Not all cavitators are created equal, learn about the different methods to achieving cavitation, and why dynamic hydrodynamic cavitation produces the best results

Hydrodynamic cavitation can be generated by static or dynamic elements

In static elements, such as venturi tubes or perforated plates, pressure energy is converted to kinetic energy, or in other words, the fluid at high pressure and low velocity experiences an increase in velocity and a decrease in pressure: ideally, when the pressure reaches the vapor pressure of the fluid, cavitation starts.

What`s wrong with this setup? Let`s follow the energy path of the fluid in a venturi tube: of course we need a pump to increase the pressure of the fluid before it enters the throat of the venturi, so electric energy is firstly converted to pressure energy, then to kinetic energy, when the fluid enters the throat, finally to pressure energy again, downstream the static element. Disadvantages are evident: with this setup we will need to pump all the fluid to be treated at high pressure, at least in the range of 4-20 bar, and there are too many energy conversions, which means high operative costs. Moreover, if we treat suspensions, liquids mixed with solids, we will experience clogging problems and high maintenance costs.

Can`t we directly apply kinetic energy to the fluid without increase its pressure?
Yes, sure we can! This is how dynamic elements work: we can pump a fluid to the dynamic hydrodynamic cavitator at near atmospheric pressure and generate cavitation by directly rotating the cavitational element, by this way we are skipping an energy conversion step to generate cavitation.

The fluid inside the cavitation chamber is accelerated by the rotor itself, so we have electric energy of the motor of the cavitator converted to kinetic energy to the fluid, which experiences cavitation.

Therefore, we don`t need to pump at high pressure all the fluid and we will not experience anymore clogging problems due to static elements.

So, a dynamic hydrodynamic cavitator should be the right way to have an efficient process, why the ROTOCAV is better than the others?
Before optimizing our ROTOCAV cavitator we deeply studied what the market could offer and what were the drawbacks of the available cavitators.

Some dynamic hydrodynamic cavitators can be effective to treat liquids only, for example to heat clean fluids and to produce biodiesel by transesterification, because elements on the rotor can be easily clogged if they are fed with a liquid-solid suspension; moreover most of them do not treat the bulk of the fluid completely and they can generate only steady cavitation, which is far less intensive than developed unsteady cavitation, as it doesn`t affect the liquid bulk too much with chemical and physical changes (you can read more here about different types of cavitation for different processes).

Moreover, some of the dynamic hydrodynamic cavitators on the market are difficult to scale-up, since the elements generating cavitation are radially arranged: this means that increasing the diameter of the rotor or changing the size of the elements for a scale-up will change the cavitation type, as the cavitation number will change too, causing loss of control on the process.

Besides these issues, it must be considered that some cavitators will also pump the treated fluid, due to their geometries, decreasing the available energy to generate cavitation, being less efficient.

Our ROTOCAV is a dynamic hydrodynamic cavitator: compared to a single passage in a static element it treats "thousands of times" the fluid in the same time, with the same energy; compared to the other dynamic hydrodynamic cavitators, it is able to generate unsteady developed cavitation and supercavitation, it treats the whole bulk of the fluid, it can treat suspensions with no clogging problems, it is not a pump, so all the energy is used to generate cavitation and it doesn`t have problems for the scale up, since operative parameters of a lab machine can be preserved for all the available industrial sizes.

Our ROTOCAV was designed maximizing the area to generate cavitation: compared to the other dynamic hydrodynamic cavitators of the same size, volume of cavitation can be 3-4 times more!

Written by Daniele Crudo of E-Pic S.r.l the father of the ROTOCAV cavitation reactor "Rotocav compared to other commercially available cavitators"

CaviMax - Hydrodynamic Cavitation Technology - Brochure