• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.275-282
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• 2024

Lead bismuth eutectic (LBE) is used as coolant for MicroURANUS, a small marine nuclear power plant, and this coolant is transported in the plant by an electromagnetic pump. Given the considerable heat generated by the electromagnetic pump, the cooling of the pump is essential. This study compared air cooling and water-cooling methods and found that the maximum temperatures during air and water cooling were 640 K and 372 K, respectively. These findings were utilized to design an electromagnetic pump with water-cooling. The maximum temperature of the pump was lower than the boiling point of water; thus, the pump did not require a separate pressurization. Consequently, the resistance problem of the coil and the deformation problem of the material caused by generated heat can be solved through water-cooling.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.599-604
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• 2008

An experimental study has been performed to investigate the air-side capacity and pressure drop of the fin-tube heat exchanger for a fan coil unit under a cooling condition. The experimental data of five kinds of slit fin-tube heat exchangers were measured using an air-enthalpy calorimeter and a constant temperature water bath. Cooling capacities at the air and water rating flow rates were larger at the lower inlet water temperature. With increasing the water flow rate, the cooling capacity increased at the constant rate. Under the lower inlet water temperature, since the condensate was generated more on the fin-tube surface, the air-side pressure drop of the heat exchanger was larger.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.1
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• pp.15-23
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• 2016

The effects of austenitizing temperature and cooling rate on precipitation behavior and tensile properties were investigated in an Mn-Mo-Nb-V pressure vessel steel. During austenitizing, it was shown that the austenite coarsening was somewhat suppressed by undissolved NbC. After cooling from austenitizing, the microstructure of all the steels mainly consisted of upper bainite. However, the steel comprised a little lower bainite and martensite in the case of aqua oil quenching from $1000^{\circ}C$, which would be due to increased hardenability by partly dissolved Nb and comparatively large austenite grains. The average size of NbC in austenite at higher temperature was analyzed to be smaller than that at lower temperature because of the more dissolution. It was found that the NbC did not grow much during fast cooling from austenitizing. Meanwhile, the NbC grew much during slow cooling, probably due to wide temperature range of cooling and sufficiently long time for NbC to grow. It was conjectured the V precipitates newly formed and/or grew during cooling from austenitizing and during tempering. On the other hand, the formation of NbC was almost completed before tempering and little more precipitated during tempering. Among the tempered steels, the steel which was fast cooled from $1000^{\circ}C$ showed the highest tensile strength, which seemed to come from the microstructure of fine upper bainite and some low temperature phases as well as the comparatively fine NbC precipitates.

• Wind and Structures
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• v.28 no.5
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• pp.299-313
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• 2019

In order to examine the effects of different wind deflectors on the wind load distribution characteristics of extra-large cooling towers, a comparative study of the distribution characteristics of wind pressures on the surface of three large cooling towers with typical wind deflectors and one tower without wind deflector was conducted using wind tunnel tests. These characteristics include aerodynamic parameters such as mean wind pressures, fluctuating wind pressures, peak factors, correlation coefficients, extreme wind pressures, drag coefficients and vorticity distribution. Then distribution regularities of different wind deflectors on global and local wind pressure of extra-large cooling towers was extracted, and finally the fitting formula of extreme wind pressure of the cooling towers with different wind deflectors was provided. The results showed that the large eddy simulation (LES) method used in this article could be used to accurately simulate wind loads of such extra-large cooling towers. The three typical wind deflectors could effectively reduce the average wind pressure of the negative pressure extreme regions in the central part of the tower, and were also effective in reducing the root of the variance of the fluctuating wind pressure in the upper-middle part of the windward side of the tower, with the curved air deflector showing particularly. All the different wind deflectors effectively reduced the wind pressure extremes of the middle and lower regions of the windward side of the tower and of the negative pressure extremes region, with the best effect occurring in the curved wind deflector. After the wind deflectors were installed the drag coefficient values of each layer of the middle and lower parts of the tower were significantly higher than that without wind deflector, but the effect on the drag coefficients of layers above the throat was weak. The peak factors for the windward side, the side and leeward side of the extra-large cooling towers with different wind deflectors were set as 3.29, 3.41 and 3.50, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.354-355
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• 2010

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.2872-2877
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• 2012

This paper discusses the development of the wearable personal cooling system for reducing thermal stress in hot environment. The personal cooling system is operated with the compact refrigeration system by compressing refrigerant. The compact refrigeration system is applied with the miniaturization and weight reduction for portable and wearable cooling system. The body heat is reduced by heat conduction with evaporator in direct cooling type. The cooling capacity of the wearable personal cooling system is approximately 100W and, the system could maintain the inside temperature of approximately 12-$13^{\circ}C$ lower than the ambient temperature. The weight of the wearable cooling system is about 3kg including vest, case, battery and all parts.

• Journal of Korea Foundry Society
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• v.35 no.2
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• pp.23-28
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• 2015

This work presents the effect of the cooling rate on the precipitation of super duplex stainless steel. Specimens of super duplex stainless steel with a specific composition were cooled at various cooling rates after being melted at $1550^{\circ}C$ in a directional solidification furnace. Ferrite (${\delta}$), Austenite (${\gamma}$), Sigma (${\sigma}$), and Chi (${\chi}$) phases were precipitated when the cooling rate was lower than 0.22 K/s. When the cooling rate was 0.22 K/s or faster, ${\sigma}$ and ${\chi}$ phases were not precipitated.

• Journal of computational fluids engineering
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• v.10 no.3 s.30
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• pp.55-62
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• 2005

Flow and temperature fields of a mid-size vehicle engine room are examined numerically to analyze the enhancement of cooling efficiency of several different design cases in a front body shape. The wall temperatures of a radiator and an engine parte are utilized to predict the effects of engine cooling on the thermal environment and the cooling efficiency in an engine room. The analyzed results are the mass flow rate at the upper and lower inlets, in the radiator, and the condenser. It is shown that the shape of the front end, lay-out of the engine parts, and the presence of the undercover greatly influence the flow and temperature fields, and the enhancement of cooling efficiency in the engine room.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.88-94
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• 1998

The thermal performance of cooling towers is affected mainly by the velocity, temperature and humidity of the entering air, In this paper, the effects of these variables are experimentally investigated for both counter-flow and cross-flow cooling towers. The cooling performance is reduced by up to 50% as the relative humidity of the entering air is increased from 40% to 80%. The higher air velocity and lower coolant flow show better cooling performance. The coolant loss rates in the present experimental conditions are in the range of 0.4 to 1.7%

• Journal of the Korean Solar Energy Society
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• v.29 no.6
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• pp.32-38
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• 2009

The effects of surface radiative properties on the radiant cooling of opaque surfaces under clear sky condition are studied. Two types of surfaces, one gray and the other selective, are compared. For the nighttime cooling, black surface gives the lowest plate temperature and on the other hand the ideal selective surface gives the highest temperature. The reverse is true when there is an insolation. Equivalent radiative heat transfer coefficient of radiant cooling without convection is about $1{\sim}7\;W/m^2-K$ for the range of values studied. The surface with black within the $6{\sim}13\;{\mu}m$ band else zero emissivity could be regarded as a black surface for the nighttime radiant cooling purposes. However, lower band limit of $4\;{\mu}m$ is preferred to $6\;{\mu}m$ for small insolation situations.