• 설비공학논문집
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• 제29권8호
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• pp.437-445
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• 2017

Because of improvement of living standards and increased use of ice at home, built-in ice makers are of interest. In this study, refrigeration cycle of a unitary ice maker for residential usage was optimized using R-404A. Optimization was achieved through a search for proper refrigerant charge amount. For the present ice maker producing ice for 24 cups, the optimum charge amount was 200 g. In this configuration, the ice making cycle time was 17 minutes 53 seconds, ice production was 1.27 kg/h and COP was 0.310. After initial start-up, condensation and evaporation temperatures gradually decreased with time. As ice builds in the cup, heat transfer performance of the evaporator decreases, that results in decrease of evaporation and condensation temperatures. Replacement of existing slit nozzles with individual circular hole nozzles improved ice production capacity by 10 percent. Through visualization of ice formation in the ice cup, growth rate of the ice in the cup was relatively uniform.

• 대한조선학회논문집
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• 제44권4호
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• pp.389-397
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• 2007

This research describes a framework to compare and analyze the icebreaker(Terry Fox) resistance in pack ice condition between with a refrigerated ice and a synthetic ice. Model tests with a refrigerated ice have been conducted at Institute for Ocean Technology (IOT/NRC) and the tests with a synthetic ice were conducted at Pusan National University towing tank. For the validation of further tests of measurement and accuracy, the open water tests were first carried out with same model ship to compare the test results of both Institutes. Two different size of the wax-type synthetic ice were used and tests were conducted in pack ice of three different concentration ice conditions. The test results show that the difference of resistance between with synthetic and with refrigerated ice becomes larger according to the increase of ship speed. Although the quantity of resistance difference is not so small in high speed range, the present study is predicted to be used as a useful correlation between synthetic and refrigerated ice.

• 한국기계기술학회지
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• 제13권1호
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• pp.23-29
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• 2011

The measurement of ice properties such as thickness, strength are important to know the performance of the ice breaking vessel. The measuring equipment of ice properties and methods are summarized in this paper. The actual measured data are also described. The strength of ice at Svalbard area on April 2010 is much stronger than the Chukchi Sea on August 2010. The mean strength of Svalbard is about 500 kPa and one of Chukchi Sea is 250 kPa. The first sea trial in Arctic sea using Araon was carried out in the Chukchi Sea. The power and speed was also measured to check the ship performance in ice. The speed was measured from GPS(Global Positioning System) and engine power was recorded from DPS(Dynamic Positioning system) of Araon. The design target of Araon in level ice is 3 knots in 1m thickness and 630 kPa flexible strength but mean speed in Chuckchi sea is 3.98 knots when 6.6 MW engine power, 2.4m ice thickness and 250 kPa strength. This results comes from the difference of ice types and the weak flexible strength of ice but it will be a good information to know the performance of Araon in similar ice condition.

• 한국해양공학회지
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• 제25권1호
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• pp.49-55
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• 2011

The EG/AD/S model ice, originally developed by Timco (1986), was selected as the primary model ice material for the newly built MOERI Ice Model Basin in Korea. However, the existence of a sugar component in the EG/AD/S mixture may cause a serious maintenance problem, as described in certain references. This study focuses on the tests of the mechanical properties of the EG/AD/S and the EG/AD model ice. In order to understand the influence of sugar in the original EG/AD/S model ice and to find a possible substitute for sugar, a series of tests with the EG/AD model ice were performed, and the results were compared to those of the EG/AD/S model ice. The relatively large size of the MOERI Ice Model Basin made it difficult to control the initial strength of model ice, so it took a much longer time to achieve the target strength. In order to obtain a lower strength and stiffness for the model ice, the amount of chemical additives may be varied to achieve the desired strength level. This paper is a preliminary study aimed at seeking a possible substitute for the original EG/AD/S model ice for utilization in a large-scale ice tank. To understand the influence of sugar in the original EG/AD/S model ice, the mechanical properties of the EG/AD/S and EG/AD model ice, such as flexural strength, compressive strength, and elastic modulus, were tested in the laboratory condition and compared to each other. The warm-up procedure seems to be an important factor to reduce ice strength in the tests, so it is discussed in detail.

• Journal of Advanced Marine Engineering and Technology
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• 제37권7호
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• pp.718-728
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• 2013

Analysis of scenarios of transportation oil and gas which produced in the Arctic and others cold seas shows that in the near-term there will be a significant increase of tonnage of tankers for oil and gas and number of ships which should be exploited in difficult ice conditions. For the construction of ice-resistant structures (IRS) intended for production of oil and gas and transportation of these products at ice-class vessels, calculating the load from ice to board the ship and on surface of supports of the platforms are the actuality and urgent tasks. These tasks have one basis in both cases: at beginning of the contact occurs fracture of edge of ice, then occurs compressing of rubble shattered of ice, then they extruding from contact area, after this next layer of ice begin to destruct. At calculating the strength of plating and elements construct of vessels, icebreakers and ice-resistant platforms the specific energy of mechanical destruction ice ${\epsilon}_{cr}$ is an important parameter. For the whole period of study of physical and mechanical characteristics of sea ice have been not many experimental studies various researchers to obtain numerical values of this energetic characteristic of the strength of ice by a method called Ball Drop Test. This study shows that the destruction of the ice from dynamic loading in zone of contact occurs in several cycles, and the ice destructed with a minimum numerical values of ${\epsilon}_{cr}$. The author offer this energy characteristic to take as a base value for the calculation of ice load on ships and offshore structures.

• 한국해양공학회지
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• 제32권3호
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• pp.184-191
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• 2018

Recently, as sea ice in the Arctic has been decreasing due to global warming, it has become easier to develop oil and gas resources buried in the Arctic region. As a result, Russia, the United States, and other Arctic coastal states are increasingly interested in the development of oil and gas resources, and the demand for offshore structures to support Arctic sea resources development is expected to significantly increase. Since offshore structures operating in Arctic regions need to secure safety against various drifting ice conditions, the concept of an ice-strengthened design is introduced here, with a priority on calculation of ice load. Although research on the estimation of ice load has been carried out all over the world, most ice-load studies have been limited to estimating the ice load of the icebreaker in a non-oblique state. Meanwhile, in the case of Arctic offshore structures, although it is also necessary to estimate the ice load according to oblique angles, the overall research on this topic is insufficient. In this paper, we suggest algorithms for calculating the ice load of managed ice (pack ice, 100% concentration) in an oblique state, and discuss validity. The effect of oblique angle according to estimated ice load with various oblique angles was also analyzed, along with the impact of ship speed and ice thickness on ice load.

• 한국해양공학회지
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• 제22권3호
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• pp.64-70
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• 2008

A full-scale field experiment is an important part in the design of ships and offshore structures. Full-scale tests in the ice-covered sea, however, are usually very expensive and difficult tasks. Model tests in a refrigerated ice tank may substitute this difficulty of full-scale field tests. One of the major tasks to perform proper model tests in an ice towing tank is to select a realistic material for model ice which shows correct similitude with natural sea ice. This study focuses on the testing material properties and the selection of model ice material which will be used in an ice model basin. The first Korean ice model basin will be constructed at the Maritime & Ocean Engineering Research Institute (MOERI) in 2009. With an application to the MOERI ice model basin, in this study the material properties of EG/AD/S model ice of IOT (Institute for Ocean Technology) Canada, were tested. Through comprehensive bending tests, the elastic modulus and the flexural strength of EG/AD/S model ice were evaluated and the results were compared with published test results from Canada. Instead of using an ice model basin, a cold room facility was used for making a model ice specimen. Since the cold room adopts a different freezing procedure to make model ice, the strength of the model ice specimen differs from the published test results. The reason for this difference is discussed and the future development for a making model ice is recommended.

• 한국해양공학회지
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• 제7권2호
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• pp.162-172
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• 1993

In the present paper, the overall state of the arts of ice mechanics which is the most typical research topic of the artic engineering field was studied. And also, ice loads genrated by ice-structure interaction were estimated using numerical approach. The effects of viscous property of ice sheets to the ice load were investigated. The time dependent deformation behaviors of ice was modeled by visco-plastic problem using the finite element formalism. Constitutive model representing the material properties of ice was idealized by comblned rheological model with Maxwell and Voigt models. Numerical calculations for the bending and crushing behavior of ice sheet which are the most typical interaction modes between ice sheets and structures were carried out. The time dependent viscous behaviors of ice sheets interaction forces acting on structures were analyzed and the results were studied in detail.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권4호
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• pp.708-719
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• 2015

The two most important tasks of icebreakers are first to secure a sailing route by breaking the thick sea ice and second to sail efficiently herself for purposes of exploration and transportation in the polar seas. The resistance of icebreakers is a priority factor at the preliminary design stage; not only must their sailing efficiency be satisfied, but the design of the propulsion system will be directly affected. Therefore, the performance of icebreakers must be accurately calculated and evaluated through the use of model tests in an ice tank before construction starts. In this paper, a new procedure is developed, based on model tests, to estimate a ship's ice breaking resistance during continuous ice-breaking in ice. Some of the factors associated with crushing failures are systematically considered in order to correctly estimate her ice-breaking resistance. This study is intended to contribute to the improvement of the techniques for ice resistance prediction with ice breaking ships.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.957-966
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• 2020

This paper presents the virtual mass method to implement the prediction of total resistance for ice-going ship in floe ice region based on the combined method of CFD and DEM. Two ways of floe ice distribution are adopted for the analysis and comparison. The synthetic ice model test has been conducted to determine the optimal virtual mass coefficients for the two different floe ice distributions. Moreover, the further verification and prediction are developed in different ice conditions. The results show that, the fixed and random distributions in numerical method can simulate the interaction of ship and ice vividly, the trend of total resistance varying with the speed and ice concentration obtained by the numerical simulation is consistent with the model test. The random distribution of floe ice has higher similarity and better accuracy than fixed distribution.