• 한국태양에너지학회 논문집
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• 제32권4호
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• pp.9-16
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• 2012

Nanofluids using Carbon Nanotubes have a excellent thermal characteristic. In this study, for increasing the efficiency of solar collector, the thermal conductivity and viscosity of Ethanol-Oxidized Multi-walled Carbon Nanofluids were measured. Nanofluids were manufactured by ultra-sonic dispersing Oxidized Multi-walled Carbon Nanotubes(OMWCNTs) in ethanol at the rates of 0.0005 ~ 0.1 vol%. The thermal conductivity and viscosity of manufactured nanofluids were measured at the low temperature($10^{\circ}C$), the room temperature($25^{\circ}C$) and the high temperature($70^{\circ}C$). For measuring thermal conductivity and viscosity, we used transient hot-wire method and rotational digital viscometer, respectively. As a result, under given temperature conditions, thermal conductivity of the 0.1 vol% nanofluids improved 33.74% ($10^{\circ}C$), 33.14% ($25^{\circ}C$) and 32.36% ($70^{\circ}C$), and its viscosity increased by 37.93% ($10^{\circ}C$), 31.92% ($25^{\circ}C$) and 29.42% ($70^{\circ}C$) than the base fluids.

• 한국지열·수열에너지학회논문집
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• 제16권2호
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• pp.7-12
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• 2020

The battery of an electric vehicle is a key part of the energy supply to operate the vehicles. There are many factors affecting battery life such as charging method, discharge rate, and ambient temperature those are requires systematic monitoring and management. To solve the issues like environmental problems and fuel consumption reduction the battery needs more performance improvement. In this study, it was analyzed the thermal characteristics and securing battery stability for electric vehicle battery cooling system. The simulation test was operated using GT-suite software with several conditions like cooling capacity 1, 2 and 4 kW, cooling flow rate 5, 10, 20 and 30 LPM, and battery initial temperatures 40, 35, and 30℃ at the temperature of ambient 25℃. The results shown that the case of cooling flow rate at 20 LPM was most efficient among all above conditions.

• Elastomers and Composites
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• 제55권1호
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• pp.59-66
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• 2020

Herein, we investigated the thermal conductivity and thermal stability of natural rubber composite systems containing hybrid fillers of boron nitride (BN) and aluminum nitride (AlN). In the hybrid system, the bimodal distribution of polygonal AlN and planar BN particles provided excellent filler-packing efficiency and desired energy path for phonon transfer, resulting in high thermal conductivity of 1.29 W/mK, which could not be achieved by single filler composites. Further, polyethylene glycol (PEG) was compounded with a commonly used naphthenic oil, which substantially increased thermal conductivity to 3.51 W/mK with an excellent thermal stability due to facilitated energy transfer across the filler-filler interface. The resulting PEG-incorporated hybrid composite showed a high thermal degradation temperature (T₂) of 290℃, a low coefficient of thermal expansion of 26.4 ppm/℃, and a low thermal distortion parameter of 7.53 m/K, which is well over the naphthenic oil compound. Finally, using the Fourier's law of conduction, we suggested a modeling methodology to evaluate the cooling performance in thermal management system.

• The Journal of Asian Finance, Economics and Business
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• 제9권5호
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• pp.475-486
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• 2022

The purpose of this paper is to examine the use of material flow cost accounting (MFCA) in Vietnam's coal-fired thermal power plants. This study is based on the contingency and system theories to explain the application of management tools and analyze steps of input, output, and process in manufacturing. Costs in producing process-based MFCA include material cost, energy cost, system cost, and waste management cost. The exploratory case study methodology is used to describe and answer two questions, namely "How coal flow cost is recognized?" and "Why waste in material consumption can be harmful to the environment?". By analyzing the Quang Ninh and Pha Lai coal-fired thermal power plants that are the typical plants, this paper identifies the flow of primary material in these plants as a basis for determining losses for the business. The material flow of coal-fired thermal power plants provides the basis for the use of the MFCA. The manufacturing of electrical items in these plants is divided into four stages, each with its own set of losses. As a result, some phases in the application of MFCA are suggested, as well as some other elements required for MFCA application in coal-fired thermal power plants.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1876-1878
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• 1999

Developed was a 5kW-class polymer electrolyte membrane fuel cell(PEMFC) system comprised of fuel cell stack, fuel processing, thermal and water management subsystems and ancillary equipments. Several large single cells have been fabricated with different gas flow field patterns and paths, and the gas flow field pattern for the stack has been determined based on the single cell performance of thin film membrane electrode assembly (MEA). The PEMFC stack was consisted of 100 cells with an electrode area of $300cm^2$, having serpentine flow pattern. Fuel processing was developed including an autothermal methanol reformer and two preferential CO oxidation reactors. The fuel processing was combined to PEMFC operation system consisted of air compressor and thermal and water management subsystems. The PEMFC stack showed performance of 5kW under the supply of $H_2$ and air, but its performance was lowered to 3.5kW under the supply of reformed gas.

• 한국주조공학회지
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• 제20권2호
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• pp.80-88
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• 2000

Continuous casting equipment was designed to cast the metallic uranium rods, and a thermal analysis was carried out to calculate the temperature and solidification profiles. Fluid flow and heat transfer analysis model including the effects of phase change was used to simulate the continuous casting process by finite volume method. In the design of continuous casting equipment, the casting speed, pouring temperature and cooling conditions should be considered as significant factors. In this study, the effects of casting speed, pouring temperature, and air gap between the uranium and mold were investigate. The results represented that the temperature and solidification profiles of continuous casting equipment varied with the casting speed, pouring temperature, and air gap.

• 자원환경지질
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• 제51권1호
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• pp.67-76
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• 2018

본 연구는 해외 친환경에너지타운에서 보어홀 지중열 저장(BTES) 기술을 활용한 융복합 열에너지 공급 시스템의 3가지 사례로서 캐나다의 ADEU(Alexandra District Energy Utility) 및 DLSC(Drake Landing Solar Community)와 덴마크의 Brædstrup Solpark를 조사하였다. 이들 지역 냉난방 시스템들은 효율과 지속가능성을 높이기 위하여 다중 에너지원을 활용하고 있다. ADEU는 리치몬드시에서 726 개의 지중열교환기로 이루어진 지열필드 및 천연 가스 백업 보일러를 이용한 대규모 지역에너지 공급을 위해 개발되었다. 그리고 캘거리시 인근 Okotoks에 위치한 DLSC는 여름철에 풍부한 태양열 에너지를 144 개의 지중열교환기를 통하여 지중에 저장하고 겨울철 난방을 위해 각 주택에 열에너지를 분배하는 계간축열 방식의 지역난방 시스템이다. Brædstrup Solpark 지역난방 시스템은 태양열, 히트 펌프, 보일러 플랜트 및 계간축열을 위한 48 개의 지중열교환기로 구성되며 다중 에너지원을 이용하여 열을 저장한다. BTES 시추공의 심도와 축열량은 지하수 유동과 지반의 열물성에 따라 영향을 많이 받는다. 이러한 시스템들은 경쟁력 있는 에너지 가격으로 장기적인 에너지를 공급함으로서 신뢰성과 경제성을 평가 받았다. 그리고 ADEU와 Brædstrup Solpark는 서비스 영역 확장을 위한 장기 에너지 공급 계획을 기반으로 확장이 진행중이다. 본 조사를 통하여 이러한 시스템들은 사회 경제적인 이익 뿐만아니라 환경적인 관점이 설계에 반영되어 있는 것을 알 수 있었다. 국내에서도 이러한 프로젝트를 실시하기 위해서는 지방 정부 또는 관련 기관의 에너지 정책 지원 뿐만아니라, 관리 기관 설치를 통한 장기적인 협력이 필요하다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.113-117
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• 2006

This paper Is for development of cooling module in order to maintain heat and water balance in fuel cell vehicle. Thermal management system for fuel cell is disadvantage because the temperature of coolant is lower than that of ICE and heat duty of radiator is higher. By CFD simulation, cool ing module was developed for water balance of system. Hot chamber test and hot area/high altitude test on cool ing module was completed.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1423-1432
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• 2016

The integrity of a reactor pressure vessel (RPV) related to pressurized thermal shocks (PTSs) has been extensively studied. This paper introduces an integrity assessment of an RPV subjected to a PTS transient based on the French codes. In the USA, the "screening criterion" for maximum allowable embrittlement of RPV material is developed based on the probabilistic fracture mechanics. However, in the French RCC-M and RSE-M codes, which are developed based on the deterministic fracture mechanics, there is no "screening criterion". In this paper, the methodology in the RCC-M and RSE-M codes, which are used for PTS analysis, are firstly discussed. The bases of the French codes are compared with ASME and FAVOR codes. A case study is also presented. The results show that the method in the RCC-M code that accounts for the influence of cladding on the stress intensity factor (SIF) may be nonconservative. The SIF almost doubles if the weld residual stress is considered. The approaches included in the codes differ in many aspects, which may result in significant differences in the assessment results. Therefore, homogenization of the codes in the long time operation of nuclear power plants is needed.

• 에너지공학
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• 제24권1호
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• pp.69-77
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• 2015

본 연구에서는 보정된 모델링 건물을 대상으로 PMV 변수에 대한 데이터베이스를 구축하였고, 다중회귀분석을 통하여 PMV 회귀모델을 도출하였다. PMV 회귀모델은 민감도 및 데이터 분석을 통하여 단순화하여 단순 PMV 회귀모델을 제시하였다. 단순 PMV 회귀모델과 Fanger PMV 모델에 대한 MAE 및 RMSE 검증을 통하여 단순 PMV 회귀모델이 Fanger PMV 모델을 대체할 수 있는 것으로 분석되었다. EnergyPlus의 EMS(Energy Management System)를 이용하여 보정된 모델링 건물에 PMV 회귀모델 제어를 적용하였다. 단순 PMV 회귀모델과 Fanger PMV 모델 제어의 온열 쾌적도를 비교한 결과, 두 제어 모두 공조기간 동안 약 90% 이상이 온열쾌적 범위를 만족하였고, 온열 쾌적 제어의 특징인 설정 PMV를 만족하는 설정온도에 의하여 제어되는 것으로 나타났다.