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

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 (P), the input electrical power (P) 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/m) 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 P (80-400 W) and o/w ratio (0-1) on temperature rise and subsequent thermo-physical properties of liquid and the indirect influence on P 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 P as a function of liquid space velocity (ϑ), temperature, Prandtl (Pr) and Ohnesorge (Oh) dimensionless groups. The results showed that under constant temperature and P, increasing Pr and Oh increased P with a similar trend for both modes of operation. An increase in temperature directly led to a decrease in P with a power factor closed to "-1". The P in continuous flow was higher compared to batch configuration at similar temperature, liquid properties, and P. This effect was more significant with increasing ϑ. An increase in ϑ at constant P led to a decrease in the inlet/outlet temperature difference in continuous flow and an increase in P. Increasing P 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.