| Summary: | A sonochemical reactor design which addresses deficiencies in current reactor designs is proposed. This
design uses a comparatively low power electrostatic transducer because electrostatics are efficient over a
wide frequency range and are not limited by their size, shape or placement in a reactor. This allows the
creation of a reactor that can match the optimal frequency of a sonochemical process, maximize its sound
field using mode shapes and resonance and, with the addition of a tracking system, follow system
resonances that change with cavitation. The cylindrical reactor cavity and co-axial cylindrical transducer
used in the design focus sound energy at the centre of the reactor, protecting the transducer from
cavitation and allowing for analytic modeling of the sound field.
A model of the proposed reactor's homogenous sound field was created in mathCAD. The model
consists of a transducer model whose stiffness and damping coefficients were derived from a new
thermodynamic model and a reactor model given by the reactor's wave equation and boundary
conditions. The pressure magnitude generated at the transducer scales the magnitude of the reactor
sound field. This allows the transducer pressure to be expressed as a relationship between its input
voltage and the reactor mode shapes.
A prototype reactor was constructed in order to verify the model experimentally. Data predicted by the
model and measured experimentally were collected over a frequency range of 4 to 38 kHz. Ratios of the
transducer's calculated electrostatic pressure to the pressure at the centre of the reactor were determined
for both data sets. The match between the curves of this pressure ratio versus frequency for the two data
sets was very good. Differences in the widths of the curve's frequency peaks were attributed to a smaller
than expected air gap in the prototype transducer. Accounting for this produced an excellent match
between the curves.
Changes to the reactor design that would allow the reactor to achieve cavitation were investigated with
the model. Both decreasing the transducer gap space and replacing the air in the gap with a gas of low
thermal conductivity and high dielectric strength significantly reduced the voltage required to induce
cavitation in the reactor. The model also revealed that the significant effect of the stiffness of small gap
space transducers on the magnitude of the reactor's pressure field at low frequencies. === Applied Science, Faculty of === Mechanical Engineering, Department of === Graduate
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