SCREW DESIGN AND NEWTONIAN FLUID-FLOW

A series of screws were evaluated with regard to their ability to conv ey two Newtonian fluids with nominal viscosity of 1000 Pa.s at room te mperature. Screws with helix angles of 7, 17, 30 and 45 degrees were c onstructed with a diameter of 50 mm. Screws at several of the angles a lso had three flight depths. The extruder-screw pump was constructed s o that both the screw and barrel could be rotated independently. We wi ll present the data for the screw rotation of 11 screws. The results s trongly suggest that the pumping, volumetric output per revolution, of the screw and the barrel are the same regardless of the screw flight height which had a maximum value of about 0.8 thus leaving the core at only 0.2 the barrel diameter. Since pressure back flow is a function of the first power of the flight with and the cube of the flight heigh t, the measured outputs had to be corrected for this in order to calcu late the actual screw forwarding ability.