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LNG 냉열을 회수하기 위해 재킷 냉각수를 열원으로 하는 유기랭킨사이클의 열교환기 설계
임태우(Tae-Woo LIM),최용석(Yong-Seok CHOI) 한국수산해양교육학회 2020 水産海洋敎育硏究 Vol.32 No.4
In this study, the thermal design of the evaporator and condenser in the ORC system using the jacket cooling water as the high temperature heat source and the cooling heat of LNG as the low temperature heat source was carried out. R134a was used as the working fluid for the ORC system. In the case of the evaporator, Shahs correlation shows the lowest heat transfer coefficient among the two-phase flow heat transfer coefficients in tubes obtained from the literature. It was found that the contribution of nuclear boiling in the low quality region was dominant. Kandlikars correlation also showed the contribution of nuclear boiling. As the quality is increased, the contribution of convective evaporation was not significant. Lims correlation showed the highest heat transfer coefficient, and the contribution of nuclear boiling in the whole quality region was not as large as that of convective evaporation. Therefore, the total heat transfer surface area of the evaporator was the highest when obtained from Shahs correlation. Low value was obtained when obtained from the correlation of Lim. In the condenser, the shell-side heat transfer coefficient obtained from Nusselt analysis was the lowest, followed by Kern and Eissenberg. The heat transfer surface area of the condenser showed the highest when obtained from Nusselt analysis.
임태우,최재혁,김준효,최용석,Lim, Tae-Woo,Choi, Jae-Hyuk,Kim, Jun-Hyo,Choi, Yong-Suk 해양환경안전학회 2012 海洋環境安全學會誌 Vol.18 No.5
$500{\mu}m$의 수력직경을 가진 마이크로 채널에서 유동 비등 시 물에 대한 마찰 압력 강하를 측정하기 위한 실험적 연구를 수행하였다. 실험은 열 유속 $100-400kW/m^2$, 증기건도 0-0.2 그리고 질량 유속 $200-600kg/m^2s$의 범위에서 이루어졌다. 유동 비등 시 마찰 압력 강하는 두 가지 모델을 사용하여 예측된다. 즉, 두 상의 속도가 동일하다고 가정한 균질 모델과 두 상 사이에 서로 다른 속도를 가지는 분리류 모델로 분류된다. 실험결과 이상 마찰 승수는 질량 유속이 증가함에 따라 감소한다는 것을 알 수 있었다. 측정된 압력 강하 데이터는 매크로 스케일과 미니/마이크로 스케일에서 제안된 기존의 여러 상관식들과 비교하였다. 균질 모델은 본 연구에서 고려한 실험 조건에서 29.4 %의 평균 오차내에서 마찰 압력 강하를 예측하였다. An experimental study was carried out to measure frictional pressure drop in flow boiling to deionized water in a microchannel having a hydraulic diameter of $500{\mu}m$. Tests were performed in the ranges of heat fluxes from 100 to $400kW/m^2$, vapor qualities from 0 to 0.2 and mass fluxes of 200, 400 and $600kg/m^2s$. The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. From the experimental results, it is found that the two phase multiplier decreases with an increase in mass flux. Measured data of pressure drop are compared to a few available correlations proposed for macroscale and mini/microscale. The homogeneous model well predicted frictional pressure drop within MAE of 29.4 % for the test conditions considered in this work.
R134a 및 Rl23과 비공비 혼합냉매 R134a/R123의 수평관내 이상유동양식에 관한 연구
임태우,김준효,Lim, Tae-Woo,Kim, Jun-Hyo 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
Two-phase flow pattern data during horizontal in-tube flow boiling are presented for pure and mixed refrigerants of R134a and Rl23, The flow pattern is observed through tubular sight glasses located at inlet and outlet of the test section, which is made of a stainless steel tube, 2m long with 10mm I.D., 1.5mm wall thickness. The obtained results are compared with the available various correlations for flow pattern. The flow pattern map of Hashizume was in good agreement with the present data except the region of low mass velocity. Weisman flow pattern map was also known to satisfactorily predict data for refrigerants in the region of annular flow. In this study, the flow pattern are simply classified into two groups; stratified(including intermittent, stratified and stratified-wavy) flow and annular flow. The transition quality from stratified to annular flow was obtained by modifying the liquid Froude number.
수평 전열관내 비공비 혼합냉매 R134a/R123의 강제대류비등 열전달에 관한 연구
임태우,한규일,Lim, Tae-Woo,Han, Kyu-Il 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.3
An experimental study was carried out to measure the heat transfer coefficient in flow boiling to mixtures of HFC-l34a and HCFC-123 in a uniformly heated horizontal tube. Tests were run at a pressure of 0.6 MPa and in the ranges of heat flux 1-50 kw/$m^2$, vapor quality 0-100 % and mass velocity 150-600 kg/$m^2$s. Heat transfer coefficients of mixture were less than the interpolated values between pure fluids both in the low quality region where the nucleate boiling is dominant and in the high quality region where the convective evaporation is dominant. Measured data of heat transfer are compared to a few available correlations proposed for mixtures. The correlation of Jung et. al. satisfactorily predicted the present data, but the data in lower quality was overpredicted and underpredicted the high quality data. The correlation of Kandlikar considerably underpredicted most of the data. and showed the mean deviation of 35.1%.
임태우(Tae-Woo LIM),유삼상(Sam-Sang YOU),김환성(Hwan-Seong KIM) 한국수산해양교육학회 2013 水産海洋敎育硏究 Vol.25 No.3
Two-phase pressure drop experiments were performed during flow boiling to deionized water in a microchannel having a hydraulic diameter of 500 ㎛. Tests were made in the ranges of heat fluxes from 100 to 400 ㎾/m2, vapor qualities from 0 to 0.2 and mass fluxes of 200, 400 and 600 ㎏/m2s. The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. From the experimental results, it is found that the two phase multiplier decreases with an increase in mass flux. Measured data of pressure drop are compared to a few available correlations proposed for macroscale and mini/microscale. Among the separated flow models, the correlation model suggested by Lee and Garimella predicted the frictional pressure drop within MAE of 47.2%, which is better than other correlations.
FC-72를 이용한 마이크로 핀 표면에서의 핵비등 열전달
임태우(Tae-Woo LIM),유삼상(Sam-Sang YOU),김환성(Hwan-Sung KIM) 한국수산해양교육학회 2008 水産海洋敎育硏究 Vol.20 No.3
To evaluate the performance of nucleate boiling heat transfer between a plain and micro-fin surfaces, the experimental tests have been carried out under various conditions with fluorinert liquid FC-72, which is chemically and electrically stable. Two kinds of micro fins with the dimensions of 200㎛ x 20㎛ and 100㎛ x 10㎛ (width x height) were fabricated on the surface of a silicon chip. The experiments were performed on the liquid subcooling of 5, 10 and 20K under the atmospheric condition. The presented data showed a similar trend in the comparison with result of Rainey & You. Due to its expanded surface areas, the heat flux properties has been significantly enhanced on micro-fin surface comparing to the plain surface.
임태우(Tae-Woo LIM),최용석(Yong-Seok CHOI),임우택(Woo-Taek LIM) 한국수산해양교육학회 2019 水産海洋敎育硏究 Vol.31 No.3
Shell and tube heat exchangers are the most common type of heat exchangers which are widely used in industrial applications. The pressure drop prediction on the shell side of a shell and tube heat exchanger is quite complicated due to taking into account of the presence of bypass and leakage streams. The Bell-Delaware method reflects the effects associated with leakage and bypass streams on the shell side pressure drop. The simulation results show that the shell side pressure drop for tube layout of 90o is lower than that of the other cases. In addition, The lower allowable pressure drop for tube side is obtained from tube layout of 90o. Finally, it is found that the overall heat transfer coefficient and surface area for tube layout of 90o are higher than the other cases.
판형 핀을 가진 원통-다관형 열교환기의 열전달 특성에 관한 연구
임태우(Lim, Tae-Woo),조동현(Cho Dong-Hyun) 한국산학기술학회 2009 한국산학기술학회논문지 Vol.10 No.1
본 논문은 세 개의 서로 다른 관수(9, 13 그리고 19)를 가지는 원통판형 핀 관의 원통 측에서의 열전달 성능을 실험적 방법으로 평가하였다. 관외를 흐르는 오일은 관내를 흐르는 냉각수에 의해 냉각된다. 오일 쿨러의 원통-다관형 열교환기는 단일 셸 통로와 두 개의 관 통로로 구성되며, 관 내경은 8.82㎜, 관 길이는 575㎜이다. 오일의 질량 유량은 1.2~6.0㎥/h이며, 냉각수의 질량 유량은 0.6~3.0㎥/h이다. 실험결과 9개의 관수를 가지는 열교환기의 총합 열전달계수는 13개와 19개의 관수의 열전달계수보다 각각 약 1.8배와 2.3배 높게 나타났다. In this work, the experimental investigation was carried out to evaluate the heat transfer performance on the shell side of shell-and-plate finned tube heat exchanger with three different tube numbers(9, 13 and 19). Oil flowing on the shell side was cooled by cold water flowing inside the tubes. A shell-and-tube heat exchanger of an oil cooler consisted of one shell pass and two tube passes with the inner tube diameter of 8.82 ㎜ and the tube length of 575 ㎜. Mass flow rate was varied from 1.2 to 6.0 ㎥/h for oil and from 0.6 to 3.0 ㎥/h for cold water, respectively. From the experiment of shell-and-plate finned tube heat exchanger, the overall heat transfer coefficient of heat exchanger with 9 tubes was compared with that of 13 and 19 tubes. It was found that the heat transfer coefficients in shell side of heat exchanger with 9 plate finned tubes showed averagely 1.8 times and 2.3 times higher than those of 13 and 19 tubes, respectively.