The next steps towards changing the heating system in our device have been made. The currently used heating system is based on the conduction of heat through a shelf under which a heating mat is placed to the product. In the prototype device, the product drying process will be based on the application of heat by means of microwaves. Below we present the preliminary numerical results of a freeze dryer equipped with three magnetrons emitting microwaves towards the product. The magnetrons were placed on three sides of the chamber, namely the upper and side walls. Numerical analyzes are performed in the Ansys HFSS program and focus on the determination of heat sources present in the food product and the distribution of microwaves in the chamber.