Design and development of drying ultrasonic systems (USDIS)

General objective of the whole project

The main aim of the project is the intensification of drying processes at low temperature by using power ultrasounds which will be undertaken under three aspects. The first consists in the design of efficient ultrasonic generating systems and associated drying chamber, considering the interaction between the chamber and the produced acoustic field. The second aspect addresses the study of the influence of pretreatments of the raw matter on its structure and the effect of such pretreatments on the subsequent drying operation and power ultrasound efficiency. The third aspect addresses the drying process itself at low temperature and its interaction with other process variables. Finally, the effects of all process variables on the final product quality and energy efficiency will be investigated and quantified. Each mentioned aspect will be undertaken preferably by one of the participating teams (subproject).

Specific objective of subproject carried out by CSIC

Subproject 1 (GUP/CSIC) will deep the knowledge of the process mechanisms and parameters due to the generated acoustic fields, processing temperature and drier design configuration. All this work will be conducted with the purpose of exploring process the intensification attained through sonication applied to low temperature drying. To achieve this aim it is necessary to perform an experimentally validated numerical design methodology for power ultrasound systems capable of efficiently transmit sound through gas media at low temperature. These systems consist in piezoelectric transducers with extended surface radiators. Ultrasonic device prototypes applicable to low temperature drying processes, based on numerical models will undergo to an experimental validation of their operational parameters, a study of their nonlinear dynamic characteristics under working conditions and the investigation of suitable redesign procedures to mitigate system nonlinearities and eliminate undesired modal interactions. It will be also necessary to model the drying chamber with the integrated power ultrasound system via the numerical simulation of the acoustic field generated inside the chamber and validate experimentally the predicted behavior of the atmospheric pressure freeze drying system with integrated power ultrasound generators.

The effects brought about by power ultrasounds can intensify the process but also affect the quality because they act over/on the materials porosity. For that reason in Subproject 3 (GIA/UIB) the influence on final product characteristics of power ultrasound applied on the different stages of atmospheric freeze drying will be quantified.

The raw materials considered include vegetal (apple, carrots, eggplant and beetroots) and animal origin (pork meat and cod).

• In order to assess the effects of power ultrasounds experiments will be carried out on the stages of pretreatments, freezing and drying.