| Summary: | 碩士 === 國立中興大學 === 機械工程學系 === 93 === Abstract
In this study, a computational fluid dynamics (CFD) code of FLOTHERM was used to simulate the heat transfer of the three-dimension single /multiple jet impinging on the heat flux flat plate. The turbulent governing equations were solved by a control -volume-based in finite difference method . The turbulent structure was described with well known Lam & Bremhorst k-e two-equation model .The turbulence model was Staggered Grid System and Hybrid Scheme . The SIMPLEST algorithm was adopted to solve the governing equations of velocity, pressure and temperature . The parameters of this study were jet number (N), jet diameter (d), Reynolds number(Re), ratio of jet height to diameter (h/d), ratio of jet spacing to diameter of (s/d).
The simulated parameters of single jet were different jet diameter (d=1.5, 3, 4.5, 6mm), Reynolds number (Re=8200, 10820, 13149) and ratio of jet height to diameter (h/d=4, 6, 8) . The thickness of stainless heating plate was 1mm. The flux of heating plate was fixed at 1500 kw/㎡, The jet length was fixed L=3mm. The simulated parameters of two jets impinging were different ratio of jet spacing to diameter (s/d=4, 6, 8) by fixed (d=3mm, Re=10820, h/d=4).Three impinging jets had two geometry array type such as in one line and in triangular . The simulated parameter was fix (d=3mm, Re=10820, h/d=4) and different ratio of jet spacing to jet diameter were (s/d=4, 6, 8).
The result of single impinging was the smaller jet diameter the better heat transfer when fixed (Re=10820, h/d=4) . The bigger Reynolds number had the better heat transfer when fixed(d=3mm, h/d=4).The smaller ratio of jet height to diameter (h/d) had the better heat transfer when fixed (d=3mm, Re=10820) . The result of multiple jets impinging was when fixed (d=3mm, Re=10820, h/d=4) the smaller ratio of space diameter (s/d) had the fountain effect and influenced the heat transfer. The result could be afforded to the designation of solid material surface cooling.
Keywords: jet, impinging flow, fountain effect
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