## 3 Results and Discussion
### The Kinetics and Energy Intensity of Drying
Due to the significant losses in ultrasound power/intensity that occur during the transfer of energy between the radiator plate and the material, only a small proportion of the acoustic energy is involved in accelerating the drying process. Nevertheless, the positive effect of the ultrasound assistance could be easily distinguished and is in agreement with the results presented by other researchers. [PERSON] et al. [37] noted a 20% reduction in processing time during the ultrasound-assisted convective drying of carrot. An analysis of the specific energy consumption (\(SEC\)) (Figure 3b) reveals that the application of additional energy-consuming devices, in the form of microwave generators or ultrasound transducer, affects the energy intensity of the process in a different manner. In the case of the microwave processes (CVMW, CVMWUS), a notable enhancement of the drying rate--which also resulted in a considerable reduction in drying time--led to a reduction in the amount of energy required to evaporate a given mass of moisture. The \(SEC_{\textit{air}}\) values for these processes were the lowest for all the schemes studied: 87 MJ/kg and 90 MJ/kg for CVMW and CVMWUS, respectively. This represents a respective 30% and 28% reduction compared to the convection CV process (Table 2). The ultrasound-assisted convective process (CVUS), despite an observable increase in drying rate and reduction in drying time, did not prove to be more energy efficient than the reference process. A notable increase (59%) in the value of specific energy consumption was observed for CVUS, reaching an approximate value of 190 MJ/kg. The considerable increase in \(SEC\) for CVUS can be attributed to the higher instantaneous energy consumption (in comparison to CV) necessitated by the requirement to power the AUS ultrasound generation system. Despite the beneficial effects of acoustic waves on the drying rate and time, their effectiveness was insufficient to compensate for additional energy expenditure, leading to an increase in total energy consumption. This \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Process**} & \multicolumn{3}{c}{**Relative Change**} \\ \cline{2-4}  & \(DR_{\textit{air}}\) & \(DT_{\textit{air}}\) & \(SEC_{\textit{air}}\) \\ \hline CV & – & – & – \\ CVUS & \(13\%\) & \(-10\%\) & \(59\%\) \\ CVMW & \(112\%\) & \(-53\%\) & \(-30\%\) \\ CVMWUS & \(140\%\) & \(-59\%\) & \(-28\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Relative change in average drying rates and specific energy consumption. phenomenon was previously reported by [PERSON] et al. [38], [PERSON] et al. [37], and [PERSON] [40]. In the case of the CVMW and CVMWUS processes, the instantaneous energy consumption was also higher. However, the kinetic benefits resulting from the use of microwave radiation (increased drying rate and reduced drying time) were substantial enough for compensate this additional energy expenditure and reduce overall energy consumption. The discrepancy between the _SEC_ values for the ultrasound- and microwave-assisted processes may also be attributed to the differing energy efficiency of the generators and the varying attenuation coefficient of the radiation along the path from the generator/transducer. The energy efficiency of microwave-assisted processes was also confirmed in studies by [PERSON] et al. [15] and [PERSON] et al. [37]. In both cases, the microwave-assisted drying of carrot was characterized by a lower energy consumption compared to the reference convective drying. The experimental data was also used to determine the drying constant, \(k\); mass transfer coefficient, \(\alpha\); and effective diffusion coefficient, \(D_{\textit{eff}}\). Table 3 presents the values obtained for each process. The values for all determined parameters corroborate the hypothesis that ultrasonic and microwave assistance has a favorable impact on convective drying kinetics.