Experimental investigation on the flow regime and impingement heat transfer of dual synthetic jet

Abstract

An experimental investigation is carried out to analyze the flow regime and impingement heat transfer of a dual synthetic jet (DSJ) actuator for the compact thermal management. The time-averaged flow field of DSJ is observed to consist of four regions, namely, the formation region, merging region, development region and decay region other than three regions of SJ without the merging region. The downstream vorticity-concentrated partitions of the SJ and the DSJ spread outwards at about 22.5° and 26.6°, respectively. The heat transfer characteristic of an impinging DSJ is analyzed by comparing with a synthetic jet (SJ). It is found that the local Nusselt number reaches a maximum at a same dimensionless impingement spacing of H/dh = 5.5 both for the SJ and the DSJ, and the maximum local Nusselt number of the impinging DSJ is 11.4% higher. The maximum area-averaged Nusselt number of the impinging DSJ is 8.6% higher at only half of H/dh than the impinging SJ, which is more preferable for the space-restricted electronic cooling. In addition, the effects of slot dimensions on the heat transfer of the impinging DSJ are studied. The peak Nusselt number is directly proportional to the slot neck length and inversely proportional to the slot aspect ratio at a same H/dh. The area-averaged Nusselt number reduces with the increase of the slot neck length at a smaller H/dh, and varies contrarily at a larger H/dh. The best heat transfer performance of the impinging DSJ is achieved at a midlevel aspect ratio. The results provide a design guideline for the cooling packages of space-restricted electronics.