Impact of Orifice Size over Mechanical, Flow and Thermal Performances of Synthetic Jets

Recent electronic systems require more aggressive cooling solutions due to their high functionality, densely packaged components and localized heating compared to low functionality systems in the last decade. Synthetic jets are efficient alternatives for active cooling of the electronics because of their compact size, performance and low cost. Operating frequency and voltage of a synthetic jet determine the cooling performance which has to be at a tolerable noise level. Orifice size and shape are two parameters that determine the vortex shedding behavior of a synthetic jet. Therefore, effect of the wall material and orifice size on the mechanical and thermal performances are studied with custom manufactured synthetic jets. A fully automated robotic dispensing system is used to control the orifice size with desired wall materials. Three different orifice sizes are studied in the current study. A robust manufacturing rig has been designed and manufactured. Geometric variation between synthetic jets is found to be less than 1%. A number of experimental studies to determine the actuator vibration, jet exit velocity and heat transfer is performed. The deflections of in-house designed and manufactured synthetic jets are measured with a laser vibrometer. Heat transfer test is then conducted for the jets at a range of frequencies to quantify the cooling performance over a PID-controlled vertical heated surface. It is found that an orifice size of 60 degrees performs slightly better than 30 degrees orifice and 40% better than 10 degrees orifice at the same actuator jet outer diameter.