Impingement Air Cooling With Synthetic Jets Over Small and Large Heated Surfaces

Increasing heat loads and the need for improving natural convection heat transfer has brought micro fluidic technology into the thermal management of electronics. A maximum air velocity of 90 m/s from an 800 μm hydraulic diameter orifice was achieved through specially designed synthetic jets. The resonance frequency for a particular jet was determined through the effect of exit velocity magnitude, as well as power consumption. During the experiments, the operating frequency for the jet was varied between 3000 and 5000 Hz. Heat transfer augmentation experiments were performed on two heaters with different sizes to understand the size effect. A microscopic infrared thermal imaging technique was used to acquire fine scale temperature measurements. While an earlier study focused on a heater with a surface area of 160 mm², the current study used a heater with a surface area of 1450 mm², which is approximately 9 times larger. The effect of jet-location, driving-voltage, frequency and heater-power were studied during the experiments. A heat transfer coefficient enhancement over natural convection of 10 times, with the smaller heater, and 5 times, with the larger heater was measured.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.