Numerical Simulation of Evaporating Two-Phase Flow in a High-Aspect-Ratio Microchannel with Bends

[+] Author and Article Information
Junsik Lee, Junsub Kim, Hyungsoo Lim, Je Sung Bang, Jeong Min Seo, Jeong Lak Sohn

Extreme Mechanical Engineering Research Division, Korea Institute of Machinery and Materials, Daejeon, 34103, Korea

Jungho Lee

Extreme Mechanical Engineering Research Division, Korea Institute of Machinery and Materials, Daejeon, 34103, Korea

J. Heat Transfer 139(8), 080905 (Jun 05, 2017) Paper No: HT-17-1180; doi: 10.1115/1.4036882 History: Received April 01, 2017; Revised April 28, 2017


Effusion cooling is one of the attractive methods for next generation high-efficient gas turbine which has a very hot gas temperature above 1,600oC. For higher effectiveness of the air cooling, the air-cooled flow through effusion-holes does not penetrate into the mainstream flow but still remains within freestream boundary layer. So the air-cooled surface temperature maintains at relatively lower than film cooling. Effusion cooling is generally known as operating in small effusion-hole size which is less than 0.2 mm. This study is intended to examine optimum effusion-hole size of the microscale effusion cooling through flow visualization. The air flow through effusion-holes is visualized using an oil atomizer, a DSPP laser-sheet illumination, and a high-speed CCD imaging. The visualized results show flow patterns and characteristics with different blowing ratio, BR = ρcUc / ρU, (BR = 0.17 and 0.53) and effusion-hole size (D = 0.2 mm, 0.5 mm and 1.0 mm). The flow visualization condition is fixed at the mainstream Reynolds number of 10,000 and hole-to-hole spacing of 4 (S/D = 4). For larger effusion-hole of 1.0 mm [(a) and (b)], the effusion flow can penetrate into boundary layer which exhibits a film cooling. However the effusion flow is observed to be remained within boundary layer which shows an effusion cooling for smaller effusion-hole of 0.2 mm [(e) and (f)]. In case of (c) and (d), a series of vortical structure is also observed to be within the boundary layer along the effusion flat plate. Note that the effusion-hole size of 0.5 mm can be a candidate for making effusion cooling possible. [This work was supported by National Research Council of Science and Technology (NST) grant funded by the Ministry of Science, ICT and Future Planning, Korea (Grant No. KIMM-NK203B).]

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