Heat transfer and flow structures in axisymmetric impinging jet controlled by vortex pairing

✍ Scribed by S.D Hwang; C.H Lee; H.H Cho

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 513 KB
• Volume: 22
• Category: Article
• ISSN: 0142-727X
• DOI: 10.1016/s0142-727x(01)00091-1

✦ Synopsis

An experimental study is conducted to investigate the ¯ow and heat transfer characteristics of an impinging jet controlled by vortex pairing. Two kinds of vortex control methods of secondary shear ¯ow and acoustic excitation are applied. Local Nusselt numbers are measured on the impingement surface. Flow visualization, measurements of velocity and turbulence intensity and FFT analysis are used to understand the ¯ow structures. The velocity ratio is changed from 0.45 to 1.75 for the shear ¯ow control and the tested Strouhal number (excitation frequency, St D ) is 1.2, 2.4, 3.0 and 4.0 for the acoustic excitation. Enhancement or reduction in heat transfer is obtained by the control of vortex pairing due to the change of ¯ow structures. When the vortex pairing is promoted by the secondary counter-¯owing (suction ¯ow) and St D 1:2, low heat transfer rates are obtained at large nozzle-to-plate distances. Conversely, the jet ¯ow has an extended potential core length with the secondary co-¯owing (blowing ¯ow) and St D 2:4 and 3.0. Thus high heat transfer rates are obtained at large gap distances.