• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.171-179
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• 2013

The thermodynamic characteristics of a combined cycle applied with a topping cycle such as a trilateral cycle at relatively high temperatures and a bottoming cycle such as an organic Rankine cycle at relatively low temperatures have been theoretically investigated. This is an electric generation system used to recover the waste heat of the exhaust gas from a diesel engine used for the propulsion of a large ship. As a result, when the boundary temperature between the topping and the bottoming cycles increased, the system efficiencies of energy and exergy were simultaneously maximized because the total exergy destruction rate (${\sum}\dot{E}_d$) and exergy loss ($\dot{E}_{out2}$) decreased, respectively. In the case of a marine diesel engine, the waste heat recovery electric generation system can be utilized for additional propulsion power, and the propulsion efficiency was found to be improved by an average of 9.17 % according to the engine load variation, as compared to the case with only the base engine. In this case, the specific fuel consumption and specific $CO_2$ emission of the diesel engine were reduced by an average of 8.4% and 8.37%, respectively.

• Journal of the Korean Solar Energy Society
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• v.38 no.2
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• pp.33-43
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• 2018

PV/Thermal module is the combined system, which consist of a photovoltaic module and solar thermal collector that can obtain electrical power and thermal energy simultaneously. Thus the power generation can be increase by decreasing the temperature of photovoltaic module and thermal energy retrieved from module also can be used for heating system. In this study, Heat transfer performance of air type PV/Thermal module was confirmed with various bottom obstacles that can be installed easily to real photovoltaic module by CFD (computational fluid dynamics) analysis. Eight type obstacles were investigated according to the shape and arrangement. As a result, nusselt number represent heat transfer performance was increased about 86% compare with the basic type PV/Tthermal module that has no obstacle and triangle type obstacle had higher value than other types. But pressure drop was also increased with increment of heat transfer enhancement. Thus the performance factor considering both heat transfer and pressure drop was confirmed and V-fin type obstacle arranged in a row for Reynolds number below 9,600 and protrusion type obstacle arranged in zigzag for Reynolds number above 14,400 were shown higher performance factor than other types. From these results, V-fin type obstacle arranged in row and protrusion type obstacle arranged in zigzag were considered as a proper type for applying to real PV/thermal module according to operating condition. But the heat transfer performance can be changed by the geometric conditions of obstacle such as height, width, length and arrangement. Thus, it could also confirmed that the optimal condition and arrangement of this obstacle need to be found in further study.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.1-10
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• 2024

In this study, we constructed a process simulation model for an agricultural by-products based Solid Oxide Fuel Cell (SOFC) combined heat and power generation system as part of the introduction of technology for energy self-sufficiency in the agricultural sector. The aim was to reduce the burden of increasing fuel and electricity consumption due to rapid fluctuations in international oil prices and the expansion of smart farming in domestic farms, while contributing to the national greenhouse gas reduction goals. Based on the experimental results of 0.3 ton/day torrefied agricultural by-product gasification experiment, a model for an agricultural by-product-based SOFC cogeneration system was constructed, and optimization of the heat exchange network was conducted for SOFC capacities ranging from 4 to 20 kW. The results indicated that an 8 kW agricultural by-product-based SOFC cogeneration system was optimal under the current system conditions. It is anticipated that these research findings can serve as foundational data for future commercial facility design.

• Journal of the Korean Solar Energy Society
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• v.35 no.4
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• pp.43-55
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• 2015

This paper presents the thermal hydraulic performance of a three dimensional rib-roughened solar air heater (SAH) duct with the one principal wall subjected to uniform heat flux. The SAH duct has aspect ratio of 12.0 and the Reynolds number ranges from 2000 to 12000. The roughness has relative rib height of 0.045, ratio of dimple depth to print diameter of 0.5 and rib pitch ratio of 8.0. The flow attack angle is varied from $35^{\circ}$ to $70^{\circ}$. Various turbulent flow models are used for the heat transfer and fluid flow analysis and their results are compared with the experimental results for smooth surfaces. The computational fluid dynamics (CFD) results based on the renormalization k-epsilon model are in better outcomes compared with the experimental data. This model is used to calculate heat transfer and fluid flow in SAH duct with the compound roughness of V-shaped ribs and dimples. The overall thermal performance based on equal pumping power is found to be the highest (2.18) for flow attack angle of $55^{\circ}$. The thermo-hydraulic performance for V-pattern shaped ribs combined with dimple ribs is higher than that for dimple rib shape and V-pattern rib shape air duct.

• Journal of environmental and Sanitary engineering
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• v.23 no.1
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• pp.1-15
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• 2008

Yanbian Korean Autonomous Prefecture(YKAP) possesses the potential to become the first testing ground for the North-East Asian Energy Cooperation in renewable energy sector. We found that production of biodiesel from rapeseed and CHP (Combined Heat and Power Plant) project utilizing abundant forest resources are the two main bioenergy development projects which may have further development potential considering the resource endowments and the focus of Chinese governments' current rural development policy. Provision of stable and transparent investment environments and the development of a close cooperation mechanism between Korea and China government are the prerequisite conditions for investments in the sector. Other international institutional agreements, such as CDM, shall be fully utilized for biomass CHP projects.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1007-1012
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• 2008

Demand for the highly efficient and high performance urban energy supply system having been continuously increased according to the rise of quality of life and continuously increased energy cost all over the world. The district heating and cooling system is very effective way for energy saving, cost reduction, and demand side management of energy. There are several district cooling supply technologies such as chilled water direct transportation, installation of absorption type chiller in the user side, and desiccant cooling. This study investigates the advantage and technical problems of each district cooling technology. Also, it is necessary political and financial support system for the extension of district cooling system.

• Journal of KSNVE
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• v.9 no.6
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• pp.1116-1122
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• 1999

HRSG, which is one of main components of the combined cycle power plant,is composed of an inlet duct, a main body and casing, an outlet duct and a stack. It is important to design HRSG wihtin the allowable noise limit. For this purpose, it is necessary to analyze and predict the noise reduction and radiation at HRSG. In this paper, the technology for the noise prediction at each part of HRSG has been based on the empirical and field data, and also the HRSG noise prediction program has been developed. In order to verify the developed technology and program a field test is conducted. The results of noise prediction show good agreement with the measured.

• Tribology and Lubricants
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• v.19 no.6
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• pp.335-341
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• 2003

Recently, the automotive industry is being developed rapidly. On this, a demand of high quality performance­test­machine is increased too. But it is progressive technology that must be combined hydraulic, mechanic and electronic technologies. To construct this system, the design of oil hydraulic circuit, interface skill between sensor and personal computer, data acquisition & display system and integrated control are very important skill. Moreover, reliable data is obtained with vacuum system and complex heat exchange system. Therefore, in this study, we designed a performance­test­machine by using above key technologies and we also made a integrated PC control system using personal computer which is more progressive and flexible method than PLC control.

• The KSFM Journal of Fluid Machinery
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• v.13 no.6
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• pp.57-62
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• 2010

MW-class gas turbines are suitable for distributed generation systems such as community energy systems(CES). Recently, biogas is acknowledged as an alternative energy source, and its use in gas turbines is expected to increase. Steam injection is an effective way to improve performance of gas turbines. This study intended to examine the influence of injecting steam and using biogas as the fuel on the operation and performance a gas turbine combined heat and power (CHP) system. A commercial gas turbine of 6 MW class was used for this study. The primary concern of this study is a comparative analysis of system performance in a wide biogas composition range. In addition, the effect of steam temperature and injected steam rate on gas turbine and CHP performance was investigated.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.551-558
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• 2005

The setting and hardening of concrete is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. Especially at early ages, this nonlinear distribution has a large influence on the crack evolution. As a result, in order to predict the exact temperature history in concrete structures it is required to examine thermal properties of concrete. In this study, the convection heat transfer coefficient which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind, curing condition and ambient temperature. At initial stage, the convection heat transfer coefficient is overestimated by the evaporation quantity. So it is essential to modify the thermal equilibrium considered with the boiling effect. From experimental results, the convection heat transfer coefficient was calculated using equations of thermal equilibrium. Finally, the prediction model for equivalent convection heat transfer coefficient including effects of velocity of wind, curing condition, ambient temperature and boiling effects was theoretically proposed. The convection heat transfer coefficient in the proposed model increases with velocity of wind, and its dependance on wind velocity is varied with curing condition. This tendency is due to a combined heat transfer system of conduction through form and convection to air. From comparison with experimental results, the convection heat transfer coefficient by this model was well agreed with those by experimental results.