Prandtl and Ohnesorge numbers dependent of ultrasonic horn energy in Newtonian liquid under batch and continuous flow

TL;DR

This study explores how ultrasonic energy conversion varies in different flow conditions and liquid properties using a horn-type sonicator.

Contribution

A new power factor correlation is proposed to predict acoustic power based on dimensionless groups and flow conditions.

Findings

Acoustic power increases with higher Prandtl and Ohnesorge numbers under constant temperature and nominal power.

Continuous flow shows lower thermal energy conversion compared to batch flow at similar conditions.

Increasing liquid space velocity in continuous flow reduces temperature difference and increases acoustic power.

Abstract

•Energy conversion in a horn type sonicator was investigated under batch and continuous flow.•Acoustic power was varied depending on the liquid properties at a fixed nominal power of transducer.•A power relation was proposed for acoustic power prediction as a function of dimensionless groups.•Temperature, Pr and Oh numbers are the mains factors affecting acoustic to nominal power ratio.•Lower thermal energy conversion was obtained in continuous flow compared to batch configuration.

Energy conversion in a horn type sonicator was investigated under batch and continuous flow.

Acoustic power was varied depending on the liquid properties at a fixed nominal power of transducer.

A power relation was proposed for acoustic power prediction as a function of dimensionless groups.

Temperature, Pr and Oh numbers are the mains factors affecting acoustic to nominal power ratio.

Lower thermal energy conversion was obtained in continuous flow compared to batch configuration.

The level of knowledge on the non-thermal contribution of ultrasonic wave’s energy to perform physico-chemical phenomena is one of the bottlenecks for the commercialization purposes. Under constant nominal power of transducer (Pn), the input electrical power (Pin) is less and sensitive to the medium’s physical properties. This study attempts to assess the conversion of acoustic to thermal power experimentally and numerically using COMSOL Multiphysis@ for a 24 kHz horn-type sonicator through a medium without any sono-chemical effect. Single- and homogeneous two-phase Newtonian mixtures of sunflower oil and water (o/w) with a relatively wide range of density (914–998 kg/m3) and viscosity (0.5–63.5 mPa.s) were irradiated in a lab-scale vessel (1 L) under batch and continuous flow configuration. The direct influence of Pn (80–400 W) and o/w ratio (0–1) on temperature rise and subsequent thermo-physical properties of liquid and the indirect influence on Pin and thermal energy conversion (TEC) were investigated employing calorimetric method. A new engineering concept including a power factor correlation was proposed and validated for prediction of Pin as a function of liquid space velocity (ϑ), temperature, Prandtl (Pr) and Ohnesorge (Oh) dimensionless groups. The results showed that under constant temperature and Pn, increasing Pr and Oh increased Pin with a similar trend for both modes of operation. An increase in temperature directly led to a decrease in Pin with a power factor closed to “-1”. The Pin in continuous flow was higher compared to batch configuration at similar temperature, liquid properties, and Pn. This effect was more significant with increasing ϑ. An increase in ϑ at constant Pn led to a decrease in the inlet/outlet temperature difference in continuous flow and an increase in Pin. Increasing Pn resulted in higher TEC for both configurations; however, TEC was relatively lower in continuous flow than batch configuration indicating more efficient sonication in continuous flow.

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