than two times compared with that without extended surface.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.540-545
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• 2001

An experimental study was conducted to compare the heat transfer characteristics of an impinging slot jet and three kinds of impinging circular jets. Thermochromic liquid crystal with an image processing system was employed to measure the temperature of impinging wall where constant heat flux condition was applied. The distribution of convective heat transfer coefficients were then evaluated for eight nozzle-to-surface distance settings for each jet cases. The cooling effect was linearly proportional to the number of nozzles for circular jet cases at the same nozzle exit speed. However, the heat transfer under constant volume flow rate was the most at single circular jet. It was concluded that the overall convective heat transfer was better at the circular jets than the slot jet.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.4
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• pp.67-77
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• 1986

The information on the heat transfer characteristics, flow pattern and pressure drop, are very important for the desing of general heat exchanger, refrigerating system, air conditioning system and energy recovery system. In these systems, water or lubricating oil contained in working fluid affects greatly the flow and heat transfer condition and this phenomena must be considered in the practical design. An experiment has been performed for studying the flow and heat transfer characteristics of the forced convective horizontal flow of R-113 under the range of the liquid single phase state to the boiling flow state. Basic experimental results are obtained in the case that water or lubricating oil does not contaminate in the test fluid. Experimental results are as follows; (1) The local heat transfer coefficients in the nucleate boiling region and transition boiling region are almostly ten times as large as that of liquid single phase flow. (2) The measured heat transfer coefficient in the present experimental range is relatively agreed well with the predicted value from the various experimental results for the boiling flow.