• International Journal of Fluid Machinery and Systems
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• 제7권3호
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• pp.86-93
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• 2014

This paper describes performance enhancement of a regenerative blower used for a 20 kW fuel cell system. Two design variables, bending angle of an impeller and blade thickness of an impeller tip, which are used to define an impeller shape, are introduced to enhance the blower performance. Internal flow of the regenerative blower has been analyzed with three-dimensional Navier-Stokes equations to obtain the blower performance. General analysis code, CFX, is introduced in the present work. SST turbulence model is employed to estimate the eddy viscosity. Throughout the numerical analysis, it is found that the thickness of impeller tip is effective to increase the blower efficiency in the present blower. Pressure is successfully increased up to 2.8% compared to the reference blower at the design flow condition. And efficiency is also enhanced up to 2.98 % compared to the reference one. It is noted that low velocity region disturbs to make strong recirculation flow inside the blade passages, thus increases local pressure loss. Detailed flow field inside the regenerative blower is also analyzed and compared.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제17권1호
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• pp.88-98
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• 2016

The Korean summer is hot and humid, and air-conditioners consume considerable amounts of electricity. In such cases, the simultaneous use of indirect evaporative coolers may help reduce the sensible heat and save electricity. In this study, heat transfer and pressure drop characteristics of indirect or regenerative evaporative coolers made from plastic/paper are investigated. The results showed that heat and mass transfer model based on the ${\epsilon}-NTU$ method predicted the indirect evaporation efficiencies, cooling capacities and pressure drops adequately. Both for indirect or regenerative evaporative cooler, the indirect evaporation efficiency increased with increasing dry channel inlet temperature or relative humidity. The indirect evaporation efficiency of the regenerative evaporative cooler was larger than that of the indirect evaporative cooler.

• The Research Journal of the Costume Culture
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• 제32권1호
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• pp.86-107
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• 2024

Although interest in eco-friendly fashion products is increasing among scholars and industry leaders, the concept of eco-friendly products remains unclear, preventing consistent assessment of which fashion products are eco-friendly. This study conducted a content analysis of eco-friendly product information from 87 domestic and 102 foreign brands to reveal key standards for categorizing eco-friendly fashion products. Product characteristic information was coded according to the four material-based standards (i.e., organic material, regenerative material, alternative material, and sustainably produced/upcycled material). Consistency between coders was confirmed by Cohen's kappa. In results, eco-friendly fashion products are categorized by four material-based standards and two certification standards (i.e., certified, not certified). Among the four material-based categories, the greatest number of domestic and foreign companies produced eco-friendly products that were classified as the regenerative material group. In addition, companies acquired eco-friendly certifications related to the use of organic, regenerative, and alternative materials. The greatest number of eco-friendly material brands used for eco-friendly fashion products belonged to the regenerative material group. Based on the study results, a typology of eco-friendly products was suggested. This typology can benefit practitioners and academics by highlighting a need for classification system for the eco-friendly fashion products, as well as by providing insight into the categorization of eco-friendly fashion products.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.647-653
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• 2000

In this research the heat regenerative technology was employed to eliminate frosting on evaporator coil and improve COP of the heat pump system. This heat regenerative device(HRD) has very simple structure consisting a geared motor and a porous fiber belt passing through alternatively between cold and warm air duct. The laboratory test showed that the heat pump system with HRD yielded an impressive COP higher than 3.5 at the outside air temperature of $-7^{circ}C$ in heating mode.

• Proceedings of the KIEE Conference
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.2181-2182
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• 2011

This paper deals with power integration of large urban railway systems for improvement of regenerative energy utilization. The main idea of this paper is that the integration of railway power systems will increase efficiency through sharing regenerative energy. To verify the effects of this system, case studies for Seoul Metro Line has been performed. Where railway data of Seoul Subway Line 5 and Line 7 are used. In this work, the integrated railway system is modelled using Compaq Visual Fortran.

• Journal of the Korean Society of Industry Convergence
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• 제13권1호
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• pp.31-39
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• 2010

An exergy analysis is carried out for the regenerative gas turbine cycle which has a potential of enhanced thermal efficiency and specific power owing to the more possible water injection than that of inlet fogging under the ambient conditions. Using the analysis model in the view of the second law of thermodynamics, the effects of pressure ratio, water injection ratio and ambient temperature are investigated on the performance of the system such as exergetic efficiency, heat recovery ratio of recuperator, exergy destruction or loss ratios, and on the optimal conditions for maximum exergy efficiency. The results of computation for the typical cases show that the regenerative gas turbine system with afterfogging can make a notable enhancement of exergy efficiency.

• The Transactions of the Korean Institute of Electrical Engineers A
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• 제52권11호
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• pp.639-646
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• 2003

Nowadays traction motors in the urban rail transit vehicle are controlled by VVVF inverter and have capability of regenerative braking. The algorithms to deal with the regenerating vehicle in simulation for the DC traction power supply is introduced in this paper. Substations have to be separated from the system to represent reverse biased rectifiers in substations. The model of the trains in regenerative braking has to be changed from the ideal current source to the constant voltage source since the train input voltage has to be controlled below the certain train maximum voltage. Some mismatches are unevitable because the constraint of the regenerated power can not be imposed with the constant voltage source. The mismatches represent the unused regenerated power. A computer program is developed to verify the validity of the algorithm. The test run result shows the program behaves as it is expected and proves the algorithm's validity.

• Journal of the Korean Society of Propulsion Engineers
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• 제7권2호
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• pp.54-61
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• 2003

This paper describes a general design procedure of regenerative cooling system for liquid rocket engine(LRE). From this design logic, cooling channels are designed and fabricated. The measured heat flux from firing test is similar to the heat flux predicted by design logic. Therefore, proposed design procedure of cooling channel can be applied to real LRE system. Also the result of firing test indicates that soot from combustion products have strong influence on the cooling characteristics of LRE.

• Proceedings of the KIEE Conference
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.282-284
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• 2001

The rail car with the regenerative brake are very efficient on energy savings. But if these cars under regeneration exist in the rail system, various problems is raised. In this paper, the characteristics of the feeding system is analyzed and the effective passage is presented when the regenerative rail cars pass through the sections.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제60권3호
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• pp.544-551
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• 2011

This paper presents the circuit arrangement and effective control method of regenerative energy storage system for an electric vehicle using super-capacitors as the braking energy storage element. A bi-directional controlled current flow of the DC-DC converters with the capacitor bank is connected in parallel with battery, and is controlled so that the whole of the braking energy is effectively absorbed into the capacitors and released back to the electric motor upon acceleration. The converter needs the series-parallel switching circuit for making the best use of the series capacitors and for limiting the step-up ratio of the boost converter. The proposed methods are verified by computer simulation and experimental set-up. They are usefully applied to the electric vehicles such as green cars, electric motorcycles, bike, etc which are power- supplied by the electric batteries.