Heat transfer and acoustic study of impinging synthetic jet using diamond and oval shape orifice

Synthetic jet is a novel flow phenomenon potentially useful for cooling of electronic devices. The heat transfer and acoustic characteristics of impinging synthetic jet are investigated experimentally using different configurations of diamond and oval shape orifices with same hydraulic diameter. The experiments are conducted at an excitation frequency of 100-250 Hz. The ratio of axial distance between the heated copper block and orifice plate to orifice diameter (z/d) is in the range of 0-16. The average heat transfer coefficient and the sound pressure level (SPL) are obtained for different configurations of the orifice. The maximum value of the average heat transfer coefficient using diamond and oval shape orifices is found to be 17% and 7% higher respectively as compared to circular orifice of the same hydraulic diameter at 200 Hz. For all the configurations of oval shape orifice experimented in the present study, Nusselt number gets maximized at the same location. However, no such behaviour is observed in case of diamond shape orifice. The sound pressure level (SPL) obtained in case of diamond and oval shape orifices is less by 7 dB as compared to circular orifice at an excitation frequency of 200 Hz. The oval shape orifice is found to perform better in terms of heat transfer and acoustic aspect. SPL obtained for all the orifice shapes considered in this study is less than 40 dB at 100 Hz which is acceptable as per the United States Environmental Protection Agency (USEPA) and therefore synthetic jet with these orifice shapes can practically be employed for cooling applications without any further efforts for noise reduction. (C) 2014 Elsevier Masson SAS. All rights reserved.