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发表于 2016-5-13 09:19:21
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ISPE——W&S system 2011
8.6.3 distribution loop velocity
The primary purpose for recirculated distribution is to reduce the release of biofilm organisms into the water by forcing them to tightly adhere to the interior surface of the pipe. For further information, see Chapter 13 of this Guide. Although the mechanisms are not universally agreed upon, it is thought that the velocity associated with turbulent flow reduces the initial attachment of bacteria to interior surfaces, as well as the development of loosely attached biofilm. It is generally recognized that turbulent flow is indicated by a Reynolds number greater than 4000. Distribution systems often are designed to operate with nominal flow velocities of 2 to 3 feet per second or higher, which greatly exceeds the turbulent flow threshold, and therefore, may have a greater detriment on biofilm development. |
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