• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.6
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• pp.521-537
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• 2012

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2011. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of fluid machinery and fluid flow, thermodynamic cycle, and new and renewable energy. Various topics were presented in the field of fluid machinery and fluid flow. Research issues mainly focused on the rankine cycle in the field of thermodynamic cycle. In the new and renewable energy area, researches were presented on geothermal energy, fuel cell, biogas, reformer, solar water heating system, and metane hydration. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, nanofluids and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer above liquid helium surface in a cryostat, methane hydrate formation, heat and mass transfer in a liquid desiccant dehumidifier, thermoelectric air-cooling system, heat transfer in multiple slot impinging jet, and heat transfer enhancement by protrusion-in-dimples. In the area of pool boiling and condensing heat transfer, researches on pool boiling of water in low-fin and turbo-B surfaces, pool boiling of R245a, convective boiling two-phase flow in trapezoidal microchannels, condensing of FC-72 on pin-finned surfaces, and natural circulation vertical evaporator were actively performed. In the area of nanofluids, thermal characteristics of heat pipes using water-based MWCNT nanofluids and the thermal conductivity and viscosity were measured. In the area of industrial heat exchangers, researches on fin-tube heat exchangers for waste gas heat recovery and Chevron type plate heat exchanger were implemented. (3) Refrigeration systems with alternative refrigerants such as $CO_2$, hydrocarbons, and mixed refrigerants were studied. Heating performance improvement of heat pump systems were tried applying supplementary components such as a refrigerant heater or a solar collector. The effects of frost growth were studied on the operation characteristic of refrigeration systems and the energy performance of various defrost methods were evaluated. The current situation of the domestic cold storage facilities was analyzed and the future demand was predicted. (4) In building mechanical system fields, a variety of studies were conducted to achieve effective consumption of heat and maximize efficiency of heat in buildings. Various researches were performed to maximize performance of mechanical devices and optimize the operation of HVAC systems. (5) In the fields of architectural environment and energy, diverse purposes of studies were conducted such as indoor environment, building energy, and renewable energy. In particular, renewable energy and building energy-related researches have mainly been studied as reflecting the global interests. In addition, various researches have been performed for reducing cooling load in a building using spot exhaust air, natural ventilation and energy efficiency systems.

• Nuclear Engineering and Technology
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• v.28 no.2
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• pp.103-117
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• 1996

A mathematical model of vapor explosion propagation is presented. The model predict two-dimensional, transient flow fields and energies of the four fluid phases of melt drop, fragmented debris, liquid coolant and vapor coolant by solving a set of governing equations with the relevant constitutive relations. These relations include melt fragmentation, coolant-phase-change, and heat and momentum exchange models. To allow thermodynamic non-equilibrium between the coolant liquid and vapor, an equation of state for oater is uniquely formulated. A multiphase code, TRACER, has been developed based on this mathematical formulation. A set of base calculations for tin/water explosions show that the model predicts the explosion propagation speed and peak pressure in a reasonable degree although the quantitative agreement relies strongly on the parameters in the constitutive relations. A set of calculations for sensitivity studies on these parameters have identified the important initial conditions and relations. These are melt fragmentation rate, momentum exchange function, heat transfer function and coolant phase change model as well as local vapor fractions and fuel fractions.

• Wind and Structures
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• v.23 no.1
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• pp.1-18
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• 2016

This work experimentally and numerically analyzes the flow configurations and the dynamic wind loads on panels of rectangular L/h 5:1 cross section mounted on a structural frame of rectangular bars of L/h 0.5:1, corresponding to a radar structure. The fluid dynamic interaction between panels and frame wakes imposes dynamic loads on the panels, with particular frequencies and Strouhal numbers, different from those of isolated elements. The numerical scheme is validated by comparison with mean forces and velocity spectra of a panel wake obtained by wind tunnel tests. The flow configuration is analyzed through images of the numerical simulations. For a large number of panels, as in the radar array, their wakes couple in either phase or counter-phase configurations, changing the resultant forces on each panel. Instantaneous normal and tangential force coefficients are reported; their spectra show two distinct peaks, caused by the interaction of the wakes. Finally, a scaled model of a rectangular structure comprised of panels and frame elements is tested in the boundary layer wind tunnel in order to determine the influence of the velocity variation with height and the three-dimensionality of the bulk flow around the structure. Results show that the unsteady aerodynamic loads, being strongly influenced by the vortex shedding of the supporting elements and by the global 3-D geometry of the array, differ considerably on a panel in this array from loads acting on an isolated panel, not only in magnitude, but also in frequency.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.463-468
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• 2001

This paper presents the methodology for thermal hydraulic analysis of Pressurized Water Reactor (PWR) steam generators. Topics include porous media approach, governing equations, physical models and correlations for solid-to-fluid interaction and heat transfer and numerical solution scheme. Some details about the ATHOS3 code currently used widely for thermal hydraulic analysis of PWR steam generators in the industry are presented. The ATHOS3 code is applied to the thermal hydraulic analysis of steam generator in the Korea YGN 3&4 nuclear power plant and the computed results are presented.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.97-102
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• 2002

The ability to pass between bars is one of the most important performance of self-compacting concrete or high-flowability concrete since it determines the final filling capacity which influences the strength and durability of hardened concrete in structure. Therefore it has been evaluated by many researchers using different kinds of testing apparatuses. The assessments of passing ability, however, differ largely according to the style, the dimension and the criteria in apparatuses, and the value obtained from one apparatus cannot be converted those of the others. There needs a rheological approach to the better understanding of the passing behavior of fresh concrete between reinforcing bars, where the flow velocity of concrete becomes slow and the blockade sometimes occurs due to the interference between aggregates and reinforcing bars. Experimental works were conducted to clarity the effects of the clearance between reinforcing bars, the volume of aggregate and the rheological properties of matrix on the behavior from the rheological point view and showed the rational mix proportioning of concrete.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.241-244
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• 2006

The analysis of propellant feeding sub-system is performed using a commercial code SINDA/FLUINT, the comprehensive finite-difference, one-dimensional, lumped parameter tool. With the code, cryogenic helium supply system, liquid oxygen supply system, helium injection cooling system are evaluated. The code gave satisfactory estimation scheme for propulsion system characterized by cryogenic temperature and high pressure, two phase flow. This paper focuses on presenting calculation scheme of propulsion sub-system using one-dimensional code like SINDA/FLUINT.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1307-1312
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• 2005

Turbulent in-situ mixing process is a new material process technology to get dispersed phase in nanometer size by controlling reaction of liquid/liquid, liquid/solid and liquid/gas, flow and solidification speed simultaneously. In this study mixing, the key technology to this synthesis method will be studied by computational fluid dynamics. For the simulation of mixing of liquid metal, static mixers will be investigated. Two inlets for different liquid metal meet and merge like 'Y' shape tube. The tube has various shapes such as straight and curved. Also, the radius of curve will be varied. The performance of mixer will be evaluated with quantitative analysis with coefficient of variance of mass fraction. Also, detailed plots of intersection will be presented to understand effect of mixer shape on mixing.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1842-1846
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• 2008

This work reports development of novel liquid-level sensors based on the $3{\omega}$ method. The sensors determine the liquid level by measuring the thermal response as in the conventional hot-wire technique. However the sensors employ an AC heating method to enhance the sensitivity, noise resistance and time response. Also, the microfabricated thin-film structure of the sensor provides mass-producibility as well as improved sensor performance owing to the increase in the surface-volume ratio of the sensor. Two different types of the sensor are developed: one for point detection of the fluid phase and the other for monitoring continuous variation of liquid level. Notable is that the performance of the sensor is not considerably affected by the liquid flow.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.351-363
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• 2001

This paper presents an experimental investigation on the heat trensfer characteristic of micro pipe (MHP) array with 38 triangular microgrooves. A heat pipe is an effective heat exchanger operating without external power. The heat pipe transfers heat by means of the latent heat of vaporization and two-phase fluid flow driven by the capillary force. The overall size of the MHP array can be put undermeath a microelectonic die and integrated into the electrronic package of a microelectronin device to dissipate the heat from the die. The MHP array is fabricated by micromachining with a silicon wafer and a glass substrate. The MHP was filled with water and sealed. The experimental results show the temperature decrease of 12.1$^{\circ}C$ at the evaporator section for the input power of 5.9 W and the improvement of 28% in the heat transfer rate.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.5
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• pp.537-551
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• 2017

In this paper, a two-phase flow solver $HiFoam^{(R)}$ has been developed based on the $OpenFOAM^{(R)}$ to predict resistance of a ship in calm water. The VOF method of $OpenFOAM^{(R)}$ was reviewed and a simple flux limiter was introduced to enhance the robustness of the solver. The procedure for predicting ship motion was modified by introducing Quasi-Steady Fluid-Body Interaction (QS-FBI) with least square regression to improve the efficiency. Other minor factors were considered as well in terms of the efficiency and robustness. The HiFoam was applied to KCS and JBC simulations to validate its efficiency and accuracy by comparing the results to experimental data and STAR-CCM+. The $HiFoam^{(R)}$ was also applied to various ships and it showed good agreements to the experimental data.