• KIEAE Journal
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• 제13권3호
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• pp.33-40
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• 2013

The world population is consuming more than 1/3 of the total energy for heating housings. Particularly in our country, 21% of the consumption energy is occupied by building section. Therefore, it is necessary to increase the energy efficiency in buildings, thus promoting a comfortable residential environment while minimizing energy consumption. Accordingly, this study presents considerations for implementing high-insulated and airtight passive houses. This study selected four houses with passive house design applied, performed building energy performance through PHPP2007, a German passive house design simulation program, and compared the building-specific heat loss and heat gain. As a result, the most vulnerable part to heat loss was turned out to be a window and the heat loss was caused by outer wall, roof, and ventilation. Accordingly, for the implementation of passive house, it is necessary to make a careful plan and airtight construction that are complementary to various parts through the energy performance analysis started from the design phase.

• 한국연소학회지
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• 제16권1호
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• pp.46-51
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• 2011

Exhaust gas of an industrial furnace used at such as metallurgy or ceramic manufacturing usually contains thermal energy with high temperature which can be recycled by heat exchanger. However, when the temperature of the exhaust gas is high such as more than $1,000^{\circ}C$, ordinary metallic heat exchanger cannot fully recover the heat due to the limitation of operating temperature depending on the material property. In the present study, a compact ceramic heat exchanger of cross flow type is introduced and evaluated by heat exchange rate and operating temperature. The ceramic heat exchanger can endure the gas temperature more than $1,300^{\circ}C$, and its volumetric heat exchanging rate exceeds 1 MW/$m^3$. The experimental data is also compared with the previous numerical result which shows reasonable agreement. Meanwhile, the gas leakage rate is measured to be about 3~4%, and heat loss to environmental air is about 23~26% of the fuel energy.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.24-31
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyzer the heat quantity of inhomogeneous charge methane-air mixture. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. It is shown that the effect of stratification is not significant in case of the overall excess air ratio of 1.1, mainly due to the higher heat loss and lower thermal efficiency compared to those of homogeneous condition. In the case of the overall excess air ratio of 1.4, as the initial charge pressure decreases, the CHR ratio has been decreased while the HL ratio has been increased, Generally, as the initial charge pressure increases, the amount of injection mixture has been decreased and has resulted in lower mean velocity and turbulence intensity for injection mixture. Also, the injected mixture is too rich to result in mixing deficiency in combustion chamber. From these results, it could be possible to acquire the improvement of thermal efficiency and the reduction of heat loss simultaneously through the 2-stage injection in CNG direct injection engine.

• 설비공학논문집
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• 제18권2호
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• pp.151-157
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• 2006

The present paper reports the method for evaluation of heat-transfer performance of finned tube heat exchangers in a low Reynolds number regime (Re = $160\~800$) and also reports the data of heat transfer and pressure loss taken from a finned tube heat exchanger with/without vortex generators (VGs) installed as a heat-transfer enhancement device. The evaluation is based on the modified single blow method conducted in a specially designed low Reynolds number duct. Three different test core geometries, i.e., fin only, fin-tube without VGs and that with VGs, are studied here. The data of heat transfer and pressure loss taken from the fin only geometry agree well with the empirical correlations, thus validating the present method as used for low Reynolds number regime. The data taken from the finned tube geometries with and without VGs are presented and compared to examine the effect of VGs in the low Reynolds number regime.

• 대한기계학회논문집
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• 제12권1호
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• pp.48-52
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• 1988

본 연구에서는 Carnot사이클로 작동되는 냉동사이클에 대하여 열교환과정 및 열손실을 고려하여 효율과 출력의 최대조건을 살펴 보고, 기존의 사이클 해석이 효율측면에서 실제장치와의 상이점으로 인하여 공학적 의미가 없어지는 문제점을 보완하고자 한다.

• 한국태양에너지학회 논문집
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• 제22권4호
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• pp.77-84
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• 2002

In order to investigate forced convection heat transfer due to the wind from the inner surface of a cavity receiver for a parabolic dish type solar energy collecting system, a two-dimensional rectangular cavity receiver is prepared and installed in a wind tunnel. The convection heat transfer coefficient of the inner surface of the receiver is dependent on the direction and the velocity of the wind. The attack angle of the cavity and the air velocity in the tunnel are controlled in a wide range so that the effects of the attack angle and the wind velocity on the heat transfer coefficient can be studied. The skirt is installed at the aperture of the cavity in order to reduce convective heat loss. The effects of the length and the installation angle of the skirt on convection heat transfer of the cavity are tested. It is found that convection heat loss can be significantly reduced by installing the skirt. Also, it is known that heat transfer from the cavity can be minimized if the angle of the skirt is $90^{\circ}$ to the outer surface of the cavity.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.21-30
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• 2005

Heat release analysis is a very importent method in understanding the combustion phenomena inside an engine cylinder. In this study, one-zone heat release analysis was used with the mesured cylinder pressures of an IDI(indirect injection), a HSDI(high speed direct injection) and a SI(spark ignition) engine. It has benefits of simple equation, fast speed, reliability. The object of the study is to compare the combustion characteristics among an IDI, a HSDI and SI engine. Result of analysis, the maximum heat release rate of a HSDI is higher than an IDI because of long ignition delay period. The heat release curve of a IDI is more linear than an HSDI, so the combustion characteristics of a IDI is similiar to that of an SI engine. There is a suggestion here that the combustion efficiency of a HSDI is highest of that of all engines because of the smallest heat transfer loss of all engines.

• 한국지구과학회지
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• 제22권1호
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• pp.40-46
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• 2001

기상청에서 덕적도와 칠발도에 설치한 해양기상 관측부이 자료를 이용하여 해양 및 대기 특성과 해양-대기간의 열교환을 살펴보았다. 각 관측지점에서의 일평균 현열속 및 잠열속은 벌크공기역학법을 적용하여 계산하였다. 표층수온은 기온과 같이 뚜렷한 연주기를 보이지만, 1달 정도 시간지연을 가진다. 해면기압은 7월에 가장 낮았고 겨울에 가장 높았으며, 습도는 5-8월 사이 비교적 높았다. 풍속은 가을과 겨울에 평균 5m/s 이상으로 강한 편이었다. 현열속 분석결과 가을부터 겨울에 걸처 해양의 열손실이 두드러졌으며, 봄과 여름에는 반대로 대기에서 해양으로의 약한 열전달이 이루어져 연중 순현열속은 해양에서 대기로의 열전달을 보여주었다. 잠열속 분석결과 봄에서 여름까지 대기의 열손실이 나타나지만, 그 외 기간에는 해양의 열손실이 월등히 크게 나타났다. 현열속과 잠열속의 크기를 비교해 볼 때,1-2월을 제외하고는 전반적으로 현열속보다 잠열속에 의한 해양의 열손실이 우세함을 알 수 있었다. 관측지점별로 분석한 열속의 크기와 변동폭은 대체적으로 덕적도에서 더 크게 나타났다. 일정 기간을 선정한 사례연구에서, 1998년 5월사례의 경우 현열속과 잠열속 모두 칠발도에서 더 크고, 1996년 11월 사례의 경우에는 덕적도에서 훨씬 크게 나타났다.

• 대한기계학회논문집B
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• 제34권4호
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• pp.399-408
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• 2010

질소 희석된 프로판 층류 부상 화염에서 화염진동 불안정성과 화염 곡률 효과를 살펴보기 위하여 실험적 연구를 수행하였다. 화염 진동은 총 3가지 영역으로 열손실에 의한 진동, 열손실 및 부력이 혼재된 진동, 그리고 열손실 및 루이스 수에 의한 영향이 혼재된 진동으로 구분되었다. 순수 열손실에 의한 진동은 루이스 수에 의한 진동과 부력에 의한 수력학적 불안정성과 관련이 없으며 연료 루이스 수에 관계없이 모든 부상화염 조건에서 관찰되었다. 화염의 시간에 따른 부상높이 변화에 대한 FFT분석을 통해 화염진동 불안정성의 실험적 증거와 특성을 명확히 제시하였고, 부상 화염의 열손실에 의한 자기진동의 메커니즘에 대한 시나리오를 논의한다.

• 한국안전학회지
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• 제36권3호
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• pp.74-80
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• 2021

Korea Atomic Energy Research Institute (KAERI) has been operating an integral effects test facility, the Advanced Thermal-Hydraulic Test Loop for Accident Simulation (ATLAS), according to APR1400 for transient experimental and design basis accident simulation. Moreover, based on the experimental data, the domestic standard problem (DSP) program has been conducted in Korea to validate system codes. Recently, through DSP-05, the performance of the passive auxiliary feedwater system (PAFS) in the event of multiple steam generator tube rupture (MSGTR) has been analyzed. However, some errors exist in the reference input model distributed for DSP-05. Furthermore, the calculation results of the heat loss correlation for the secondary system presented in the technical report of the reference indicate that a large difference is present in heat loss from the target value. Thus, in this study, the reference model is corrected using the geometric information from the design report and drawings of ATLAS. Additionally, a new heat loss correlation is suggested by fitting the results of the heat loss tests. Herein, MSGTR-PAFS accident analysis is performed using MARS-KS 1.5 with the improved model. The steady-state calculation results do not significantly differ from the experimental values, and the overall physical behavior of the transient state is properly predicted. Particularly, the predicted operating time of PAFS is similar to the experimental results obtained by the modified model. Furthermore, the operating time of PAFS varies according to the heat loss of the secondary system, and the sensitivity analysis results for the heat loss of the secondary system are presented.