The Relationship of
Flow Characteristics to Changes in
Sludge Consistency
WILLIAM L. CARPENTER, Research Associate
National Council of the Paper Industry for Air and Stream Improvement, Inc.
The John Hopkins University
Baltimore, Maryland
JACK GROSSMAN, Development Engineer
Tippetts, Abbett, McCarthy, Shatton Engineers
New York, New York
INTRODUCTION
Most previous investigations relating to the problem of fluid transmission in
the paper industry have included studies on the flow characteristics of fibre suspensions (1) and on the effects of deaeration of pulp suspensions (2). Although the
nature of the paper mill sludges are similar to the fibre suspensions previously
studied and concurrent conclusions might be drawn regarding flow characteristics,
there still existed a sparcity of information dealing specifically with the flow
characteristics of sludges. Limited knowledge existed concerning the effects of
changes in sludge consistency or transmission distances on pipeline head losses.
This study was undertaken with the objective of providing some of that information. More specifically, the effect of solids concentration, velocity and
fibre content of representative sludges were examined to determine their relationship to pipeline head losses.
HISTORICAL REVIEW OF PIPELINE SLUDGE FLOW BEHAVIOR
At the onset, it is necessary to review previous investigations aimed at the
correlation of non-Newtonian flow data. One of the first efforts related to the
problem of computing head loss in pipelines transporting sludge was reported in
1929 (3). This study indicated that sludge behaves more like water at higher velocities. Later on Hatfield (4) expanded the original work by relating a friction
factor, Reynolds Number plot, but the work was limited due to the choice of a
single flow property, the apparent viscosity. The first generalized flow equation
relating viscometric data to sizing of pipelines transporting sludge was completed
by Merkel (5). Perhaps the most outstanding early contribution to this area of
study was made by Babbitt and Caldwell (6) who developed much of the basic engineering theory of pipeline sludge flow behavior which included non-Newtonian
turbulent-flow correlations (7,8,9). The works of Babbitt and Caldwell have
been somewhat enlarged by Chou (10) and a study of basis problems related to
sludge pumping distance was undertaken by Wirts (11). The role of roughness in
pipes carrying non-Newtonian liquids in the turbulent flow range have been
studies by Dodge (12).
More recently and perhaps the most comprehensive review and tabulation of
equations derived by others and covering time-in dependent non-Newtonian liquid
flows are found in the works of Behn (13,14). This review and study concluded
that sludge flow behavior could not be defined by less than two flow parameters;
since  non-Newtonian fluids do not exhibit the straight proportionality between
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