Pressure Losses and Rheological Properties of Flowing Butter

Abstract

SUMMARYThe pressure losses and rheological properties of butter flowing through stainless‐steel tubing were investigated. Since viscosity is a measure of internal resistance to flow, an extrusion riscometer was constructed to measure apparent viscosity. The apparent viscosity was calculated from the extrusion viscometer data using the Hagen‐Poiseuille equation for flow through tubing. Flow profiles were obtained by alternately forcing butter of different colors through the various lengths of tubing at different temperatures. The velocity gradient was small within the butter except near the wall. A linear relationship was found between the logarithm of apparent viscosity and the logarithm of bulk velocity for a range of 0.001 to 1 ft/sec. The average slope of the regression line was –0.846. As the length of the tubing increased, the average apparent viscosities decreased, though at a decreasing rate. Very small differences were found between the apparent viscosities obtained with 10.5.in. and 14.0.in. lengths of tubing. The influence of temperature on the logarithm of the apparent viscosity was found to be linear, having a slope of ‐0.059 for the range of 55–75°F. A general empirical equation was determined relating the influence of bulk velocity (v, ft/sec) and temperature (T, °F) to the decrease in apparent viscosity (η, lb/ft see):log η= 4.762 – 0.846 log v– 0.59 T which is considered valid for temperatures between 55 and 75°F.