Inter-Operational Conveying of Processed Cheese Spreads: Permissible Rotation Speed of Rotary Lobe Pump

The article proposes a method for determining the permissible speed of rotary lobe pumps for inter-operational conveying of processed cheese spreads. The performance of rotary lobe pumps increases together with the rotor speed. Technical documentation usually provides the permissible dynamic viscosity values for rotary lobe pumps at different rotor speeds. If the dynamic viscosity exceeds the permissible values, the manufacturer cannot guarantee reliable operation of the rotary lobe pumps. However, only Newtonian liquids can benefit from such limitations. Most food media, including cheese spreads, have rheological properties of non-Newtonian liquids, in which the effective dynamic viscosity depends on the velocity gradient ω and hence on the rotor speed. The new method makes it possible to determine the permissible rotation speed of the lobe pump if the dependance of the effective dynamic viscosity on the velocity gradient is known. The article provides a set of examples for Vitalobe rotary pumps and two different cheese spreads at several temperature modes.