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Eulerian-Granular method를 사용한 고체 입자 유동 모델 개발
이태규(T. G. Lee),신승원(S. W. Shin) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.2
In this paper, we have developed numerical model for particulated flow through narrow slit using Eulerian-Granular method. Commercial software (FLUENT) was utilized as simulation tool and main focus was to identify the effect from various numerical options for modeling of solid particles as continuos phase in granular flow. Gidaspow model was chosen as basic model for solid viscosity and drag model. And lun-et-al model was used as solid pressure and radial distribution model, respectively. Several other model options in FLUENT were tested considering the cross related effect. Mass flow rate of the particulate through the slit was measured to compare. Due to the high volume density of the stacked particulates above the slit, effect from various numerical options were not significant. The numerical results from basic model were also compared with experimental results and showed very good agreement. The effects from the characteristics of particles such as diameter, angle of internal friction, and collision coefficient were also analyzed for future design of velocity resistance layer in solar thermal absorber. Angle of internal friction was found to be the dominat variable for the particle mass flow rate considerably. More defined 3D model along with energy equation for complete solar thermal absorber design is currently underway.
Loop형 Thermal Diode의 열성능에 관한 기초 연구
천원기(W.G.Chun),Kuan Chen,이태규(T.K.Lee),김형택(H.T.Kim) 한국태양에너지학회 1994 한국태양에너지학회 논문집 Vol.14 No.3
본 논문은 루프형 열다이오드의 열 성능에 관하여 시험적 연구를 수행하였다. 다이오드는 두 개의 튜브로 만든 수평 부분과 이 두 수평부분을 연결하는 두 개의 PVC 튜브로 구성되어 있다. 작동유체로는 물과 공기가 사용되었으며, 특히 물의 경우 낮은 열전도도와 유동저항의 영향으로 좋은 열성능을 보여 주었다. 본 연구에서는 순방향과 역방향일 경우의 열전달율과 열전달 비를 구하였으며 여러 차례에 걸친 실험을 반복 수행하였다. 이와 같은 형태의 열다이오드는 바로 태양열의 이용에 효과적으로 응용될 수 있다. The thermal performance of a loop thermal diode is presented. This diode in composed of the horizontal segments(metal tubes) and two branches(PVC tubes) connecting the horizontal segments. For the working fluid(filling the loop), water and air are tested where water has shown remarkable performance due to its low thermal conductivity and frictional resistance. A number of tests are done to estimate the heat transfer rate and ratio of heat transfer rates of the diode under forward and reverse bias. This type of thermal could be used at hand to harness the solar energy.
Myristic acid를 사용한 축열장판의 열성능 연구
곽희열(H.Y.Kwak),강용혁(Y.H.Kang),전명석(M.S.Jeon),이태규(T.K.Lee),이동규(D.G.Lee),한귀영(G.Y.Han) 한국태양에너지학회 1998 한국태양에너지학회 논문집 Vol.18 No.3
본 논문은 미세캡슐을 함유한 축열장판의 열성능에 관해서 조사였고 기존 시판되고 있는 장판과 비교를 하였다. 상변화물질로는 myristic acid (CH₃(CH₂)_12COOH)를 사용했고 이물질을 PMMA와 왁스로 3중 코팅을 하였고 1~1.5mm인 캡슐로 제조를 하였다. ANSI/ASHRAE를 토대로 하여 열전달 매체로 공기를 사용한 밀폐형 실험장치를 구성하였으며, 공기유량은 오리피스를 통해서 측정된다. 실험에 사용된 두 개의 서로다른 장판(미세캡슐 함유율 중량비 10% 장판, 0% 장판)의 열성능을 평가하기 위해서 서로다른 공기유량에 대해서 방열시 열전달 특성에 관한 실험을 수행하였다.<br/> 실험결과를 보면 방열과정시 미세캡슐 함유율이 10%인 장판의 표면온도는 미세캡슐을 함유하지 않은 장판보다 더 높은 온도를 유지했다. 그리고 장판표면에서의 열전달계수는 미세캡슐을 함유하지 않은 장판과 비교해 볼 때 미세캡슐을 함유한 장판에서 더 높게 나타났다. The thermal performance of a heating board with microencapsualted PCM was investigated and compared to conventional heating board. The employed PCM was the myristic acid <CH₃(CH₂)_12COOH> and was encapsulated by the multiple layers of PMMA and paraffin wax. The size of encapsulated PCM was 1 ~ 1.5mm.<br/> Accoring to ANSI/ASHRAE test procedure, the close-loop test configuration was installed. Air was used as the heat transfer fluid and a calibrated orifice was employed for the measurement of air flow rates. The thermal performance test of two different heating boards (with 10 wt% PCM and without PCM) was conducted for different air flow rates and the heat transfer characteristics during cooling was compared.<br/> The test results showed that the surface temperature of heating board with 10 wt% PCM maintained higher during the cooling process than that of the heating board without PCM and experimentally determined heat transfer coefficient in heating board with PCM showed higher value compared to heating board without PCM.