• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.8-12
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• 2019

Combined Cycle Unit(CC) generates the primary power from the Gas Turbine(GT) and supplies the remaining heat of the GT to the Steam Turbine(ST) to generate the secondary power from the ST. It plays a major role in terms of energy efficiency and Load Frequency Control(LFC). Incremental Heat Rate(IHR) curves of economic dispatch(ED) of CC is applied differently by GT/ST combination. But It is practically difficult because of performance test by all combinations. This paper suggests a reasonable method for estimating IHR curves for partial combinations(1:1~(N-1):1) using IHR curves when operating with GT alone(1:0) and with all(N:1) combinations of CC.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.91-98
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• 2010

The increasing of power and processing speed and miniaturization of central processor unit (CPU) used in electronics equipment requires better performing thermal management systems. A typical thermal management package consists of thermal interfaces, heat dissipaters, and external cooling systems. There have been a number of experimental techniques and procedures for estimating thermal conductivity of thin, compressible thermal interface material (TIM). The TIM performance is affected by many factors and thus TIM should be evaluated under specified application conditions. In compact packaging of electronic equipment the chip is interfaced with a thin heat spreader. As the package is made thinner, the coupling between heat flow through TIM and that in the heat spreader becomes stronger. Thus, a TIM characterization system for considering the heat spreader effect is proposed and demonstrated in detail in this paper. The TIM test apparatus developed based on ASTM D-5470 standard for thermal interface resistance measurement of high performance TIM, including the precise measurement of changes in in-situ materials thickness. Thermal impedances are measured and compared for different directions of heat dissipation. The measurement of the TIM under the practical conditions can thus be used as the thermal criteria for the TIM selection.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.593-601
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• 2011

An analysis program to simulate the operation of a polymer electrolyte membrane fuel cell (PEMFC) system was set up, and system operation with variations in the working conditions of various components (especially the thermal management system) was simulated. The entire system included a PEMFC stack and balance-of-plant components such as an air-supply unit, a fuel-supply unit, and a heat-management unit (cooling system). Thermodynamic models of all components were made to evaluate the design performance of the entire system, and then off-design models were set up to simulate the operation of the entire system under arbitrary working conditions. A parametric study was carried out to examine the effects of varying the operating conditions (especially the ambient conditions and the operating conditions of the cooling system) on the operation and performance of the entire system.

• Journal of Digital Convergence
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• v.10 no.4
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• pp.37-43
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• 2012

LED TV integration test unit are the equipment for testing LED BLU as LED BLU's operation, error check, AGING work. The previous test unit were inconvenient because it must change test unit in production line according to LCD's kind and size. This paper develops by integration style test unit that can accommodate various LED TV BLU model of 32 ~ 52 inch that is not one LED TV BLU model. We make that output current is various to dimension of 80 ~ 215 mA. We make functions that are LED BLU state check, Diming and heat occurrence mitigation. Also we develop firmware program and that the program can be upgraded and that can support new panel.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.9 no.3
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• pp.11-18
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• 2013

Small and medium-size buildings employ a multi-distributed individual air-conditioning system utilizing package air conditioners instead of centralized cooling systems, which can allow easier building management and maintenance along with a diversification of facility use. Inverter driven system heat pumps have been developed to achieve not only easy distribution control allowing free combination of indoor units with different models and different capacities, but also wide applications to an intelligent air conditioning. In this study, the transient performance of a system heat pump was analysed with the variation of compressor speed and EEV openings. The superheat was selected as a control parameter of the system, because the variation of it was consistent with each indoor unit capacity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.7
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• pp.308-314
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• 2014

A heat pump has been considered as a thermal management unit for electric vehicles, including the heating and cooling of the cabin. However, the heat pump shows performance degradation at low outdoor temperatures or high compressor speeds. In this study, a R-134a heat pump for an electric vehicle was designed to improve system efficiency, by applying vapor injection with an internal heat exchanger. The heating performance characteristics of the vapor injection heat pump were analyzed at various compressor speeds and outdoor temperatures. The vapor injection heat pump showed 13.3% COP improvement over the non-injection heat pump, when the heating capacity was fixed at 5.2 kW. In addition, the heating capacity of the vapor injection system increased by 9.6%, as compared to the non-injection system.

• Journal of computational fluids engineering
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• v.19 no.1
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• pp.47-56
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• 2014

Since a typical plate heat exchanger is made up of a huge number of unitary cells, it may be impossible to predict the aero-thermal performance of the full scale heat exchanger through three-dimensional numerical simulation due to the enormous amount of computing resources and time required. In the present study, a simple flow-network model using the friction factor correlation and a thermal-network model based on the effectiveness-number of transfer units (${\varepsilon}$-NTU) method has been developed. The complicated flow pattern inside the cross-corrugated heat exchanger has been modeled into flow and thermal networks. Using this model, the heat transfer between neighboring streams can be considered, and the pressure drop and the heat transfer rate of full-scale heat exchanger matrix are calculated. In the calculation, the aero-thermal performance of each unitary cell of the heat exchanger matrix was evaluated using correlations of the Fanning friction factor f and the Nusselt number Nu, which were calculated by unitary-cell CFD model.

• Korean Journal of Organic Agriculture
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• v.4 no.1
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• pp.45-58
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• 1995

This paper studied production characteristics of organic farming products and analyzed management income and production cost of organic farming(rice). In order to analyze these points actually, this study was focused on pruduction activities of a producers' organization, Pulmoo Cooperatives in Hong-Dong Myun, Hong-Seong Region, Chung Nam Province. So the following results were obtained : In 1994, output level and an income rate of rice per unit area(10a) which was produced in organic farming method(O.F.M) was higher than those of general farming method(G.F.M) as about 5%, 7.4%. And management income size of the former was 1.8 times as large as that of the latter. But rice production cost of O.F.M was 1.93 times as much as that of G.F.M, particularily in labor cost and farming equipment cost, light and heat expenses, many other material costs. For the progress of organic farming O.F.M and equipmets should be developed much more, for example, the technics of prevetion against damages by blight and harmful insects and improvement of varieties, natural pesticides, agricultual application of microorganisim, construction of compost heat factory, etc. Since these technics and establishments have taken on the public goods, the development of those should be supported by government.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.7
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• pp.354-360
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• 2008

Power-related issues have become important considerations in current generation microprocessor design. One of these issues is that of elevated on-chip temperatures. This has an adverse effect on cooling cost and, if not addressed suitably, on chip reliability. In this paper we investigate the general trade-offs between temporal and spatial hot spot mitigation schemes and thermal time constants, workload variations and microprocessor power distributions. By leveraging spatial and temporal heat slacks, our schemes enable lowering of on-chip unit temperatures by changing the workload in a timely manner with Operating System (OS) and existing hardware support.

• The Journal of Advanced Prosthodontics
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• v.4 no.4
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• pp.248-253
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• 2012

Maxillary obturator prosthesis is the most frequent treatment option for management of partial or total maxillectomy. Heavy weight of the obturators is often a dislocating factor. Hollowing the prosthesis to reduce its weight is the well established fact. The alternate technique to hollow-out the prosthesis has been described in this article which is a variation of previously described processing techniques. A pre-shaped wax-bolus was incorporated inside the flasks during packing of the heat-polymerized acrylic resin to automatically create the hollow space. The processing technique described is a single step flasking procedure to construct a closed-hollow-obturator prosthesis as a single unit. To best understand the technique, this article describes management of a patient who had undergone partial maxillectomy secondary to squamous cell carcinoma rehabilitated with a hollow-obturator prosthesis.