• International Journal of Air-Conditioning and Refrigeration
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• 제17권2호
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• pp.61-67
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• 2009

In the present study, an experiment was conducted to investigate the heat and mass transfer performance of heat exchangers used in the condensing gas boiler. Two types of spiral circular fin-tube heat exchangers and a plain tube were tested in the flue gas of propane and dry air. Heat and mass transfer coefficients were measured and compared with the previous correlations. The experimental data for the sensible heat transfer of the plain tube reasonably agreed with the previous correlations for dry air and flue gas. However, the mass transfer coefficient of the plain tube was greater than the previous correlations. The pH, $NO_x$, and $SO_x$ data of condensate were provided.

• 한국수산과학회지
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• 제55권3호
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• pp.338-344
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• 2022

This study evaluated the external form of Rhodeus notatus TSV (transparent-scaled variant) type identified in Korea for the first time and compared it with that of the normal type. The TSV units newly found on Rhodeus notatus are iii10 of dorsal fin and anal fin iii10, which are similar to that in the normal type, considering the observing coefficient of each part's fins. The external form is, transparent enough to see the red gill filament in the operculum, the spiral digestive organ is observed opaquely, and numerous melanophores are stained at the upper part of abdomen. The coloration and scales are different between TSV type and normal type; however, there is no difference in the external form and meristic character.

• 수산해양교육연구
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• 제5권2호
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• pp.119-127
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• 1993

This work studies for heat transfer and pressure drop performance of integral inner and outer fin tubes, designed to enhance the heat transfer performance of smooth tubes for in recipro and turbo refrigerator or high performance compact heat exchangers. Eight different inner spiral fin copper tubes with integral fin at outside surfaces were employed to improve boiling heat transfer coeffcient. For comparison, tests were made using a plain tube having the inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. Pool boiling heat transfer is investigated experimentally and theoretically on single tube arrangement. The refrigerant evaporates at a saturation state of 1 bar on the outside tube surface heated by hot water. The refrigerant R11 ($CFCl_3$) was used at a pressure of $P_s=1bar$ as a convenient test fluid with a boiling temperature of $T_s=23.6^{\circ}C$. The observed heat transfer enhancement of boiling for finned tubes significantly exceeded that to be expected on grounds of increased area. The maximum Vapor - side enhancement(i.e., vapor - side heat transfer coefficient of finned tube/vapor - side coefficient for plain tube) was found to be around 4 at 1299fpm - 30grooves tube.

• Journal of Advanced Marine Engineering and Technology
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• 제29권6호
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• pp.685-691
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• 2005

In this study, high performance waste heat recovery heat exchanger was developed using the bayonet tube with spiral serrated fins. Especially, heat exchanger of the bayonet tube type was operated well because of double water passes mechanism and characteristics. A cooling water Passes down inner tubes to thimble-form tubes, then flows back up as it boils. The heat exchanger of bayonet tube type was composed of steel tube with 7channels$(I.D_1\;14mm.\;I.D_2\;31.6mm)$ and spiral serrated fins. The performance tests were conducted under the following conditions A cooling water flow rate was 273kg/h and engine l·pm was varied from 750rpm to 3500 rpm. From the experimental result. waste heat recovery was 9.21kW when engine rpm was 3500. and pressure drop was $15\~260mmHg/m^3$ The effectiveness of heat exchanger was about /$0.7\~0.9$. The performance of heat exchanger was evaluated by using the $\varepsilon-NTU$ method. In the study the NTU of the heat exchanger was $1.57\~2.33$.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권4호
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• pp.163-168
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• 2007

The feature of six existing condensation heat transfer correlations for microfin tubes were evaluated with the consideration of vapor quality, mass flux, geometries, and various refrigerants. The Kosky and Staub [15] and the Jaster and Kosky [16] correlations for smooth tube were used for the evaluation of the heat transfer enhancement factor (EF). For the prediction of zeotropic mixtures, most correlations show discrepancy with previous measurements. The Yu and Koyama [4] and the Shikazono et al. [8] correlations do not consider spiral angle effect. The Han and Lee [10] correlation shows fin height growth deteriorates heat transfer. Experimental verification to develop reliable condensation heat transfer correlation for microfin tubes is still needed with the consideration of geometrical effects and working conditions.

• 한국양식학회지
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• 제19권3호
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• pp.197-204
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• 2006

넙치 치어 3 cm와 5 cm 그룹을 이용하여 Philasterides dicentrarchi에 대한 병원성과 감염경로를 조사하였다. 소형수조에서 넙치치어에 스쿠티카충을 인위감염시킨 결과 3 cm 그룹인 경우 접종 4일 후에 40%가 감염되었으며, 24일 후에는 감염률이 90.1%로 대부분의 실험어가 감염되었다. 5 cm 그룹은 3 cm그룹에 비해서 초기 감염률이 현저히 낮았다. 접종 8일 후에 최초로 20%의 감염률을 보였으며 16일 후에도 42%로 완만한 속도로 감염률이 증가하였다. 그러나 그 이후에는 감염률이 급격히 증가하여 24일 후에는 81%에 달했다. 반면에 스쿠티카충을 접종시키지 않은 대조구에서는 스쿠티카충이 감염되지 않았다. 인위감염시킨 스쿠티카충의 어체내 침투는 몇 가지 경로로 이루어졌는데, 지느러미 연조막에 감염된 후 지느러미 조직과 근육에 침투하는 경로, 주둥이 부위의 부드러운 표피를 통하여 감염 된 후 두부 골격과 근육 결을 따라 안구와 뇌로 침투하는 경로, 꼬리지느러미를 통해서 미병부에 침투한 후 척수에 도달하고, 척수를 따라 뇌에 침투하는 경로 등이었다. 이외에도 복강에 침투하는 경우도 있었는데, 항문주위에 다량으로 증식하며 조직을 괴사시킨 후 복강으로 침투하였다. 치명적인 피해를 입히는 뇌 침투는 3cm그룹은 충 접종 후 14일 만에, 5cm그룹은 20일 만에 각각 확인되어 어체가 작을수록 빨리 이루어졌다.

• 한국어병학회지
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• 제17권1호
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• pp.21-28
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• 2004

양식 미꾸라지 (Misgurnus mizolepis)가 수중으로 잠입하지 못하고 양어지의 물표면에 배를 위로 한 채 힘없이 회전 유영을 하는 질병이 발생하였다. 병어는 복부가 팽만되어 있었으며, 해부하여 보면 소화관에 커다란 공기방울의 축적, 장염이 현저하였다. 병어를 혈액학적으로 조사한 결과 적혈구수, Ht치 및 Hb 농도는 건강어와 차이가 없었다. 병리조직학적으로는 아가미의 호흡상피의 증생과 새변의 유착, 소화관 상피세포의 출혈, 괴사 및 박리가 관찰되었다. 뒷지느러미와 항문사이를 실로 결박하여 항문으로부터 공기의 배출을 억제한 재현 실험에서 발병어와 같은 증상이 재현되었다. 따라서 이 병은 빠른 성장을 목적으로 고단백질 사료를 투여함으로서 장호흡을 위하여 마신 공기가 소화관내에 축적되고, 축적된 공기의 부력 때문에 물속으로 하강하지 못하게 되고, 또 소화관을 압박하여 소화관에 순환장애를 일으킨 결과 폐사한 것으로 추정된다.