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Ultrasonic Aerosolization is the
physical process that applies ultrasonic energy to breaking up of a liquid
into a very large number of droplets suspended in air. It is a quick and
efficient method of generating Aerosols from different liquids. |
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The liquid attributes that have the greatest
impact on Aerosolization are: Density
the ratio of liquid mass to its volume.
Viscosity
The resistance of the liquid to its motion. It is caused by the cohesive forces between molecules in the liquid.
Surface Tension
A property possessed by liquid surfaces whereby they appear to be covered by a thin elastic membrane in a state of tension. The surface tension is measured by the force normally acting across a unit length in the surface. The phenomenon is due to unbalanced molecular cohesive forces near the surface. |
Since every liquid has its specific Density, Viscosity
and Surface Tension, Ultrasonic Aerosolization cannot achieve identical
results for all sorts of liquids. Hence, liquids are grouped by the degree
of difficulty they pose to the aerosolization process.
Easy Aerosolization
Water, water solutions, light hydrocarbons, light oils, light organic solvents, short chain polymer solutions.
Medium Difficulty
Oil-based paints, oil-based coatings, medium-weight oils, coal slurries, emulsions, suspensions.
Very Difficult or Impossible to Aerosolize
Heavy hydrocarbons, long-chain polymer solutions, latex paints, some coatings
and adhesives, ceramic slurries.
A measure of the difficulty of Aerosolizing a liquid is its Viscosity. The lower the viscosity is the easier it is to Aerosolize the liquid.
Easier Aerosolization is also obtained by decreasing the Surface Tension of the liquid.
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An Ultrasonic Piezoelectric Transducer
is a disc shaped artificial crystal. When it receives a suitable electric
charge it immediately starts to vibrate and to generate Ultrasonic waves
of a predetermined frequency.
Ultrasonic Piezoelectric Transducers are manufactured to vibrate in a
wide range of frequencies from 0.2 MHz to 1 GHz. Green Gloud's transducers
operate within the range of 0.5 to 3 MHz.
The frequency of the transducer is important because it determines the
size of the droplets. The higher the frequency, the smaller the size of
the droplets. |
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Liquid Spout |
To simplify the explanation of the process, imagine
that the UAG has only one Ultrasonic Piezoelectric Transducer in operation.
The transducer is mounted on the base of the reservoir. The reservoir
is filled with a liquid up to a predetermined level completely covering
the transducer. An electrical current activates a proprietary Power
Oscillator, which supplies the required frequency to the transducer,
which in turn produces the Ultrasonic Waves. These waves travel upward
in the liquid to form a spout, 2-3 inches high above the liquid surface,
which continuously disintegrates and produces a large number of liquid
droplets.
These droplets are carried out of the reservoir, by a directed flow
of incoming air to form a continuous stream of superfine aerosol.
The liquid spout continuously regenerates itself as long as electric
power and liquid are supplied to the unit.
The Ultrasonic Aerosolization generates the
Aerosol at an ambient temperature and regular atmospheric pressure.
The power consumption is approximately 70 watts per one liter of processed
liquid. For practical reasons the quantity of Aerosol produced is measured
by the rate of liquid processed (liters/hour).
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