Cooling Water Makeup (Cycles of Concentration)
Evaporation, blowdown, drift, and total makeup flow from recirculation, range, and cycles of concentration.
Example
You enter
- Recirculation flow (GPM) 1000
- Cooling range delta-T (°F) 10
- Cycles of concentration 4
- Drift fraction (e.g. 0.002) 0.002
You get
- Evaporation (GPM) 10
- Blowdown (GPM) 3.3333
- Drift (GPM) 2
- Total makeup 15.33 GPM
Details, formula, and sources
Evaporation, blowdown, drift, and total makeup flow from recirculation, range, and cycles of concentration, with scaling and drift flags. Per CTI and ASHRAE Systems and Equipment 2020 Ch. 40.
Evaporation (GPM) = recirculation x delta-T / 1000. Blowdown (GPM) = evaporation / (COC - 1). Drift (GPM) = recirculation x drift fraction. Makeup (GPM) = evaporation + blowdown + drift.
Cooling Technology Institute (CTI) publications; ASHRAE Systems and Equipment 2020 Chapter 40 (cooling towers).
cti.org and ashrae.org for the TOCs.
Estimate. Operator of record and primacy agency govern.
Field names used by the API: recirculation_gpm, delta_T_F, coc, drift_fraction, evaporation_gpm, blowdown_gpm, drift_gpm, makeup_gpm
- Evaporation rule evaporation = recirculation x delta-T / 1000CTI / ASHRAE rule of thumb
- Drift default 0.002 (0.2%) for a modern drift eliminatorCTI drift-eliminator practice
- COC scaling flag > 10 cycles flagged as a scaling riskcooling-water treatment practice