What is Ultrasound?
Sound waves with frequency of about 20kHz and what are more than 20kHz is called ultrasound. Ultrasound is applied to various industrial technologies. Now, we introduce a new word in ultrasonic technology, based on magnetostrictive material -Co-Fe Alloy.
What is Co-Fe Alloy?
This is a new kind of Iron -Cobalt (Co-Fe) alloy, produced by the non-metallurgic technology. The main problem of ultrasonic technologies (in case of magnetostrictive transducer) is high cost or low energy power of magnetostrictive materials -nickel (Ni) or iron-aluminium(Diferal)alloy.
It is known iron -cobalt (Co-Fe) alloy which is good for soldering and welding, has higher efficiency & energy power than Ni or Diferal alloy, and also it has higher working temperature than Ni.
Scale
Managers usually don't know the scale problem, but it is the problem of safety, durability of equipment, energy conservation, and environment preservation - that is, in the end, the problem of money. Water treatment can't solve the problems of scale completely, and sometimes it's impossible or unprofitable to use it. Water treatment is usually computed for basis regime of equipment's working, but some times, for example in winter, it is necessary to use peak regimes. In this case salt hardness ions can flow through water treatment system and then scale layer is formed. During cycle time between regeneration, the capacity of ions-exchange decreases.
Sometimes operators are not so attentive. Average leakage of fuel, as a result, is about 4~20%. It needs to stop operating the equipment and to make mechanical or chemical cleaning.
Scale Prevention
Scale prevention by ultrasonic helps to:
- increase the interval stopping of equipment for cleaning, or eliminate cleaning work;
- increase the safety of equipment;
- decrease the cost of fuel;
- decrease pollution by chemical substances.
The principles of scale preventing and removing are as follows.
It is known that crystals of salts of hardness are forming on the surfaces of heat exchange or on the surfaces of crystal centers.
Volume of scale depends on salts concentration in water.
Ultrasound can increase number of crystal centers in water and decrease concentration of salts of hardness by influence of cavitation.
Cavitation
Ultrasonic cavitation is the formation of bubbles (cavities) in liquids at the low-pressure part of wave cycle. The bubbles are filled with gases or vapor coming out of water. When sizes of bubbles reach a resonance sizes, collapse of bubbles takes place.
The collapse formed extremely high stress shock waves in water. Shock waves are formed in water a lot of crystal centers, and centers became overgrown by crystallization of salts dissolved in water, destroyed by influence of shock wave in several solid particles - new crystal centers and s.o.
At the same time, decontamination of water takes place. Oxygenium, nitrogenium, CO2 (CO2 formed in water like result of disintegration of metastable hydrocarbonates of calcium and magnesium) are removed by the influence of cavitation from water.
Inside bubbles, free chemical radicals are produced. The processes change chemical data of water, including pH, salts and gases concentration.
Experiments show that the main part of scale in water (not on the heat exchange surfaces) forms in the shape of small crystals by influence of cavitation. Its sizes are about 1µm
Depending on water speed and designs of equipment, crystals can be removed by water flow or falling to the bottom like slime and can be removed by blow down. Scale layers, including those formed before installation of ultrasonic devices, will be destroyed by influence of cavitation.
Micro-Flows in Water
Ultrasound is radiated in water by metallic details of equipment shells, walls of tubes and others. Microflows in the water are formed by radiation and they are directed from metallic surfaces into the water.
Microflows in the water move the particles of scale from surfaces of heat - exchange into the water. In layers of water close to radiated surfaces, the turbulence of water will increase.
Microflow and turbulence in the water help scale prevention and increase heat transfer.