Flow and heat transfer characteristics in a microchannel with a circular synthetic jet

The combination of a micmchannel and a circular synthetic jet has been proven as a promising cooling technology for microelectronic devices. However, the flow control and heat transfer characteristics of a circular synthetic jet in a microchannel are still not clear. This work numerically investigates the interaction between a circular synthetic jet and a cross flow in a microchannel using an in-house solver based on the finite volume method and analyzes its impact on the heat transfer process to further understand the heat transfer enhancement induced by a circular synthetic jet in a microchannel. The effects of the synthetic jet Reynolds number (Re-sj = 0 to 324), dimensionless stroke length (L/H = 1.8432 to 92.16), and cross-flow Reynolds number (Re-c = 188 to 470) are studied herein. The results show that the main body of the vortex structure generated by the circular impinging synthetic jet during the discharge stage is a hairpin vortex. During the downstream motion of the hairpin vortex, the vortex legs gradually stretch and evolve into a pair of large-scale longitudinal vortex. The heat transfer enhancement induced by a circular synthetic jet can be divided into two parts according to the difference in acting mechanism: an impinging region with severe heat transfer fluctuation and an entraining region with a relatively stable heat transfer performance. The parametric study demonstrates that the enhancements of the time-area-averaged Nusselt number and the total pressure drop are mainly affected by Re-sj, while the transient heat transfer performance is determined by L/H. Furthermore, the growth rates of the time-area-averaged Nusselt number and the total pressure drop are almost independent of Re-c.

Automated summary

This study numerically investigates the interaction between a circular synthetic jet and a cross flow in a microchannel to understand the heat transfer enhancement induced by the circular synthetic jet. The effects of synthetic jet Reynolds number, dimensionless stroke length, and cross-flow Reynolds number are studied. The heat transfer enhancement can be divided into an impinging region with severe heat transfer fluctuation and an entraining region with relatively stable heat transfer performance. The enhancements of the time-area-averaged Nusselt number and the total pressure drop are mainly affected by the synthetic jet Reynolds number, while the transient heat transfer performance is determined by the dimensionless stroke length.