• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.338-344
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• 2008

The improvement of energy conservation is mandatory to decrease consumption of fossil fuels and to minimize negative impacts on the environment which originates from large cooling and heating demand. The absorption heat pump technology has a large potential for energy-saving in this respect. Absorption heat pump is a means to upgrade waste heat without the addition of extra thermal energy. The higher performance of absorber is of great importance for absorption heat pump cycle. In this study, in order to improve the performance of absorber, the absorber of tangential feed of a liquid phase with spiral tube has been investigated using methanol-glycerine as a working fluid. The spiral tube and tangential feeding generate the turbulence into the liquid flow while increasing the mass and heat transfer coefficients. The simultaneous heat and mass transfer were found to take place in a liquid turbulent film in the absorber with the spiral tube during the process of gas absorption. By calculating mass and heat transfer coefficients by measurement of the concentration and the temperature of each position in the absorber, the entrance was found to be more effective in enhancing mass and heat transfer.

• Journal of Adhesion and Interface
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• v.4 no.1
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• pp.9-17
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• 2003

The UV hard coating materials are attracting more and more attention to modern industry, in terms of the development of low or non solvent coating materials which will contribute to economizing both materials and energy and to reducing pollution. This study was performed in order to invent UV curable coating materials containing colloidal silica which have actual industrial applications. As results of experiments, the oligomers type and the concentration of colloidal silica acrylate oligomer (SAOC) have an influence on various especially, The properties of UV hardening cooling, such as chemical, abrasion resistance and weatherability, were greatly enhanced, the impact properties of coated polycarbonate substrate were improved compared with the noncoated that. The UV cured films containing 30 wt% SAOC obtained showed the best properties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.319-323
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• 2018

Ferronickel slag is a by-product from the ferronickel smelting process and it is divided into air-cooled ferronickel slag and water granulated ferronickel slag according to cooling system. The purpose of this experimental resesrch is to investigate the mechanical properties and resistance to freezing and thawing of concrete using air-cooled ferronickel slag(ACFNS) fine aggregate. For this purpose, the concrete specimens with water-cement ratio of 50% were made with ACFNS's replacement ratios of 0%, 20%, 30%, 40%, 50%, 70%, and 100% by volume of fine aggregate. It was observed from the test results that the compressive strength and static modulus of elasticity of ACFNS fine aggregate concrete were increased with increasing replacement ratio of ACFNS and the resistance to freezing and thawing of this was similar to reference concrete which had the relative dynamic modulus of elasticity of more than 90% during the freezing and thawing of 300 cycles.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.33-40
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• 2021

Current industrial flow is directed toward reducing the usage of raw materials by reusing parts, which is referred to as a circular economy (CE). Repair is one of the most value-added approaches in CE, which can be efficiently accomplished via additive manufacturing. The repair technology of metallic parts via the directed energy deposition process, which includes the selective removal and redeposition of damaged regions of metallic parts. Residual stress characteristics depend on the shape of the part and the shape of the redeposition region. The objective of this study is to investigate the effects of the radius and corner position of the substrate on the residual stresses for repair by using finite element analysis (FEA). The residual stress distribution of the 45° angle groove at the edge of the circular shape models on the outer and inner radii was analytically investigated. The analysis was accomplished using SYSWELD software by applying a moving heat source with defined material properties and cooling conditions integrated into the FEA model. The results showed a similar pattern of concentrated stress distribution for all models except the 40-mm and 60-mm radii, for which the maximum stress locations were different. The maximum residual stresses are high but lower than the yield strength, suggesting the absence of cracks and fractures due to residual stresses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.721-728
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• 2016

97% of water on earth exists in the form of seawater. Therefore, the use of marine resources is one of the most important research issues at present. The use of seawater is expanding in various fields (seawater desalination, cooling water for nuclear power plants, deep seawater utilization, etc.). Seawater intake systems utilizing sand filters in order to take in clean seawater are being actively employed. For the intake pipe used in this system, assuring equal intake flows through the respective holes is very important to improve the efficiency of the intake and filtering process. In this study, we analyzed the efficiency of the dual structure perforated pipe used in the seawater intake system using 3D numerical simulations and the inflow rate according to the gap of the up holes. In the case of decreasing gaps in the up holes toward the pipe end, the variation of the total inflow rate was small in comparison with the other cases. However, the standard deviation of the inflow rate through the up holes was the lowest in this case. Also, stable flow occurred, which can improve the efficiency of the intake process. In the future, a sensitivity analysis of the various conditions should be performed based on the results of this study, in order to determine the factors influencing the efficiency, which can then be utilized to derive optimal designs suitable for specific environments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.673-680
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• 2017

sump pump is a system that draws in water that is stored in a dam or reservoir. They are used to pump large amounts of water for cooling systems in large power plants, such as thermal and nuclear plants. However, if the flow and sump pump ratio are small, the flow rate increases around the inlet port. This causes a turbulent vortex or swirl flows. The turbulent flow reduces the performance and can cause failure. Various methods have been devised to solve the problem, but a correct solution has not been found for low water level. The most efficient solution is to install an anti-vortex device (AVD) or increase the length of the sump inlet, which makes the flow uniform. This paper presents a computational fluid dynamics (CFD) analysis of the flow characteristics in a sump pump for different sump inlet lengths and AVD types. Modeling was performed in three stages based on the pump intake, sump, and pump. For accurate analysis, the grid was made denser in the intake part, and the grid for the sump pump and AVD were also dense. 1.2-1.5 million grid elements were generated using ANSYS ICEM-CFD 14.5 with a mixture of tetra and prism elements. The analysis was done using the SST turbulence model of ANSYS CFX14.5, a commercial CFD program. The conditions were as follows: H.W.L 6.0 m, L.W.L 3.5, Qmax 4.000 kg/s, Qavg 3.500 kg/s Qmin 2.500 kg/s. The results of analysis by the vertex angle and velocity distribution are as follows. A sump pump with an Ext E-type AVD was accepted at a high water level. However, further studies are needed for a low water level using the Ext E-type AVD as a base.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2596-2603
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• 2013

The precision and endurance of tire mold are very important factors to decide the quality of tire. However, the investigation on the thermal deformation of tire mold has a lot of trouble because the tire mold is produced in airtight permanent casting material. In this study, the thermal deformations such as temperature, displacement and stress distributions inside the AC7A tire mold casting material were analyzed by numerical analysis according to the preheating temperature of permanent casting device. In order to verify the results of numerical analysis, the experiments for temperature measurement of the AC7A casting material were carried out under the same condition with numerical analysis. For the numerical analysis, "COMSOL Multiphysics" was used. The preheating temperatures were set up $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$ and $300^{\circ}C$, respectively. The thermal deformations were calculated in each case. When the preheating temperature is $300^{\circ}C$, displacement and stress are the lowest with 0.25mm and 0.351GPa, but the temperature is the highest with $374.27^{\circ}C$. When the experimental results were compared with the numerical results, there were some temperature differences because of the latent heat by phase change heat transfer. However, the cooling patterns were almost similar except for the latent heat section.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.2919-2924
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• 2011

The automatic drawer is used to absorb the movement shock and adjust its velocity when it opens and closes. The tube in shock-absorber is the cylindrical case which surrounds its parts and is made of acetal. The purpose of this study is to determine the quality stability of the tube in the shock-absorber in injection molding process. The tube which had been manufactured in the process with 4 cavity cooling unit was used. In this study, the analysis and test are carried out to determine its quality stability. Which are the quality analysis with numerical simulation and performance tests of the tube compared with one of foreign make. It is calculated that the injection press is 87.6 MPa and the deflections in X, Y, Z directions are ranged in 0.07~1.00 mm. When the researched tube is compared with the foreign made tube, the maximum bending compressive load is 231 kgf higher, average axial compressive load is 0.05 kgf higher, and the roughness(Ra) on the inner surface is $0.02\;{\mu}m$. lower. In the result, it is known that the quality of researched tube in injection mold process is stable and its performance is superior.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.33-39
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• 2021

As the interest and demand in the recycled yarn field has increased rapidly worldwide, domestic companies are also promoting research and development and business on recycled yarn. The chemical and thermal properties of four types of virgin and recycled PET samples from A and B company, which are the leading domestic companies in the recycled polyester yarn business, were confirmed through infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Virgin and recycled PET from two companies were compared. FT-IR spectroscopy revealed the typical spectra of PET for both companies and a different peak at 872 cm-1. DSC confirmed that the melting point and crystallization temperature of recycled PET were lower than those of virgin PET. These results indicate that small amounts of contaminants are an important parameter affecting the thermal properties of recycled PET. In the DSC results after seven repeats of the heating and cooling processes, all four samples showed that a lower melting point, crystallization temperature, and low heat flow intensity increased with increasing number of cycles. The results of melting and crystallization enthalpy also showed similar patterns.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.803-811
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• 2024

Nuclear accidents such as Fukushima Daiichi have highlighted the potential of passive safety systems to replace or complement active safety systems as part of the overall prevention and/or mitigation strategies. In addition, passive systems are key features of Small Modular Reactors (SMRs), for which they are becoming almost unavoidable and are part of the basic design of many reactors available in today's nuclear market. Nevertheless, their potential to significantly increase the safety of nuclear power plants still needs to be strengthened, in particular the ability of computer codes to determine their performance and reliability in industrial applications and support the safety demonstration. The PASTELS project (September 2020-February 2024), funded by the European Commission "Euratom H2020" programme, is devoted to the study of passive systems relying on natural circulation. The project focuses on two types, namely the SAfety COndenser (SACO) for the evacuation of the core residual power and the Containment Wall Condenser (CWC) for the reduction of heat and pressure in the containment vessel in case of accident. A specific design for each of these systems is being investigated in the project. Firstly, a straight vertical pool type of SACO has been implemented on the Framatome's PKL loop at Erlangen. It represents a tube bundle type heat exchanger that transfers heat from the secondary circuit to the water pool in which it is immersed by condensing the vapour generated in the steam generator. Secondly, the project relies on the CWC installed on the PASI test loop at LUT University in Finland. This facility reproduces the thermal-hydraulic behaviour of a Passive Containment Cooling System (PCCS) mainly composed of a CWC, a heat exchanger in the containment vessel connected to a water tank at atmospheric pressure outside the vessel which represents the ultimate heat sink. Several activities are carried out within the framework of the project. Different tests are conducted on these integral test facilities to produce new and relevant experimental data allowing to better characterize the physical behaviours and the performances of these systems for various thermo-hydraulic conditions. These test programmes are simulated by different codes acting at different scales, mainly system and CFD codes. New "system/CFD" coupling approaches are also considered to evaluate their potential to benefit both from the accuracy of CFD in regions where local 3D effects are dominant and system codes whose computational speed, robustness and general level of physical validation are particularly appreciated in industrial studies. In parallel, the project includes the study of single and two-phase natural circulation loops through a bibliographical study and the simulations of the PERSEO and HERO-2 experimental facilities. After a synthetic presentation of the project and its objectives, this article provides the reader with findings related to the physical analysis of the test results obtained on the PKL and PASI installations as well an overall evaluation of the capability of the different numerical tools to simulate passive systems.