The flow behavior of a Newtonian fluid through special mixing enhancers in a modular intermeshing co-rotating twin screw extruder has been examined. The mixing enhancers are slotted screws and gear mixing elements. Particular attention has been directed to drag and pressure flow characteristics and residence tune distribution in such devices. The data obtained are useful for guidance in the selection of appropriate mixing elements and validation of flow simulation models for twin screw extruders.