What is the ultrasonic degassing and defoaming machine?

What is the ultrasonic degassing and defoaming machine?

Ultrasonic defoaming is a method that uses the physical effect of ultrasound to eliminate foam in liquids. Ultrasonic defoaming is mainly based on the cavitation effect and mechanical effect of ultrasound. When ultrasound propagates in liquid, it will generate a series of sparse and dense longitudinal waves, resulting in the formation of local high-pressure and low-pressure areas inside the liquid. In low-pressure areas, tiny bubbles in the liquid will expand rapidly, while in high-pressure areas, these bubbles will shrink sharply or even burst. This rapid expansion and rupture process of bubbles, namely the cavitation effect, will produce strong impact and shear forces, thereby destroying the liquid film of the foam and causing the foam to burst and disappear. At the same time, the mechanical effect of ultrasound will also cause violent vibrations in the liquid molecules, promote the flow and mixing of the liquid, accelerate the drainage process of the foam, and further promote the collapse of the foam.

Ultrasonic degassing is a method of removing dissolved gases from liquids using ultrasonic technology. The vibration of ultrasound can

accelerate the diffusion rate of gas molecules in liquids. On the one hand, ultrasound causes liquid molecules to vibrate violently, disrupting the distribution of gas molecules in the liquid and causing gas molecules to diffuse from areas of high concentration to areas of low concentration; on the other hand, vibration changes the microstructure of the liquid, reducing the diffusion resistance of gas molecules in the liquid, accelerating the migration speed of gas to the surface of the liquid, and facilitating the discharge of gas. The ultrasonic degassing device is mainly composed of an ultrasonic generator, a transducer, and a degassing container. The ultrasonic generator is used to generate high-frequency electrical signals, and the output power and frequency can generally be adjusted according to different application requirements. The transducer converts the electrical signal into ultrasonic mechanical vibration and transmits it to the liquid in the degassing container. The design of the degassing container needs to take into account the flow characteristics of the liquid and the propagation effect of ultrasound to ensure that the ultrasound can act evenly on the liquid and achieve efficient degassing. Some more complex devices may also be equipped with auxiliary equipment such as liquid circulation systems and temperature control systems to optimize the degassing process.

Ultrasonic equipment can effectively degas and defoam liquids. In this case, ultrasound removes small suspended bubbles from the liquid and reduces the level of dissolved gas to below the natural equilibrium level.

01
There are many uses for liquid defoaming and degassing:
--Particle size measurement before sample preparation to avoid measurement errors;
--Degassing of oil and lubricating oil before pumping to reduce pump wear due to cavitation;
--Degassing of liquid foods (such as juice, soy sauce or alcoholic products) to reduce microbial growth and extend shelf life;
--Defoaming of toiletries (hand soap, shampoo, laundry detergent, etc.);

When ultrasonically treating a liquid, the sound waves propagating from the radiating surface into the liquid medium create alternating cycles of high pressure (compression) and low pressure (rarefaction) at a rate that depends on the frequency. During the low pressure cycles, the high intensity of the ultrasound waves creates small vacuum bubbles or voids in the liquid. A large number of small bubbles are evenly distributed in the liquid, creating a large bubble surface area. Dissolved gases migrate into these vacuum (low pressure) bubbles through the larger surface area and increase the size of the bubbles.

The sound waves support the contact and merging of neighboring bubbles, thus accelerating bubble growth. The sound waves will also help to detach bubbles from the container surface and force smaller bubbles located below the liquid surface to rise and release entrained gas into the environment.
The degassing and defoaming process of a liquid is easy to see. In a glass beaker filled with fresh tap water, ultrasonic treatment will force small suspended bubbles to coalesce and move upward rapidly. You can see this effect in the progress image below

The original liquid contains a large number of suspended bubbles. This is a problem especially in coolants, as the bubbles promote cavitation in pumps and nozzles, causing wear. The progress graph below shows the effect of ultrasonic defoaming.

Ultrasonic treatment also produces bubbles in clear water after leaving the water to stand for 24 hours. The gas migrates into the bubbles, which fill with dissolved gas. As a result, the bubbles grow and move upward. The degassing effect is noticeable in any translucent liquid.
Since ultrasound improves the rise of small suspended bubbles to the surface of the liquid, it also reduces the contact time between the bubbles and the liquid. Therefore, it also limits the redissolution of gas from the bubbles into the liquid. This is particularly interesting for high viscosity liquids, such as oils or resins. Since the bubbles have to move to the surface of the liquid, ultrasonic degassing is better if the container is shallow, so the time to the surface is shorter.