Heat transfer enhancement of an impinging synthetic air jet using diffusion-shaped orifice

Yao-Hsien Liu*, Tsung Han Chang, Chi-Chuan Wang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Impingement heat transfer from a synthetic air jet through a diffusion-shaped orifice was investigated in this study. The effect of the opening angle (60° and 90°), orifice thickness (1-3mm), and driven frequencies (400-800Hz) were examined. Hot-wire anemometry was used to measure the instantaneous and average flow velocities ejected from the jet holes. At a small jet-to-surface spacing, synthetic jets from a diffusion-shaped orifice produced higher heat transfer than that from a round orifice. The highest heat transfer enhancement from using a diffusion-shaped orifice was approximately 30% compared with the round orifice at an opening angle of 60°. The diffusion-shaped orifice achieved the highest area-averaged heat transfer coefficient and Nusslet number of 80W/m2·K and 8.9, respectively. When the opening angle increased to 90°, heat transfer enhancement was degraded because of increased flow circulation and reduced ejection flow velocity. The effect of orifice configuration on the heat transfer diminished as the jet-to-surface spacing increased.

Original languageEnglish
Pages (from-to)178-185
Number of pages8
JournalApplied Thermal Engineering
StatePublished - 5 Feb 2016


  • Diffusion-shaped orifice
  • Heat transfer enhancement
  • Jet impingement
  • Micro nozzle/diffuser
  • Synthetic jet

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