• 한국가스학회:학술대회논문집
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• 2005.10a
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• pp.123-127
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• 2005

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.521-528
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• 2008

The micro-porous asymmetric PVDF hollow fiber membranes for gas-liquid contactor were prepared by the dry-jet wet phase inversion process and the characteristics of hollow fiber membranes were evaluated by the gas permeation method and scanning electron microscope. The chemical absorbent for removal of $SO_2$ gas was sodium hydroxide at bench scale hollow fiber membrane contactor. The experiments were performed in a counter-current mode of operation with gas in the shell side and liquid in the fiber lumen of the module to examine the effect of various operating variables such as concentration of absorbent, gas flow rate, L/G ratio and concentration of inlet $SO_2$ gas on the $SO_2$ removal efficiency using PVDF hollow fiber membrane contactor. Membrane mass transfer coefficient($k_m$) was calculated by mathematical modeling. The volumetric overall mass transfer coefficient increased with increasing the concentration of absorbent and L/G ratio. The increase of the absorbent concentration and L/G ratio not only provides more sufficient alkalinity but also decreases liquid phase resistance. The volumetric overall mass transfer coefficient increased with increasing gas flow rate due to decreasing the gas phase resistance.

• Journal of the Korean Institute of Gas
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• v.11 no.3
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• pp.19-25
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• 2007

The heat transfer phenomena in a coil-typed LPG vaporizer with a hot water bath employed an electrical heating system were experimentally analyzed. The heat energy is initially used to sensible heat region to heat LPG and then is done to latent heat region to vaporize LPG and to heat up the vaporized gas. A two-phase flow region could be found from periodic temperature fluctuations, and only sensible heat effect was found after passing through the region. The overall heat capacity was defined as multiplying the overall heat transfer coefficient by the heat transfer area and we found a correlation employing the heating water temperature and LPG flow rate. The results of this work can effectively be applied for the design of field scale LPG vaporizers in the near future because they can predict the features of heat transfer on a kind of coil type LPG vaporizer.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.26-36
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• 1996

The fully developed turbulent momentum and heat transfer induced by the square-ribbed roughness elements on both the inner and outer wall surfaces in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fuid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity positions and friction factors, and etc. shown in Fig.1. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt bumber and Prand시 number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view by investigating turbulent flows and heat transfer in Fig.1.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.2
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• pp.165-172
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• 1998

An experimental study on the heat transfer of the inclined thermosyphon with low integral-fins in which boiling and condensation occurred is performed to investigate its heat transfer performance. Water and CFC-30 have been used as the working fluids. The operating temperature and the inclination angle of thermosyphon have been used as the experimental parameters. The heat flux input and the inclination angle $\theta$ towards the vertical position were varied in steps. The heat transfer rate in the thermosyphon was depended upon the inclination angle. In addition, it is to obtain the overall heat transfer coefficients and the characteristics as a operating temperature for the practical applications.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2082-2087
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• 2008

The heat transfer process from steam to web through the cylinder drum consists of the thermal resistance by condensate thickness. thickness of shell, and the contact resistance between cylinder and web. The most thermal resistance in conventional cylinder drum dryer is generated by condensate, which is increased by the increase on revolution per minute(RPM). Therefore, the increase of RPM for the production enhancement results in the more thermal resistance, and eventually RPM is restricted. In this study, the theoretical analysis on the characteristics of heat transfer in cylinder drum for paper dryer was performed in the stationary state of steam in drum. The overall heat transfer coefficient, steam quantity and heat transfer quantity were predicted by diameter and length of drum, condensate thickness, revolution per minute and steam temperature for experimental apparatus design.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1864-1869
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• 2007

In this study, we compare thermal performance between four different types of cold plates for humanoid robot cooling. Two commercially available cold plates made of copper have different dimensions and internal flow paths: One has $20{\times}20$ $mm^2$ base area with micro-channels and the other has $62.5{\times}62.5$ $mm^2$ base area with 85 round pin-fins. And two different types of cold plates of $20{\times}20$ $mm^2$ base area with 7 mm high are made of PC (polycarbonate), which aims to reduce the weight of cooling system. All cold plates are mounted on a $20{\times}20$ $mm^2$ copper block with two cartridge heaters of 30 $W/cm^2$. The overall heat transfer coefficient and thermal resistances for the liquid-cooled cold plates are obtained. The copper cold plate with micro-channels showed the best performance. Polycarbonate cold plates display fairly good thermal performance with more reduced system weight.

• Journal of Ocean Engineering and Technology
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• v.32 no.2
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• pp.84-94
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• 2018

Subsea pipelines are designed to transport mixtures of oil, gas, and their associated impurities from a wellhead that can be in excess of approximately $100^{\circ}C$, while the external temperature may be approximately $5^{\circ}C$. Heat can be lost from a subsea pipeline containing a high-temperature fluid to the surrounding environment. It is important that the pipeline be designed to ensure that the heat loss is small enough to maintain sufficient flow from the unwanted deposition of hydrate and wax, which occurs at a critical temperature of about $40^{\circ}C$. Therefore, it is essential to estimate the heat loss of a subsea pipeline in various circumstances. In previous studies, overall heat transfer coefficient(OHTC) formulas were considered only for a single soil type. Thus, it is difficult to characterize the OHTC of the actual seabed with multiple soil layers. In this paper, an OHTC formula that considers multi-layered soils is proposed for more precise OHTC estimation.

• Journal of Environmental Science International
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• v.24 no.7
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• pp.947-954
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• 2015

Dielectric barrier discharge plasma is a new technique in water pollutant degradation, which that is characterized by the production of chemically active species such as hydroxyl radicals, ozone, hydrogen peroxide, etc. If dissolving of plasma gas generated in the plasma reaction has increased, it is possible to increase the contaminant removal capacity. In this study, the improvement on the dissolving performance of plasma gas was evaluated by the indirect method measuring the overall oxygen transfer coefficient. Experiments were conducted to examine the effects of nozzle type, distance from water surface, air supply rate and liquid circulation rate. The experimental results showed that the $K_{La}$ value of the 3-prong nozzle is 2.67 times higher than the diffuser. The order of $K_{La}$ value with nozzle type ranked in the following order: 3-prong nozzle (inner diameter, less 1 mm) > circular nozzle (inner diameter, 1.5 mm) > ellipse nozzle (short diameter 1 mm, long diameter 2.5 mm) > circular nozzle (inner diameter, 3 mm). Optimal liquid circulation rate was appeared to be 1.7 L/min, the value of $K_{La}$ was 0.510 1/min. The value of $K_{La}$ with increasing air supply rate was revealed in the form of an exponential such as $K_{La}=0.3581e^{0.2919^*air\;flow\;rate}$.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1556-1565
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• 2017

This paper depicts the design, implementation and analysis of efficient resonant based wireless power transfer (WPT) technique using three magnetic coupled coils. This work is suitable for mid ranged device due to small form factor while minimizing the loading effect. A multi turned loop size resonator is exploited for both the transmitter and receiver for longer distance. In this paper, class-E power amplifier (class-E PA) is introduced with an optimum power tracking mechanism of WPT system to enhance the power capability at mid-range with a flat gain. A robust method of finding optimum distance is derived with an experimental analysis of the designed system. In this method, the load sensitive issue of WPT is resolved by tuning coupling coefficient at considerable distances. Our designed PA with a drain efficiency of 77.8% for a maximum output of 5W is used with adopted tuning technique that improves the overall WPT system performance by 3 dB at various operating points.