PIPE BRANCHING

Neben-quantenzahl, /. secondary (or subsidiary) quantum number, -raum, m. additional space anteroom, -reaktlon, /. by-reaction, side reaction, secondary reaction, -rechnung, /. auxiliary calculation, -reihe,/. = Neben-serie. -rohr, n. side tube (or pipe), branch tube (or pipe). -roUe, /. subordinate r61e. -sache, /. secondary matter. 

Design Considerations of Long-Distance Pneumatic Transport and Pipe Branching... 

A significant number of developments have occurred over the past decade to address these important issues of pneumatic conveying (Wypych, 1995a). This chapter summarizes some of the major design considerations that have resulted from this work in relation to long-distance and pipe branching applications. 

Some of the important issues that should be considered when designing, improving or operating any such pipe branching applications are described in the following sections. 

By employing accurate test-design procedures (Pan and Wypych, 1992a), it is possible to model and design each pipe branch separately so that the system ultimately is well balanced. However, such a system may not be reliable over time due to uneven wear in the pipes/bends, changes in material property and/or on-site conditions. 

Figure 22. Traditional method of pipe branch layout for injection systems.

Cone splitter, as shown in Fig. 25, used in general injection applications for up to 8-way splitting and claimed (Hilbert, 1982) to achieve 10% accuracy in splitting. It should be noted that such figures depend more on the design of the pipe branches downstream of the splitter, rather than the splitter itself. 

Induced swirl, as shown in Fig. 27, which imparts to the solids-gas flow a swirling action and also controls the rate and direction of rotation of swirl via tangential nozzles. However, the residual swirl that would occur in the downstream pipe branches may cause problems if several swirl inducers follow one another (Selves et al., 1995). This problem could be eliminated by introducing the dropout box splitter shown in Fig. 28. 

For dust extraction systems, the concentration of solids usually is quite low. For this reason, the methods employed to calculate pressure loss are based on air-only conditions. Comprehensive information is available (ASHRAE, 1985 ACGIH, 1992) to assist the designer in estimating the pressure loss caused by pipe branches, ducts, elbows, etc. 

In contrast, the amount of material being conveyed inside each pipe branch of a flow splitting application is very high and hence, design cannot be based on air-only analyses alone. For example, Low et al., 1987 have proposed the following empirical relationship to determine the head loss of a pipe branch. 

K Pipe branch head loss for solids-gas flow... 

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