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냉각유로방식 변화에 따른 슬롯 막냉각에서의 유동 및 열전달 특성
함진기,조형희,Ham, Jin-Ki,Cho, Hyung-Hee 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.6
An experimental investigation is conducted to improve a slot film cooling system which can be used for the cooling of gas turbine combustor liner. The tangential slots are constructed of discrete holes with different injection types which are the parallel, vertical, and combined to the slot lip. The investigation is focused on the coolant supply systems of normal-, parallel-, and counter-flow paths to the mainstream direction. A naphthalene sublimation technique has been employed to measure the local heat/mass transfer coefficients in a slot with various injection types and coolant feeding directions. The velocity distributions at the exit of slot lip for the parallel and vertical injection types are fairly uniform with mild periodical patterns with respect to the hole positions. However, the combined injection type increases the nonuniformity of flow distribution with the period equaling twice that of hole-to-hole pitch due to splitting and merging of the ejected flows. The secondary flow at the lip exit has uniform velocity distributions for the parallel and vertical injection types, which are similar to the results of a two-dimensional slot injection. In the results of local heat/mass transfer coefficient, the best cooling performance inside the slot is obtained with the vertical injection type among the three different injection types due to the effect of jet impingement. The lateral distributions of Sh with the parallel- and counter-flow paths are more uniform than the normal flow path. The averaged Sh with the injection holes are $2{\sim}5$ times higher than that of a smooth two-dimensional slot path.
함진기(Jin-KI Ham),김영기(Young-Ki Kim),이희원(Hee-Won Lee),김진수(Jin-Soo Kim),송석현(Seok-Hyun Song) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The thermal design of the bus bur of a Gas-Insulated Switchgear(GIS) becomes important since the current-carrying capacity of the GIS is limited by maximum operating. In order to predict temperature rise of the bus bar, a program has been developed. Various heat sources possibly generated in the bus bar are calculated in the program. To estimate temperature rises at the bus bar caused by the heat balance between the heat generation and heat transfer, the finite volume method as well as the 4th order Runge-Kutta method has been employed. In the experiment, temperature rises at conductor, contast part and external tank are measured for full-scale gas-insulated bus bars. The comparisons of the predicted values of balance calculation to the experiments are made. From the comparisons. it is conaluded that the developed program can predict the temperature rise of the bus bar quite well.
가스절연 변압기용 열교환기의 열전달 및 압력손실 특성 연구
함진기(Jin-Ki Ham),이준엽(Joon-Yeob Lee),김영기(Young-Ki Kim),송석현(Seok-Hyun Song) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
A plate-fin-tube heat exchanger used for a SF6 gas-insulated transformer is extremely important since the dissipation of the heat generated from inside coils has a significant effect on the performance as well as the durability of the transformer. The heat exchanger consists of corrugated plate fins and staggered array tube bundles for coolant. In order to find out heat transfer and pressure drop characteristics, series of numerical analyses for plate fins with enhanced surface geometries were conducted. Based on the results of the numerical analyses, an improved model of the plate fin has been proposed.
ITER 진공용기 중성자 빔 Liner Liner의 열ㆍ유동 설계 검증
함진기(J.K. Ham),김영기(Y.K. Kim),김동해(D.H. Kim),사정우(J.W. Sa),김병철(B.C. Kim),안희재(H.J. Ahn) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The ITER vacuum vessel provides a high quality vacuum for the plasma as well as the first confinement barrier of radioactive materials. It has upper, equatorial and lower port structures used for equipment installation, utility feedthroughs, vacuum pumping and access inside the vessel for maintenance. The neutral beam (NB) ports located side by side at two equatorial ports provide a path of neutral beam for plasma heating and current drive. An internal duct liner around the NB is built in the NB ports, and copper alloy panels are placed in the top and bottom of the liner to protect duct surface from high-power heat loads. Global NB liner models for the upper panel and the lower panel have been developed, and flow field and conjugate heat transfer analyses have been performed to find out pressure drop and heat transfer characteristics of the liner. Heat loads such as NB power, volumetric heating and surface heat flux are applied in the analyses for beam steering and misalignment conditions. For the upper panel, it is found that unbalanced flow distribution occurs in each flow path, and this causes poor heat transfer performance as well. In order to improve flow distribution and to reduce pressure losses, hydraulic analyses for modified cooling path schemes have been carried out, and design recommendation is made based on the analyses results. For the lower panel, local flow distributions and pressure drop values at each header and branch of the tube are obtained by applying design coolant flow rate. Together with the coolant flow field, temperature and heat transfer coefficient distributions are also acquired from the analyses. Based on the analysis results, it is concluded that the lower panel for the NB liner is relatively well designed even though the given heat loads are very severe.
전기자동차용 Cold Plate의 열전달 및 압력손실 특성 연구
함진기(Jin-Ki Ham),이준엽(Joo-Yeob Lee),송석현(Seok-Hyun Song) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The cold plate used for a CEU(Control Electronics Unit) of an EV(Electric Vehicle) is extremely important since the dissipation of the heat generated from power devices like IGBT(Insulated Gate Bipolar Transistor) and diode has a significant effect on the performance as well as the durability of the CEU. The cold plate consists of seven power devices, and coolant flows through the passage bonded to a groove of the cold plate. In order to find out heat transfer and pressure drop characteristics, series of numerical analyses for the cold plate with enhanced coolant passages were conducted. Based on results of the numerical analyses, an improved model of the cold plate has been proposed. The experiments under the varioius conditions have been conducted to compare the performance of the proposed cold plate to the present one. As a result of the numerical analyses together with the experiments, the ideal design of the cold plate could be offered.