Ultrasonic equipment can effectively degassing and defoaming liquid. In this case, ultrasound removes small suspended bubbles from the liquid and reduces the level of dissolved gas below the natural equilibrium level.
Degassing and defoaming of liquids have many uses, such as:
Particle size measurement before sample preparation to avoid measurement error.
Before pumping, the oil and lubricating oil are degassed to reduce pump wear caused by cavitation.
Degassing liquid food (such as juice, soy sauce or wine) to reduce microbial growth and extend shelf life.
When a liquid is treated by ultrasonic wave, the sound wave propagating from the radiation surface to the liquid medium will produce alternating cycles of high pressure (compression) and low pressure (rarefied), and the rate depends on the frequency. During the low-pressure cycle, high-intensity ultrasound will produce small vacuum bubbles or voids in the liquid. A large number of small bubbles are evenly distributed in the liquid, resulting in more bubble surface area. The dissolved gas migrates to these vacuum (low pressure) bubbles through a large surface area and increases the bubble size.
Sound waves support the contact and coalescence of adjacent bubbles, thus accelerating bubble growth. Sound waves will also help to separate bubbles from the surface of the container and force smaller bubbles below the surface of the liquid to rise and release the entrained gas into the environment.