Primary/Secondary-Loop vs. Primary-Loop-Only Systems

This article compares the operational modes and performance of primary/secondary- (P/S-) loop and primary-loop-only-variable-flow (PLOVF) chilled-water-plant systems.

Subdividing various systems into a primary/secondary (P/S) loop via a hydraulically dependant interconnection long has been a standard solution for central chilled-water plants in the United States and Europe. This achieves, at a relatively low cost, reasonably good hydraulic separation of central-water-plant cooling-generation systems (primary loop) from distribution piping and terminal units (secondary loop). Primary-loop flow is relatively constant, while secondary-loop flow varies b

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