• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.3
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• pp.309-314
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• 2000

Experimental results for heat transfer characteristics of natural refrigerants R-290, R-600a and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The experimental apparatus is basically a vapour heat pump system, composed of a compressor, a condenser, expansion devices, a evaporator, and some other peripheral devices. The test sections were horizontal double pipe heat exchangers, which were a pair of smoothed tube, having 10.07 mm ID, 12.07 mm OD, and grooved inner fin tube, having 12.70 mm OD, 0.25 mm fin height, and 75 fins. The local evaporating heat transfer coefficients of natural refrigerants were not much affected with the mass velocity than R-22 and it could be interpreted that the local evaporating heat transfer coefficients of R-22 were increased more than those of R-290, R-600a according to the increment of mass velocity. Moreover, the maximum increment of the heat transfer coefficient was found in R-290. The average heat transfer coefficient was obtained the maximum value in R-290 and the minimum value in R-22. It reveals that the natural refrigerant can be used as a substitute for R-22. In the grooved inner fin tube, 70% of the increment of the heat transfer coefficient was obtained compared to the smoothed tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.20-25
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• 2000

An experimental study on the condensation heat transfer coefficients of R-22, R-290 and R-600a inside horizontal tube was performed. Heat transfer measurements were performed for smooth tube with inside diameter of 10.07 mm and outside diameter of 12.07 mm and inner grooved tube having 75 fins whose height is 0.25 mm. This study was performed for condensation temperatures were from 308 K to 323 K, and mass velocity of $51 kg/m^2s - 250kg/m^2s$. The test results showed that the local condensation heat transfer coefficients increased as the mass flux increased, and also the effect of mass flow rate on heat transfer coefficients of R-290 was less than R-22. In addition, heat transfer coefficient of R-22 increased to a larger extent than R-290 and R-600a as the mass flow rate increased. Average condensation heat transfer coefficients of natural refrigerants were superior to that of R-22. The present results had a good agreement with Cavallini-Zecchin's correlation for smooth and inner grooved tubes.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.941-952
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• 2017

Using the Generation of Thermal-Hydraulic Information for Containments (GOTHIC) code, thermal-hydraulic phenomena that occur inside the containment have been investigated, along with the preliminary design of the passive containment cooling system (PCCS) of an innovative pressurized water reactor (PWR). A GOTHIC containment model was constructed with reference to the design data of the Advanced Power Reactor 1400, and report related PCCS. The effects of the design parameters were evaluated for passive containment cooling tank (PCCT) geometry, PCCS heat exchanger (PCCX) location, and surface area. The analyzed results, obtained using the single PCCT, showed that repressurization and reheating phenomena had occurred. To resolve these problems, a coupled PCCT concept was suggested and was found to continually decrease the containment pressure and temperature without repressurization and reheating. If the installation level of the PCCX is higher than that of the PCCT, it may affect the PCCS performance. Additionally, it was confirmed that various means of increasing the external surface area of the PCCX, such as fins, could help improve the energy removal performance of the PCCS. To improve the PCCS design and investigate its performance, further studies are needed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1017-1022
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• 2021

We collected a specimen of Heniochus diphreutes Jordan, 1903 belonging to the family Chaetodontidae on December 26, 2020 in Pohang-si, Gyeongsangbuk-do, using the set net. Although, H. diphreutes is morphologically very similar to Heniochus acuminatus, it can be distinguished from the latter based on the number of dorsal fin spines, mostly 12 in H. diphreutes vs 11 in H. acuminatus, and the percentage of snout length in head length, which is less than 12% in H. diphreutes vs more than 13% in H. acuminatus. Compared to H. acuminatus, H. diphreutes has a shorter snout, two-three rows of teeth, convex ventral profile of the head, more angular anal fins, and a black pattern extending to the longest soft rays on the posterior part of the anal fin. Molecular analyses showed that our specimen perfectly matched H. diphreutes based on mtDNA COI sequences data. We propose a new Korean name for H. diphreutes, "Jjal-beun-ib-du-dong-ga-li-dom".

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.609-615
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• 2021

Three-dimensional numerical study was carried out to evaluate the aerodynamic characteristics of the supersonic grid fins installed on SpaceX Falcon 9. The present three-dimensional flow results were compared to the results by the concept of the unit grid fin previously introduced for more efficient and simpler flow calculations, and the validity of the approach of the unit grid fin were evaluated. The aerodynamic characteristics in supersonic flights Mach 2.8 of SpaceX Falcon 9 with various angle of attacks were also obtained.

• Korean Journal of Ichthyology
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• v.32 no.4
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• pp.251-256
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• 2020

We described the first record of Callogobius shunkan from Korea, based on two specimens (54.9~66.1 mm in standard length) collected from the southern coastal waters of Jejudo Island. These specimens were characterized by prominent papillae ridges on the head, including postnasal and postorbital rows, well-developed pelvic frenum, dark brownish head, scattered whitish flecks on the body, and three blackish spots on the basal portion of dorsal fins. We proposed a new Korean name, "Ju-reum-mang-dug" for the species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.4
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• pp.418-423
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• 2019

We report the first occurrence of Ophichthus erabo (Jordan and Snyder, 1901) collected in the waters around Jeju Island. The morphologic characteristics of this species include rich brown semicircular spots distributed on the head, the back, and the dorsal fins. Ophichthus erabo has a similar body color to Ophichthus polyophthalmus but can be clearly distinguished from the latter by the number of vertebrae (152-155 in O. erabo vs. 147-149 in O. polyophthalmus) and the existence of a white spot at the center of a semicircle (i.e., no white spot in O. erabo vs. a white spot in O. polyophthalmus). We suggest a new Korean name for O. erabo to be "Mul-bang-ul-ba-da-baem-gang-eo".

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.117-123
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• 2018

Automotive headlamps have been continuously developed as one of the most important devices for securing the driver's view, and the LED lamps are getting popular in recent years. However, in case of the LED lamps, because the heat generated by the LED lamps are too high, it shorten the product life and lower the LED efficiency. Therefore, this study was investigated the cooling characteristics of the LED lamp heat sink for automobile by forced convection for LED heat generation control. In order to analyze the cooling characteristics of the heat sink, the temperature distribution results were investigated through the experiment and computational analysis under the increase of the air flow velocity, and the convective heat transfer coefficient was obtained. Also, convective heat transfer coefficient was calculated by the theoretical formula under the same condition and compared with experimental and computational results. From the result of this study, as the air flow velocity around the heat sink fins increased, the convective heat transfer coefficient significantly increased, confirming the improvement in the cooling effect.

• Advances in Computational Design
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• v.6 no.1
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• pp.31-42
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• 2021

This research aims to demonstrate the optimal geometrical design of splayed multiple cross-sectional pin fin heat sinks (SMCSPFHS), which are a type of side-inlet-side-outlet heat sink (SISOHS). The optimiser strength Pareto evolutionary algorithm2 (SPEA2)is employed to explore a set of Pareto optimalsolutions. Objective functions are the fan pumping power and junction temperature. Function evaluations can be accomplished using computational fluid dynamics(CFD) analysis. Design variablesinclude pin cross-sectional areas, the number of fins, fin pitch, thickness of heatsink base, inlet air speed, fin heights, and fin orientations with respect to the base. Design constraints are defined in such a way as to make a heat sink usable and easy to manufacture. The optimum results obtained from SPEA2 are compared with the straight pin fin design results obtained from hybrid population-based incremental learning and differential evolution (PBIL-DE), SPEA2, and an unrestricted population size evolutionary multiobjective optimisation algorithm (UPSEMOA). The results indicate that the splayed pin-fin design using SPEA2 issuperiorto those reported in the literature.

• Journal of fish pathology
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• v.34 no.1
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• pp.9-15
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• 2021

Rock bream (Oplegnathus fasciatus) is a highly valued aquaculture species in Korea. However, the aquaculture industry suffers huge economic losses due to rock bream iridovirus (RBIV) infection in summer. The objective of this study was to determine genetic diversity and relationships of DNAs isolated from two groups of rock bream after RBIV infection using five microsatellite (MS) markers. The first group of fish died early and the second group of fish died later after RBIV infection. In this experiment, 90 fish (5.1±1.0 cm and 4.1±1.3 g) were injected with 50 μl of RBIV (10⁴ TCID⁵⁰/ml) and maintained at 26℃ for 15 days. Genomic DNAs were extracted from fins of 20 fish that died earlier or later after RBIV infection. These DNAs were subjected to genotyping using five MS markers (CA-03, CA3-05, CA3-06, CA-10, and CA3-36). Of these markers, CA3-05 (early death group), CA3-06 (late death group), and CA3-36 (both early and late death groups) showed different alleles distribution rates. In-depth studies are needed to provide valuable information for selecting RBIV-resistant fish. In conclusion, microsatellite marker distribution pattern differences between early- and late- death groups of rock bream after RBIV infection showing different RBIV susceptibilities were determined using MS markers and genotyping. Results of this study suggest that MS markers could be used to facilitate the selection of RBIV resistant rock bream.