For Better Beer, Note Ale Speed
Pipe diameter can become a significant factor in the brewery process. Most fluid transfer operations are best performed within a range of recommended fluid velocities; others are less sensitive to flow conditions.
For example, turbulent flow in pipes might be detrimental to carbonated beverages, yeast suspensions, etc. To prevent turbulence inside pipes, flow rates must be kept below the critical velocity at which turbulence initiates. This is considered laminar flow. Laminar flow can be thought of as a condition where all fluid droplets are moving through a pipe in parallel with minimal mixing across the cross-section of the pipe. In contrast, eddy currents can form at higher velocities. These cause turbulence and vigorous mixing across the inside diameter of pipe. The maximum permissible velocity to maintain laminar flow is a function of pipe size, velocity, fluid density, and fluid viscosity. Table 1 lists the maximum flow rates permissible to maintain laminar flow, and avoid turbulence in a variety of pipe sizes.
The flow rates listed in Table 1 are relatively low compared to typical commercial operations. Most process fluids move at higher velocities and are turbulent. Clean-In-Place (CIP) is a specific application where turbulent flow is desirable. Turbulence improves the scrubbing action of CIP fluid inside pipes. CIP flows should be at velocities between 1.5 and 2.4 M/sec (5 and 8 ft/s). This range is also acceptable for other common fluid transfers that do not require laminar flow. Table 2 lists flow rates which correspond to this range of velocities.
To learn more about pipe sizing, fluid transfer and clean-in-place, contact Bruce Smith at 231.670.1465.
 Food Engineering Magazine, “Tech Update: Clean-in-Place Equipment”, October 1, 2010.
Beer tank photo credit: Bernt Rostad via photopin cc Second beer tank photo credit: Beertographer via photopin cc
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