Hydrodynamic Cavitation
HYDRODYNAMIC CAVITATION
Venturi hydrodynamic cavitation
Rotational
Hydrodynamic Cavitation
Hydrodynamic cavitation is a process of vaporization, bubble
generation, and bubble implosion which occurs in a flowing liquid as a result of
a decrease and subsequent increase in local pressure. Cavitation will only
occur if the local pressure declines below the saturated vapor
pressure of the liquid. The bubble generated will collapse with a subsequent recovery
above the vapor pressure.
Hydrodynamic cavitation can be produced by passing a liquid
through a constricted channel at a specific flow velocity or by mechanical
rotation of an object through a liquid. Based on the geometry of the system,
the combination of pressure and kinetic energy create the hydrodynamic
cavitation cavern downstream of the local constriction generating high energy
cavitation bubbles. Different cavitation types can be generated by liquid flow
initial steady cavitation, developed cavitation or supercavitation
The process of bubble generation, and the subsequent growth
and the collapse of the cavitation bubbles may result in very high energy
densities and in very high local temperatures and local pressures at the
surface of the bubbles for a very short time. The global liquid medium the temperature of the liquid, however, remains at ambient conditions.
When uncontrolled, cavitation is damaging for the equipment.
The cavitation phenomenon can be controlled to enhance the performance of
high-speed marine vessels and projectiles, as well as in material processing
technologies, in medicine. Controlled cavitation can be used to enhance
chemical reactions which results in either the intensification of the chemical
reaction or may even result in the propagation of certain reactions not
possible under otherwise ambient conditions. Due to free radicals generation in
the process hydrodynamic cavitation or in the destruction of pollutants.
Hydrodynamic cavitation can also improve some industrial processes. For
instance, cavitated corn slurry shows higher yields in ethanol production
compared to uncavitated corn slurry in dry milling facilities. This is also
used in the mineralization of bio-refractory compounds which otherwise would
need extremely high temperature and pressure conditions.
The efficient killing of bacteria with hydrodynamic cavitation
We have used hydrodynamic cavitation to destroy Gram-positive and Gram-negative bacteria such as E. coli, L. pneumophila, B.
subtilis. The larges effect was observed with supercavitation. With the use of
rotational cavitation the number of passes of liquid over cavitation has been
significantly reduced. Recently it has been shown that small scale hydrodynamic
cavitators can be very efficient in destroying viruses.
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