• Journal of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.135-142
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• 2015

The Anti-Rolling Tank(ART) has an advantage over the other roll stabilizing devices, when ship is staying and working at one site of sea. An important design point of ART is the tank tuning, that is, matching the tank natural period to the ship's roll natural period. Since the load condition and consequently the roll natural period of ship is to be changed widely, the natural period of ART also has to be changed widely. In case of the existing U-tube type ART with a single layer duct, the tank natural period can be changed in a relatively narrow range. This paper suggests a new U-tube type ART system using a double layer duct to enable wide change of ART natural period. Through the roll experiments performed in regular beam waves for a box-type model ship, it is shown that the double layer duct ART has about two times wider period range and a better reducing effect of roll magnitude than the single layer duct ART.

• Journal of Ship and Ocean Technology
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• v.7 no.1
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• pp.19-28
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• 2003

The systematic results of anti-rolling tanks tests obtained by bench tester and roll test in towing tank have been examined. The effects on the oscillating period of fluid transfer through the duct of U-tube tank due to damper plates and the effects on roll damping moment of the tank due to swash plates are alto evaluated from the results. A simple control algorithm for a forced fluid transfer in U-tube tanks if devised to active operation of the tank by air blower. The active performances of the tank are confirmed very effective through the tank tests carried out in the irregular waves.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1244-1251
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• 2022

Marine accidents due to a loss of stability, have been gradually increasing over the last decade. Measures must be taken on the roll reduction of a ship. Amongst the measures, building an anti-roll tank in a ship is recognized as the most simple and effective way to reduce the roll motion. Therefore, this study aims to develop a computational model for a U-tube type anti-roll tank and to validate it by experiment. In particular, to validate the developed computational model, the height of the free surface in the tank was measured in the experiment. To develop a computational model, the mesh dependency test was carried out. Further, the effects of a turbulence model, time step size, and the number of iterations on the numerical solution were analyzed. In summary, a U-tube type anti-roll tank simulation had to be performed accurately with conditions of a realizable k-𝜖 turbulence model, 10^-2s time step size, and 15 iterations. In validation, the two cases of measured data from the experiment were compared with the numerical results. In the present study, STAR-CCM+ (ver. 17.02), a RANS-based commercial solver was used.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.30-35
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• 2004

Several roll motion reduction devices are reviewed and suggested for the application in FPSO. The firstly suggested solution is the shape of the bilge. The next is a bilge keel. The last suggestion is the ART (anti-rolling tank). Typical U-tube type ART is designed for a FPSO and examined extensively by model experiment. The model section was made of transparent acryl. Free decay test, forced oscillation test and wave test were carried out at a two-dimensional wave flume. U-tube type ART is effective only when the natural periods of ART and ship are same. Therefore, the divided U-tube type ART with split plate is suggested for the reduction of the roll motion of a FPSO over the wide range of the roll period.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.4
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• pp.206-216
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• 2013

The present study considers the prediction of wind-induced heel of cruise ship and its stabilization. Wind load in ocean exerts on the surface of superstructure of cruise ship, which causes the heel moment on the ship. The calculation of wind load starts from choosing wind speed profile, so that the logarithmic wind profile model is applied in this study. Heel moment by wind load is calculated by adopting approximate formulation and applied to the ship motion analysis in time domain. Motion stabilizers, such as stabilizing fin and U-tube tank, are considered to reduce the heel effect as well as excessive roll motion. From this study, it is expected that the present method can be applied to the prediction and stabilization of the heel motion of cruise ships.

• Bulletin of the Society of Naval Architects of Korea
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• v.8 no.2
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• pp.35-44
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• 1971

In terms of this paper, concerning primarily with the U-tube tank stabilizer, the authors' aim is to clarify and consolidate the theory as it has been developed thus far, and to provide with the certain additions which will make it more complete, more accurate, and more practical. And then we can know that the effect of the vertical tank position from the C.G., $a_{st}=1-w^2/{w^2}_{st}$, is very important, on account for the fact that the position factor, $a_{st}$, increase when the anti-rolling tank attaches to higher position vertically, but $a_{st}$ does not increase in proportion to the distance of the tank position. Measuring many characteristic coefficients by experiment, in the equation of the ship-tank system motion, such as the inertia coefficient, the damping coefficient, the natural frequency and so on, they can also give a guess that the higher position will accompany the non-linear motion of the tank water, but the non-linear effect will decrease the tank ability. In this study, they deal with not only the optimum damping coefficient of tank, which has very simply been expressed by the strength ratio, $\lambda$, but also the effect of the tank top, which has experimentally been treated when the water has hit the tank top. As this result, we can immediately find that the ability of the anti-rolling tank decrease at w/ws=0.9 generally low frequency.

• Journal of the Korean Solar Energy Society
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• v.28 no.4
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• pp.43-49
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• 2008

The purpose of this study is to present the simulation results and an overview of the performance assessment of a solar heating & cooling system by means of the $200m^2$ evacuated tube solar collector. The simulation was carried out using the thermal simulation code TRNSYS with new model of a single-effect LiBr/$H_{2}O$ absorption chiller developed by this study. The calculation was performed for yearly long-term thermal performance and for two design factors: the solar hot water storage tank and the cold water storage tank. As a result, it was anticipated that the yearly mean system efficiency is 46.7% and the solar fraction for the heating, cooling and hot water supply are about 84.4 %, 41.7% and 72.4%, respectively.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.663-668
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• 2008

This study was carried out solar heating system design for district heating and it's the performance analysis by experiment. This experimental system was installed in Bundang district heating area in the end of 2006. The flat plate and vacuum tube solar collector are combined in one system. So district heating water is heated first by flat plate solar collector and than by vacuum tube solar collector. This solar heating system has not a solar buffer tank and is operating with variable flow rate to obtain a setting temperature of $90{\sim}95^{\circ}C$. As a result, the daily solar thermal collection efficiency is about 30 to 40% for the plate type and 50 to 55% for the vacuum tube solar collector. It varied especially depend on the weather condition like as solar radiation and ambient temperature. This variable flow rate system can be also reduced much pumping power more than 50%.

• Environmental Engineering Research
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• v.21 no.3
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• pp.233-240
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• 2016

The research aims to study the different flexible rubber tube diffusers used in urban wastewater treatment processes and aquaculture systems. The experiment was conducted in small-scale aeration tank with different physical properties of the tubes that were used as aerators. The volumetric mass transfer coefficient ($k_La$), oxygen transfer efficiency (OTE) and aeration efficiency (AE) were measured and determined to compare the diffusers. Moreover, the bubble hydrodynamic parameters were analyzed in terms of bubble diameter ($d_B$) and rising velocity ($U_B$) by a high speed camera (2,000 frames/s). Then the interfacial area (a) and liquid-side mass transfer coefficient ($k_L$) can be calculated. The physical properties (tube wall thickness, tensile strength, orifice size, hardness and elongation) have been proven to be the key factor that controls the performance (kLa and OTE). The effects of hardness and elongation on bubble formation, orifice size and a-area were clearly proved. It is not necessary to generate too much fine bubbles to increase the a-area: this relates to high power consumption and the decrease of the kL. Finally, the wall thickness, elongation and hardness associated of the flexible tube diffuser (tube No. 12) were concluded, to be the suitable properties for practically producing, in this research.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.167-173
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• 2007

This study analyzed by simulation using TRNSYS as well as by experiment on the solar district heating system installed for the first time for the district heating system in Bundang. Simulation analysis using TRNSYS focused on the thermal behavior and long-term thermal efficiency of solar system. Experiment carried out for the reliability of simulation system. This solar system where the circuits of two different collectors, flat plate and vacuum tube collector, are connected in series by a collector heat exchanger, and the collection characteristics of each circuit varies. Therefore, these differences must be considered for the system's control. This system uses variable flow rate control in order to obtain always setting temperature of hot water by solar system. Specifically, this is a system that heats returning district heating water (DHW) at approximately $60^{\circ}C$ using a solar collector without a storage tank, up to the setting temperature of approximately $85{\sim}95^{\circ}C$ To realize this, a flat plate collector and a vacuum tube collector are used as separate collector loops. The first heating is performed by a flat plate collector loop and the second by a vacuum tube collector loop. In a gross collector area basis, the mean system efficiency, for 4 years, of a flat plate collector is 33.4% and a vacuum tube collector is 41.2%. The yearly total collection energy is 2,342GJ and really collection energy per unit area ($m^2$) is 1.92GJ and 2.37GJ respectively for the flat plate vacuum tube collector. This result is very important on the share of each collector area in this type of solar district heating system.