Power Plant · Flow
Tracer Dilution Flow (Constant-Rate & Slug)
Primary flow reference by tracer dilution: constant-rate injection with background correction and a first-order GUM uncertainty, or slug injection integrated from a sampled response curve. Used to calibrate cooling-water and large-pipe flow meters.
Verified against published standard
Tracer test
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About This Calculation
Tracer dilution is a primary flow method that does not depend on pipe geometry: a known amount or rate of a conservative tracer is injected and its dilution is measured downstream. It is used to calibrate large cooling-water and penstock meters.
Frequently Asked Questions
How far downstream should the sample be taken?
Far enough for complete cross-section mixing; poor mixing is the dominant error and must be verified by multi-point sampling.
Why subtract the background?
Natural background of the tracer species would otherwise bias C2 and so the computed flow.
When should I use constant-rate injection instead of slug injection?
Constant-rate injection suits steady flow and lets you average a plateau, which is more tolerant of mixing problems. Slug injection needs less tracer and is convenient for large flows, but the full response curve must be recorded until the concentration returns to background.
What limits the accuracy of a tracer test?
Mixing and analysis. If the tracer has not mixed across the section at the sampling point, the sample is not representative; and an inaccurate calibration of the concentration analyser biases the result directly.