• Title/Summary/Keyword: Fishing experiments

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Evaporating heat transfer characteristics of Aluminum-brass tube for seawater cooling system using R-134a (해수냉각시스템용 Aluminium Brass Tube의 R-134a 증발열전달 특성)

  • Kang, In-Ho;Seol, Sung-Hoon;Yoon, Jung-In;Son, Chang-Hyo
    • Journal of Advanced Marine Engineering and Technology
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    • v.41 no.3
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    • pp.197-201
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    • 2017
  • Most fishing vessels use an ice cooling system to manage and store captured fish. However, it is difficult to maintain an adequate temperature and salt concentration as well as operating time limitations in ice cooling systems. The purpose of this study is to investigate the heat transfer characteristics of flooded-type evaporators for a seawater cooling system to maintain proper seawater temperature in a fish tank. Experiments were conducted to investigate the heat transfer characteristics by changing the seawater temperature, flow rate, and saturation temperature of the refrigerant. It was confirmed that the heat transfer coefficient of an aluminum-brass tube was approximately 10% higher than that of a copper-nickel tube at the same heat flux. Furthermore, it was confirmed that applying the aluminum-brass tube to the heat transfer tube of a seawater heat exchanger was effective in terms of heat transfer. A comparison of the overall heat transfer coefficient of a single-tube heat exchanger and the flooded-type multi-tube heat exchanger for an 18-kW cooling system showed that the heat transfer coefficient of the single-tube heat exchanger was 25% higher under the same conditions. These results are considered to be important data for designing a flooded-type multi-tube heat exchanger.

MODEL EXPERIMENT OF STOW NET (안강망어구의 모형실험)

  • KO Kwan Soh;KIM Yong Hae
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.12 no.4
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    • pp.201-207
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    • 1979
  • The stow net now used in the Yellow Sea, are traditional bag net with the opening held by a lighter upper and a weighted lower beams standing against the current. Such bag net anchored at the bottom are known in many countries, particularly in the estuaries of large rivers, but more rarely in sea fisheries, because they are too much affected by the weather, moreover a permanent strong current is necessary. Some scientists intended to improve this fishing gear, using the shearing devices instead of a lighter upper and a weighted lower beams in order to widen mouth of the stow net however they are unsuccessful. One-fortieth scale model net of the stow net was tested in a circular water tank with an effective volume of $5.67m\times1.76m\times1.00m$ of observing the configuration and tension of the net. Experiments were carried out under the various combination including water velocity, spherical floats and elevating floats with the shearing hoods instead of the upper beam. We found those devices offered a very low resistance per net area to current compared with the spherical floats or upper beam, and had a fairly good shearing power at any velocity and direction of the current. The total resistance (R) of the model net to which shearing hoods and floats are attached can be induced by the following formula under the condition of 0.25m/sec to 0.5m/sec, $$R(kg)=3.11V^{1.54}$$ The height (h) of the improved model net (m-B) is higher than traditional model net(m-A) with upper and lower beams, m-A: h(cm)=89.22-2.42(V-15). $V\geqq15,\;cm/sec$ m-B: h(cm)=89.20-0.78V (V:cm/sec) The catch efficiency of improved model net is 1.5 times traditional model net.

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A Study on the Telemetry System for the Inhabitant Environment and Distribution of Fish-II -Current Direction, Velocity, Sea Ambient Noise and Distribution of Fishes- (어류의 서식환경과 분포생태의 원격계측에 관한 연구 - II -유향, 유속 및 환경소음과 어류의 분포생태-)

  • 신형일;안영화;신현옥
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.35 no.2
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    • pp.129-135
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    • 1999
  • The telemetry system for the current speed and direction, the underwater ambient noise and the distribution ecology of fishes was constructed by the author and his collaborator in order to product and manage effectively in shallow sea culture and setnets fisheries, and then the experiments for the telemetry system carried out at set net fishing ground located Nungpobay in Kojedo from October 1996 to June 1997. As this results, the techniques suggested in the telemetry system gave full display its function even though far away 1.5 km from transmitting part, but with the suggested telemetry system could not be ascertained relationship between physical environment and distribution ecology of fishes.

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Resistance to Weathering with Materials for fisheries Facilities 1. Photodegradation Mechanisms of Netting Twines for Fisheries Facilities (수산시설용 재료의 내후성에 관한 연구 1.그물실의 자외선 열화기구)

  • 김태호
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.36 no.1
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    • pp.45-53
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    • 2000
  • To analyze the photodegradation mechanism of materials for fisheries facilities which stand for considerable time immediately under or even partly above the water surface, such as cage collar, cage net, stationary fishing gear, egc. after 900 hours exposure, weathering experiments on 3 kinds of netting twines like dyed polyethylene(PE) and nylon, and non-treated high strength PE(Hi-PE) were carried out by using xenon light source. The results obtained are as follows : It was observed by scanning electron micrograph(SEM) that a good protection by pigments was obtained in PE and nylon specimen, while crack was rapidly progressed at the surface of Hi-PE one owing to etching by UVR. There was a little increase in density resulting from reorientation of polymer chain, chain scission, etc. in Hi-PE specimen. A wide angle X-ray diffraction showed that 3 kinds of specimens had no fundamental changes in polymer crystalline structure considering each 2$\theta$ of diffraction peak. Remaining tenacity of netting twines was in order of PE, nylon, and Hi-PE after having been exposed to the effect of 900 hours. PE and nylon treated with stuffs were shown to be more resilient than non-treated Hi-PE as confirmed by SEM.

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Estimation of demersal fish biomass using hydroacoustic and catch data in the marine ranching area (MRA) of Jeju (제주바다목장해역에서 수중음향과 어획데이터를 활용한 저층 어류의 현존량 추정)

  • Lee, Jae-Bong;Oh, Taeg-Yun;Yeon, In-Ja;Kim, Byung-Yeob;Shin, Hyeon-Ok;Hwang, Bo-Kyu;Lee, Kyung-Hoon;Lee, Yoo-Won
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.48 no.2
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    • pp.128-136
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    • 2012
  • Hybrid surveys using hydroacoustic and fish sampling gears such as trammel net, trap were conducted to investigate total biomass, distribution and dominant fish species of the demersal fishes in the marine ranching area (MRA) of Jeju. Four surveys were carried out in June, August, October and November using 38kHz quantitative echo sounder. Catch data using trammel net and trap were used to calculate biomass and to examine dominant fish species. Fish schools were mainly detected in the waters of 20 meters below and around Chagwido waters. By the result of fishing experiments, fish species living in MRA of Jeju were about 40 species, dominant fish species of a detectable fish such as Family Sparidae and Family Monacanthidae etc. were identified 59.4~68.8% of total biomass. Based on the hydroacoustic data, fish length-weight function and target strength information, mean density of the demersal fish estimated were as follows; 0.88g/$m^2$ on June, 1.12g/$m^2$ on August, 1.35g/$m^2$ on October and 1.18g/$m^2$ on November. An estimated average biomass in MRA of Jeju was founded 20.5 tons in 2007, 20.6 tons in 2008, 23.0 tons in 2009, 25.9 tons in 2010. The results showed that biomass of MRA is getting increased slowly. Therefore the hybrid survey method using hydroacoustic and fish sampling gears is assured an effective biomass survey in the waters of mixed species.

Characteristics of Bottlenose Dolphin(Tursiops truncatus) Whistle (큰돌고래의 휘슬음 특성)

  • 신형일;서두옥;이대재;황두진;배문기;이유원
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.38 no.4
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    • pp.271-277
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    • 2002
  • This paper was described on the characteristics of bottlenose dolphin (Tursiops truncatus) whistle to develop a warning and attracting acoustic system which can be made friends woith environment and minimized to the fishing pollution from Cetaceans. The experiment for the acoustics of bottlenose dolphin whistle was carried out in dolphin performance hall at Seoul Grand Park during 18th~19th April, 2002. The frequency and the spectrum level of whistle a same pool were revealed 6~10KHz and 85㏈ but those revealed two harmonic waves a 6.7KHz and 21.3KHz for the frequency and 110㏈ and 94㏈ for the spectrum level, respectively, when a dolphin isolated from others. The range of frequency change of whistle was 3.86KHz and continuous time was 0.08 sec. The range of frequency change 10.20 KHz higher as 14.06 KHz and continuous time was 0.11sec longer as 0.19sec when a dolphin isolated from others. By the Mann-Whitney test for the result, there was a significant difference for the range of frequency change and continuous time between normal condition and when a dolphin was isolated from others. The pattern of whistle at the dolphin performance hall was five types and the frequency was getting increased slowly in the range of 5~10KHz at normal condition but there were pattern change of 5~20KHz at the isolated condition. Therefore it is thought that these experiments would be valuable for the development of acoustic system.

Flow resistance of bottom pair trawl nets and scale effect in their model experiments (쌍끌이 기선저인망의 유수저항 특성 및 모형 실험시의 축척비 영향)

  • Kim, Dae-Jin
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.51 no.2
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    • pp.203-211
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    • 2015
  • The purpose of this study is to identify the flow resistance of the bottom pair trawl nets. The bottom pair trawl nets being used in fishing vessel (100G/T, 550ps) was selected as a full-scale net, and 1/10, 1/25 and 1/50 of the model nets were made. Converted into the full-scale net by Tauti's modeling rule and Kim's modeling rule, when resistance coefficient k of each net was calculated by substituting into above equation for flow resistance R and wall area of nets S values of each net ${\upsilon}$. Because resistant coefficient k decreases exponentially according as flow velocity ${\upsilon}$ increases to make $k=c{\upsilon}^{-m}$, c and m values of each net were compared. As a result, as the model was smaller, c and m values was smaller in the two rule into standard of 1/10 model value, decrease degree of 1/25 model was almost same in the two rule, decrease degree of 1/50 model was very big in Tauti's modeling rule. Therefore, in the result of experiment, because average of c and m values for similarly 1/10 and 1/25 model were given $c=4.9(kgf{\cdot}s^2/m^4)$ and m=0.45, R (kgf) of bottom pair trawl net could show $R=4.9S{\upsilon}^{1.55}$ using these values. As in the order of cod-end, wing and bag part for 1/25 and 1/50 model net were removed in turn, measured flow resistance of each, converted into the full-scale, total resistance of the net and the resistance of each part net were calculated. The resistance ratio of each part for total net was not same in 1/25 and 1/50 model each other, but average of two nets was perfectly same area ratio of each part as the wing, bag and cod-end part was 43%, 45% and 12%. However, the resistance of each part divided area of the part, calculated the resistance of per unit area, wing and bag part were not big difference each other, while the resistance of cod-end part was very large.

Fluid Drag of a Trawl Net and Otter Board Spread in a Midwater Trawl (중층트롤 어구의 그물저항과 전개판 간격)

  • PARK Hae-Hoon;YOON Gab-Dong
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.34 no.3
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    • pp.238-244
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    • 2001
  • A method of estimating the fluid drag of a fishing gear and otter board spread in a midwater trawl on full scale was described by implementing a three-dimensional semi-analytic treatment of the towing cable (warp) of a trawl system with the field experiments obtained with the SCANMAR system. The shape of hand rope, bridle and float(or ground) rope attached behind otter boards in a horizontal plane was assumed to be of form $y_r=Ax_r^B$. The distance between otter boards (otter board spread) obtained by the three dimensional analysis of a towing cable must be equal to that obtained by the functional equation of the shape of ropes behind otter boards, The angle of attack of ropes which can be obtained from the functional equation enables one to estimate the fluid drag of trawl net (net drag) by subtracting the fluid drag of the hand rope and bridles from the drag component of the tension of hand rope attached just behind the otter boards.

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Assessment on the Mechanical-Chemical Stabilities of Coal Ash Blocks in Sea Water (석탄회 블록의 해양환경에서 역학적-화학적 안정성 평가)

  • Kim, Pil-Geun;Sung, Kyu-Youl;Park, Maeng-Eon
    • Economic and Environmental Geology
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    • v.41 no.4
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    • pp.383-392
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    • 2008
  • This study aims to evaluate the mechanical-chemical stability of used coal ash blocks, for improving fishing grounds. The surface of weathered ash blocks in seawater showed a decrease in the Ca and an increase in the Mg contents, compared to that of fresh blocks. This result reflects the substitution of Ca by Mg in seawater. The compressive strengths of ash blocks submerged into seawater during 12 months ranged from 235.23 to $447.43\;kgf/cm^2$; this is higher than the standard strength of wave-absorbing blocks($180\;kgf/cm^2)$ that are used for harbor construction. In addition, the compressive strength of ash blocks tends to increase with increasing installation time in seawater. The result of leaching experiments on coal ash blocks by Korean Standard Leaching Test(KSLT) method showed that leached concentrations of most metals except Cr(that leached up to 50 ppb, approaching standard concentration) do not exceed the seawater quality standards. A long-term(112 days) heavy metal leaching test to analyze seawater without mixing-dilution also showed that the concentrations of leached heavy metals, except for Cu, under anaerobic conditions do not exceed the seawater quality standards. Accordingly, the use of coal ash blocks in marine environments appears to be safe from chemical and mechanical factors that decrease the efficiency of concrete. Also, leaching concentration of Cu seems to be stable by decrease of leaching concentration due to dilution of seawater.

A Study on Safety and Performance of Rope Cutter for Ship's Propeller (선박추진기 로프절단장치의 안전성 및 효용성에 관한 연구)

  • Lee, Won-Ju;Kim, Jong-Ho;Jang, Se-Hyun;Lee, Kyoung-Woo;Kim, Bo-Young;Lee, Woo-Kun;Rho, Beom-Seok;Kim, Jun-Soo;Choi, Jae-Hyuk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.4
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    • pp.475-481
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    • 2018
  • In this study, the safety and effectiveness of ope cutter, developed to prevent frequent accident propeller windingness at sea. First, we calculated the bolt strength of the three types of rope cutting devices used in the experiment and the torsional stresses on the shafting system theoretical equation and the finite element method. As a result, the bolts used in the rope cutter confirmed from the viewpoint of safety life design and fail safe design. Also, safety satisfactory because of the small effect on the shaft system when locking up. Experiments were carried out to cut ropes and fishing nets from the sea using the ships equipped with three types of rope cutters verified to be safe. As a result, ropes of 20 to 50 mm in thickness were generally cut. It was found that the cutting efficiency of a rope cutter attached to shafting decreased when cutting thick ropes.