(Δ H/L) w = 0.58 V 1.75 D -1.25 (ft/1OOft),
where V bulk velocity (ft/s), and D pipe diameter (in).
Previously published methods. for calculating pipe friction loss of pulp suspensions gave a very conservative estimate of head toss. The method just described gives a more accurate estimate of head loss due to friction, and has been used successfully in systems in North America and world-wide. Please refer to Appendix for equivalent equations for use with metric (SI) units. Tables 1 and IA are located in Appendix B;Tables II and IIA are located in Appendix C.
Pertinent equations, in addition to those herein presented, are located in Appendix D. Example problems are located in Appendix E.
V. HEAD LOSSES IN BENDS AND FITTINGS
The friction head loss of pulp suspensions in bends and fittings may be determined from the basic equa-tion for head loss, Equation [5]
H = K V 12/2g (ft) ,
where K = loss coefficient for a given fitting,
V = inlet velocity (ft/s), and g = acceleration due to gravity (32.2 ft/s2).
Values of K for the flow of water through various types of bends and fittings are tabulated in numerous reference sources (Reference 3, for example). The loss coefficient for valves may be obtained from the valve manufacturer. The loss coefficient for pulp suspensions in a given bend or fitting generally exceeds the loss coefficient for water in the same bend or fitting. As an approximate rule, the loss coefficient (K) increases 20 percent for each 1 percent increase in oven-dried stock consistency. Please note that this is an approximation; actual values of K may differ, depending on the type of bend or fitting under consideration (4).
