with an active area of 59.6 cm2
. The transducer is driven with electronics
of Prosys Inc., which are capable of pulsing the acoustic
field. For each pulse period, the pulse on time ðTonÞ and pulse off
time ðToffÞ can be varied, as long as the duty cycle (Ton/(Ton + Toff))
is between 10% and 90%. The system is hooked up to a ‘gasification
system’ that first degasses the liquid before the liquid is gasified in
a controlled manner with membrane contactors (Phasor II, Entegris)
[10]. The liquid is gasified with oxygen and the dissolved oxygen
content is measured with a dissolved oxygen probe (Oakton
DO600) based on a galvanic measuring element. A diffuser is
placed at the bottom of the cleaning tank in order to optimize flow
uniformity inside the tank. A flow controller is installed in order to
stabilize the liquid flow rate around 28 l/min. This flow rate results
in a tank refresh time of 2.3 min., which is chosen to prevent
degassing of the liquid due to the applied ultrasound. The high flow
rate requires the use of 3 degassing and 3 regassing membrane
contactors in parallel. An anechoic material (Aptflex F28, Precision
Acoustics) can be placed along the walls inside the cleaning tank.