of the shaft 20 when the stirrer 12 is in place in this manner the area of contact between the hub 16 and the shaft 20 is minimized the combination of minimum area of contact and the inherent lubricious nature of the teflon material provides a structure having extremely low rotational friction losses in the microwave oven illustrated in fig1 the microwave power and control components are located generally on the right side of the oven adjacent the cavity a fan is provided in the area to draw in outside air and blow it across the electrical components for cooling the air is then routed or ducted at least in part to the feed box 14 which it enters through perforations 30 formed in one wall of the feed box and exits through similar perforations in the opposite wall the perforations 30 are positioned so that the air flow as shown by the arrows in fig4 passes across the tips of the stirrer blades 12 on one side of the axis of rotation and exits the feed box on the same side of the axis of rotation this insures a preselected rotational direction for the stirrer compatible with the pitch of the stirrer blades and also provides for an essentially dead air space on the opposite side of the axis of rotation this dead air space has been found to be of assistance in dampening the rotation of the stirrer 12 to assist in keeping its rate in the range of 20 70 rpm which is desired for optimum energy distribution pattern the stirrer mounting arrangement disclosed herein provides the basis for an air driven stirrer system achieving.