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저속 영역에서 루버휜이 장착된 평판관형 알루미늄 열교환기의 공기측 전열 성능에 대한 실험적 연구
조진표,오왕규,김내현,윤백,Cho, Jin-Pyo,Oh, Wang-Kyu,Kim, Nae-Hyun,Youn, Baek 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.12
The heat transfer and pressure drop characteristics of heat exchangers with louver fins were experimentally investigated. The samples had small fin pitches (1.0 mm to 1.4 mm), and experiments were conducted up to a very low frontal air velocity (as low as 0.3 m/s). At a certain Reynolds number (critical Reynolds number), the flattening of the heat transfer coefficient curve was observed. The critical Reynolds number was insensitive to the louver angle, and decreased as the louver pitch to fin pitch ratio (L$_{p}$F$_{p}$) decreased. Existing correlations on the critical Reynolds number did not adequately predict the data. It is suggested that, for proper assessment of the heat transfer behavior, the louver pattern in addition to the flow characterization need to be considered. The heat transfer coefficient increased as the fin pitch decreased. At low Reynolds numbers, however, the trend was reversed. Possible explanation is provided considering the louver pattern between neighboring fins. Different from the heat transfer coefficient, the friction factor did not show the flattening characteristic. The reason may be attributed to the form drag by louvers, which offsets the decreased skin friction at a low Reynolds number. The friction factor increased as the fin pitch decreased and the louver angle increased. A new correlation predicted 92% of the heat transfer coefficient and 90% of the friction factor within $\pm$10%.10%.
조진표(Jin-Pyo Cho),오왕규(Wang-Kyu Oh),김내현(Nae-Hyun Kim),윤백(Beak Youn) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
The heat transfer and pressure drop characteristics of heat exchangers having louver fins were<br/> experimentally investigated. The samples had small fin pitches (1.0 mm to 1.4 mm), and experiments were<br/> conducted up to a very low frontal air velocity (as low as 0.3 m/s). The heat transfer coefficient curves crossed<br/> over as the Reynolds number decreased. Possible explanation is provided considering the louver pattern<br/> between neighboring fins. Different from the heat transfer coefficient, the friction factor did not show the<br/> flattening characteristic. The reason may be attributed to the form drag by louvers, which offsets the<br/> decreased skin friction at a low Reynolds number. The friction factor increased as the fin pitch decreased and<br/> the louver angle increased.
조진표 ( Jin-pyo Cho ),고영웅 ( Young-woong Ko ),조영일 ( Young-il Cho ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.1
데이터 주소의 계수를 위한 하드웨어 설계가 없는 본 노이만(von Neumann) 개념(SISD)의 컴퓨터에서 데이터의 주소지정은 소프트웨어적으로 수행된다. 그러므로 벡터 데이터 요소들의 주소지정은 인덱싱 기법에 의해 그 요소 수만큼 해당 변수들을 만들어서 사용해야 한다. 이것은 데이터 계수기 없이 명령어 계수기, 즉 PC(program counter)만 하드웨어로 설계되기 때문이다. 본 연구에서는 중앙처리장치 외부에 외형적 구조와 크기를 갖는 단위 벡터의 요소를 액세스하는 하드웨어 유닛의 설계를 제안한다. 제안한 방법은 시뮬레이션을 통하여 성능 검증을 하였으며, 실험 결과 동일한 프로세싱 유닛을 가지는 벡터 머신 아키텍쳐보다 12 - 30 % 정도 우수한 성능을 내는 것을 확인하였다.
김정오,조진표,김내현,Kim, Jung-Oh,Cho, Jin-Pyo,Kim, Nae-Hyun 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.2
In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the followin~ range of variables ; vapor quality($0.1{\sim}0.9$), mass flux($200{\sim}600kg/m^2s$) and heat flux($5{\sim}15kW/m^2$). The micro-fin tube showed higher heat transfer coefficients compared with those of the smooth tube. The difference increased as the vapor quality increased. Surface tension force acting on the micro-fin surface at the high vapor quality is believed to be responsible. Different from the trends of the smooth tube, where the heat transfer coefficient increased as the mass flux increased, the heat transfer coefficient of the micro-fin tube was independent of the mass flux at high vapor quality, which implies that the surface tension effect on the fin overwhelms the vapor shear effect at the high vapor quality. Present data(except those at low mass flux and high quality) were well correlated by equivalent Reynolds number, Existing correlations overpredicted the present data at high mass flux.
사인 웨이브 휜-관 열교환기의 공기측 성능에 관한 실험연구
김내현,조진표,윤백,Kim, Nae-Hyun,Cho, Jin-Pyo,Yoon, Baek 대한설비공학회 2004 설비공학 논문집 Vol.16 No.4
The heat transfer and friction characteristics of the heat exchangers having sinusoidal wave fins were experimentally investigated. Twenty-nine samples having different waffle heights (1.5 mm and 2.0 m), fin pitches (1.3mm to 1.7mm) and tube rows (one to three) were tested. Focus was given to the effect of the waffle configuration (herringbone or sinusoidal) on the heat transfer and friction characteristics. Results show that the sinusoidal wave geometry provides higher heat transfer coefficients and friction factors than the herringbone wave geometry, and the difference increases as the number of row increases. The i/f ratios of the herringbone wave geometry, however, are larger than those of the sinusoidal wave geometry. Compared to the herringbone wave geometry, the sinusoidal wave geometry yielded a weak row effect, which suggests a superior heat transfer performance at the fully developed flow region. Possible explanation is provided considering the flow characteristics in wavy channels. Within the present geometric range, the effect of the waffle height on the heat transfer coefficient was not prominent. The effect of the fin pitch was also negligible. Existing correlations highly overpredicted both the heat transfer coefficients and friction factors. A new correlation was developed using the present data.
제습이 수반된 공조용 증발기 습표면의 열전달계수 데이터 리덕션
김내현,오왕규,조진표,박환영,윤백,Kim, Nae-Hyun,Oh, Wang-Kyu,Cho, Jin-Pyo,Park, Hwan-Young,Yoon, Baek 대한설비공학회 2003 설비공학 논문집 Vol.15 No.1
Four different methods of reducing the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two different heat and mass transfer models and two different fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the data with the reduction methods revealed that the single potential heat and mass transfer model yielded the humidity independent heat transfer coefficients. Two different fin efficiency models - enthalpy model and humidity model - yielded approximately the same fin efficiencies and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.
전성택(Jeon, Sung-Taek),조진표(Cho, Jin-Pyo) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.7
현대의 공동 주택은 에너지 효율을 높이기 위해 고기밀, 고단열 방식으로 지어지고 있는데 이러할 경우 환기량 부족 에 따른 각종 부작용이 발생을 한다. 본 연구에서는 우리나라의 겨울철 대표적인 난방원으로 사용되고 있는 온돌시스템을 기본으로 구성하고 환기방법에 따른 실내 열환경을 평가하여 환기 방식에 따른 에너지 절감 요인을 분석하였다. 실험장치는 일정한 외기 조건을 모사하기 위해 항온항습 챔버에 뜬바닥 온돌 시스템을 설치하고 온돌시스템의 외기온도/습도 조건은 3조건(10℃/50%Rh, 0℃/-, -10℃,-)으로 설정 하였다. 공급되는 온수온도는 2 조건(60℃, 50℃) 설정하여 설정된 환기 방식에 따라 성능시험을 수행 하여 열 환경 및 에너지 절감 요인을 비교 분석 하였다. 실험결과 급기온도는 온수온도가 높을수록 급기풍량이 적을수록 높았으며 바닥 급/배기 > 전열교환 급/배기 > 강제 급/배기 순으로 나타났다. 본 연구를 통해 다양한 환기 방식의 적용 가능성에 대하여 검토 할 수 있었다. Modern apartment houses are constructed to be relatively airtight with a high heat insulation system to increase the energy efficiency. Such a system has a range of deleterious effects due to the insufficient ventilation. In this study, the ondol system, which is used as a heat source typical of winter in Korea, was set as the default system to evaluate the indoor heat environment according to the ventilation method, the factors of energy reduction by the ventilation system was analyzed. The experimental apparatus was used to simulate the ambient conditions for a certain constant temperature and humidity chamber. The experimental results showed that the supply water temperature higher air volume decreases with increasing supply air temperature in the following order: floor supply/exhaust > total heat exchange supply/exhaust > forced supply/exhaust. Through this study, the applicability of various ventilations could be examined.