• 동력기계공학회지
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• 제18권5호
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• pp.22-27
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• 2014

The objectives of this paper are to obtain an empirical equations regarding the correlations between heat transfer and pressure drop of oval fin-tube heat exchanger having large diameter using wilson plot method. It was difficult to find any recommendable heat transfer and friction factor correlation available for our large diameter experimental cases. Overall heat transfer coefficients are composed of the heat transfer coefficients both inside and outside tubes. The resulting empirical correlations for the Nui and f-factor are given as $Nu_i=0.0146Re^{0.809}Pr^{0.3}$ and $f=4.366Re^{-0.64}$, respectively. The empirical correlations of the Nui and f-factors were developed for the large diameter oval finned-tube heat exchanger as a function of the Reynolds number. As the EG(Ethylene glycol) and air flow rate increases, the heat transfer rate and pressure drop is increased largely.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1059-1070
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• 2016

The Prototype Gen IV sodium cooled fast reactor (PGSFR) has been developed for the last 4 years, fulfilling the technology demonstration of the burning capability of transuranic elements included in light water reactor spent nuclear fuel. The PGSFR design has been focused on the robustness of safety systems by enhancing inherent safety characteristics of metal fuel and strengthening passive safety features using natural circulation and thermal expansion. The preliminary safety information document as a major outcome of the first design phase of PGSFR development was issued at the end of 2015. The project entered the second design phase at the beginning of 2016. This paper summarizes the overall structures, systems, and components of nuclear steam supply system and safety characteristics of the PGSFR. The research and development activities to demonstrate the safety performance are also briefly introduced in the paper.

• 한국태양에너지학회 논문집
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• 제25권2호
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• pp.19-26
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• 2005

Concentric evacuated tube solar energy collector has been interested recently since government has driven to install alternative energy systems in new large building. In this paper, testing of the evacuated tube collector is conducted in outdoor during daytime by transient method. The collector thermal efficiencies are plotted in term of $(T_{in}-T_a)/Ic$, where $T_{in}$ is inlet working fluid temperature, $T_a$ is atmospheric temperature and $I_c$ is solar irradiation on the collector surface. The evacuated tube collector efficiency is ranged from 50% to 63% in real outdoor condition. In addition, the total overall heat loss coefficient is found to have an inverse variation to $(T_{in}-T_a)/I_c$ so that the coefficient becomes very high when $(T_{in}-T_a)/I_c$ is small.

• 설비공학논문집
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• 제22권3호
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• pp.165-170
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• 2010

Experiments have been performed to investigate the key parameters determining the performance of thermoelectric power generation. The experimental results obtained show that the power output significantly increases with the temperature difference between cold and hot sides of thermoelectric generator. However, the effect of the hot side temperature under the identical temperature difference on the overall performance of a thermoelectric generator is meager. The conversion efficiency defined as the ratio of the power generated to the heat absorbed at the hot side increases with the temperature difference. The behavior of the thermoelectric generator is shown to be consistent with the theoretical analysis. The optimum current giving the maximum conversion efficiency and the maximum conversion efficiency are linearly increased with the temperature difference.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.1096-1101
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• 2005

In this study, the experiment of thermal performance about closed-type hybrid cooling tower was conducted. A closed type cooling tower is a device similar to a general cooling tower, but with cooling tower replaced by a heat exchanger. The test section for this experiment has the process that the cooling water flows from top part of heat exchanger to bottom side in the inner side of tube, and spray water flows gravitational direction in the outer side of it. Air contacts of tube outer side are counterflow. The heat transfer pipe used in this experiment is a bare type tube having an outside diameter of 15.88mm. In this experiment, heat performances of the cooling tower are calculated such as overall heat transfer coefficient of between the process fluid and air, cooing capacity and pressure drop.

• 설비공학논문집
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• 제22권8호
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• pp.545-552
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• 2010

Research and development efforts to reduce $CO_2$ emission are in progress to cope with global warming. $CO_2$ emission from fossil fuel fired power plants is a major greenhouse gas source and the post-combustion $CO_2$ capture is considered as a short or medium term option to reduce $CO_2$ emissions. In this study, the application of the post-combustion $CO_2$ capture system, which is based on chemical absorption and stripping processes, to typical fossil fuel fired power plants was investigated. A coal fired plant and a natural gas fired combined cycle plant were selected. Performance of the MEA-based $CO_2$ capture system combined with power plants was analyzed and overall plant performance including the energy consumption of the $CO_2$ capture process was investigated.

• 한국유체기계학회 논문집
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• 제18권1호
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• pp.37-43
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• 2015

A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

• 한국추진공학회지
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• 제25권2호
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• pp.98-109
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• 2021

극초음속 비행체용 능동냉각시스템의 전체적인 운용 성능을 결정하는 주요 요소는 크게 탄화수소흡열연료, 재생냉각 채널, 시스템 소재 및 구조로 구분되며, 그 중에서도 효율적인 재생냉각시스템 개발을 위한 일련의 연구는 탄화수소 항공유의 흡열반응 성능 향상으로부터 시작된다. 따라서 이전 연구에서는 탄화수소 항공유 자체의 흡열분해 특성에 대한 광범위한 연구 동향을 정리하였으며, 본 연구에서는 그에 대한 후속 연구로서 효과적인 흡열분해 특성 개선 및 성능 향상 방안으로 다양하게 시도되고 있는 촉매 분해와 수증기 개질 연구들에 대한 세부기술 분석을 수행하였다.

• 대한기계학회논문집A
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• 제41권7호
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• pp.665-671
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• 2017

알칼리금속을 이용한 열전기변환장치(Alkali-Metal Thermal-to-electric Converter)는 열을 전기로 직접 변환하는 기술이다. AMTEC 기술은 기존 에너지기술 대비 고효율성과 고밀도성을 지니는 정적 에너지 변환 장치로서 이론 발전효율이 40%로 높고 단위발전량이 500 W/kg, $2.01W/cm^2$로 우수하다. AMTEC의 작동원리는 작동유체인 소듐이 분압차이에 의해서 고체전해질인 베타알루미나(BASE)의 내부에서 외부로 이온화를 거쳐며 통과하는데, 이때 전자를 주고 받으며 전기를 생성한다. BASE내외부의 분압차 형성을 위해서는 고온내구성과 기밀성이 높은 접합기술이 요구된다. 개발된 접합기술을 이용하여BASE/절연부/금속부 시스템의 안정적인 전기적/구조적 시스템을 구성하고 멀티-셀 모듈들을 제작하여 개방회로 전압과 전류-전압특성을 측정하는 방법으로 AMTEC 모듈전지들의 출력성능과 수명을 평가하였다.

• KIEAE Journal
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• 제15권5호
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• pp.113-118
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• 2015

Purpose: In Korea, buildings make up 20.5% (2012) of the gross national energy consumption, so they are a major target for greenhouse gas reduction. In particular, energy consumption in multihousing represents approximately 32.6% of the entire building sector. With improving energy performance being the focus, efforts are continuously being made to reinforce standards and systems in greenhouse gas reduction. This study investigated the current status of multihousing in Korea in terms of energy performance as described in the performance evaluation reports submitted (to an institution that specializes in reviewing the performance evaluation of green homes) based on the construction criteria and performance codes for green homes and examined if the evaluation criteria using related methodologies were appropriate. The results will provide helpful information for reviewing the future directions of operations and amendments to the systems. Method: The overall characteristics of the system were examined using the evaluation methodologies (and current state of revisions) of the performance codes for green homes and comparing them with similar systems. Also, the current state of application and energy performance (conducted according to the evaluation methodologies) were compared by the evaluation institution for multihousing neighborhoods that were assessed for five years from 2010 to 2014. Result: It has been confirmed that the performance codes for green homes are different from other similar systems in evaluating performances of multihousing in that they allow both quantitative and qualitative methods of evaluation, and they consider both energy and sustainability simultaneously in the evaluation. Furthermore, regarding the adoption rate of the forms for the two evaluation methods (Form 1 - quantitative and Form 2 - qualitative), the rate preferring Form 2 increased gradually in time to reach 55.3% in 2014. In analyzing the rate of overall energy reduction (submitted in Form 1) and the coefficient of thermal transmission for each part (submitted in Form 2), it was observed that the deviation between the performance submitted and the criteria decreased in line with the level of reinforcement.