Active Flow Control of Sprays with Synthetic Jets

Active performance enhancement of spray cooling

“…9b), data at nine flow rate ratios were collected, a set of three air flow rates (5.5 l/min, 11 l/min, and 16.5 l/min) at three normalized distances between the water intake level and the face of the spray nozzle, L w /d s = 0, 144, and 288. Note that for a given air flow rate, as L w /d s increases Q a /Q w decreases, as the volumetric flow rate of water increases when the nozzle siphons from a higher location (see Pavlova et al, 2007Pavlova et al, , 2008. Fig.…”

“…Shadowgraphy measurements were acquired at 45 locations in the spray, such that the effect of active flow control could be determined for the entire three-dimensional spray. In the present paper, only data along the centerline of the spray are presented for brevity [for more details about the Shadowgraphy technique, including a complete description of droplet sizing and velocity measurements, as well as for the full 3D field, see previous work by Pavlova et al (2007Pavlova et al ( , 2008]. In these measurements, the resulting uncertainty in the velocity is ±0.1 m/s and ±0.5 lm in the droplet diameter.…”

“…10a) flow control with four jets operating together has the greatest enhancement of heat removal (for example, for heat flux of 30 W/cm 2 out of the top DT is 14% lower than the baseline). This is probably due to the focusing of the spray, and a higher droplets velocity (Pavlova et al, 2007).…”

“…7. For brevity, data are presented only for the centerline plane (detailed results are presented in recent work by Pavlova et al (2007Pavlova et al ( , 2008. Fig.…”

“…Thus, a precise control of the amount of water siphoned, for a given air flow rate, was enabled. Note that the water flow rate through the spray nozzle depended on two parameters: the water intake level elevation L w , and the air flow rate (the relationship between the water flow rate and the air flow rate was presented in our previous papers, Pavlova et al, 2007Pavlova et al, , 2008. Water was pumped from a 37.9 l container, equipped with a water level meter and a type-T thermocouple, by a diaphragm pump through a closed 7.6 l pressure vessel, which was used to damp out the unsteadiness associated with the pump.…”